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Institute of Medicine (US) Committee on Dietary Supplement Use by Military Personnel; Greenwood MRC, Oria M, editors. Use of Dietary Supplements by Military Personnel. Washington (DC): National Academies Press (US); 2008.

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Use of Dietary Supplements by Military Personnel.

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2Recent Survey Findings and Implications for Future Surveys of Dietary Supplement Use

INTRODUCTION

Dietary supplements are widely available through a rapidly expanding market of products that are commonly advertised as being beneficial for health, performance enhancement, and disease prevention. These claims may influence the use of dietary supplements by military personnel, given the importance and frequent evaluation of physical performance and health as criteria to join and remain in the military. Given the large number and wide variety of supplements readily available, as well as a lack of scientific evidence addressing health benefits or safety, it is important to monitor the use of supplements by military personnel. One effective approach to this is the use of surveys with comprehensive data collection (e.g., well-designed questions on patterns of use). Previous reports from the Institute of Medicine (IOM) have recommended monitoring dietary intake and supplement use (IOM, 1999, 2006).

Two national surveys have recently collected data on dietary supplement use, the National Health and Nutrition Examination Survey (NHANES) and the National Health Interview Survey (NHIS), both conducted by the Centers for Disease Control and Prevention’s National Center for Health Statistics (see Gardiner et al. in Appendix B). These data, collected through in-home interviews, are representative of the U.S. population. Although to conduct military surveys might be perceived as duplicative, there is ample justification for such surveys, given the differences in population, settings, and products used.

The specific characteristics of some military subpopulations (e.g., Rangers, Special Forces) justify the continuation and improvement of data collection from distinct dietary supplement use surveys from military personnel for the following reasons: (1) the higher physical fitness demands of some military subpopulations (e.g., Rangers, Special Forces) compared to those of the general population, (2) the lower proportion of women in these subpopulations, (3) the differences in motivation for using dietary supplements (e.g., meeting military weight standards and improving performance), and (4) differences in military culture and behavior patterns. As an example, the military imposes serious consequences for weight gain and substandard performance, which likely lead to supplement use in the military that differs from that of the civilian population. Data from civilian populations may also not provide an accurate description of the prevalence, patterns of use, and key issues of certain military populations (e.g., Rangers, Special Forces).

In general, survey research uses questionnaires or interviews in relatively large groups of people and, if appropriately planned and conducted, gathers reliable and valid data on various characteristics of the population of interest. The use of survey methodology can be effective to investigate and monitor supplement use in the military. Since it is not feasible to survey everyone, survey data can be collected from a well-defined sample of individuals and, from this, generalized to an entire group (e.g., all military personnel or all Rangers). Challenges in performing surveys include ensuring high response rates, comprehensive data collection, and the validity of the individual responses. The validity of the data from these surveys may be compromised by several factors: incorrect sample selection, unclear terminology (common usage terms versus scientifically defined terms), or survey respondents’ lack of knowledge of and inability to determine total dose of or exposure to supplements or inability to remember their supplement use accurately. A low response rate can lead to a biased sample that does not represent the supplement use of the targeted military population.

The benefits of survey use include having data on the extent of the use of dietary supplement products, changes in patterns of use, and insights on specific health behaviors (e.g., reasons for use, degree of consultation with physician, views on dietary supplements). As also recommended in Chapter 5, an important application of survey data on changes in patterns of use is their utilization as a trigger to initiate a safety review of a specific dietary supplement when there is an initial signal for concern (e.g., because it chemically resembles a hazardous product or there are adverse events associated with its consumption). The outcome of this safety review should be the basis for policy-making decisions by military leadership. A systematic evaluation of patterns of use can therefore be used to develop effective educational messages for military personnel and to formulate health policy. If survey data are representative of the targeted military subpopulation, then the frequency of use can also be used to calculate the reporting proportion (adverse events associated with a particular dietary supplement divided by level of use), an estimate of the occurrence of adverse events compared to the level of use.

When using surveys to track supplement use, it is important to clearly define the term dietary supplement. Published literature often includes various products in the category of dietary supplement that might not conform with the legal definition.1 These include sport drinks, bars, or gels—products not legally qualifying as dietary supplements but which include dietary supplement ingredients in their formulas. For practical purposes, however, it is justifiable to include them in the surveys as dietary supplements. In this report, the committee’s deliberations about dietary supplements also included products that meet the legal definition as well as food products that are commonly perceived as nutritionally enhanced with dietary ingredients, botanicals, or vitamins and minerals (e.g., sports drinks, sports bars). Fortified foods were not included in the report because they are not generally perceived as dietary supplements.

Several surveys (published and unpublished) have been conducted on dietary supplement use by military personnel (Tables 2-1 and 2-2). Most of these surveys have been administered in the U.S. Army, with a focus on Rangers and members of Special Forces. This chapter briefly reviews the questionnaires and findings from the latest unpublished surveys on dietary supplement use conducted among various military groups and makes recommendations to improve various aspects of survey design and administration. A summary of the survey results is shown in Table C-1 (Appendix C). Table 2-1 describes the surveys’ populations and focus. This chapter examines limitations of the data that decrease the value of the survey findings; it also provides recommendations for overcoming these limitations and improving the design of the surveys, including suggestions for the phrasing of specific questions and for collecting additional information. Published data from the civilian and military populations are also reviewed for comparison. For the purposes of this chapter, supplement use will be characterized by the available research (published and unpublished) in three separate general supplement categories: multivitamins, single vitamins/minerals, and ergogenic/health enhancement food supplements, including botanicals. Er gogenic dietary supplements are those that may improve performance, remove psychological constraints that affect performance, and increase the speed of recovery from training and competition. The committee did not attempt to analyze the data collected but relied on analyses provided to them; in some instances, the committee requested that further analyses be conducted, and results were provided by military researchers. Likewise, this chapter does not provide an account of the statistical methods used; the reader is referred to excellent publications in this matter (Aday, 1996; Bernard, 1999; Converse and Presser, 1986).

TABLE 2-1 Most Recent Surveys (Unpublished Data), Presented at February 2007 Workshop “Dietary Supplement Intake by Military Personnel”.

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TABLE 2-1 Most Recent Surveys (Unpublished Data), Presented at February 2007 Workshop “Dietary Supplement Intake by Military Personnel”.

TABLE 2-2 Published Surveys Used to Collect Data on Supplement Use by Military Personnel.

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TABLE 2-2 Published Surveys Used to Collect Data on Supplement Use by Military Personnel.

PREVALENCE OF USE OF DIETARY SUPPLEMENTS BY MILITARY PERSONNEL

Overall Use and Behavioral Patterns

This section summarizes the results from surveys (published and unpublished) conducted on dietary supplement use by military personnel (Tables 2-1 and 2-2). Most of these surveys have been administered in the U.S. Army, with a focus on Rangers and members of the Special Forces. The reliability of the survey results depends strongly on the response rate. Therefore, the committee emphasizes the importance of obtaining response rates on the surveys. As Table 2-1 shows, the committee did not obtain the response rate for all surveys. The conclusions from those surveys for which response rate is not available should be drawn with this limitation in mind.

Surveys performed in the general population might not be directly applicable to military surveys because of variation in respondent demographics or differences in the questionnaires themselves. Comparison of the results can nonetheless suggest some differences in the rate of use. Gardiner et al. (2007) (see Appendix B) provides a summary of the NHANES III (1999–2002) and NHIS (2002) data on dietary supplement use for a cohort close in age to military personnel. The NHANES data from 1971–1974, 1976–1980, and 1999–2002 in response to the question, “Have you used or taken any vitamins or other dietary supplements in the last month?” indicate that the rate of dietary supplement use has increased from 23 percent to 37 percent of the U.S. population (see Gardiner et al. in Appendix B; Radimer et al., 2004). Results from NHANES I (1971–1974) showed that the prevalence rate for dietary supplement use in adults was 23 percent; NHANES II (1976–1980), 35 percent; and NHANES III (1999–2002), 37 percent (see Gardiner et al. in Appendix B; Radimer et al., 2004).

In contrast, the 2005 DoD Survey of Health Related Behaviors found that 60 percent of active duty personnel reported using a dietary supplement at least once a week over the previous 12 months (Marriott, 2007). In the 2006 survey of active duty Air Force personnel, only 31 percent of respondents had never used a dietary supplement (Thomasos, 2007), and data published by Arsenault and Kennedy (1999) show that 85 percent of those entering Special Forces and Ranger training reported current or previous use of dietary supplements, and 64 percent reported current usage.

The patterns of dietary supplement use among athletes might be expected to be similar to those of military populations. A review of 51 studies found that among athletes participating in various sports, the overall mean prevalence of supplement use was 46 percent, and most studies reported over half the athletes used vitamins and minerals (ranging from 6 to 100 percent). Larger studies, however, found lower prevalence levels. They also found that patterns of supplement use varied by sport, with weight lifters and bodybuilders consuming the most supplements. Elite athletes were also found to use supplements more than high school and college athletes, and women used them more often than men. Only 32 of the 51 studies provided information about the types of supplements used. The most frequently used supplements, in descending order, were multivitamins/multiminerals, vitamin C, iron, B-complex vitamins, vitamin E, calcium, and vitamin A (Sobal and Marquart, 1994).

Lieberman and colleagues (2007) reported the Army-wide usage in ranges of number of supplements used per week (one or two; three or four; and five or more). Those figures showed that 30–36 percent reported using one to two different supplements per week. Among males, 12–14 percent reported using five or more supplements per week compared to 18–23 percent of females; among elite units, 41–45 percent of Special Forces and Rangers reported using one to two different supplements per week and 7–15 percent reported using more than five supplements (Lieberman et al., 2007).

Multivitamin/Multimineral Supplement Use

Vitamin and mineral supplements are often used in combination by athletes as ergogenic aids. The composition of products with vitamin and mineral combinations varies; this chapter refers to this range of supplement products as multivitamins/multiminerals (MV/MMs). National surveys report that 18–26 percent of Americans routinely take MV/MMs (see Gardiner et al. in Appendix B; French, 2007; Kaufman, 2007). The usage of MV/MM supplements by military personnel varies from 23 to 45 percent (Lieberman et al., 2007; Marriott, 2007). In a 2005 survey conducted by French (2007), 18 percent of civilians reported using MV/MMs as the only supplement versus 23 percent of those serving on active duty, in the National Guard, or in the Reserves. This contrasts with the 45 percent of active duty service members reporting such use in the 2005 DoD Survey of Health Related Behaviors (Marriott, 2007), a difference perhaps reflecting a higher use of dietary supplements among active duty personnel compared to those in the National Guard or Reserves, although they might also be on active duty. Various smaller surveys suggest a similar level of usage among active duty military personnel. In the ongoing Army-wide survey, 30 percent of male respondents reported using MV/MM supplements (Lieberman et al., 2007). Among active duty Army personnel assigned to Europe from 2003 to 2005, 33.8 percent reported using them (Corum, 2007). Another survey found that 39 percent of active duty senior Army officers attending the U.S. Army War College in 1999–2001 used MV/MMs (Lieberman et al., 2007). Within the subpopulations of special interest—active duty Rangers and Special Forces—23 and 32 percent, respectively, were routinely taking MV/MMs (Lieberman et al., 2007).

Although perhaps a less definitive source because it requires users to have reported to a physician, 13 percent of 573 Army physicians surveyed indicated that their patients reported using MV/MM supplements and 20 percent of 614 ancillary health care personnel surveyed indicated that their patients reported using MV/MM supplements (Jaghab, 2007).

The available survey data also report usage of individual vitamin and mineral supplements (see Table 2-3); however, only one set of survey data (personal communication, Sonya Corum, U.S. Army Training and Doctrine Command, April 10, 2007) was analyzed for use of MV/MM supplements concurrent with the use of single-nutrient supplements. The single nutrients most prevalently taken in conjunction with MV/MMs were vitamin C (43 percent) and calcium (38 percent).

TABLE 2-3 Percentage Ranges of Respondents Using Individual Nutrient Supplements (from military and civilian surveys).

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TABLE 2-3 Percentage Ranges of Respondents Using Individual Nutrient Supplements (from military and civilian surveys).

Single Vitamin/Mineral Supplement Use

A previous IOM report (IOM, 2006) suggested that in addition to strategies to increase nutrient intake from foods, dietary supplements may be warranted for some individuals, such as iron and folate for women of childbearing age and MV/MMs for individuals restricting calorie intake for weight loss. Intake levels higher than the Tolerable Upper Intake Level might incur hazardous consequences to health. As with MV/MMs, it is likely that most users take individual vitamins or minerals to supplement their diets or with expectations of improving general health.

Table 2-3 shows the percentage of individuals (by gender, when known) of both military and civilian populations using single-nutrient supplements. In the 2005 DoD Survey of Health Related Behaviors (Marriott, 2007), 27 percent of respondents reported taking a single mineral or vitamin supplement. Based on the limited survey results reported, compared to civilians, usage by military personnel of three (i.e., vitamins E, B complex, and D) of the four single vitamin supplements appears to be similar, and usage of vitamin C and iron is slightly higher. However, the military population reported usage of single nutrients (vitamin A/beta-carotene, vitamin B6, folate, magnesium, and potassium) not reported in the civilian surveys. Except for the 2005 DoD Survey of Health Related Behaviors (Marriott, 2007), the surveys did not define the term antioxidant, so it is unclear if it was understood to refer to a specific individual ingredient, a specific combination of vitamins and minerals, or botanicals. No statistical comparisons can be made between the military and civilian survey results.

Ergogenic/Health Enhancement Dietary Supplements

The third category of supplements includes single bioactive substances or combinations, other than vitamins or minerals, that are intended to enhance performance or health (e.g., creatine, ginseng). Bathalon et al. (2000) reported that 54 percent of senior officers attending the U.S. Army War College reported using “health-promoting” dietary supplements, and among Rangers, 30 percent used performance-enhancing supplements.

Analysis of data from NHANES 1999–2002 shows that dietary supplements other than vitamins and minerals are used by 7 percent of the U.S. population (see Gardiner et al. in Appendix B). Among these products, echinacea, ginseng, Ginkgo biloba, and garlic are the most popular. The 2005 Slone Survey reported that among Americans older than 18 years, 23 percent had taken herbals or other “natural supplements” during the week preceding the interview (Kaufman, 2007). The most commonly used herbal/natural supplements were lutein (9.4 percent), lycopene (7.8 percent), glucosamine (4.0 percent), garlic (2.6 percent), chondroitin (2.5 percent), Ginkgo biloba (1.6 percent), and coenzyme Q10 (1.5 percent). It should be noted that the most commonly used botanical supplements, lutein and lycopene, appear almost exclusively as ingredients in MV/MM supplements. The 2002 Health and Diet Survey, a national telephone survey sponsored by the U.S. Food and Drug Administration, found that 73 percent of participants (n=2,743) had consumed dietary supplements (including vitamins, minerals, MV/MMs, herbs, and/or other supplements) in the preceding 12 months. Of this number, 42 percent reported taking an herb, botanical, or other nonvitamin dietary supplement. The nonvitamin supplements most commonly reported used were echinacea (19.5 percent), garlic (16.6 percent), Ginkgo biloba (14.6 percent), ginseng (11.7 percent), and glucosamine (10.9 percent) (Timbo et al., 2006).

When categorized by perceived effect, the 2005 DoD Survey of Health Related Behaviors indicated that among active duty military users of dietary supplements other than vitamins and minerals, 21 percent used “bodybuilding” supplements, 18 percent used “weight-loss products,” 9 percent used “joint health” products, 8 percent used “performance-enhancing” products, and 9 percent reported using other types of supplements (Marriott, 2007). Among active duty Air Force personnel, the nonvitamin, nonmineral supplements most commonly reported being used five or more times are creatine, glutamine, caffeine, protein powders, fish oils, Hydroxycut (a multi-ingredient product containing botanicals and minerals, sold to promote weight loss), chondroitin, and nitric oxide (Thomasos, 2007). The use of single bioactive substances seen in data from the surveys reviewed varies significantly, but the following examples show the percentage of respondents reporting use of androstenedione (6–13 percent); glucosamine/chondroitin (glucosamine hydrochloride and sodium chondroitin sulfate) (7–11 percent); conjugated linoleic acid (3 percent); garlic (5–7 percent); ginseng (7–21 percent); Ginko biloba (4–5 percent); caffeine (3–18 percent); Ephedra, ephedrine, or ma huang (15–21 percent); echinacea (4 percent); creatine (5–45 percent); coenzyme Q10 (2 percent); protein (5–16 percent); arginine (1 percent); and lycopene (2 percent) (Brasfield, 2004; Corum, 2007; French, 2007; Johnson et al., in press; Lieberman et al., 2007; Sheppard et al., 2000).

Of the 573 Army physicians surveyed, 32.5 percent listed creatine as one of the top 10 supplements used, 7.7 percent reported Ephedra, and 3.5 percent reported glucosamine/chondroitin. Results from other health care personnel supported these findings (Jaghab, 2007).

Consumption of caffeine—a substance included as powdered instant coffee in rations and in the form of chewing gum as a supplement to enhance performance in some specialized military rations—was reported by 18 percent of respondents (Corum, 2007). However, this level is likely underreported, since respondents might not consider caffeine a dietary supplement or might not include other dietary intake of caffeine. Only one study specifically included both dietary supplement and dietary sources of caffeine (see Lieberman et al. in Appendix B), asking respondents to indicate the serving size for each caffeinated product consumed, including various coffee beverages, sodas, and other beverages, with clear instructions on how to measure consumption. The data from these questions have not been analyzed yet.

Sports drinks and sports bars (or gels) are a broad and undefined category of dietary supplements that may contain a combination of vitamins, minerals, and other bioactive substances and essential nutrients and that are widely used. For example, 41 percent of Rangers and 36 percent of Special Forces reported using sports drinks (Lieberman et al., 2007). Within the overall Army population, 20 percent of males and 28 percent of females reported using sports drinks (Lieberman et al., 2007). Corum (2007) reported that 43 percent of active duty Army personnel assigned to Europe between 2003 and 2005 reported using sports drinks. The only military subpopulation reporting a relatively low usage of sports drinks was officers attending the Army War College, of whom only 10 percent reported routinely using sports drinks (Lieberman et al., 2007).

The use of sports bars and gels is much higher among Special Forces (15–43 percent of Special Forces use sports bars) than among Rangers (6 percent and 3 percent of Rangers reported using sports bars and sports gels, respectively). This high use is also in contrast to the lower rate (5 percent) of use among general Army personnel surveyed (Bovill et al., 2000; Lieberman et al., 2007). Those assigned to Europe had also much higher rates of use (17 percent reported use of sports bars in 2003–2005) (Corum, 2007). Some of the questionnaires (e.g., DoD Survey of Health Related Behaviors in 2005) did not have specific questions on these types of products, but reported on the use of unspecified “bodybuilding supplements” (20.5 percent) and performance-enhancing supplements (8.4 percent) (Marriott, 2007).

Protein powders are also popular dietary supplements, their use being reported by 13 percent of males and 8 percent of females in the general Army population and by as many as 18 percent of Rangers and 16–22 percent of Special Forces (Bovill et al., 2000; Lieberman et al., 2007).

Only one survey analyzed the concurrent use of other dietary supplements by MV/MM users (Personal communication, Sonya Corum, U.S. Army Training and Doctrine Command, April 10, 2007). It was found that among those taking MV/MMs , the performance enhancers most frequently reported used were creatine (13 percent), sports drinks (11 percent), and arginine (10 percent).

In general, products perceived as bodybuilders, weight-loss promoters, and performance enhancers are the most popular nonvitamin, nonmineral products. Among Special Forces and Rangers, the use of sports drinks, protein bars, and protein powders was notable, supporting one of their major reported reasons for taking supplements, that is, for increased energy intake.

Differences in Supplement Use by Demographic Factors

In the military, age and rank are closely related. Some surveys presented data categorized by rank but not age; not all of the data sets presented were analysed by demographic factors such as age or gender. Among the surveys reviewed, the greatest quantity of demographic data is available for Special Forces and Rangers, who have a distinctly higher dietary supplement use, specifically for performance-enhancing supplements (Lieberman et al., 2007).

The ongoing Army-wide survey of active duty personnel suggests that younger military members are more likely to use sports bars or gels, sports drinks, and dietary supplements believed to enhance physical performance than other products. Similarly, the 2005 DoD Survey of Health Related Behaviors indicates that dietary supplement usage is highest among the oldest survey respondents; however, bodybuilding supplements are most likely to be used by service members less than 43 years old, and weight-loss products and performance-enhancing supplements are used most frequently by service members less than 34 years old. Military members over 44 years of age are more likely to be taking multivitamins and single-ingredient dietary supplements for health enhancement, such as individual vitamins and minerals, antioxidants, and products to improve joint health (see Marriott et al. in Appendix B).

Some surveys also show differences in usage between men and women; for instance, preliminary results show that in the Army-wide survey, women appear to be more likely than men to take any dietary supplements (71 versus 58 percent) and more likely than men to take MV/MM supplements (37 versus 32 percent), but they are less likely than men to take protein supplements (10 versus 14 percent) (see Lieberman et al. in Appendix B).

Behavioral Patterns

Some questions in dietary supplement surveys are meant to elicit information on factors affecting use (e.g., consultation with health care providers, reasons for use, sources of information) to help develop effective educational programs and policies. Findings from survey questionnaires and published literature revealed that neither the general population nor military personnel typically discuss their dietary supplement usage with their health care providers. The 2002 NHIS survey showed that only about 24 percent of those who reported use of dietary supplements disclosed such use to their health care providers (see Gardiner et al. in Appendix B). Similarly, among those responding to the DoD Survey of Health Related Behaviors, 36.6 percent indicated they reported dietary supplement use to their physicians and 21.7 percent to a nurse practitioner or physician’s assistant. More women (62.5 percent) than men (45.2 percent) reported usage to a health care provider. A higher percentage (47.8 percent) of service members above 35 years of age report usage to medical professionals compared to service members less than 20 years old (23.5 percent). Among all military services, approximately 50 percent of Air Force personnel report usage to health care professionals compared to 32.6 percent of Navy personnel, 31.5 percent of Army personnel, and 25.3 percent of Marines (Marriott, 2007). Even the highest percentage of those reporting usage (50 percent for Air Force personnel) is quite low, and efforts to increase reporting (e.g., educational programs) are necessary.

In response to behavioral questions about expectations of benefits and reasons for use, “health and well-being” was the top reason (given by 19 percent of respondents) to use dietary supplements in the general population (see Gardiner et al. in Appendix B). Members of the Army assigned to Europe reported different motivations for using different types of supplements. As might be expected, improvement of health and prevention of illness were more often linked with use of vitamin or mineral supplements, while performance enhancement and strength were more likely to be associated with ergogenic aids (Corum, 2007). Health improvement was consistently listed as the first or second most important reason for taking dietary supplements (Corum, 2007; Lieberman et al., 2007; Marriott, 2007; Thomasos, 2007). The ranking of other benefits was fairly consistent across surveys, as shown in Table 2-4. Other behavioral questions of interest include those related to users’ sources of information or their perception of beneficial effects, because these findings may help with the design of education programs.

TABLE 2-4 Reported Reasons for Taking Supplements Among Military Personnel (and, for comparison, the general U.S. population).

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TABLE 2-4 Reported Reasons for Taking Supplements Among Military Personnel (and, for comparison, the general U.S. population).

Adverse Events

In addition to asking questions about expectations of benefits, some surveys included questions about adverse events reported or experienced. This information is particularly valuable when obtained from the special military subpopulations facing higher risks because of demanding mental or physical tasks, and more likely to use dietary supplements. These types of survey questions are not meant to be used to draw causal inferences about dietary supplements and adverse events. Instead, they present a general view of the totality of adverse events in a representative sample and may signal a problem and corresponding need for action, for example, the need for focused attention during collection of data through the adverse event reporting system. Adverse events listed through the military surveys reviewed by the committee included abdominal pain, chest pain, dehydration, palpitations, numbness in extremities, and loss of consciousness. Corum (2007) reported that of 5,206 active duty Army survey respondents, 951 reported some adverse events they believed were associated with dietary supplement use (Table 2-5) and also indicated that they usually did not report these adverse events to health care personnel.

TABLE 2-5 Adverse Event Reports.

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TABLE 2-5 Adverse Event Reports.

The committee inquired about additional information on potential associations between specific dietary supplements and adverse events and received one such analysis. The frequency of adverse effects across each category of dietary supplement (vitamins, performance enhancers, and herbal) frequency of use (rarely/never, 1–2× weekly, 3–4× weekly, and ≥5× weekly) was analyzed by Corum (personal communication, Sonya Corum, U.S. Army Training and Doctrine Command, April 10, 2007). Of reported adverse events, the highest percentage, 19.4 percent, was associated with performance-enhancing supplements, compared to vitamins (5.9 percent) and herbal supplements (5.6 percent). Again, these individual incidents of association are not necessarily a cause for concern on their own, but they may signal a potential problem if the adverse event is severe or frequent and may prompt focused attention on a particular dietary supplement. With data from only one analysis, concrete conclusions about cause and effect could not be made. The committee’s best conclusion is that the rate of adverse effects was higher than normal, especially for performance enhancers.

Of the approximately 11,000 service members who responded to the Air Force survey, about 8 percent reported adverse events. While these results may not be comparable to those from clinical drug trials, this rate exceeds the typical rate of adverse events resulting from placebo effects (3–5 percent). The most common adverse effects included heart palpitations, anxiety, dehydration, nausea/vomiting, chest pain, dizziness/confusion, abdominal pain, and tremors. Among those reporting adverse events, only about 15 percent reported discussing them with a health care provider. Serious adverse events were more likely to be reported to a health care provider; for example, 75 percent (3 of 4) of heart attacks were reported while only 7 percent (8 of 92) of cases of diarrhea were reported to the health care provider. Except for heart attacks, fewer than 50 percent of the perceived side effects from dietary supplements were reported to the health care provider (Thomasos, 2007). The percentage of Air Force personnel (50 percent) who indicated they discussed with their health care provider adverse effects they believed to be related to dietary supplement usage was higher than in other military services (31 and 33 percent in the Army and Navy, respectively) (Marriott, 2007).

RECOMMENDATIONS FOR CONDUCTING SURVEYS

If the military elects to use surveys for surveillance, the committee urges attention to three broad areas of survey activities: (1) planning, (2) survey administration, and (3) data processing and analysis. This chapter provides general recommendations, followed by more specific recommendations in the planning and survey administration stages. The development of a sampling plan and the data processing and analysis are beyond the scope of this chapter, but a biostatistician can provide valuable assistance in these efforts. In the planning stage, the survey objectives must be formulated, the relevant scientific literature reviewed, variables and units of analysis selected (i.e., individuals, groups, communities), a population sampling plan developed, and the survey constructed. The design of the survey involves decisions about using a structured or unstructured approach and data collection mode. Use of highly structured surveys generally results in higher quality data by minimizing measurement error between respondents. However, efforts must be made to ensure validity as respondents may interpret the same questions differently. Unstructured interviews (open-ended questions) require administration by highly trained personnel as well as complex data analysis, and are more expensive to conduct than structured surveys. There are trade-offs that need to be considered when determining whether questions should be open-ended or structured. Because of limitations with open-ended questionnaires (e.g., need for highly skilled interviewer) the committee recommends the use of a structured questionnaire with some options for open-ended questions. Obtaining additional information from participants through the use of some open-ended questions could be valuable, but such information should be obtained using a highly skilled interviewer to conduct structured prompting of survey respondents. In addition, for open-ended questions statisticians, design experts, and researchers should be engaged from the time of the planning stage, because the analysis of open-ended data requires more coding than structured questions.

In the survey administration stage, respondents are recruited, survey data are collected by interviewers or self-reported, and nonrespondents are followed up. The basis for surveillance and research questions of interest should drive data collection and analysis efforts. In addition to survey instruments, other methods to routinely monitor use may be included in the larger surveillance program, for example, extracting data from electronic health records and monitoring sales data from installation sources.

Monitoring Surveys: Overall Recommendations

Recommendation 1: Surveys to collect data on the use of dietary supplements need to continue. The committee recommends that the DoD continue to exploit a large, generic survey by expanding the DoD Survey of Health Related Behaviors managed by the Office of the Assistant Secretary of Defense (Health Affairs) with questions related to adverse events and beneficial outcomes as well as the use of specific dietary supplements that might be of concern.

Given the specific needs and challenges of military personnel, particularly of some military subpopulations, supplement use among military personnel is a special concern for the DoD. This committee recommends that the DoD continue to conduct the generic DoD Survey of Health Related Behaviors with the purpose of collecting data on use of dietary supplements. The survey should include multiple-choice questions, following the format of the current questionnaire. The value of this survey would be improved by the following:

  1. Addition of a question prompting for adverse events (e.g., palpitations, seizures) experienced
  2. Addition of a question prompting for beneficial outcomes (e.g., improved performance, alertness, delayed fatigue) experienced
  3. Improvement of questions on frequency of use, health outcomes, and adverse events by specifying the time and circumstances surrounding the use of a product (e.g., respondent reports used creatine once a day from December through March while deployed)
  4. Expansion of questions on types of dietary supplements used by adding a list of specific dietary supplements that might be of concern at the time of the survey (e.g., add entry about the use of a supplement recently suspected of causing seizures). This list must be kept up to date to reflect changes in marketing, habits of use, and occurrence of adverse events

Recommendation 2: More comprehensive data collection is needed from select populations. The committee recommends that in-depth, anonymous surveys about dietary supplement use be administered at select military installations. These select sites would be chosen because their military populations (e.g., Special Forces or Rangers) would be more likely to use dietary supplements and face higher or unknown risks due to greater mission demands and harsher environments (e.g., high altitude, extreme temperature) than most military personnel.

For example, these in-depth surveys should capture data during intense military operations that are similar to combat (e.g., Special Forces training or situations of deployment), when data collection will not interfere with the completion of the mission). Military subpopulations currently deployed in Iraq and Afghanistan could be selected to participate in surveys because of the tasks (i.e., combat service) and extreme environments they encounter. For this study, however, the committee received no data from Iraq or Afghanistan. Periodically, these surveys might also be conducted at gymnasiums and fitness centers where military service members are more likely to be using performance-enhancing dietary supplements. These in-depth surveys or interviews should incorporate the improvements for questions recommended in the section below; it is also important that questions be included about dietary supplements of particular concern.

This kind of more comprehensive survey would be expensive, especially if administered as an interview; if the less costly self-reported survey is administered, then a subset of the survey population should be recruited for in-depth probing about amount, frequency, and pattern of supplement use to verify the accuracy of the self-reported survey data. Data from surveys conducted in these select locations would complement the data collected from DoD’s Survey of Health Related Behaviors Among Active Duty Military Personnel. The study designers should coordinate with the designated oversight committee (see Chapter 6) to determine specific research questions and study design. The committee believes it would be appropriate for the military to manage such surveys as separate subcontract(s) funded by DoD Health Affairs.

To develop the surveys, the military should consult with experts in the fields of nutrition, nutrition epidemiology (for survey design), pharmacognosy (for terminology used), and biostatistics (for analytical needs). Most important, it is vital that the military consult with individuals with in-depth expertise in survey design. To obtain a comprehensive description, these reports must be combined with other data, for example, data about dietary supplement use derived from electronic health records (see also Chapter 5) and sales data from military installations both on the base and at temporary duty stations (e.g., BX/PX, GNC outlets, Fitness Centers, and commissaries). Surveillance efforts should also consider monitoring of new supplements that enter the market. The DoD can develop contractual limitations for products sold on installations to require manufacturers to at least meet U.S. Pharmacopeia requirements. Contract requirements could also specify that suppliers of dietary supplements notify an appropriate health care professional when new dietary supplements in categories of interest are being introduced for sale on base. Nevertheless, electronic health records are unlikely to contain accurate information on dietary supplement use because of low report rates, while sales data do not reflect actual consumption. For example, sales data would be underestimated since they will not include purchases made off base. Thus, the best source of information on supplement use remains the results from surveys. To improve the accuracy of data on dietary supplement use in electronic health records, this committee recommends that efforts be directed to educate health care personnel (see Chapter 6).

Recommendation 3: Data quality needs to be improved. Surveys should be designed in consultation with the proposed designated oversight committee, which could oversee many aspects of dietary supplement management including adverse event reporting, as described below.

Improvement of Survey Design

The committee recommends modifications and additions to surveys to improve the design (i.e., terminology, wording, and order) and comprehensiveness of the questions. Regardless of the methodology used to administer it (i.e., self-reported questionnaires or one-on-one interviews), a comprehensive survey should include questions on dose, frequency of use, duration of use, user demographics, adverse events, motivation and expectations for use, health and performance outcomes for all dietary supplements of interest, and opportunities to review dietary supplement containers. For example, survey data that estimate total dietary exposure to a dietary supplement ingredient have been limited to sources of caffeine. As recommended above, questionnaires need to be more comprehensive, particularly when administered at installations with special subpopulations (e.g., Rangers or Special Forces). Such a comprehensive survey requires more respondent time as well as careful thought to steps from sample selection to survey design and administration.

Approaches to Increase Sample Selection and Response Rate

Sampling—the process of selecting a subset of cases that allow conclusions to be drawn about the entire population—should be designed in consultation with a survey statistician; the committee recommends that a probability sampling design be used to minimize researcher bias in selecting survey respondents. Power calculations should be conducted to ensure that the study is large enough to detect the associations for which the military is interested in testing.

Increasing the rate of response for surveys is a common challenge with population surveys. A generally acceptable range of response rate is 60–80 percent. Researchers should attempt to increase response rates by following up with people and communicating the importance of the survey, as well as providing appropriate incentives.

Obtaining Data from Longitudinal Studies Needs to Be Considered

All of the research data reviewed on dietary supplement surveys were collected from cross-sectional study designs. Patterns of behavior are likely to be affected by changes in supplement policies, and this needs to be monitored. If resources permit, the committee recommends that the military conducts surveys over an extended period of time or repeat them at certain intervals in order to evaluate time trends in supplement use. Longitudinal data would provide the opportunity to discern trends in dietary supplement use and patterns of behavior that are affected by changes in supplement policies, as well as examine relationships between dietary supplement use and health outcomes. Health- or performance-related outcomes of interest to the military would include those that are suspected of being affected by dietary supplements, such as weight loss, cardiovascular disease, palpitations, headaches, diminished alertness, or gastrointestinal disturbances. As part of the analysis of trends in use, longitudinal assessment of use of new supplements introduced into the market could be conducted. Longitudinal studies can be conducted by following up the same individual over a period of time and collecting information at prescribed times or by using a different sample each time data is collected. By following the same individuals, the variances in estimated changes in use may be lessened but other factors need to be considered, such as a higher level of dropouts. If different samples are selected, investigators need to ensure the selection of appropriate samples throughout the length of the study to minimize within-sample variance.

Planning Stage: Recommendations for Better Survey Designs

This committee believes that making a few adjustments to the surveys could remarkably improve the quality and value of the information collected. Important information gaps identified in surveys include the inability to accurately characterize respondents as users or nonusers of supplements, since frequency of use is not well characterized; and the incomplete assessment of total dose/exposure, especially of potentially important types of supplements (e.g., caffeine). Some surveys are also limited in their ability to assess prevalence of use (e.g., frequency) and difference in use by demographic factors. The surveys also, unfortunately, often used a convenience sample of respondents, making it difficult to ensure that data were adequately representative of the entire military population and decreasing the value of the data.

A common challenge in conducting surveys is ensuring the data’s validity. Although complete verification of the information reported about dietary supplement use by respondents could not be attained, the validity of the questionnaires would be enhanced by greater attention to improvement of areas such as the use of defined terminology, assesing total dosage/exposure, and verifying self-reported data. This section describes overall pitfalls of the questionnaires reviewed and makes recommendations for enhancing them. Table 2-6 includes specific examples of how to improve the language and format of questions. These questions should be taken only as examples; prior to their use in questionnaires, they should be validated in the military context (i.e., in the field) so it is understood how they are interpreted and answered.

TABLE 2-6 Suggestions for Improving Survey Questions.

Table

TABLE 2-6 Suggestions for Improving Survey Questions.

Terminology

A critical issue in using survey methods is ensuring that information is elicited in a manner that is reliable and unbiased. There is a lack of consistency in terminology used across questionnaires. If clear definitions are not provided to respondents, simple words can be misinterpreted, which may compromise the validity of a survey. The committee reviewed some questionnaires that used ambiguous terms such as energy and health, which consumers might define differently. If left undefined, interpretation of results by analysts might be difficult. Other examples include terms such as antioxidants, multivitamins/multiminerals, or anabolic supplements. Antioxidants might be understood as referring to vitamins and minerals, botanicals, or some combination of both. Sports drinks, sports bars, and protein powders are highly variable in their composition and may contain any combination of vitamins, minerals, caffeine, botanicals, or other ingredients.

The committee recommends that decisions be made early in the planning stage about the appropriateness, wording, and order of questions. Ambiguous terms such as health and antioxidants should be clearly defined. To the extent possible, if ambiguous terms are necessary, they should be used in a consistent manner. To help ensure the use of accurate, clear dietary supplement terminology as well as with interpretation of data, a pharmacognosist or similar expert with in-depth knowledge of botanical and bioactive substance sources and nomenclature should be included as a member of the survey design team or as a consultant.

Ingredient Identification and Total Dosage

Questions pertaining to product dosage, composition, and frequency of use are difficult for respondents to answer. This information, however, is critical to identify signals of harm or benefit. Unfortunately, dietary supplement surveys rarely capture dosage or intake details, as questionnaires do not include entries for the number of capsules taken, weight of the product consumed, or the concentration of the active ingredients. Survey questions to establish use and determine frequency vary, as shown in Table 2-7. More attention is needed to improve accuracy in data on supplements used and quantities taken.

TABLE 2-7 Examples of Questions Used in Military Surveys to Characterize Frequency of Use of Dietary Supplements.

Table

TABLE 2-7 Examples of Questions Used in Military Surveys to Characterize Frequency of Use of Dietary Supplements.

To complicate the exposure question, many foods and medications can contribute significantly to the total consumption of a particular substance, a factor that has not been adressed in the military dietary supplement questionnaires reviewed. This might be the case for vitamins and minerals, for example, as well as other bioactive substances such as caffeine, for which the dietary intake from several sources must be included in order to determine potential impact on military personnel. Given the broad range in caffeine content in products in the market, this is a challenging task, as shown by a recent publication that analyzed products sold in various delivery forms and found that taking the amount of product recommended on the label resulted in intake of amounts of caffeine ranging from 1 to 820 mg/day (Andrews et al., 2007). One survey (see Lieberman et al. in Appendix B) reviewed included an assessment of caffeine intake from dietary sources as well as from supplements, but the results were not available at the time of this publication. In summary, acquiring data on prevalence of use is a first step in determining the extent of dietary supplement use by military personnel; however, total dose/exposure data (e.g., from dietary supplements, food, and medication sources) is necessary to determine whether military personnel are exposed to hazardous levels of a particular dietary supplement.

The committee recommends that dietary supplement surveys be complemented with questions about intake from dietary sources (foods and beverages) as well as from pills or powders. This was also supported by the IOM Committee on Mineral Requirements for Military Personnel (IOM, 2006). Special attention needs to be paid to the changing ingredients and amounts in military rations, and future determinations of total dosage and exposure should also incorporate emerging vehicles of dietary supplement ingredient delivery, such as lotions, patches, swabs, and intradermal routes. If it is not feasible to collect data on total dose, it is important to collect descriptive data on the supplements being taken and the frequency and timing of their use.

The validity of survey responses is also compromised when the respondents are not fully aware of the ingredients of the dietary supplement product they are consuming. This lack of knowledge was evident in one ongoing Army-wide survey in which only 16.7 percent of respondents reported knowing all the ingredients in their supplements, and 9.3 percent of those taking supplements were unable to identify any of their ingredients (see Lieberman et al. in Appendix B). The majority reported knowledge of some or most of the ingredients. Some questionnaires to the general population (see Gardiner et al. in Appendix B; Kaufman, 2007) expanded this question to request that the subjects bring in containers to have the product ingredients verified, but the majority of the surveys were based on self-reporting, when verification of ingredients was unlikely. These figures demonstrate that the difficulty in acquiring dosage data on specific ingredients originates not only from the questionnaire design but also from poor consumer knowledge and lack of label accuracy. One feasible approach to address the challenge of obtaining accurate ingredient information from survey respondents would be to record detailed information about the product name and usage. The emphasis in product information collection should be on obtaining a comprehensive list and quantities of the products used so that the ingredients can be identified later. As Kaufman (2007) observes (Appendix B), when questionnaires are self-administered, as was the case with the ones reviewed, there is no control over the quality of the information received. Data quality is also easily compromised when obtaining information about dosage. Because there are many approaches to obtaining dosage information, such as open-ended questions or collection of product containers from users, it is important to establish an unbiased, practical approach to gather this information. One approach is to provide instructions on how to record product names, ingredients, and quantities.

Frequency of Use

Although none of the surveys of military populations was designed to obtain dose information, some surveys ask questions regarding frequency of use (e.g., “Are you taking it five or more times per week?”). However, the number of pills or doses per day or the amount of active component per dose was not requested. With the amount of active substance in products varying substantially, it is critical that survey respondents note the amount from the product label (though it should be noted that product labels can also be inaccurate [Andrews et al., 2007]).

In an effort to define a true “user” of supplements, the committee recommends that future surveys assess the time period of use more accurately. This would allow for consistency and clarification of prevalence of use of dietary supplements. For example, supplement use might be characterized as episodic (e.g., for short-term weight management), long-term (e.g., most of adult life), short-term (e.g., before a physical assessment), current (recently began regular use), past, or never (Table 2-6). When respondents are properly characterized by usage categories, analyses can be conducted by subgroups of users of interest (e.g., those who use only sports bars or gels) who are subsequently classified by types of dietary supplements and doses.

As mentioned above, questions on frequency should be expanded to specify the period of time and circumstances surrounding the use of a product (e.g., respondent reports used creatine once a day from December to March while deployed).

Association Between Adverse Effects and Dietary Supplement Consumed

The committee recommends enhancement of questions intended to assess associations between consumption of dietary supplements and adverse events. For example, given the common use of caffeinated products in the military and their potential synergistic effects with other stimulants, there is a need to better characterize total intake of caffeine. Several surveys included self-reported (with no adjudication) adverse effects perceived to be attributable to dietary supplements. In-depth probing about adverse events or outcomes (heart palpitations, headaches, etc.) thought to be associated with supplements should be added to the surveys. These questions are especially relevant when conducting surveys in special subpopulations, such as Rangers and Special Forces, with heightened risks and higher dietary supplement usage.

As with the data on frequency of use, questions on adverse events should be linked to information about the environment and conditions in which respondents consume the specific dietary supplement (e.g., soldiers might be taking creatine only before deployment or in between sustained missions). Questions on adverse events and beneficial outcomes should be posed prior to questions on dietary supplement use to minimize the potential for biases in responses.

Demographic Factors

Differences between U.S. military personnel and the general population (e.g., service members have higher socioeconomic status and education, different age distribution, a higher minority representation, and different levels of stress) are substantial enough to require specific military surveillance.

Available survey data on supplement use by military personnel give important clues about such use; however, they are limited in their ability to allow assessment of prevalence of use and differences in use by demographic factors across multiple studies. Surveys conducted to date do not collect this information consistently; even demographic data (e.g., age, rank, geographic area, organizational unit) collected varies among surveys. A consistent method of collecting and analyzing data by demographic characteristics would allow for a comprehensive, comparable description of dietary supplement use in various populations and across time.

Additional Questions

Questions on health and performance The committee recommends the collection of data on the association of dietary supplement use with health and performance outcomes. Data should be linked to information about the environment and conditions in which respondents consume the specific dietary supplement.

Such data would provide evidence of whether the expectations of benefit are being met under the real-life circumstances of the U.S. military. In addition, these questions help determine whether there are differences in outcomes for individuals with healthy lifestyle patterns versus those who use supplements to counter unhealthy behaviors such as smoking, drinking alcohol to excess, and eating a poor-quality diet. Such analyses may be possible if the DoD links dietary intake to dietary supplement intake. Although one survey collected self-reported Army Physical Fitness Test (APFT) results and would therefore allow correlation between dietary supplement use and APFT scores, the data to evaluate the impact of confounding factors (e.g., training regimen) are not available. Data on possible confounders are needed in the analyses of relationships between health outcomes and dietary supplement intake. Potential confounders (i.e., variables that are related to both supplement use and the health outcome of interest but are not in the causal pathway between these two variables) should be considered prior to creating surveys so that they are included in the questionnaire; it may be helpful to consult with an epidemiologist for assistance with determining confounders a priori.

Questions on effectiveness of communication The committee recommends that questions about sources of information on dietary supplements that military personnel consult be added to questionnaires as these would help determine the most effective methods to disseminate accurate information. Once strategies to disseminate information are implemented, survey questions to measure the level of outreach and effectiveness of the information strategy will also be needed.

Administration Stage: Recommendations for Data Collection

In the survey administration stage, respondents are recruited, survey data are collected by interviewers or self-report, and nonrespondents are followed up. Each survey should be pretested. Follow-up efforts may be necessary to ensure an adequate response rate. During this stage, data should also be inspected for systematic biases in response patterns and efforts made to adjust the participant demographics or account for bias in the data analysis stage.

Presurvey a Few Individuals

To validate the survey, the committee recommends that it be pretested on a small number of persons with characteristics similar to the target group of respondents. These data should also be inspected for systematic biases in response patterns. Statistical expertise should be sought prior to survey administration to prevent biases in the questions or the demographics of participants.

Verify Self-Reported Data in a Subpopulation

A choice must be made between a self-reported or personal interview survey, and the questionnaire should be designed accordingly. When validated, self-reported questionnaires provide higher quality data if designed as highly structured surveys because they minimize biases caused by misinterpretation of questions. Unstructured surveys (using open-ended questions) work better when interviews are conducted; however, they require administration by trained personnel and entail complex data analysis, resulting in higher expenses than structured surveys. Although a personal interview may be more informative than self-reported surveys, responses can be influenced by the manner, tone, and opinion of the interviewer. Thus, while personal interviews offer better survey compliance and in-depth information, interviewer training and quality control are key elements to minimize potential sources of data bias.

Surveys will likely be administered more often with self-reported questionnaires than with personal interviews due to cost considerations. Self-reported surveys present the following limitations: (1) lower response rates; (2) a higher rate of incomplete or inaccurate responses; and (3) a need for simpler, structured designs to elicit reliable responses. The committee recommends the application of strategies to overcome these limitations, which will assist with interpreting self-reported data and revising the questionnaires and, ultimately, help improve self-reported data. One strategy consists of conducting personal interviews with a smaller group of individuals, and correlating these results with self-reported data. These personal interviews allow for more controlled resposes and ensure higher accuracy and data quality. For example, to verify responses related to ingredient accuracy, this subgroup could be asked to bring in the bottles/containers of the products consumed. Lack of statistical power limits comparisons, so statistical power calculations should be conducted to ensure sufficient ability to relate findings from this group to those of the targeted military population. Another strategy to verify responses on use patterns is to compare survey results to sales data from military bases, considering both the types of products that are being purchased and the ingredients in those products.

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Footnotes

1

As defined by Congress in the Dietary Supplement Health and Education Act (http://www​.fda.gov/opacom/laws/dshea​.html#sec3), which became law in 1994, a dietary supplement is a product (other than tobacco) that is intended to supplement the diet; contains one or more dietary ingredients (defined as vitamins, minerals, herbs or other botanicals, amino acids, or other dietary substances for use by man to supplement the diet by increasing the total dietary intake, or concentrates, constituents, metabolites, extracts, or combinations of any of the aforementioned dietary ingredients); is intended to be taken by mouth as a pill, capsule, tablet, or liquid; and is labeled on the front panel as being a dietary supplement.

Copyright © 2008, National Academy of Sciences.
Bookshelf ID: NBK3967

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