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Planning Committee for a Workshop on Potential Health Hazards Associated with Consumption of Caffeine in Food and Dietary Supplements; Food and Nutrition Board; Board on Health Sciences Policy; Institute of Medicine. Caffeine in Food and Dietary Supplements: Examining Safety: Workshop Summary. Washington (DC): National Academies Press (US); 2014 Apr 23.

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Caffeine in Food and Dietary Supplements: Examining Safety: Workshop Summary.

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2Intake and Exposure to Caffeine1

Given the large and growing number of different sources of caffeine, assessing the level of caffeine exposure is an important and complex first step toward understanding the safety of such exposure. In the Day 1, Session 1, panel, moderated by Barbara J. Petersen, Ph.D., M.P.H., of Exponent, panelists considered different methods being used to assess levels of caffeine exposure in the U.S. general population. Petersen emphasized that different methods yield different results and that the results presented here should not be interpreted as final answers. For her, a key question to consider is how people behave when a source of caffeine disappears or a new source appears and whether people substitute one source for another. This chapter summarizes the panelists' presentations and the discussion that followed. Key points made by each speaker are shown in Box 2-1.

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BOX 2-1

Key Points Made by Individual Speakers. According to Diane Mitchell, most studies examining exposure to caffeine in the United States were conducted more than 10 years ago. Mitchell described the methods and results of a recent study on caffeine intakes (more...)

CAFFEINE INTAKE FROM BEVERAGES IN THE UNITED STATES

Presented by Diane C. Mitchell, M.S., R.D., Pennsylvania State University

The International Life Sciences Institute (ILSI) has supported research on caffeine since 1983, resulting in several publications (e.g., Knight et al., 2004, 2006). Diane Mitchell presented ILSI's most recent caffeine study, which was conducted in collaboration with Kantar Worldpanel (Mitchell et al., 2013). The primary objective of the study was to estimate caffeine intakes in the United States from the consumption of caffeinated beverages using a current (2010–2011) population-based beverage survey. According to Mitchell, the study was conducted primarily because of the lack of comprehensive, current, and reliable population-based data on caffeine intakes. Most studies examining exposure to caffeine in the United States were surveys conducted more than a decade ago, including research sponsored by ILSI. The data provide a current perspective on patterns of beverage caffeine exposure in the United States in the total population as well as in demographic subgroups. They not only update past ILSI-sponsored research, but they also provide an opportunity to compare trends in beverage caffeine intakes between then and now.

Methods

Mitchell described the study methodology and analysis. Data were collected from the Kantar Worldpanel Beverage Consumption Panel survey. Kantar Worldpanel is a global consumer panel company focused on the continuous measurement and analysis of consumer behaviors. This company has been conducting a continuous annual survey for more than 30 years, targeting U.S. consumers of all ages.

About 42,000 respondents were recruited from a panel of about 1 million people, with U.S. Census Bureau data used to ensure that the selection of participants was representative of the U.S. population. Sample selection criteria included age, gender, race, income, geographic region, household size, and presence of children in the household. Invitations were sent to English-speaking participants via e-mail and were staggered in batches sent weekly to ensure a balanced sample across all months of the year. Data were collected from the beginning of October 2010 through the end of September 2011. All panel participants were 1 year of age or older, with respondents consuming less than 21 beverages in 7 days excluded from the dataset.

Mitchell reported that participants were asked to begin completing their online surveys on a specific day for a total of 7 days. The online surveys required dragging and dropping beverage categories (soda/pop, hot coffee, iced coffee, milk, bottled water, and so forth) into different drinking occasion slots and then entering product details, including the type of beverage, amount consumed, where it was consumed, brand name, and other descriptive information. Beverages consumed both inside and outside the home were included. In addition, participants were asked to complete a “my info” questionnaire, which contained demographic, lifestyle, attitude, health, and nutrition questions. Height and weight data were also collected, with weight data for children collected for only 9 months of the 12-month data collection period (i.e., January through September 2011).

From this detailed beverage diary, Mitchell and colleagues were able to obtain a consolidated beverage list for each of the beverage categories (i.e., total beverages [i.e., all caffeinated beverages reported in the survey], carbonated soft drinks, energy drinks, energy shots, chocolate drinks, total coffee, total tea) and then, using the lists, develop a database. Developing the database required identifying which beverage categories contained beverages with caffeine. Information was obtained from manufacturers where possible, although the researchers also used a number of other resources as well. Mitchell emphasized that no single resource was comprehensive enough to capture information for all of the beverage and beverage types reported in the survey. Even the large national and research databases do not contain brand-specific data for the variety of beverages reported in the survey. The researchers assigned default values for beverages with no data available, insufficient detail, or no specified brand name. For example, the default value for a regular, brewed, nonspecialty brand of caffeinated coffee was 11.9 mg per fluid ounce. According to Mitchell, the range of default values reflects the variability in caffeine among different coffee types, with values ranging from 4.1 to 20.0 mg/fluid ounce for ready-to-drink bottle or canned coffee to 46.7 to 62.8 mg/fluid ounce for specialty espresso.

Once the database was developed, the researchers consolidated caffeine beverages into a more manageable set of categories for detailed analysis. The researchers were consistent with previous ILSI work with respect to the types of beverages included in each beverage category with one notable exception: energy drinks and energy shots were included as separate beverage categories. Neither was considered in the 1999 ILSI survey; energy drinks were not introduced into the market until 1997.

Although Mitchell and colleagues analyzed total caffeine intakes for all age groups across all categories, because coffee, carbonated soft drinks, tea, and energy drinks contributed approximately 98 percent or more of the caffeine consumed, Mitchell presented data only for those four categories.

The analysis covered only caffeinated beverage consumers, that is, consumers who drank 1 or more caffeinated beverages in 7 days, and only consumers 2 years of age and older. The researchers relied on parental reports for children, with two exceptions (i.e., data excluded from the analysis) to control for implausible survey entries: children with body weight data below the 3rd percentile or above the 97th percentile based on weight for age, using the Centers for Disease Control and Prevention (CDC) growth chart data as a reference, and children with total fluid intakes greater than two standard deviations above the mean fluid intake within a specific age year.

The small sample sizes for some subgroups in some beverage categories created another challenge. This was of particular concern for energy drinks for several age groups and for coffee for children between 2 and 5 years of age. In those cases, sample size was considered too small to provide reliable population estimates.

Results

Of the more than 42,000 survey respondents, 37,602 (85 percent) were caffeine consumers, that is, individuals who consumed at least one caffeinated beverage over a 7-day period of time (see Table 2-1). By age group, the proportion of the population consuming caffeine ranged from 43.0 percent in children 2 to 5 years of age to almost 100 percent of adults over the age of 65. This trend is consistent with previous reports in the literature, according to Mitchell.

TABLE 2-1. Number of Users and Mean and 90th Percentile Daily Intakes of Total Caffeinated Beverages, by Age.

TABLE 2-1

Number of Users and Mean and 90th Percentile Daily Intakes of Total Caffeinated Beverages, by Age.

Mean daily intake, expressed as both milligrams per day and milligrams per kilograms of body weight, steadily increased with age up to 65 years, when it fell slightly (see Table 2-1). The 50- to 64-year-old age group showed the highest intake. For the most part, the 90th percentile data follow the same trend. Again, the pattern is similar to what was reported almost a decade ago, although the intakes are higher. Mitchell noted that although there were some differences in mean daily intakes between men and women, the differences disappeared after adjusting for body weight.

When examined by beverage category, coffee, carbonated soft drinks, tea, and energy drinks together accounted for nearly all caffeine intake (see Table 2-2). As far as which type of beverage contributed the most, it was clearly coffee for all ages combined and for adults. For children, intakes were distributed fairly equally across coffee, carbonated soft drinks, and tea. Energy drinks contributed very little to beverage caffeine intakes.

TABLE 2-2. Mean Caffeine Intake by Age and Beverage Category.

TABLE 2-2

Mean Caffeine Intake by Age and Beverage Category.

Mitchell mentioned again that chocolate-containing beverages were not included in the data she presented because their contribution to total caffeine intake was so small, even though about 14 percent of the population surveyed reported consuming them. In the case of energy shots, the proportion of consumers in the sample was too low to estimate even when combining all ages. Together, chocolate-containing beverages and energy shots contributed less than 1 to 4 percent to total caffeine intake depending on age group. The amount of caffeine intake from those two categories is included in the estimates of the total caffeinated beverage category, however.

In order to understand more clearly what drives caffeine intake, Mitchell and colleagues examined caffeine intake within each beverage category for users only (i.e., users of that beverage category) (see Table 2-3). Among all ages, 55 percent of all caffeinated beverage consumers consumed coffee, 63 percent carbonated soft drinks, 53 percent tea, and 4 percent energy drinks. As an example of how to read Table 2-3, within the 50–64-year age group, 71 percent of caffeine users consumed coffee, with an estimated average daily intake among coffee users of 223 mg and a 90th percentile of 452 mg. Table 2-3 also shows where sample size was too low to obtain reliable estimates, which includes coffee among the youngest children and energy drinks among several age groups.

TABLE 2-3. Caffeine Intakes for Users Within Each Beverage Category (mg/day).

TABLE 2-3

Caffeine Intakes for Users Within Each Beverage Category (mg/day).

Summary of Caffeine Intake in the United States

In summary, caffeine intake in the United States comes primarily from four beverage types: coffee, tea, carbonated soft drinks, and energy drinks. In this recent ILSI survey, of those who reported consuming caffeinated beverages, more than half consumed each of three types of beverages (i.e., carbonated soft drinks [63 percent], coffee [55 percent], and tea [53 percent]), reflecting a significant number of caffeine consumers consuming more than one type of beverage. Although consumption of chocolate-containing beverages was high, the caffeine content of such beverages was low and contributed little to total caffeine intake.

Mean daily caffeine intake was 165 mg. Intakes were higher than previously reported in the 1999 ILSI-sponsored beverage survey, when mean daily intake was 120 mg. The difference represents about half a cup of coffee or a can of carbonated soft drink. Mitchell cited several possible explanations for the increase. First, there were slightly more caffeine-consuming occasions reported in the more recent survey: 1.8 compared to 1.5. Second, there was a slight increase in the amount of coffee consumed (by fluid ounce) and a decrease in the amount of carbonated soft drinks consumed, and carbonated soft drinks have less caffeine. Third, the database values used for the more recent survey reflect higher caffeine values for specialty brand coffees, which may also have contributed.

A notable finding of the survey was the low consumption of energy drinks. Energy drinks were relatively new to the marketplace in 1999, and thus their intake was not estimated in the previous survey. So even though some energy drinks contain levels of caffeine similar to those of coffee, consumption of caffeine from energy drinks contributed little to total caffeine intake.

Caffeine intakes, in particular from coffee, for children between the ages of 2 and 12 years were higher than previously reported. But to keep that finding in perspective, Mitchell noted that only 9 percent of children between the ages of 2 and 12 years were reported to have consumed coffee.

Mean daily caffeine intake at the 90th percentile for all caffeinated beverages and among all ages was 380 mg or 5 mg per kg of body weight, most of which came from coffee. Daily caffeine intake at the 90th percentile for adults 35 years of age and older was slightly higher (420–467 mg/day) than the recommended maximum of 400 mg/day. Mitchell noted that the 400 mg/day threshold is not an official recommendation for caffeine in the United States. It is a Health Canada recommended level that is often used as a reference value. In addition, the FDA released two letters in 2012 stating that 400 mg per day was not associated with any adverse health effects and that the 400 mg per day value reflects recommendations set forth by Health Canada. For women of childbearing age (the 18- to 24-year-old and the 25- to 34-year-old age groups), both mean and 90th percentile caffeine intakes were below the <300 mg/day recommended levels for pregnancy. For children younger than 12 years of age and older children aged 13 to 17 years, 90th percentile intakes were slightly higher than the recommended 2.5 mg/kg/day.

In conclusion, as far as Mitchell was aware, the survey she described was the first population-based study in more than a decade to estimate caffeine intakes from beverages. The increase in accuracy afforded by the caffeine database developed for this study was a major strength, in Mitchell's opinion, although it may have contributed to the slightly higher caffeine intakes than previously reported. Overall, caffeine intakes remain largely driven by coffee consumption and, to a lesser extent, tea and carbonated soft drinks. Energy drink intakes contribute very little. In Mitchell's opinion, the data do little to support the notion that the introduction of additional caffeinated beverages into the marketplace has resulted in proportionately higher caffeine intakes by any of the various subpopulations of consumers.

VARIOUS ASPECTS OF CAFFEINE INTAKE IN AMERICA: ANALYSIS OF NHANES

Presented by Victor Fulgoni III, Ph.D., Nutrition Impact, LLC

Victor Fulgoni III described four ways that data from the National Health and Nutrition Examination Survey (NHANES) have been used to assess caffeine intake among Americans: (1) current usual intake of caffeine; (2) current usual intake of caffeine per consumption event; (3) trends in caffeine intake over the past decade; and (4) food sources of caffeine intake over the past decade. Data from multiple sets of surveys were used: 2001–2010 (N = 42,154) for the trend analyses and 2007–2010 (N = 17,387) for the intake analyses, with individuals under the age of 2 years and pregnant and/or lactating females excluded. Data include caffeine intake from all foods and beverages, but not dietary supplements.

To determine usual intake and usual intake per consumption event, Fulgoni and colleagues used the National Cancer Institute method (Tooze et al., 2010), which allows assessment of multiple days of intake and removal of intraperson variation. According to Fulgoni, the method provides a reasonable estimate of habitual chronic intake, which is what usual intake is intended to reflect. For trend data, Fulgoni and colleagues used 1-day intakes regressed over time, with p < 0.01 deemed significant.

Fulgoni reiterated what Mitchell had emphasized regarding evidence showing that more than 90 percent of the caffeine intake among Americans is from beverages, mostly coffee, tea, soda, and energy drinks. For coffee, caffeine levels included in the NHANES database range from 0.4 to 509 mg per reference amounts customarily consumed (RACCs). The RACC for coffee is usually around 8 ounces. So, the range of caffeine levels is quite high, with the most frequently consumed coffee, that is, a typical brewed coffee, having 95 mg per RACC. For tea, the range is 0 to 48 mg/RACC, which covers all hot and cold tea beverages including zero-caffeine herbal tea. The most commonly consumed tea, a standard cup of leaf tea, has 48 mg/RACC. For soda, the range is 0 to 65 mg/RACC, with the most commonly consumed soda being a cola-type soda containing about 20 mg/RACC. Finally, for energy drinks included in the NHANES database, the range is 45 to 86 mg/RACC, with the most frequently consumed energy drink containing 72 mg/RACC.

Usual Intake

For caffeine consumption per day, among the total sample population (N = 17,387), mean intakes ranged from about 25 mg among 2- to 11-year-old children to more than 200 mg in older adults (see Figure 2-1). Among consumers only (N = 13,923), daily consumption ranged from less than 50 mg in 2- to 11-year-old children to more than 250 mg in the 50- to 59-year-old age group (see Figure 2-1).

FIGURE 2-1. Mean usual intake of caffeine for total sample population (top) and caffeine consumers only (bottom).

FIGURE 2-1

Mean usual intake of caffeine for total sample population (top) and caffeine consumers only (bottom). SOURCE: NHANES.

Even at the 90th percentiles of intake, daily intake was only about 50 mg among young children (2 to 11 years) and barely more than 100 mg in adolescents (12 to 17 years) (see Figure 2-2). The highest-consuming age group, those 50 to 59 years of age, had a percentile intake of about 450 mg/day. Among consumers only, with the approximately 4,000 noncaffeine consumers removed from the dataset, the only age group that showed a noticeable difference from the total population 90th percentile intake was the 50- to 59-year-old age group, which jumps up to about 515 mg/day (see Figure 2-2). In sum, Fulgoni noted, for both mean usual intake and at the 90th percentile, caffeine intake is highly age-dependent. Both mean intake and the 90th percentile of intake were lowest in children 2 to 11 years and adolescents 12 to 17 years and highest in adults 50 to 59 years.

FIGURE 2-2. The 90th percentiles of usual caffeine intake for total sample population (top) and caffeine consumers only (bottom).

FIGURE 2-2

The 90th percentiles of usual caffeine intake for total sample population (top) and caffeine consumers only (bottom). SOURCE: NHANES.

Usual Intake by Consumption Event

A consumption event was defined as every time an individual consumed a food or beverage with caffeine, whether it was chocolate milk, coffee ice cream, coffee, an energy drink, cola, or something else. Again, both mean and the 90th percentile of usual intake per consumption event are highly age-dependent. The total population mean per consumption event was 65 mg. But among children 2 to 11 years, mean usual intake per consumption event was about 15 mg per event; among adolescents, it was about 35 mg; and among adults, it was 70 to 80 mg, depending on the age group (see Figure 2-3). At the 90th percentile, again, as with usual intake, among children the usual caffeine intake per consumption event was low: only about 25 mg, increasing to about 60 mg among adolescents and about 140 mg among adults (see Figure 2-3).

FIGURE 2-3. Mean and percentiles of usual caffeine intake (mg) per consumption event.

FIGURE 2-3

Mean and percentiles of usual caffeine intake (mg) per consumption event. SOURCE: NHANES.

Trends in Caffeine Intake

Trends in caffeine intake data were assessed using single 24-hour recall information collected over time, using data from 2001 to 2010. Most age groups showed flat regression lines over time, meaning that caffeine intake has remained relatively stable over the past decade. The only statistically significant regression coefficients were for the 2- to 11-year-old age group (p < 0.01) and the 35- to 39-year-old age group (p <0.01). Both of those age group's regression coefficients were actually negative, suggesting slightly lower intake over time. For the 2- to 11-year-old age group, caffeine intake decreased about 2.5 mg on average per data release (i.e., data are released every 2 years); for the 35- to 39-year-old age group, it decreased about 19 mg on average per data release. In sum, intakes did not change much between 2001 and 2010. If anything, there were slight decreases in two age groups.

Trends in Caffeine Intake by Food Sources

Trends in caffeine intake by food sources were analyzed using the total sample population (thus not just consumers). For the 2- to 11-year-old age group, sodas, the major source of caffeine in that age group, showed a statistically significant downward trend in consumption from 2001 to 2010 (p < 0.01). The other beverage categories (coffee, tea, and energy drinks) showed no change over time. Fulgoni emphasized that one of the limitations of this analysis was the very low sample size for energy drinks.

In the 12- to 17-year-old age group, again soda was the major source of caffeine, and, again, it showed a statistically significant decline over time (p < 0.01). Caffeine intake from soda also decreased over time among the 18- to 35-year-old age group (p < 0.01). This is the only age group for which a statistically significant increase in energy drinks was observed (p < 0.01). Fulgoni noted that it was a small increase, but it was statistically significant. In the 51-years-and-older age group, despite being the highest caffeine consumers, researchers saw no change in intake by food source over time. Coffee remains by far the number-one source of caffeine in adults.

In sum, sodas are the largest source of caffeine in children 2 to 11 years and in adolescents (12 to 17 years). In both groups, caffeine intake from soda has actually decreased over the past decade. Coffee is the largest source of caffeine in adults. Energy drinks contribute little to the caffeine intake for any age group, although a small increase in intake (1 mg per 2-year data release) was detected for one age group.

Conclusion from the NHANES Analysis

With trends in caffeine intake remaining stable, or decreasing in some age groups, but with new sources of caffeine entering the marketplace, Fulgoni suggested that new sources of caffeine may be replacing older sources. Studies specifically designed to assess trade-off of caffeine sources would need to be conducted to confirm this suggestion.

Fulgoni concluded by remarking that, as is true of any study, there are strengths and limitations to these NHANES analyses. Their strengths are that they are based on a large nationally representative sample of children and adults and that usual intakes were analyzed using sophisticated statistical techniques. None of the data were adjusted for body size, although those data are available if necessary. Their limitations are that intake data were self-report; intake data were limited by what was available through NHANES (i.e., 2001–2010, with 2009–2010 the last publicly released data available); and some age groups had a small number of consumers of energy drinks.

PANELIST DISCUSSION WITH THE AUDIENCE

Following Fulgoni's presentation, workshop participants were invited to ask questions of the two panelists. This section summarizes the discussion that occurred. Most questions revolved around data and clarification of how those data have been analyzed and whether the same data can be analyzed in other ways to address additional questions, such as questions about vulnerable populations.

The 90th Percentile

The panelists were asked whether the data they presented allow for an examination of exposure among even heavier caffeine consumers—for example, consumers at the 95th or even 99th percentile. If not, are there other data available that can be used to examine exposure among the heaviest caffeine consumers in the population? Fulgoni replied that some intake estimates can be calculated at both the 95th and 99th percentiles, depending on gender and age.

Overweight and Obesity

There was some discussion about whether recent increases in overweight and obesity in the United States have implications with respect to the way caffeine is distributed in the body (e.g., in fat cells) and what the most appropriate metric is for evaluating or recommending dosage. Mitchell replied that estimates of caffeine exposure in terms of milligram per kilogram of body weight is probably not the best metric for heavier people if caffeine is not distributed in body fat the same way that it is distributed in lean mass. Fulgoni suggested that one possible solution might be to do what is done with protein recommendations, that is, use measure of height to determine ideal body weight (i.e., based on a 24.9 body mass index, or BMI) and then set a recommended exposure level on that basis.

Use of Averages to Estimate Caffeine Intake

Some participants expressed concern that “key facts” have been buried under the weight of averages, especially with respect to potentially vulnerable populations. For example, how many exposures of 150 mg, 200 mg, or 400 mg or more per event are occurring among adolescents yearly? And how has the number of those exposures changed over the years as the use of caffeine-containing energy drinks has increased? Mitchell and Fulgoni agreed that such an analysis could be done, for example, by analyzing consumption events per single day. Still, there might not be enough people consuming energy drinks to examine energy drink exposures in particular, depending on the age group. Fulgoni further remarked that the analyses he described were conducted before this workshop was conceived, and thus they did not separately examine pregnant and lactating women. But that group could be analyzed separately, he said.

The NHANES Database

One audience member asked Fulgoni whether the analyses he presented accounted for the fact that caffeine concentrations in products change over time. Fulgoni explained that all data releases are updated as necessary and that, in fact, one could use the NHANES database to analyze change in composition over time.

Another audience member asked about the accuracy of self-report data, especially with parents self-reporting consumption among their children. Fulgoni repeated that self-report is a limitation of the NHANES data. With respect to parental self-reporting of their children's consumption, parents report food and beverage consumption for children up to the age of 6 years. Between 6 years and 12 years, analysts use a combination of child and parental data. He was not aware of any study validating the NHANES self-report data for those younger ages.

Workshop planning committee chair Lynn Goldman commented on the number of new caffeinated products, such as candies and marshmallows, that are entering the marketplace and asked whether those types of products will be identifiable in the NHANES database in the future. Fulgoni replied that, although those specific products are not yet in the database, the product forms are. So, for example, marshmallows are in the database, making it possible to identify the age groups most likely to consume marshmallows and modeling intake on that basis.

Finally, Fulgoni highlighted the public availability of the NHANES database and remarked that any of his analyses could be repeated by others.

Dietary Supplement Exposure Among Fitness Enthusiasts

There was some discussion about caffeine use among individuals consuming sports nutrition supplements and whether that consumption might be skewing results for the intake of caffeine. Regan Bailey observed that when she dug into the NHANES database, she found only 17 reports of a caffeine-containing dietary supplement between 2007 and 2010. Fulgoni agreed that there is very little consumption of caffeine-containing dietary supplements. When asked whether the data he presented included Monster Energy consumption, given that Monster Energy was classified as a dietary supplement until recently, he replied “yes.” If the interest is in sports and fitness, Fulgoni pointed out, it would be possible to analyze caffeine intake based on the activity metrics that are included in some of the NHANES datasets.

Energy Drink Marketing Data

Speaker John Higgins pointed out that marketing data indicate that 2.5 gallons of energy beverage per person, including babies and children, were consumed in the United States in 2009. He also observed that energy beverages are marketed very heavily to the teenage through 35-yearold age range. He asked, who is drinking all the energy beverages? Babies are clearly not drinking them, so who is? And is it possible that the data Mitchell and others are collecting are not capturing all energy beverage consumption events? He said he expected greater energy consumption events, given how marketing data indicate a high consumption of energy beverages. Mitchell reiterated that she and her colleagues found very low consumption. She suggested that the limitations of self-report data may have been a factor. Fulgoni observed that 2.5 gallons per year, or 320 ounces, amounts to less than an ounce a day, implying that it is not much. Higgins reiterated that the 2.5 gallons per year is across the total population and that some people consume more than others. Goldman pointed out the time lag between the NHANES data release and marketing data, noting that the NHANES data are “always a few years behind.”

Addition or Substitution of Caffeine Sources

The panelists were asked their thoughts on whether consumers are substituting new sources of caffeine for old sources or consuming multiple types of caffeine-containing foods and beverages. Mitchell observed that consumers are “obviously” consuming more than one type of caffeinated beverage. Although she and her colleagues did not separately examine multiple users—for example, to assess what and when they were consuming—the data are robust and could be analyzed to answer those types of questions. Likewise, with the NHANES database, according to Fulgoni, its robustness would allow for analyzing consumption of multiple types of beverages. He cautioned, however, that a robust estimate of energy drink consumption in children would probably require future oversampling.

REFERENCES

  • Knight CA, Knight I, Mitchell DC, Zepp JE. Beverage caffeine intakes in U.S. consumers and subpopulations of interest: Estimates from the Share of Intake Panel survey. Food and Chemical Toxicology. 2004;42:1923–1930. [PubMed: 15500929]
  • Knight CA, Knight I, Mitchell DC. Beverage caffeine intakes in young children in Canada and the U.S. Canadian Journal of Dietetic Practice and Research. 2006;67:96–99. [PubMed: 16759437]
  • Mitchell DC, Knight CA, Hockenberry J, Teplansky R, Hartman TJ. Beverage caffeine intakes in the U.S. Food and Chemical Toxicology S0278-6915(13)00717-5. 2013;63:136–142. [PubMed: 24189158]
  • Tooze JA, Kipnis V, Buckman DW, Carrolee RJ, Freedman LS, Guenther PM, Krebs-Smith SM, Subar AF, Dodd KW. A mixed-effects model approach for estimating the distribution of usual intake of nutrients: The NCI method. Statistical Methods. 2010;29(27):2857–2868. [PMC free article: PMC3865776] [PubMed: 20862656]

Footnotes

1

The words “exposure” and “intake” were used interchangeably throughout the workshop.

Copyright 2014 by the National Academy of Sciences. All rights reserved.
Bookshelf ID: NBK202226

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