1Basic Concepts

MILITARY INTEREST IN CAFFEINE

Optimal job performance without compromising the health and well-being of the worker is the goal of employers regardless of the field of endeavor. Intermittent or prolonged physiological and psychological stressors that employees bring to the workplace have an impact not only on their own performance but also on those with whom they work and interact. The internal stressors an individual brings to his or her job are compounded by the day-to-day physical and mental stressors of the job itself. Military personnel in combat settings endure highly unpredictable timing and types of stressors as well as situations that require continuing vigilance for long periods of time.

The U.S. military's concerns about the individual war fighter's ability to avoid performance degradation and the need to enhance mental capabilities in highly stressful situations have led to an interest in devising military ration components that could enhance physical and cognitive performance.

HISTORY OF CAFFEINE USE

In addition to its natural occurrence in some foods, caffeine is used as a food additive and as a drug or a component of many pharmaceutical preparations. It is the most widely consumed psychoactive or central nervous system (CNS) stimulant in the world (Curatolo and Robertson, 1983). When administered in the doses commonly found in beverages and drugs, it has measurable effects on certain types of human performance. It is readily available to both the civilian and the military populations as a beverage (coffee, tea, maté), food (cocoa products), food additive (soft drinks, bottled water), and pharmaceutical (over-the-counter pain and weight-loss medications, numerous prescription drugs). No other substance has this combination of uses.

As a food additive caffeine is generally considered safe based on its long history of use and on extensive research conducted throughout the world for more than a century. However, despite this long history of use, modern epidemiological techniques have raised concerns about associations between continued use of high levels of caffeine and long-term health.

Caffeine (1,3,7-trimethylxanthine) and the related methylxanthines, theobromine (3,7-dimethylxanthine) and theophylline (1,3-dimethylxanthine), are widely distributed in plants throughout the world. More than 60 different plant species containing caffeine have been identified, and history suggests that it may have been consumed, in one form or another, as far back as the Paleolithic period (Barone and Roberts, 1996). The primary sources of these compounds are coffee (Caffea arabica), kola nuts (Cola acuminata), tea (Thea sinensis), and chocolate (Cocoa bean). Although the actual discoverer of caffeine as a stimulant is unknown, legend has it that it was first discovered in Ethiopia in the third century AD when a shepherd noticed that his goats became very frisky and agitated after eating coffee berries or “beans”. The shepherd tried chewing some of the berries and noted their stimulant properties. An abbot at a nearby monastery brewed the beans in hot water and found that the beverage helped him to stay awake during long nights of prayer. Cultivation of the coffee plant may have begun as early as the sixth century AD, probably in Ethiopia. Elsewhere in Africa, coffee berries were crushed and mixed with fat to serve as a food to stimulate warriors in battle. By approximately 1000 AD, coffee reached Yemen, where the beverage became very popular and drinking it a social ritual among Muslims. From there it spread to Europe and the Americas. All stable indigenous cultures having access to caffeine-containing plants have developed drinks or foods containing these stimulant products. The earliest recorded use of caffeine-containing beverages dates back to the Tang Dynasty of China (618–907 AD) where tea was a popular drink believed to prolong life.

THE COMMITTEE'S TASK

Surveys indicate that more than 90 percent of the military population consumes caffeine at some level on a daily basis. A small-sample survey reported by Lieberman (1999) indicated that mean caffeine intake among military personnel was 340 mg/d. The majority of those sampled consumed 200 mg/d or less; however, consumption levels were highly variable and thus physiological effects cannot be generalized. Typically, older personnel consumed more caffeine than younger ones, and males consumed slightly more than females. The majority of caffeine (about 70 percent) was consumed as coffee, 23 percent as soda, 5 percent as tea, and slightly less than 2 percent as chocolate, with the remainder coming from medications. These factors make it difficult to determine risk and to make risk management decisions on the use of caffeine for maintenance and enhancement of cognitive performance in military operations.

The military requested the committee's assistance in this decision-making process. The CMNR was requested to evaluate the relevant caffeine research, including all relevant studies performed since the 1992 workshop, and address in a brief report the following proposal and questions to assist the Department of Defense in the transition of research to military application. Specifically, the military provided the following information and questions for the committee's response.

A specific transition opportunity could take the following form: a “HOOAH” food bar (a nutrient-dense energy bar developed by the Army) containing 600 mg of caffeine, scored in 150-mg increments, with labeling that provides specific guidance for use of up to one food bar (600 mg) to offset deficits in cognitive function and situational awareness produced by inadequate restorative sleep and during military operations at night. The label should also contain warnings, especially for infrequent or noncaffeine users, that no more than one scored segment (150 mg) should be used in the first hour and should be discontinued if undesirable changes in hand steadiness, pulse, and respiration occur. This performance-enhancing ration component could be provided separately or as part of operational rations. Alternatives to be considered include coffee, caffeinated soft drinks, modifications of the HOOAH bar dose, caffeinated chewing gum, caffeine pills, amphetamine pills (dexedrine), and sustained-release caffeine. The intent is to provide a pharmacological/dietary supplement strategy to significantly counter performance deficits in special circumstances when doctrinal and behavioral solutions (adherence to appropriate work-rest cycles, naps, etc.) are not possible or break down. The key questions to be addressed:

1.

Efficacy: Does the committee stand by its earlier recommendation that there are sufficient data to recommend a caffeine product to enhance performance, and what are the specific indications for use (e.g., vigilance activities following inadequate sleep) and contraindications for use (e.g., tasks involving fine motor coordination)?

2.

Safety: What are the medical risks to individuals associated with ready availability of caffeine, including acute health risks (e.g., cardiac arrhythmia, caffeine psychosis), long-term health risks (e.g., hypertension, hypercholesterolemia), potential interactions with other drugs (e.g., ephedra-containing supplements) or factors specific to military operations (e.g., heat stress, stress reactions), and potential problems of habituation of use (e.g., tolerance, caffeine dependence)?

3.

Dose and warning labels: What dose level(s) should be recommended to (a) habituated caffeine users and (b) nonhabituated users? What warnings should be provided on such a product in the context of ethical, religious, and potential caffeine habituation concerns?

4.

Alternatives: Are there practical alternatives to caffeine, which would better serve the intended purpose of enhancing performance in fatigued service members (e.g., amphetamine)?

5.

Formulation: (a) Does the inclusion of other components (e.g., glucose) improve beneficial effects of caffeine in sustained operations (SUSOPS), as previously suggested by the committee? (b) Is there a better approach to caffeine delivery than the HOOAH bar (e.g., is it better to have more rapid absorption and action using caffeinated chewing gum, longer duration of action using sustained-release caffeine products, or pill or beverage formulations)?

A workshop was organized to review the scientific data on the efficacy of caffeine in maintaining physical and cognitive performance in military operations, its safety, and appropriate formulations for administration during military operations and to identify any ethical or other considerations. Another purpose of this workshop was to compare the effectiveness of caffeine to other pharmaceuticals that have CNS effects.

The research presented at this workshop addressed many of these issues. Information from the speaker presentations and the published scientific literature, as well as the deliberations of the CMNR, were used in the preparation of this report.