| ||||||||||||||||||||||||||||||
|
|
|||||||||||||||||||||||||||||
| Copyright © 2009. National Academy of Sciences. All rights reserved. Terms of Use and Privacy Statement |
Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 84
Use of Dietary Supplements by Military Personnel
4
Other Dietary Supplements for Military Personnel
INTRODUCTION
The committee was asked to select a limited number of dietary supplements from those identified as commonly used and, on the basis of published reports, to identify those that may be of benefit or might pose serious hazards. The committee used the information provided at the February 12–13, 2007, workshop to select dietary supplements to review based on their frequency of use, potential for adverse events, and interest for the military. This chapter includes a review of the following dietary supplements: caffeine, chromium, creatine, dehydroepiandrosterone (DHEA), Ephedra, garlic, Ginkgo biloba, ginseng, β-hydroxy-β-methylbutyrate (HMB), melatonin, quercetin, sports bars, sports drinks, tyrosine, and valerian. HMB, creatine, sports drinks and bars, garlic, Ginkgo biloba, and ginseng were reviewed owing to their high frequency of use (see Appendix C). A review of DHEA was conducted because the use of anabolic supplements was shown as high, it is legally considered a dietary supplement, and because DHEA is popular among athletes.
The committee also considered other factors in their selection, such as severity and number of adverse events reported for a supplement or interest of the military in a particular dietary supplement. Ephedra was selected for review by the committee owing to its high frequency of use by military personnel in the past, mainly to achieve weight loss and enhancement of performance, and its adverse event profile. Ginkgo biloba extracts were selected based on their potential to enhance mental performance. Although quercetin is not frequently used by military personnel, research evaluating
OCR for page 85
Use of Dietary Supplements by Military Personnel
its effects on performance and immune response was partially supported by the Department of Defense (DoD), indicating the level of military interest in this dietary supplement. Likewise, although the frequency of use of tyrosine was not apparent, this amino acid has been of interest to the military and the object of research investigations to counteract the decrements in cognition that are associated with stress. Because of the reported use of weight-loss products, chromium was chosen as an example of a dietary supplement ingredient that is often found in such products. The known chronobiotic effects of melatonin may justify its use to ease the effects of jet lag as well as of long or night shifts, and therefore it was included for review. Similarly, valerian could be used for its alleged sedative properties and potential to alleviate sleep disorders, common in military life especially during demanding military operations that require long periods of wakefulness or unusual working shifts.
Details about the strategies used in conducting literature searches are described in Chapter 5. In general, the committee evaluated reviews that concentrated on safety and efficacy. For some dietary supplements (e.g., Gingko biloba), research on use is so broad and encompasses so many areas that the committee decided to focus the review on effects that would be of interest to the military (e.g., effects on cognition). This is especially recommended for those supplements that have already been extensively studied. Reviews of safety emphasized two areas: bioactivity and interactions with other dietary supplements or medications. For the latter, a list of the medications most frequently dispensed to active duty U.S. Army personnel was obtained from the DoD Pharmacy Operations Center, as a representation of typical medications used by military personnel. Although the committee was also asked to provide information on potential withdrawal effects, and the committee recognizes their importance, caffeine is the only supplement for which such information was found. The committee did not perform an evidence-based classification of original research on each supplement. As requested in the statement of task for this study and in accordance with the primary intent to identify supplements that pose serious concerns, the committee relied, as much as possible, on existing reviews by other authors to produce the summaries for each dietary supplement. If a review was not available for the last 10 years, original research was included. In those cases, limitations were noted where appropriate (see tables in Chapter 4).
Although the committee emphasized review of safety, the management of dietary supplements for the military needs to follow an evaluation of both risks and benefits, as the recommended framework notes. The reviews therefore also include information about benefits. When reviewing safety, effects judged to be especially pertinent to specific military subpopulations because of performance demands (e.g., cognitive or physical fitness), mission environments (e.g., high altitude, extreme temperatures), or the impact
OCR for page 86
Use of Dietary Supplements by Military Personnel
of adverse events associated with the supplement (e.g., bleeding, gastrointestinal disturbances, infectious diseases) received particular attention. The committee recognizes that when trying to identify safety concerns, the fact that dietary supplements are taken in combination and also with medications is a challenge. The committee emphasizes that it is very important that interactions between dietary supplements, medications, nutrients, and other dietary supplements be considered in all elements of this framework: when conducting surveys, when applying the framework and conducting reviews, and when examining and associating adverse events with dietary supplement use. However, when conducting the reviews, it would not be feasible for this committee to address all the potential combination scenarios for dietary supplements, and only a few known and potential interactions with medications have been noted. Because new dietary supplements are being rapidly introduced into the market, information about their quantity and purity would quickly become obsolete and, therefore, it was not included in this chapter.
Although many other dietary supplements could have been reviewed, this chapter provides a selected subset as examples of monographs developed for each dietary supplement. For example, although there are risks from the misuse of growth hormones and anabolic steroids, a review of those substances is beyond the scope of this report because they are illegal, and/or there is also no evidence of use among the military. The monographs in this chapter were developed in order to evaluate the review process outlined in Chapter 5. They present scientific reviews of safety and efficacy, but do not attempt to provide a final assessment of safety or efficacy. Monographs are intended to serve as one key tool for making decisions about how to manage each dietary supplement. Other factors affecting the decision-making process on managing use of a specific dietary supplement relate to the characteristics of the targeted population (see Box 1-3 in Chapter 1); that is, decisions about weighing benefits and risks as well as the level of concern will have to consider the tasks (i.e., mission risks and environments) of the subpopulation. The committee recognizes that the military leadership (e.g., local commanders, or leadership at the service or DoD level) is best informed to make such assessments. Examples of how conclusions from the panel of experts could be synthesized are shown in Chapter 5, Table 5-3. This table includes summary conclusions about the level of concern and the putative benefits that will be useful in making management decisions and for developing outreach materials. Also, Appendix D shows examples of how these monographs could serve as a scientific basis for decision making and includes suggestions for management actions for DHEA, melatonin, and Ephedra.
A barrier to the application of the committee’s framework was the lack of data from studies designed with subpopulations or circumstances simi-
OCR for page 87
Use of Dietary Supplements by Military Personnel
lar to those of the military. Also, data from interactions with medications were infrequently found. It should be noted that the monographs are not exhaustive and present mainly data from reviews. The committee did not provide a list of research recommendations for each dietary supplement because research priorities need to be outlined within the scope of an overall research agenda for dietary supplements; such priorities are delineated in Chapter 7.
CAFFEINE
Background
Caffeine1 [1,3,7-trimethyl-1H-purine-2,6(3H,7H)-dione] is arguably the most widely consumed psychoactive substance in the world. It is an alkaloid that occurs naturally in the leaves, seeds, and fruit of tea, coffee, cacao, kola trees, and more than 60 other plants (Reid and Sacha, 2005). It is rapidly absorbed from the gastrointestinal tract into the bloodstream. Within 1–1.5 hours following ingestion, maximum caffeine concentrations are reached in blood, and it is readily distributed throughout the body (Nawrot et al., 2003). Natural sources of caffeine generally also contain varying mixtures of other xanthine alkaloids, including the cardiac stimulants theophylline and theobromine, and other substances such as polyphenols that can form insoluble complexes with caffeine. Caffeine is metabolized in the liver by the cytochrome P450 oxidase enzyme system (1A2 isozyme) into three metabolic dimethylxanthines: (1) paraxanthine, which increases lipolysis, leading to elevated levels of glycerol and free fatty acids; (2) theobromine, the principal alkaloid in cocoa and chocolate, which dilates blood vessels and increases urine volume; and (3) theophylline, which relaxes smooth muscles of the bronchi, and is therefore used to treat asthma (but at therapeutic doses much higher than those achieved from caffeine metabolism).
Caffeine is a central nervous system (CNS) stimulant that can also have physiological effects on the autonomic nervous system as well as the cardiovascular, respiratory, and renal systems. The actions of caffeine and its metabolites on these systems are mediated by way of several mechanisms, including antagonism of adenosine receptors (caffeine and paraxanthine are nonselective antagonists for A1 and A2a receptors, but the effect of caffeine on A3 receptors is unknown). A1 receptors have been identified in many brain regions, including the hippocampus, cerebral cortex, cerebel-
1
The monographs were developed in order to evaluate the review process outlined in Chapter 5. The monographs present scientific reviews of safety and efficacy, but do not attempt to provide a final assessment of safety or efficacy.
OCR for page 88
Use of Dietary Supplements by Military Personnel
lar cortex, and thalamus (Porkka-Heiskanen, 1999). Other mechanistic pathways for the effects of caffeine and its metabolites include inhibition of phosphodiesterase activity, increased calcium mobilization, and antagonism of benzodiazepine receptors. Caffeine’s inhibition of phosphodiesterase activity may account for its effects on both the cardiovascular and respiratory systems in that nonxanthine phosphodiesterases are cardiac stimulants as well as effective bronchiolar and tracheal relaxants (IOM, 2001).
Caffeine in Dietary Supplements
A recent review of caffeine content in common U.S. dietary supplements evaluated 53 products with caffeine-containing ingredients as part of a study initiating the development of an analytically validated Dietary Supplement Ingredient Database (Andrews et al., 2007). Selection of products for analysis was based on market share information and included those sold as tablets, caplets, or capsules and listing at least one caffeine-containing ingredient, including botanicals such as guarana, yerba mate, kola nut, and green tea extract on the label. Products were analyzed using high-pressure liquid chromatography. Caffeine intake per serving and per day was calculated using the maximum recommendations on each product label. Laboratory analyses revealed product means ranging from 1 to 829 mg caffeine per day. “For products with a label amount for comparison (n=28), 89 percent (n=25) of the products had analytically based caffeine levels per day of between −116 percent and +16 percent of the claimed levels. Lot-to-lot variability (n=2 or 3) for caffeine in most products (72 percent) was less than 10 percent” (Andrews et al., 2007). This review article also noted that caffeine can be present in supplements as a proprietary blend, but not be listed as an ingredient on the label. Less than one-third (11 of 36) of the products whose caffeine content was more than that of one cup of brewed coffee per day listed caffeine as an ingredient, although a majority of these products (27 of 36) did voluntarily list a caffeine level on the label (Andrews et al., 2007).
Changes in Caffeine Consumption Over the Past Several Decades
It appears that coffee remains the primary source of caffeine in the diets of persons in the United States. However, the Continuing Survey of Food Intakes by Individuals (CSFII) found the consumption of caffeine from soft drinks now exceeds the consumption of caffeine from tea (Frary et al., 2005). Frary et al. compared mean values of caffeine consumption as reported by the 1989 Market Research Corporation of America (MRCA) study and the CSFII study. MRCA reported a daily mean consumption value for tea of 0.54 mg/kg, and for soft drinks, 0.27 mg/kg. In contrast, the
OCR for page 89
Use of Dietary Supplements by Military Personnel
more recent CSFII study showed that soft drink consumption exceeded tea consumption, reporting mean values of 30.6 mg (16 percent of sample size) and 23.4 mg (12 percent of sample size) respectively (Frary et al., 2005).
Table 4-1 (see pages 94–95) summarizes what is known about changes in caffeine consumption over the past several decades. Most studies do not find an increase in caffeine consumption, although in 2005, Frary et al. concluded that “During the past 20 years it appears the percentage of persons consuming caffeine has increased while mean caffeine intakes may have decreased” (Frary et al., 2005). With regard to overall changes in beverage consumption, Nielsen and Popkin (2004) concluded that “Within every age group for all other beverages—including coffee and tea, alcohol, fruit drinks, and fruit juices—the changes have been minor between 1977 and 2001.”
Caffeine in Energy Drinks
Energy drinks have acquired a considerable market in recent years, substantially contributing to caffeine consumption. Consumers Union recently tested 12 carbonated energy drinks and found caffeine levels ranging from 50 mg to 145 mg per 8-ounce serving (Energy drinks, 2007). Most of the drinks tested were sold in packages containing more than 8 ounces, so consumption of the entire contents could amount to intake of over 200 mg of caffeine. Furthermore, most of the energy drinks tested contained multiple stimulants, and because caffeine content is not required by law to be listed, the amount of caffeine in an energy drink (or any food for that matter) is often unknown (Energy drinks, 2007).
Although caffeine is not classified as addictive in the Diagnostic and Statistical Manual of Mental Disorders of the American Psychiatric Association (APA, 1994), it has been asserted in a comprehensive review of caffeine that habitual daily use of over 500 mg of caffeine (i.e., four to seven cups of coffee or seven to nine cups of tea) represents a significant health risk and may therefore be regarded as abuse (Nawrot et al., 2003). Other mental disorders such as dependence, withdrawal syndrome, and intoxication can be caused by caffeine (Pardo et al., 2007). Therefore, “depending on its use, caffeine can be considered a nutrient, a drug, or a drug of abuse” (Pardo et al., 2007, p. 225).
Update on Institute of Medicine Caffeine Report (2001)—Putative Benefits
The Institute of Medicine (IOM) Committee on Military Nutrition Research (IOM, 2001) concluded in its report on the use of caffeine for the sustainment of mental task performance for military operations that
OCR for page 90
Use of Dietary Supplements by Military Personnel
“Research shows that caffeine in the range of 100–600 mg is effective in increasing the speed of reaction time without affecting accuracy and in improving performance on visual and audio vigilance tasks” (IOM, 2001, p. 7). The report indicated that caffeine in doses of 100–600 mg can be used to maintain cognitive performance—particularly in situations of sleep deprivation—and doses of 200–600 mg can be effective in enhancing physical endurance. Moreover, caffeine ingestion has been often associated with a increase in endurance time in physical activities of moderate intensity and long duration (IOM, 2001). Caffeine improves aerobic endurance by increasing fat oxidation and sparing muscle glycogen (IOM, 2001). Four separate reviews (Dodd et al., 1993; Graham et al., 1994; Spriet, 1995; Tarnopolsky, 1994) concluded that caffeine consistently “enhances endurance performance in a variety of activities (i.e., running, cross-country skiing, cycling), with doses from 2 to 9 mg/kg, in naïve and habituated, trained and untrained test subjects” (IOM, 2001).
Similar conclusions and recommendations regarding the effects of caffeine on cognitive performance during sleep deprivation were reached in a 2005 review of stimulants by the Sleep Deprivation and Stimulant Task Force of the American Academy of Sleep Medicine. Their review concluded that
Caffeine is a readily available, short-acting stimulant that has been shown to reduce some of the deficits associated with sleep loss. Studies suggest that caffeine can provide improved alertness and performance at doses of 75 to 150 mg after acute restriction of sleep and at doses of 200 to 600 mg after a night or more of total sleep loss. Caffeine is unlikely to have major disruptive effects on the sleep that follows 8 hours or longer after administration. However, frequent use of caffeine can lead to tolerance and negative withdrawal effects. (Bonnet et al., 2005, p. 1168)
While caffeine consumed too close to sleep time can interfere with sleep, caffeine appears to help reverse the effects of sleep inertia (i.e., grogginess and psychomotor lethargy immediately upon awakening from deep sleep) (Van Dongen et al., 2001).
Update on IOM Caffeine Report (2001)—Safety Concerns
The safety of caffeine as a food and beverage additive has been evaluated several times (IOM, 2001). In 1987, the U.S. Food and Drug Administration (FDA) concluded that caffeine added to beverages at a level of 0.02 percent (200 mg/L) or less did not present a health risk. Another FDA review in 1992 concluded that there was no evidence that the consumption of 100 mg per day or less of caffeine in cola beverages posed a hazard to human health (but this does not imply safety at higher doses) (Bonnet
OCR for page 91
Use of Dietary Supplements by Military Personnel
et al., 2005). It was also noted in the 2001 IOM report that caffeine might be associated with a small increase of spontaneous abortion in the first trimester of pregnancy and that it can significantly increase 24-hour urine output. These effects were not seen as limitations on the military use of caffeine, although increased urine output could provide practical problems under some operational conditions. It was recommended that daily doses should not exceed 600 mg due to possible negative effects on mood and performance at higher doses.
Nawrot et al. (2003) concluded that there is ample evidence indicating that for healthy adults, there is no association between caffeine intakes of 400 mg per day and general toxicity, increase in incidence of cancer, adverse effects in the cardiovascular system, behavior, or male fertility.
However, recent data from studies at the Walter Reed Army Institute of Research (WRAIR) show that caffeine may not benefit all aspects of neurobehavioral function in sleep-deprived subjects. During military operations, the ability to make advantageous and safe decisions is vital. A 2007 WRAIR study demonstrated that after 51 continuous hours of sleep deprivation, the decision-making process was impaired under conditions of uncertainty on the Iowa Gambling Task (Killgore et al., 2007). Caffeine was reported to have no significant beneficial effects that compensated for the detriments of sleep deprivation on the performance of this risk-taking task. Even when administered caffeine, sleep-deprived study participants frequented disadvantageous high-risk scenarios as opposed to the advantageous low-risk scenarios that were learned prior to sleep deprivation (Killgore et al., 2007).
Additional effects of caffeine may be undesirable in certain environmental conditions. Among the other physiological effects of caffeine that are relevant to the military are its effects on thermoregulation. While these effects are advantageous to tolerance of cold temperatures, in a heat stress situation, the effects would be undesirable. A review of the literature found no conclusive evidence of caffeine’s effect on body temperature (Armstrong et al., 2007). However, a carefully controlled study of sustained low-dose (0.3 mg/kg/hour) caffeine intake (in tablet form) by healthy adults undergoing sleep deprivation found a reliable increase in core body temperature (measured with a continuous rectal probe) (Rogers et al., 2001). It was also found that caffeine markedly increased circulating levels of noradrenaline relative to a placebo (Price et al., 2000). Research on effects of an ephedrine–caffeine mixture showed that this mixture might also have beneficial thermoregulatory effects for cold tolerance. This effect might be in part due to an 18.6 percent increase in energy expenditure compared to placebo (Vallerand et al., 1989). In a different experiment the additive effects of caffeine and cold water exposure on energy production during submaximal exercise were observed (Doubt and Hsieh, 1991). In another
OCR for page 92
Use of Dietary Supplements by Military Personnel
placebo-controlled experiment where individuals were subjected to heat stress through physical activity, Bell et al. (1999) reported that although caffeine and ephedrine treatment increased metabolic rate during moderate exercise in a hot, dry environment, there was no increase in internal body temperature; this was possibly due to heat-loss mechanisms that offset the increase in metabolic rate.
At higher dosages and/or sustained intake, caffeine can have unwanted physiological and neurobehavioral effects. In addition to the elevated core body temperature and increased plasma noradrenaline levels described by Rogers and Dinges (2005), the adverse effects of caffeine can include locomotor agitation, tachycardia, diuresis, and increased anxiety. Numerous studies of the effect of caffeine on fluid homeostasis (diuresis) have generally found a positive correlation between caffeine consumption and increased urine output (IOM, 2001). For example, Neuhäuser-Berthold et al. (1997) administered coffee containing 642 mg of caffeine to healthy volunteers over a single day and monitored fluid homeostasis in comparison with a control group given an equal amount of mineral water. The caffeine group had a highly significant increase in 24-hour urine output, corresponding to negative fluid balance and a decrease in body weight (IOM, 2001). Decreased electrolyte (sodium and potassium) levels have also been documented as a result of diuresis; however, a normal diet will restore the homeostatic balance (Armstrong et al., 2007; IOM, 2001). Moreover, fluid and food intake should be monitored under conditions of sustained military operations in hot and cold environments or at high altitudes, as these may present potential for augmented risk of dehydration (IOM, 2001).
Interactions with Other Dietary Supplements or Medications
Research has shown that caffeine interacts with other drugs in many different ways, although the magnitude of interaction is dependent on dosage. For example, diazepam (i.e., Valium) is an anxiolytic that is prescribed as a muscle relaxant, sedative-hypnotic, and anticonvulsant (Roache and Griffiths, 1987). Caffeine and diazepam produce disparate effects on the CNS through functionally opposing mechanisms. Caffeine has been demonstrated to antagonize subjects’ ratings of sedation and impairment of psychomotor vigilance caused by diazepam, while diazepam countered the restlessness and subject ratings of tension, alertness, and arousal caused by caffeine (Roache and Griffiths, 1987). Less is known about the extent to which caffeine has synergistic effects with other stimulants.
OCR for page 93
Use of Dietary Supplements by Military Personnel
Caffeine Withdrawal
The most commonly reported symptoms following withdrawal of caffeine, even at doses as low as 100 mg, are headache, irritability, increased fatigue and drowsiness, decreased alertness, difficulty concentrating, nervousness, confusion, depressed mood, and decreased energy and activity levels (Nehlig, 1999). These symptoms are typically short-lived and mild to moderate in severity. Despite the long history of use of caffeine, there have been few studies that systematically examined the nature of caffeine withdrawal (Rogers and Dinges, 2005). Depending on dosage and proximity to sleep time, caffeine can disturb sleep by lengthening sleep latency and reducing total sleep time and sleep efficiency (Rogers and Dinges, 2005). Care should therefore be taken to ensure that caffeine use by military personnel does not interfere with sleep when the latter is desirable.
Considerations Specific to the Military
Military engagements often involve extended periods of sleep restriction that are accompanied by well-documented physical and cognitive impairment (Killgore et al., 2007). Consistent with the 2001 IOM report on the military use of caffeine, studies continue to find that caffeine is an effective countermeasure to the detriments of sleep deprivation. These studies support “the recommendation for the use of caffeine to extend the period of operational effectiveness during the conduct of military operations that involve unavoidable periods of sleep loss over a three to four day period” (McLellan et al., 2007). In this 2007 study, the use of 800 mg of caffeine throughout three overnight periods maintained alertness and vigilance in comparison to a placebo group (without caffeine) (McLellan et al., 2007). However, it must also be noted that chronic frequent use of caffeine can lead to tolerance and reduce the benefits of caffeine as a countermeasure for sleep deprivation during military operations. To the extent that caffeine is being consumed in ever-larger doses via coffee, soft drinks, energy drinks, and dietary supplements or medications, the military benefits of caffeine as a cognitive and physical performance enhancer may be reduced by tolerance from such widespread consumption of caffeine (see also Chapter 2, regarding the need for obtaining ingredient identification in dietary supplement products and total dosage consumed). In addition, caffeine may not benefit all aspects of cognitive and neurobehavioral functions (e.g., risk-taking decisions), and it may produce physiological effects (e.g., heat retention, diuresis) that may compromise physical performance in certain environments (e.g., hot climates).
A summary of average daily consumption (ADC) of caffeine in the United States is shown in Table 4-1.
OCR for page 94
Use of Dietary Supplements by Military Personnel
TABLE 4-1 Summary of Average Daily Consumption (ADC) of Caffeine in the United States
Reference
Source Data
Mean ADC
Graham, 1978
NASa: Generally Recognized as Safe (GRAS) survey, 1977
Adults: 227 mg/day
Children: 101 mg/day
Pao et al., 1982
USDAb: Nationwide Food Consumption Survey (NFCS), 1977–1978
Coffee drinkers: 3.3 mg/kg
Tea drinkers: 1.1 mg/kg
Cola drinkers: 0.4 mg/kg
Barone and Roberts, 1996
MRCA: National Household Menu Census Survey, 1989
Adults: 2.4 mg/kg
Children: <1 mg/kg
Knight et al., 2004
NFO WorldGroup: Share of Intake Panel Survey, 1999
Adults: 1.5–2.3 mg/kg
Frary et al., 2005
USDA: CSFII, 1994, 1996, and 1998
ADC calculations in this paper are unreliable
NOTE: Average consumption numbers are based on responses from “caffeine consumers,” not the entire population. The most recent paper attempting to determine average caffeine intake was published in 2004, using data from a survey taken in 1999. Thus, none of the data takes into consideration the recent surge in sales of energy drinks. In addition, the results of different
References
Andrews, K. W., A. Schweitzer, C. Zhao, J. M. Holden, J. M. Roseland, M. Brandt, J. T. Dwyer, M. F. Picciano, L. G. Saldanha, K. D. Fisher, E. Yetley, J. M. Betz, and L. Douglass. 2007. The caffeine contents of dietary supplements commonly purchased in the U.S.: Analysis of 53 products with caffeine-containing ingredients. Annal Bioanal Chem 389(1):231-239.
APA (American Psychiatric Association). 1994. Diagnostic and statistical manual of mental disorders (DSM-IV). Arlington, VA: APA.
Armstrong, L. E., D. J. Casa, C. M. Maresh, and M. S. Ganio. 2007. Caffeine, fluid-electrolyte balance, temperature regulation, and exercise-heat tolerance. Exerc Sport Sci Rev 35(3): 135-140.
Barone, J. J., and H. R. Roberts. 1996. Caffeine consumption. Food Chem Toxicol 34(1): 119-129.
Bell, D. G., I. Jacobs, T. M. McLellan, M. Miyazaki, and C. M. Sabiston. 1999. Thermal regulation in the heat during exercise after caffeine and ephedrine ingestion. Aviat Space Environ Med 70(6):583-588.
Bonnet, M. H., T. J. Balkin, D. F. Dinges, T. Roehrs, N. L. Rogers, N. J. Wesensten, and Sleep Deprivation and Stimulant Task Force of the American Academy of Sleep Medicine. 2005. The use of stimulants to modify performance during sleep loss: A review by the Sleep Deprivation and Stimulant Task Force of the American Academy of Sleep Medicine. Sleep 28(9):1163-1187.
Dodd, S. L., R. A. Herb, and S. K. Powers. 1993. Caffeine and exercise performance: An update. Sports Med 15(1):14-23.
OCR for page 285
Use of Dietary Supplements by Military Personnel
Outcomes Measured
Conclusions/Results
Adverse Events Profile
Interactions with Pharmaceuticals, Foods, or Other Dietary Supplements
Body mass, performance on 2 half marathons
Mean body mass change of approximately 2.4%.
Gastrointestinal discomfort
None reported
Three runners reported gastrointestinal discomfort after consuming gel, which impaired marathon performance. The effect of gel on performance was insignificant (time was improved by 0.3% or 14 sec compared with placebo). No benefits of carbohydrate gel intake on half marathon performance.
Maximal aerobic power, hydration status, body mass changes, sweat rate, blood glucose, blood lactose, rating of exertion, thermal sensation, and stomach fullness
No differences in bicycle treadmill speed, blood glucose, blood lactose, hydration status, perceived exertion, thermal sensation, or stomach fullness.
None reported
None reported
Significantly lower absolute power output in water plus gel group to maintain same speed as carbohydrate-electrolyte drink group during treadmill test.
Time to exhaustion was significantly shorter in water plus gel group.
Ingestion of water and a sport gel reduced the exercise capacity of trained cyclists during laboratory cycling hill-climbing.
Maximal oxygen consumption, respiratory exchange ratio, heart rate, fat oxidation, perceived exertion
Fat oxidation rates were greater in subjects who ingested energy bar compared to those ingesting carbohydrate gel.
None reported
None reported
Ingestion of a sports bar significantly enhanced fat metabolism during prolonged submaximal exercise.
Ingestion of sports bar containing carbohydrate, fat, and protein during exercise, led to impaired performance on subsequent high-intensity exercise.
OCR for page 286
Use of Dietary Supplements by Military Personnel
TABLE 4-13 Relevant Data and Conclusions on Efficacy and Safety Reviews and Publications Identified for Sports Drinks
Review/Clinical Trial Reference
Type of Study and Subjects
Indication
Control
Dose
Product Specification
Gibala, 2007
Review
Protein metabolism
Various
Various
None reported
Jeukendrup, 2004
Review
Exercise performance
Various
Various
None reported
Maughan and Murray, 2001
Review
Exercise performance
Various
Various
None reported
Nieman, 2007
Review
Immune function
None reported
None reported
None reported
Winnick et al., 1995
Double-blind, randomized, counter-balanced n=20 active adults (10 men, 10 women), mean age 23.9 y
Peripheral and central nervous system function
Placebo
6% carbohydrate solution: 5 mL/kg before exercise, 3 mL/kg after exercise, 8 mL/kg during exercise
Gatorade Sports Science Institute, Barrington, IL
OCR for page 287
Use of Dietary Supplements by Military Personnel
Outcomes Measured
Conclusions/Results
Adverse Events Profile
Interactions with Pharmaceuticals, Foods, or Other Dietary Supplements
Endurance performance, repair and synthesis of muscle proteins, synthesis of muscle glycogen
One study found that ingestion of a sports drink with added protein provided no additional benefit on athletic performance. There is no established mechanism by which protein intake during exercise should improve acute endurance performance.
None reported
None reported
Ingestion of protein with carbohydrate improves net protein balance during exercise and recovery compared with carbohydrate alone, but it remains to be determined whether this practice facilitates the adaptive response to chronic training.
Endurance capacity and performance
Ingestion of small amounts of carbohydrate (16 g/h) during exercise has positive ergogenic effects on performance. Larger amounts do not show any further benefits.
None reported
None reported
Various
Rehydration with sports drinks can restore the negative fluid balance caused by exercise. Sports drinks can also restore muscle glycogen after exercise.
Ingestion of a sports drink at regular intervals during physical activity may enhance performance.
Immune dysfunction
Ingestion of carbohydrate beverages during exercise is an effective countermeasure to exercise-induced immune suppression in marathon athletes.
None reported
None reported
Carbohydrate supplementation decreases exercise-induced increases in plasma cytokines and stress hormones, but is largely ineffective against other immune components including natural killer cell function and salivary IgA, with an undetermined influence on incidence of upper respiratory tract infections.
Tests of peripheral and central nervous system function (sprints, jumping, mood evaluation, cognitive function, force sensation, motor skills tests, and target jumping accuracy)
Carbohydrate intake during exercise resulted in significantly faster 20-m sprint times and higher average jump height at the end of the exercise period. Carbohydrate intake also reduced force sensation, enhanced motor skills, and improved mood late in exercise.
None reported
None reported
Carbohydrate intake during intermittent high-intensity exercise similar to that of team sports improved peripheral and central nervous system function late in exercise.
OCR for page 288
Use of Dietary Supplements by Military Personnel
TABLE 4-14 Relevant Data and Conclusions on Efficacy and Safety Reviews and Publications Identified for Tyrosine
Review/Clinical Trial Reference
Type of Study and Subjects
Indication
Control
Dose
Product Specification
Banderet and Lieberman, 1989
Double-blind, crossover n=23 male U.S. soldiers, ages 18–20 y
Mood, physical condition, and cognitive performance under environmental stress
Placebo
2 gelatin capsules adjusted to contain 50 mg/kg tyrosine
None reported
Wiegmann et al., 1993
Controlled n=20 male U.S. Marines, ages 21–27 y
Cognitive performance after sleep loss and sustained work
Placebo
2 doses of 75 mg/kg tyrosine
Ajinomoto Company, Inc.
Deijen and Orlebeke, 1994
Double-blind, randomized n=9 male and 7 female healthy subjects, ages 25–35 y
Cognitive performance
Placebo
100 mg/kg L-tyrosine
Country Life, Hauppauge, NY
Shurtleff et al., 1994
Controlled n=8 men
Cognitive performance
Placebo
Applesauce adjusted to contain 150 mg/kg tyrosine
Tysons & Assoc., Santa Monica, CA (crystalline tyrosine)
Neri et al., 1995
Double-blind n=20 male U.S. Marines, ages 21–27 y
Cognitive performance after sleep loss
Placebo
150 mg/kg tyrosine
None reported
OCR for page 289
Use of Dietary Supplements by Military Personnel
Clinical Details and Outcomes Measured
Conclusions/Results
Adverse Events Profile
Interactions with Pharmaceuticals, Foods, or Other Dietary Supplements
Mood states, sustained attention, vigilance, processing spatial and verbal information, math skills, number coding, pattern recognition
Individuals were exposed to environmental stressors: Two levels of decreased temperature and reduced atmospheric pressure versus normal temperature and pressure. Relative to placebo, tyrosine significantly reduced symptoms of headache, coldness, distress, fatigue, muscular discomfort, and sleepiness in subjects who responded adversely to environmental stress. Tyrosine also reduced dizziness, feelings of confusion, unhappiness, hostility, and tension, and reversed the adverse effects of environmental stressors on cognitive performance on tasks measuring math skills, pattern recognition, vigilance, and coding.
None reported
None reported
Eye-hand coordination, short-term memory, dichotic listening, mood, sleepiness, blood pressure, heart rate
Participants tested under conditions with noise stressor. Across night performance on cognitive tasks decreased. However, tyrosine administration led to smaller decrements in performance in eye-hand coordination, and short-term memory than placebo. Additionally, participants reported being less sleepy after tyrosine than placebo.
None reported
None reported
Perceptual motor tasks, vigilance task, short-term memory test, Stroop task, and adjective checklist of mood
Relative to placebo, tyrosine improved performance on short-term memory and Stroop task.
None reported
None reported
Performance on delayed matching to sample test of working memory
Tested at ambient temperatures of 4°C and 22°C. Relative to placebo, tyrosine prevented cold-induced memory deficit.
None reported
None reported
Performance on psychomotor tasks and mood scales
Tyrosine prevented performance decline on a psychomotor task and exhibited reduction on lapse responses on a vigilance task in sleep-deprived participants.
None reported
None reported
OCR for page 290
Use of Dietary Supplements by Military Personnel
Review/Clinical Trial Reference
Type of Study and Subjects
Indication
Control
Dose
Product Specification
Deijen et al., 1999
Double-blind, randomized n=20 male and 1 female military cadets, ages 18–27 y
Cognitive performance
Carbohydrate-rich drink
2 g tyrosine in a protein-rich drink
PROTIFAR powder
Thomas et al., 1999
Double-blind, crossover n=10 male and 10 female active duty personnel and civilians, ages 20–38 y
Cognitive performance under stress condition
Placebo
Applesauce adjusted to contain 150 mg/kg tyrosine
None reported
Chinevere et al., 2002
Double-blind, randomized, counter-balanced n=9 male competitive cyclists
Endurance exercise performance
Polydextrose solution or aspartame solution
25 mg/kg tyrosine dissolved in a polydextrose solution or water
None reported
Magill et al., 2003
Double-blind, randomized n=76 men, ages 18–35 y
Cognitive performance when sleep deprived
Placebo
150 mg/kg
None reported
O’Brien et al., 2007
Double-blind n=15 soldiers (14 men, 1 women)
Cognitive and psychomotor performance after cold water immersion
Placebo
2 energy bars adjusted to each contain 150 mg/kg tyrosine
None reported
OCR for page 291
Use of Dietary Supplements by Military Personnel
Clinical Details and Outcomes Measured
Conclusions/Results
Adverse Events Profile
Interactions with Pharmaceuticals, Foods, or Other Dietary Supplements
Memory, perceptual, motor, vigilance tasks, and mood scales
Tyrosine supplementation reduced cognitive deficits associated with psychosocial stress and fatigue associated with combat training. Tyrosine did not affect mood.
None reported
None reported
Study design does not eliminate the possibility that other amino acids contributed to the observed results.
Simple task battery measuring working memory and multiple task battery consisting of four simultaneously occurring tasks measuring memory, math skills, visual monitoring, auditory monitoring
Tyrosine improved performance on multiple task battery, but not on simple task battery.
None reported
None reported
Tyrosine might be beneficial to memory under conditions of increased cognitive stress (e.g., multiple cognitive demands placed on military personnel).
Time trial performance test on a stationary bicycle
Tyrosine, either alone or with carbohydrates did not improve cycling time trial performance.
None reported
None reported
Visual scanning, memory, logical reasoning, mathematical processing, reaction time, vigilance, pursuit tracking
Tyrosine showed positive effects for overcoming performance deficits due to prolonged sleep deprivation. Effects most pronounced for deficits in tasks measuring memory and mathematical processing.
None reported
None reported
Skin folds, U.S. Special Operations Command standardized tests of cognitive and physical performance evaluating short-term spatial memory and pattern recognition, complex reaction time, visual vigilance, mathematical reasoning, logical reasoning, psychomotor performance, marksmanship, grip strength, pull-ups, cycle ergometer, step ups
Tyrosine mitigated cold-induced decrements in performance on tasks measuring short-term memory, pattern recognition, and marksmanship.
None reported
None reported
OCR for page 292
Use of Dietary Supplements by Military Personnel
Review/Clinical Trial Reference
Type of Study and Subjects
Indication
Control
Dose
Product Specification
Mahoney et al., 2007
Double-blind n=19 military members
Cognitive performance and mood after acute cold stress
Placebo
2 energy bars adjusted to each contain 150 mg/kg tyrosine
None reported
OCR for page 293
Use of Dietary Supplements by Military Personnel
Clinical Details and Outcomes Measured
Conclusions/Results
Adverse Events Profile
Interactions with Pharmaceuticals, Foods, or Other Dietary Supplements
Visual vigilance, reaction time, short-term memory, mood state, muscle discomfort, alertness
Tyrosine reduced cold-induced decrements in working memory and mitigated cold-induced increased score on tension subscale of mood test.
None reported
None reported
OCR for page 294
Use of Dietary Supplements by Military Personnel
TABLE 4-15 Relevant Data and Conclusions on Efficacy and Safety Reviews and Publications Identified for Valerian
Review/Clinical Trial Reference
Type of Study and Subjects
Indication
Control
Dose
Product Specification
Leathwood et al., 1982
Randomized, controlled n=128
Improvement of sleep quality and latency
Placebo
400 mg
Valerian aqueous extract
Donath et al., 2000
Randomized, double-blind, crossover
n=16 (4 men, 12 women), ages 22–55 y, with psychophysiological insomnia
Sleep quality and structure
Placebo
600 mg/d for 8 d
Valerian extract (300 mg) pills as Sedonium
Beaubrun and Gray, 2000
Review
Sleep latency, nocturnal awakenings, and subjective sleep quality
Placebo
400 mg to 900 mg
Valerian extract
Bent et al., 2006
Review n=16 studies
Improving sleep quality
Placebo
Variable
Variable
Diaper and Hindmarch, 2004
Double-blind, crossover n=16 (5 men, 11 women) sleep-disturbed patients
Insomnia and improving sleep quality
Placebo
300 mg and 600 mg for 1 d
Valerian extract (300 mg) Sedonium
Hallam et al., 2003
Randomized, double-blind, crossover
n=9 (5 men, 4 women) healthy subjects
Cognitive and psychomotor effects of valerian
Placebo
500 mg and 1,000 mg for 1 d
Valerian extract (500 mg) Herb Valley
aElectroencephalography is the technique of using electrodes placed on the scalp to measure electrical activity of the brain.
bElectro-oculography is a technique for measuring the resting potential of the retina.
OCR for page 295
Use of Dietary Supplements by Military Personnel
Outcomes Measured
Conclusions/Results
Adverse Events Profile
Interactions with Pharmaceuticals, Foods, or Other Dietary Supplements
Subjective ratings of sleep quality, sleep latency, night awakenings, dream recall, next morning sleepiness
The aqueous extract of valerian produced a significant improvement in sleep quality in young, poor sleepers as well as a significant improvement in sleep quality in women who were poor sleepers. There were no differences between placebo and valerian in dream recall, night awakenings, or next morning sleepiness.
One person withdrew from the study because they experienced nausea. However, it was not possible to attribute the nausea definitively to valerian
None reported
Sleep structure changes as measured by EEG,a EOG,b EMG,c and ECGd Subjective sleep quality
In insomnia patients, valerian had positive effects on sleep structure and sleep perception. It can be recommended for the treatment of patients with mild psychophysiological insomnia.
More adverse events were seen under the placebo condition (18 vs. 3)
None reported
Sleep latency, nocturnal awakening, subjective sleep quality
Valerian generally produced decreased sleep latency and nocturnal awakenings and improved subjective sleep quality. However, in some studies the placebo effect was large and in others the beneficial effects of valerian were not seen until after 2 to 4 wk of therapy.
Rare, but may include headache, restless sleep, allergies, gastrointestinal problems, and mydriasis
Potential interaction with other sedative hypnotics
Sleep quality
Valerian may be an effective treatment for insomnia; larger studies needed.
Time in bed, total sleep time, sleep latency, number of awakenings, total slow-wave sleep
No significant difference was found between either dose of valerian and placebo. Valerian is ineffective as an acute treatment for sleeping problems at these doses.
None reported
None reported
Critical flicker fusion, choice reaction time, digit symbol substitution test, symbol search test, digit span test, and visual analogue scales of mood
Valerian was without effect on either cognitive or psychomotor performance at the doses used in this study.
None reported
None reported
cElectromyography is a technique for evaluating physiologic properties of muscles.
dElectrocardiogram is a recording of the electrical activity of the heart over time.
Items in cart [0]
