A new book based on research funded by the National Institutes of Health explores the use of dietary supplements by military personnel. One of the best things about this book? It’s available online in its entirety, HERE. It reports on research conducted by a committee chosen to “identify those that may be of benefit or might pose serious hazards.” the committee selected supplements to review “based on their frequency of use, potential for adverse events, and interest for the military.” The supplements considered in the book are caffeine, chromium, creatine, dehydroepiandrosterone (DHEA), Ephedra, garlic, Ginkgo biloba, ginseng, β-hydroxy-β-methylbutyrate (HMB), melatonin, quercetin, sports bars, sports drinks, tyrosine, and valerian. Overall, the book takes a skeptical view of these supplements, mostly because of insufficient high quality research. Here are some highlights:
Caffeine: Using HPLC, researchers evaluated 53 caffeine containing products, and found an extremely wide range of caffeine contents, from one to 829 mg of caffeine per day. Average American adult consumption of caffeine is around 225 mg per day. Interestingly, consumption of caffeine by children averages 105 mg per day, more than a cup of coffee.
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).
Chromium: Although chromium picolinate continues to be vigorously marketed and used, the supplement’s ability to alter body composition is questionable (Hallmark et al., 1996; Lukaski et al., 2007; Nissen and Sharp, 2003; Pittler et al., 2003; Stallings and Vincent, 2006; Vincent, 2003a,b). A 2003 meta-analysis of 10 double-blind, randomized control trials concluded that individuals taking 200 to 400 µg of chromium picolinate on a daily basis for 6 to 14 weeks lost approximately 1.1 kg more (i.e., 0.08–0.2 kg/week) during the intervention and increased lean body mass to a slightly greater degree than those taking a placebo (Pittler et al., 2003). More detailed examination revealed that data from only two of the trials accounted for most of the observed differences in body composition between individuals taking chromium picolinate and those taking a placebo. These findings suggest that the effects of chromium picolinate on weight loss and body composition are small and of marginal clinical significance (Pittler et al., 2003). More recent studies have confirmed this suggestion (Lukaski et al., 2007). Taken together, the results of studies evaluating the effects of chromium picolinate on body weight and composition indicate that the supplement is not a useful adjunct to either weight reduction or body building programs.
DHEA: while DHEA may be of medical value for people with certain clinical problems, including adrenal insufficiency, or for those under chronic glucocorticoid treatment, the largest, longest, and best-designed studies do not identify benefits of DHEA on body composition, muscle function, or cognitive function.
Ephedra: An increase in athletic performance is a uniform finding observed during submaximal steady-state aerobic exercise, short- and long-distance running, and maximal and supramaximal anaerobic cycling, as well as weight lifting. The ingestion of ephedrine in combination with caffeine increases blood glucose and lactate concentrations during exercise, whereas similar qualitative effects on lipid fuels (free fatty acids and glycerol) are less pronounced. In parallel, epinephrine and dopamine concentrations are significantly increased, while the effects on norepinephrine are not significant. Finally, evidence to date strongly suggests that the combination of caffeine and synthetic ephedrine HCl may be effective in decreasing the rating of perceived exertion; this appears to be independent of the type of activity being performed (Magkos and Kavouras, 2004). While the effects of ephedra on alertness, physical activity, and caloric intake may be beneficial, the ingestion of products containing ephedra alkaloids is more likely to have negative effects on hydration, thermal regulation, gastrointestinal tract function, kidney stone development, liver function, mood, and recovery from injury, and be dangerous to cardiovascular health.