Caffeine has received mixed reviews over the years. It's been implicated in promoting everything from breast cysts In women to various cancers and heart-rhythm disturbances. In most cases, these initially alarming reports didn't bold up under the scrutiny of subsequent
scientific study. For most people, caffeine Is a relatively benign drug. One report last year even showed that it might help prevent suicides. Concerning athletics, the research on caffeine is equivocal. Early studies showed that it might spare muscle glycogen by promoting
faster fat release in the body. That theory was based on caffeine's ability to stimulate the flow of epinephrine, an adrenal hormone that fosters fat release from fat cells.
Other data, however, show that this ergogenic effect wears off in habitual caffeine users. Still other research shows that combining caffeine with carbohydrates totally negates the fat-releasing effect. Studies that examined the effects of caffeine on anaerobic training (this includes weight training) also evinced mixed results. Caffeine may increase strength by promoting calcium transport in a part of muscle tissue called the sarcoplasmic reticulum. Another study found that caffeine increases strength by altering the perception of effort; that is, it makes you think you're stronger. Some people favor caffeine for its thermogenic effect - the conversion of fat calories into beat. Even a single cup of coffee, which contains approximately 100 milligrams of caffeine, can elevate the resting metabolic rate in overweight and lean individuals alike by three or four percent over a two-hour period. And consuming caffeine at two-hour intervals for 12 hours leads to an eight to 11% increase in energy expenditure. Caffeine's thermogenic effect is enhanced by exercise, as well as by combining it with other thermogenic agents, such as ephedrine and aspirin.
The best way to obtain ergogenic benefits inherent in caffeine is through caffeine Itself, rather than from a caffeine-containing product, such as coffee This was pointed out by Canadian researchers, who found that an unidentified component present in coffee inhibits the ergogenic effect of caffeine, Including the increased epinephrine secretion that promotes fat-cell release. A study reported in this column last year noted that caffeine interferes with the ergogenic effects of creatine That investigation did not offer a reason, but it may relate to the increased acid secretion caused by typical caffeine-containing beverages, such as coffee. Excess acid converts creatine into creatinine, a useless byproduct. This still fails to explain the initial positive findings concerning the ergogenic effects of creatine reported in 1992. That research involved supplying creatine mixed in tea - which also contains caffeine - yet the beverage didn't interfere with creatine uptake in the body.
A new study, published in the American Journal of Epidemiology (144:642-44, 1996), reports the most ominous finding yet for bodybuilders: Caffeine may interfere with testosterone activity. Apparently, caffeine increases the liver's synthesis of a blood protein, called sex- hormone binding globulin (SHBG), that binds to testosterone. Research shows that 50-65% of all testosterone circulating in the blond is bound to SHBG, with the rest bound to another blood protein called albumin. The binding action of testosterone to SHBG Is much stronger than it is to albumin, making all testosterone bound to SHBG Inactive. Only about one or two percent of circulating testosterone Is unbound, or free, and only this form can enter cells. SHBG levels are lower in obese people, which explains why they rarely show decreased testosterone activity, even though they usually produce less testosterone than their leaner peers. Several substances can raise or lower SHBG levels. Substances that increase SHBG include estrogen, thyroid hormone and, according to this new study, caffeine. Substances that lower SHBG include growth hormone, insulin and androgens. For this reason, the substances in the latter category will increase testosterone activity in the body.
This study did not explain how caffeine increases. In addition, the study subjects were older women, which Immediately raises a red flag. Several years ago, the trace mineral boron was found to increase testosterone levels. It did but only in older women. Subsequent research involving athletes found no testosterone-increasing effect from boron. The same may hold true for this new caffeine study. The side effect may be limited to older women, possibly through an interaction with estrogen, which is known to increase SHBG levels in the liver. Since no reports exist that testosterone activity is reduced in males who are heavy caffeine users, the effect may be limited to older women. Let's hope so: I'd hate to give up my two morning cups of java!
By the way, if you've ever wondered about lethal doses of caffeine some people have died from ingesting too much - here's a rundown of over dosage: 200 caffeinated sodas, 125 cups of tea or 75 cups of coffee, consumed at one sitting. You will die from either respiratory failure or cardiovascular shock.