Testosterone is a vital sex hormone that boosts muscle formation, facial hair and genital development. In an effort to avoid substances that may decrease testosterone, some athletes and bodybuilders shun caffeine, but it appears that caffeine may actually increase testosterone. Caffeine doesn't come without side effects, however, so it shouldn't be used to excess or to treat severe testosterone imbalances.
Testosterone is the main male sex hormone produced by the testicles and is identified with masculine characteristics, but it's also produced in a woman's body in the ovaries and adrenal glands. Male bodies generate about 7 mg of testosterone, more than 20 times the levels produced in female bodies. However, the hormone is important to both men and women. In men, it helps increase bone density, improve muscle mass and strength, assist in red blood cell production and play a role in sperm production and sex drive. In women, testosterone also plays an important role in sex drive. A decline in testosterone levels as men age can lead to diminished athletic and sexual performance.
Caffeine, Exercise and Testosterone
Caffeine used during exercise has a surprising effect on testosterone levels. Professional rugby players were given caffeine supplements, in doses ranging from 200 to 800 mg, an hour before lifting weights. The results, published in the "International Journal of Sport Nutrition and Exercise Metabolism" in April 2008, found that power training without caffeine caused a rise in testosterone concentrations by 15 percent, while power training with an 800-mg dose of caffeine led to a testosterone increase of 21 percent.
Caffeine, Testosterone and Semen
Caffeine may also be linked to testosterone-induced semen quality and volume. One study reported in a 2008 issue of "Human Reproduction" looked at the adult sons of mothers who had participated in a long-term study and consumed caffeine during their pregnancies. Mothers who drank four to seven cups a day produced sons with a small to moderate reduction in semen volume and testosterone levels. Also, the adult sons who drank the most caffeine had testosterone levels 14 percent higher than those with a low caffeine intake, although there were no appreciable differences in in semen quality or volume.
Caffeine Effects in Women
Caffeine seems to affect testosterone levels differently in women than in men. A 1996 study in the "American Journal of Epidemiology" found that the women who drank the most caffeine-containing beverages --- equivalent to more than two cups of coffee or four cans of caffeinated soda daily --- had the lowest levels of testosterone.
A moderate amount of caffeine, or the equivalent of three 8-oz. cups of coffee per day, provides about 250 mg of caffeine. Consuming 10 8-oz. cups or more daily is considered to be excessive. High amounts of caffeine can lead to insomnia, accelerated heart rate, tremors and anxiety and can contribute to fibrocystic breast disease and menstrual disorders in women. If you are pregnant or have heart disease or stomach ulcers, you should reduce or avoid caffeine.