Zinc & Testosterone in Healthy Adults

This article, co-authored by a team of five researchers headed by Ananda S. Prasad, M.D., Ph.D., has enormous implications for all bodybuilders, especially those who are “natural.” It was originally published in the peer-reviewed medical journal Nutrition, Volume 12, No.5, 1996, pp. 344-348.

Dr. Prasad is considered to be the world expert on the trace mineral zinc and its metabolic effects on human beings. He has somewhere between 200 and 300 peer-reviewed publications to his credit and knows very well how to design a research project. He notes at the beginning of the research report’s abstract that “Zinc deficiency is prevalent throughout the world, including the USA.”

In this article, Dr. Prasad discusses an investigatioin of the effect of “mild zinc deficiency” on the serum testosterone levels of men.

BACKGROUND: Testosterone, as the reader may know, is the male sex hormone that many steroids are formulated to mimic. It is produced naturally in men and signals the body to develop male characteristics, including increased muscle mass. Certain background information here is very important. At BALCO Laboratories, Inc., of Burlingame, California, where the trace mineral levels of more than 200,000 people, including thousands of athletes, have been measured, a test called multi-element analysis has shown that approximately 70% of all athletes tested have been shown to have either a depletion (which is what Prasad calls a “mild deficiency”) or an outright deficiency. In either case, in one or more ways health and performance may be impaired. In the case of a deficiency, the individual will have one or more overt symptoms identifiable by any knowledgable physician.

Let us emphasize this point more strongly. Over 70% of the serious athletes BALCO has tested have proven depleted or deficient in zinc. This includes entire professional football and basketball teams, many amateur and professional bodybuilders, hundreds of Olympic athletes scattered among many different events, karate champions, and even elite tennis players.

By and large, these athletes are people who pay careful attention to their diet, yet the majority are still they are depleted or deficient in zinc.

According to a conversation we have had with Dr. Prasad, bodybuilders are prone to zinc depletion or deficiency for a number of reasons.

First, one of the best sources of zinc is red meat. Many bodybuilders eat a reduced amount of meat, concentrating instead on chicken and fish as their main protein sources.

Second, bodybuilders lose more zinc than do non-exercisers. Zinc exits the body in a number of ways, including through sweat. On an exercise day, an athlete will lose 50% more zinc through sweat than on a non-exercise day.

Third, bodybuilders require significantly more zinc than do non-exercisers.

In fact, because bodybuilding involves the infliction of a great deal of micro-damage to cells and tissues that must be repaired, and because the muscle are stimulated through exercise to grow, the director of BALCO Labs estimates that bodybuilders may require up to twice as much zinc as do non-exercisers.

This means that if you are a bodybuilder, you are very likely to have either a zinc depletion or deficiency. And if you are using steroids, which depress the body’s zinc, magnesium and copper levels, you are even more likely to be zinc deficient.

Dr. Prasad’s study involved several different populations.

The most important for bodybuilders is the group of four normal adult men approximately 27 years old. He measured their serum testosterone levels, then fed them a diet low in zinc for six months, thus inducing a “mild zinc deficiency” in them. As they progressed through the diet, he measured their serum testosterone levels two more times, once after eight weeks and once again after 20 weeks. As these men became progressively zinc depleted, their serum testosterone concentrations dropped. The chart Dr. Prasad has included on page 347 of the study indicates that by the end of the 20 weeks they had approximately ¼ the testosterone that they had had at the study’s beginning.

The implictions of this for bodybuilders and other athletes is clear. If you are depleted or deficient in zinc—and BALCO’s clinical experience indicates that you probably are—you can significantly increase your testosterone level through zinc supplementation.

In another group of nine older men 55 to 73 years old, Prasad and his fellow researchers measured serum testosterone levels. These men, he notes, were “marginally zinc deficient” (what BALCO calls “depleted”) at the time of the first measurement. After three to six months of zinc supplementation, he measured their serum testosterone levels again. Their testosterone levels had approximately doubled.

For many bodybuilders, this also has important implications. As you get older, your testosterone levels decline. That’s one reason why older bodybuilders have more difficulty adding muscle mass than the younger men in the gym. Many bodybuilders begin to sense at the age of 35 or 40 that adding muscle has become more difficult. For someone around this age who is zinc depleted or zinc deficient, supplementation with a highly absorbable form of zinc (monomethionine or asparate or a combination of the two) can make a noticeable difference.

Warning: Do not buy an ineffective zinc supplement. Do not buy tablets. Capsules are more absorbable. Do not buy zinc oxide. This is not a very absorbable form of zinc. Do not buy any zinc supplement that lists any calcium compound in the ingredients because the presence of calcium will reduce your absorption of zinc.

If the capsule contains a filler, it is probably a calcium compound, which will reduce your absorption of the zinc. Fillers are often not mentioned on the list of ingredients. If you are buying a supplement from a health food store and the clerk doesn’t know what the filler of a product is, ask him or her to call the company to find out.

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