Zinc (Zn) and magnesium (Mg) may enhance levels of Insulin-like Growth Factor-I (IGF-I)(1); and zinc, in particular, may contribute to elevating serum testosterone (2). Both IGF-I and testosterone are anabolic factors that enhance muscle function and physical performance. Testosterone's role in physical performance enhancement has been studied for a number of years. The IGF-I response to intense muscular activity has not been well defined, relatively. Training may lead to a short-term catabolic state hormonally expressed by reductions in IGF-I. Baseline serum concentrations of testosterone, GH, and IGF-I were unaffected by 16-wk resistive training program which elicited an approximate 40% increase in muscular strength in men, 60 4 yr. It was intimated that training-induced increases in IGF-I could occur in muscle without altering serum IGF-I concentration (3).
A double-blind, randomized study was conducted to determine the effect of a novel zinc and magnesium formulation (ZMA) on anabolic hormone levels and strength in athletes. Members of the University football team (n=27) had blood collected at the beginning and end of an 8 week period of intensive training. Subjects were supplemented with ZMA (n=12) or placebo (n=15) for the 8 weeks. The ZMA group took 3 capsules nightly that contained a total of 30 mg of ZN as monomethionine/aspartate, 450 mg of Mg as aspartate and 10.5 mg of vitamin B-6.
A double blind study conducted by Anthony A. Conte, M.D. found that 23 subjects taking a capsule containing 250 mg of HCA plus 100 mcg of chromium three times daily lost an average of 11 lbs. Over two months compared to 4 lbs. For 17 subjects taking a placebo (control group). The volunteers taking the HCA plus chromium lost over 2 ½ times as much weight as those on the placebo. The study included male and female subjects 21 to 55 years of age. Dietary instructions were given to all subjects in an identical manner; emphasis was placed on the values of low-fat, low sugar, low sodium, high fiber, variety, moderation and balance. The study was published in the The Bariatrician (June 1993), the official journal of the American Society of Bariatric (Weight Loss) Physicians.
1. The effect of zinc depletion on muscle function was tested in 8 male subjects. After receiving 12 mg Zn/day for 17 days, the subjects received 0.3 mg Zn/day for either 33 or 41 days. The subjects were then divided into two groups for zinc repletion. Group A subjects received overnight infusion of 66 mg of Zn on Day 1 and 10 and then were fed 12 mg Zn/day for another 16 days. Group B subjects were fed 12 mg Zn/day for 21 days. Peak force and total work capacity of the knee and shoulder extensor and flexor muscle groups were assessed using an isokinetic dynamometer at baseline, at two points during depletion, and at repletion. Plasma zinc levels decreased by an average of 67% during depletion and remained 9% below baseline after repletion.