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Minerals And Strength-Power Athletes
Phosphorous/ Phosphate
    Among the inorganic elements, phosphorous is second only to calcium in abundance in the human body. Phosphorous is of vital importance in metabolism of the energy nutrients, contributing to the metabolic potential in the form of high-energy phosphate bonds, such as ATP and creatine phosphate, and through phosphorylation (activation) of substrates. Phosphate also functions in acid-base balance. In fact, phosphate is the main intracellular buffer. Furthermore, phosphate is involved in oxygen delivery. In red blood cells, synthesis of diphosphoglycerate requires phosphorous. Decreased diphosphoglycerate diminishes release of oxygen to tissues. Phosphorous is widely distributed in foods. The best food sources are meat, poultry, fish, eggs and milk products. Nuts, legumes, cereals, grains and chocolate also contain phosphorous; however, animal products are superior sources of available phosphorus compared with cereals and soy-based foods.

    There is some evidence that so-called phosphate loading can improve endurance performance. This ergogenic effects may have something do with the fact that phosphate loading can increase red cell 2,3-diphosphoglyserate levels, and in turn diphosphoglyserate increases the availability of oxygen to peripheral tissues. However, this effect is hardly relevant to gym rats, so I'm not going to discuss it here. I think gym rats are more interested in the findings that phosphate supplementation may boost creatine's effectiveness. In their book Supplements for Strength-Power Athletes, Jose Antonio and Jeffrey Stout cited the study by Wallace and co-workers published in a lesser-known publication Coaching and Sports Science Journal. I was not able to get the full text paper of the Wallace study, so I will simply repeat what Antonio and Stout wrote in their book. Wallace and colleagues investigated the effects of creatine alone versus creatine + phosphate on muscle power. Male and female subjects were given either five grams of creatine four times per day or five grams of creatine plus one gram of phosphate four times per day for five days. The combination of creatine plus phosphate resulted in a significantly higher muscle power output, suggesting that the combination of creatine and phosphate has stronger ergogenic effect than creatine alone. Although more research is certainly needed, it might be a good idea to take in some extra phosphate while loading creatine.

    Magnesium is the fourth most abundant mineral in the body. Magnesium is needed for more than 300 biochemical reactions. For example, it helps maintain normal muscle function, supports a healthy immune system and keeps bones strong. Magnesium is also involed in energy metabolism and protein anabolism. In addition, a growing body of evidence indicates that magnesium may play an important role in preventing and managing disorders such as high blood pressure and diabetes. Good sources of magnesium include green vegetabes, nuts, seeds and unrefined whole grains.

    While there is some evidence that magnesium supplementation can improve muscle function, it is unclear whether the ergogenic effect of supplementation is attributable to a magnesium deficiency or to a pharmacological response. Nevertheless, I feel it is a good idea to use supplemental magnesium (e.g., 300 milligrams/day) during rigorous exercise program. Interestingly, magnesium supplementation may be effective in treatment of leg cramps. For example, Roffe and co-workers investigated whether magnesium citrate is effective in the treatment of leg cramps in individuals suffering regular cramps. In this study, magnesium citrate equivalent to 300 milligrams of magnesium and matching placebo (fake supplement) were given for 6 weeks each. The results indicated that significantly more subjects thought that the treatment had helped after magnesium than after placebo (78 and 25%, respectively), and this subjective impression was supported by cramp diaries.

    Chromium is a mineral that humans require in trace amounts. It is well-established that chromium enhances the action of insulin. It now appears that chromium is also directly involved in carbohydrate, fat and protein metabolism. In Chromium supplementation is of benefit only to inviduals showing signs of deficiency (e.g., decreased insulin sensitivity). Now, I'm not suggesting that supplemental chromium is largely waste of money. Quite to the contrary. A recent review by Anderson concluded, "Dietary intakes of [chromium] are often suboptimal, based upon the fact that there are numerous peer-reviwed studies documenting beneficial effects on insulin sensitivity, body composition, and related variables... Chromium is safe at all of the levels tested for oral intakes and therefore may be a safe and inexpensive aid to improve glucose and insulin metabolism and body composition." My recommendation is 50 to 100 mcg/day of supplemental chromium. Higher doses are likely waste of money.

    Zinc is an essential mineral that is found in almost every cell. It stimulates the activity of over 100 enzymes. Simply put, zinc supports normal growth and development. Good sources of zinc include beans, nuts, whole grains and dairy products. Zinc supplementation may be of some benefit for strength-power athletes. A recent study by Kaya and colleagues investigated how rigorous exercise affects thyroid hormones and testosterone levels in elite wrestlers who are supplemented with oral zinc sulfate (3 mg/kg/day) for 4 weeks. The resuls revealed that exercise led to a significant inhibition of both thyroid hormones and testosterone concentrations; however; zinc supplementation prevented these effects. Thus, zinc supplementation may have some favourable effects on hormonal adaptations.

References 1. Lukaski HC. Magnesium, zinc, and chromium nutriture and physical activity. Am J Clin Nutr. 2000 Aug;72(2 Suppl):585S-93S.
2. Antonio J, Stout JR. Phosphates and creatine. In: Supplements for Strength-Power Athletes. Champaign, IL: Human Kinetics, 2002, pp. 115-118.
3. Roffe C et al. Randomised, cross-over, placebo controlled trial of magnesium citrate in the treatment of chronic persistent leg cramps. Med Sci Monit. 2002 May;8(5):CR326-30.
4. Anderson RA. Chromium: roles in the regulation of lean body mass and body weight. In: Kohlstad I, ed. Scientific Evidence for Musculoskeletal, Bariatric, and Sports Nutrition. Boca Raton, FL: CRC Press, 2006, pp. 175-189.
5. Kilic M et al. The effect of exhaustion exercise on thyroid hormones and testosterone levels of elite athletes receiving oral zinc. Neuro Endocrinol Lett. 2006 Apr 25;27(1-2):247-252.