Phosphorus

Phosphorus is present in most foods and is especially plentiful in protein-rich foods (meat, poultry, fish, and dairy products) and cereal grains. It combines with calcium (about two parts calcium for every part phosphorus) to produce healthy bones and teeth. It also plays an important role in energy metabolism, affecting carbohydrate, fat, and protein. The energy derived for muscular work comes largely from phosphorus-containing compounds called adenosine triphosphate (ATP) and creatine phosphate (CP). As with calcium, the absorption of phosphorus is dependent on vitamin D, and the adult RDA is 700 milligrams per day.

Because phosphorus is so omnipresent in the food supply, phosphorus deficiencies are uncommon. If deficiencies occur, they are most likely to be seen in people on long-term antacids containing aluminum hydroxide. This type of antacid binds with phosphorus, making it unavailable for absorption. The adult UL for phosphorus is 4,000 milligrams per day, above which there may be interference with calcium absorption.

Phosphorus supplementation has been used for a long time to enhance physical activity. During World War I, Germany commonly provided its soldiers with high-phosphorus foods and supplements for the purpose of improving strength and endurance. This large-population experience with phosphorus suggests that large doses of phosphorus are relatively well tolerated over time. However, there is no direct evidence that strength and endurance were actually improved with this high intake. The results of more recent studies on the effect of phosphorus supplementation yield mixed results. Runners, rowers, and swimmers taking 2 grams of sodium dihydrogen phosphate 1 hour before exercise all experienced performance improvements, while only half the unsupplemented athletes showed improvements. Another study foundthat VO2max was improved on a treadmill test after short-term phosphorus supplementation. However, a study evaluating the effect of phosphate supplementation on muscular power observed no apparent benefit from taking the phosphate. The mixed results of these studies make it difficult to conclude that a preexercise supplement of phosphorus actually improves performance. Clearly, more well-designed studies are needed before an answer to this question can be attempted.