Evidence Level
Strong
Phosphorus is well-characterized biochemically but understudied as a supplement because deficiency is rare. The primary clinical research focuses on the dangers of excess phosphorus. Calvo and Uribarri (2013) highlighted that phosphorus food additives in processed foods add 250-1,000mg/day to dietary intake, and this "hidden phosphorus" is 90-100% absorbed compared to 40-60% from natural food sources. For athletic performance, a systematic review by Buck et al. (2013) found that sodium phosphate loading (50mg/kg/day for 3-6 days) may improve VO2max and endurance performance, though results are inconsistent across studies.