Sodium Phosphate
A phosphate salt loaded over several days to raise phosphate availability, proposed to enhance oxygen delivery and aerobic capacity. Trials are mixed but lean toward small improvements in VO2max and endurance. Evidence is older and less consistent than for creatine or bicarbonate.
01 Overview
Sodium phosphate loading aims to increase erythrocyte 2,3-diphosphoglycerate (2,3-DPG), which shifts the oxygen-haemoglobin dissociation curve to favour oxygen release to tissues, and to support high-energy phosphate metabolism.
Studies from the 1980s onward report improvements in VO2max, ventilatory threshold and time-trial performance, but the literature is heterogeneous, with several null results and methodological limitations. It sits mid-range: a plausible mechanism and some supportive trials, short of the consistency seen with the best-established ergogenic aids.
02 Mechanism
Loading raises phosphate availability, proposed to increase erythrocyte 2,3-DPG (enhancing tissue oxygen offloading), buffer capacity and myocardial/high-energy phosphate metabolism.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Loading | 3–4 g/day | Oral | ~1 g four times daily for 3-6 days before competition; split to limit GI upset. |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Improved aerobic capacitySeveral trials report improved VO2max and endurance after loading, though results are inconsistent across studies. | Small VO2max/endurance gains | Disputed |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Gastrointestinal upsetNausea, cramping or diarrhoea during loading. | Mild | Frequent | Observational | |
| Electrolyte/mineral disturbanceHigh phosphate intake can disturb calcium-phosphate balance and burden the kidneys, a concern with renal impairment. | Moderate | Rare | Observational |