In a study using calcium pyruvate capsules, dosages of 7-25g pyruvate equivalence did not influence blood pyruvate levels nor did they influence whole body pyruvate levels. The lack of urinary pyruvate (less than 0.1%) indicated poor bioavailability. The authors hypothesized that either pyruvate is being lost in the feces, or is being decarboxylated in the stomach and intestines, although low fecal loss rates have been noted in humans.
Multiple studies have been conducted in persons with pyruvate for fat loss, although the most promising studies were done in the early 90s. When energy intake is restricted to 500kcal, weight loss is enhanced (6.5kg rather than 5.6kg) over a period of 21 days with 12g pyruvate. A lesser deficit, 1015kcal, also results in some weight loss, although the degree was lessened to about 0.4kg more than placebo, and very high dosages (22-44g) can induce some fat loss even near caloric maintenance, although the degree is minor (0.7kg versus 0.1kg loss over 6 weeks).
When dosed at 2g per day, pyruvate appears to be ineffective at changing parameter of body mass even in conjunction with an exercise program although it shows trends of fat loss. This may be a dose issue, as 6g pyruvate appears to be statistically significant, with 2.5kg fat loss rather than 1.2kg over a period of 6 weeks in otherwise healthy overweight persons.
It has been hypothesized that the mechanism is through preserving muscle glycogen by acting directly as a fuel source, and thus prolonging time to glycogen exhaustion.
Studies in humans using large amounts of pyruvate (100g of a Dihydroacetone:Pyruvate mixture in a 3:1 ratio) find increased time to exhaustion in exercises of muscular endurance. This dosage increased blood glucose extraction, which can reduce the rate of perceived exertion.
An oral dose of 7g dose not increased blood levels in trained athletes, nor does it increase performance on aerboic exercise.
One review notes that there do not appear to be any significant adverse effects noted with pyruvate supplementation, but that no long term studies are done in humans at this moment in time.
The most common side effect is gastrointestinal upset, which occurs with higher dosages. One study noted loose stools in 58% of the pyruvate group relative to 28% of the control group, which was significantly different. A pharmacodynamic study using 15-25g noted that all subjected complained of increased gurgling/rumbling (borborygmus) and flatulence.