Androstenedione (aka "Andro") is a steroid precursor that was available as an unregulated food supplement until the professional athletic steroid doping scandals popularized the subject. It naturally occurs and is ingested in meat products.
From the Wikipedia entry:
Androstenedione has been shown to increase serum testosterone levels over an eight-hour period in men when taken as a single oral dose of 300 mg per day, but a dose of 100 mg had no significant effect on serum testosterone. However, serum levels of estradiol increased following both the 100 mg and 300 mg doses. The study also reported that the serum level of estrogens and testosterone produced varied widely between individuals.[11] A 2006 review paper summarized several studies that examined the effect of androstenedione on strength training. At dosages of 50 mg or 100 mg per day, andro had no effect on muscle strength or size, or on body fat levels. One study used a daily dosage of 300 mg of androstenedione combined with several other supplements, and also found no increase in strength when compared to a control group that did not take the supplements. The review authors speculate that sufficiently high doses may indeed lead to increased muscle size and strength. However, due to the federal ban on androstenedione supplements, it is difficult to carry out new research on its positive and negative effects. The review authors conclude that individuals should not use androstenedione supplements due to the lack of evidence of beneficial effects, the wide variation in individual responses to the supplement, and the risk of unknown side-effects.[12]
