Soya does not cause breast growth in men
To claim that soya milk can result in men growing breasts is a scaremongering story which has appeared online recently. The Japanese and Chinese populations, who traditionally consume high levels of soya foods daily, do not show evidence of hormonal problems.
There have been several studies that have examined the impact of heavy consumption (up to a litre a day) of soya milk on young and older men. And these studies have all shown that there are no significant hormonal changes as a result of men consuming soya milk and there is no link between soya milk and breast growth in men.
In 2009 a meta-analysis* covering the results from 32 trials found no effect from isoflavones (approximately 125mg a day or around 950mls of soya milk) on male reproductive hormones after one year regardless of age. In fact studies investigating populations who traditionally eat soya foods have found that men who eat more soya foods have a lower incidence of prostate cancer compared to those that eat less and they haven’t started growing breasts.
Soya milk does not contain estrogens. It contains natural plant compounds called isoflavones. These have a chemical structure similar to estrogen but are far weaker than the actual hormone. In fact it is has been estimated that between 1000 and 400,000 more isoflavones would be needed in the human body to have the same biological effect as estrogen. Furthermore, the majority of human studies investigating the effects of isoflavones on hormone levels show no effects.
*Hamilton-Reeves JM, Vazquez G, Duval SJ, Phipps WR, Kurzer MS, Messina MJ. Clinical studies show no effects of soy protein or isoflavones on reproductive hormones in men: results of a meta-analysis. Fertil Steril 2009, April 17
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