Recently patients have been asking me about long this study which was based on research at The Harvard School of Public Health and published in the journal Human Reproduction. It seems to suggest that men* who eat a lot of soy are more likely to have a low sperm count. It also showed that overweight men were the most likely to be affected by soy consumption.
The researchers point out that their findings are preliminary and it is too early to say why soy has this effect. However, they think that the likely culprits are the phytoestrogens that soy contains. We already know that overweight men* have higher estrogen levels which is presumably why they are more affected by the phytoestrogens in soy.
At The Yinova Center, we suggest limiting soy to two servings a week when it comes to improving sperm count. We also suggest switching to fermented soy products, such as miso, tempeh, natto, or tamari, which seem to be more beneficial. This is because soy contains phytic acid which can block the absorption of some minerals. Phytic acid is neutralized during the process of fermentation. Consuming fermented soy is also good for digestion because it recolonizes the friendly bacteria in the large intestine.
* Language used in the study referenced.