In the past, when a man was diagnosed as infertile, it was usually blamed on his wearing of too-tight jeans and underwear, or drinking too much coffee, or spending too much time in hot tubs. But now, new research is linking soy-based products to low sperm count. Can soy really have an affect on fertility? Keep reading for more information on this recent scientific development.

As an inexpensive source of protein, soy-based products have risen steadily in western diet popularity since the 1940s and soy is now included in many products, including sweets, pastas, and bread. However, a study that closely followed a hundred men who ate soy has revealed that the men that ate more than two portions of soy-based foods a week had, on average, 41 million fewer sperm per milliliter of semen than men who had never eaten soy foods.

This reduction in sperm count is unlikely to make healthy men infertile, but some experts said it could have a significant impact on men who already have a lower than average sperm count. A sperm count of 80 million to 120 million per milliliter is considered normal, while men who produce fewer than 20 million sperm per milliliter are regarded as clinically infertile.

The study, by Dr. Jorge Chavarro at the Harvard School of Public Health, builds on research in animals and on human tissues that suggested certain ingredients in soy could harm sperm production. Dr Chavarro and colleagues at Massachusetts General Hospital recruited 100 men who had visited a fertility clinic between the years 2000 and 2006. They were requested to fill out a survey that asked them about the amounts of 15 different soy foods they had eaten over the previous three months. The researchers then divided the men into four groups according to the levels of chemicals called isoflavones (ingredients in soy products that mimic the female sex hormone, estrogen) in their diets.

The results found that men who consumed at least half a portion of soy food a day had the lowest sperm count, leading researchers to conclude that the greater the soy food intake, the lower the sperm concentration, compared with men who never consume soy food at all.

Given this recent research, if you are a man trying to start a family it might be a good idea to consult with your doctor or healthcare provider about your soy intake.