Hard facts on a common bean

The impact of soy-based foods on fertility

Soy-based food products, like soy milk and tofu, are often considered a healthy alternative to meat and dairy. However, numerous scientific studies have shown that soy can actually cause unwanted side effects and more alarmingly, negatively impact fertility.

The main reason why soy is bad for fertility is that it contains phytoestrogens. This plant-based chemical mimics estrogen and disrupts the body’s endocrine function.  Although few people realise the dangers of soy, this knowledge is not exactly new. Scientists have known about the ill-effects of soy since at least the early 1990s.

A study conducted in 1992 by the Swiss Health Service estimated that drinking two cups of soy milk per day has the same effect as taking one birth control pill. Then, a study published in 2000 by the Departments of Preventive Medicine and Obstetrics and Gynecology, University of Southern California, Los Angeles, USA found that soy decreases luteal estrogen levels and lengthens menstrual cycles.

Meanwhile, a 2005 study conducted by researchers at the National Institute of Environmental Health Sciences, North Carolina, USA found that soy causes miscarriage and infertility in mice. Another study, conducted by the Harvard Public School of Health in 2008, found that men who drank one cup of soy milk per day had a 50% lower sperm count than men who didn’t take soy.

Because soy has been proven to cause abnormal menstrual cycles, altered ovarian function, early reproductive deterioration and subfertility/infertility, it is considered particularly harmful for women and men who are trying to conceive. Women who are pregnant or breastfeeding and infants are also discouraged from consuming soy-based products.

But even if you rarely eat tofu or drink soy milk, you’re not completely out of the woods. In fact, you may be consuming soy in other forms. These days, many processed and refined foods contain soybean oil, soy flour, soy lecithin or soy protein. Therefore, you may not know that you’re actually eating soy-based foods as they’re hidden away in the ingredients list.

It is important to note, however, that traditional fermented soy products, like miso and tempeh, may be beneficial to health. But the high intake of processed soy has a less desirable effect on health. Therefore, if you’re trying to get pregnant, it is best for both you and your partner to exclude soy from your diets. If you have any doubts or questions, as always, be sure to consult with your fertility consultant.