Soy foods and fertility
Published by Bronwyn Schweigerdt on June 18, 2009 at 3:30 AMI promise this will be the last blog post on soy foods for a long time. Even though I am a strong advocate of a plant-based diet (vegetarian or vegan), I don't believe soy foods are any more essential to such a diet than garbanzo beans. I'm not saying soy foods aren't great - garbanzo beans are great too - they're just not the focus of this blog. A healthy plant-based diet is possible with or without soy foods.
However, there is some confusion regarding soy foods and fertility. Because soy is loaded with isoflavones (plant-estrogens that can mimic estrogen), it is believed to affect the likelihood of pregnancy. Some studies have shown soy estrogens have no impact whatsoever on a woman trying to conceive, as soy foods do not interfere with menstrual cycles or ovarian function.
This makes sense because soy estrogens (along with other plant-estrogens) only raise estrogen levels when they are low. This also makes sense when we look at Asian women, who consume more soy foods than any other people group and yet have an extremely low prevalence of infertility. So low in fact, certain Asian countries have to put limits on population growth. (Obviously, soy is not hindering fertility in China).
There is a recent study (July 2008) that has linked soy foods with a decreased sperm count in men (published in the Journal of Human Reproduction). However, they found that men who were overweight or obese experienced a significantly lower sperm count than men who had healthy weights. One of the reasons for this is because fat cells, even in men, produce estrogen, which can hinder sperm production in men. Considering that 72% percent of the men with decreased sperm counts were overweight or obese, I would say this seems to be more of an impediment to fertility than soy consumption.
On a personal note, my husband and I both consumed tofu pretty regularly before we had our daughter, and we had no problem getting pregnant. (That was also when my husband was in the best shape of his life!)
So I would conclude that a healthy weight in men is more important than soy intake. And a plant-based diet - with or without soy - is the best fertility diet.
Labels: fertility, soy estrogens
4 comments:
Hi Bronwyn,
This is totally unrelated to soy but I was at a health book club and the topic of B-12 came up and how to get this if you have a vegan diet. Could you chat with me about how to avoid a deficiency in this, are supplements enough? Where can I get it in vegan foods? Thank you for your help!
Hi Jennifer!
Most vegans get plenty of B-12 through their soy (or almond or rice) milk, since they're fortified with B-12. Also, many cereals are fortified with B-12.
B-12 deficiency is rare even in vegans, since the flora in our intestines produces some and the liver can store up to 5 years' worth of it. The greatest population at risk for deficiency is in pregnant and nursing women who are vegans, who definately should have fortified foods or a supplement.
Thanks for this post. I'm happy to hear the news! :)
Around 30 years ago, word was going around that changing to a vegetarian diet would promote fertility... also, that royal jelly would aid conception (all those baby bees, you know) -- I've heard this from several people who credit rj for their pregnancies.
Regarding B12, after 30+ years as a healthy vegetarian, I seemed to be in a fog. I found an excellent liquid methylcobalamin B12, resurfaced to clarity almost immediately. Now I take it once or twice a week, as I feel the need. Aging may be more of a factor than my diet in developing a need for supplemental B12.