Soy Does Not Affect Fertility, U of G Study Finds

Soy Does Not Affect Fertility, U of G Study Finds

Guelph – Men no longer have to fear that eating soy-based foods will jeopardize their chances at fatherhood.

A new University of Guelph study has revealed that contrary to a widely-held perception, consuming soy does not harm male fertility.

Soy contains isoflavones, which function similarly to estrogens in the body.

“It is perceived that soy can increase estrogen levels, which is why there is a concern that it will have an adverse effect on male fertility,” said Alison Duncan, the study’s author and a professor in Guelph’s Department of Human Health and Nutritional Sciences.

“But we found that consuming soy on a regular basis had no effect on semen quality, which is a direct measure of fertility.”

Published recently in the American Society for Reproductive Medicine’s official journal Fertility and Sterility, the study is the largest to look at the impact of soy consumption on male fertility.

As part of the research, participants were asked to drink a soy protein beverage high in isoflavones, a soy protein beverage low in isoflavones and a milk protein beverage each for 57 days each. There was a four-week break between participants switching drinks.

Duncan found the participants’ semen volume, sperm count, sperm motility and sperm morphology remained the same throughout.

Although previous studies on animals have shown soy consumption to have adverse effects on fertility, the current study reveals that this does not apply to humans, she said.

“These findings are important because soy consumption has many benefits for men such as reducing the risk of cardiovascular disease and prostate cancer.”

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The soy Asians really eat?

In my non-expert opinion there is a lot of intentional and unintentional anti-soy hysteria. Asians have been eating soy for centuries. A frequent counterpoint made by anti-soy fear mongers is that Asians don’t really use that much soy.

A while back I found a good article debunking much of this counterpoint.

Today, I found a new article by author Virginia Messina R.D. debunking this counterpoint and from a different perspective:

The confusion about how much soy Asians consume is based partly on a simple mathematical misunderstanding. In studies of intake, findings are sometimes expressed as the amount of soy protein that people consume—which is different from the total amount of soy food in their diets. For example, according to surveys in Japan, older adults consume around 10 grams of soy protein per day, which is the amount of protein in about 1 to 1 ½ servings of traditional soyfoods. Because a number of authors have misunderstood the relationship between soy protein and soyfood, they’ve greatly underestimated the amount of soy in Japanese diets.

One question I always ask is “how do you know what Asian’s eat?”. Seriously, China alone has about a billion people. Do Americans eat a lot of potatoes? Yes, many Americans do, but a large number of Americans probably never touch the things. The population of the U.S. is about 300 million people. Asia consists of a large number of countries, cultures and people. They aren’t all going to be the same,so I am suspicious of the “Asians don’t eat a lot of soy” point:

The results show a fairly wide range of intake among different countries and even within populations. While average Japanese intake is 1 to 1 ½ servings, the surveys reveal that the upper range among older Japanese—who would be expected to eat a more traditional diet—is about 3 servings of soyfoods per day.

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Soy & Hypothyroidism

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Interesting news from those pro-vegan hippies at the Mayo Clinic:

Is it true that people who have hypothyroidism should avoid soy?

Answer from Todd B. Nippoldt, M.D.

Hypothyroidism is generally treated with synthetic thyroid hormone — and soy has long been thought to interfere with the body’s ability to absorb the medication. However, there’s no evidence that people who have hypothyroidism should avoid soy completely.

If you have hypothyroidism, take thyroid hormone replacement as directed by your doctor — typically on an empty stomach. Generally, it’s best to wait four hours after taking thyroid medication to consume any products that contain soy. The same guidelines apply to other products that may impair the body’s ability to absorb thyroid medication, including high-fiber foods, iron and calcium supplements, and antacids that contain aluminum or magnesium.