Being a Soy Boy Won’t Make You a Girlie Man


According to the sales data from Soyfoods Association of North America, between the years 1996 and 2009, soy food sales have increased from $1billion to $4.5 billion in North America. (See Similar trends have been seen in Europe as well.

This increase is attributed to the many new and delicious soy foods that have hit the marketplace to meet the demands of the rising numbers of vegetarian and vegan consumers. (There was also dramatic growth in the soy market after FDA approval of a health claim linking soy to heart disease reduction.) Included in these new soy foods are many different forms of soy protein powders taken by athletes, as well as soy versions of meat and cheese alternatives. As one might expect, there has been a backlash against soy products, and there has been much rhetoric slung about soy, in as vigorous a manner as a dirty political campaign on the eve of election.

But what could they say against soy? The USDA has even stated that “Soy protein products can be good substitutes for animal products because…soy offers a ‘complete’ protein profile…Soy protein products can replace animal-based foods - which also have complete proteins but tend to contain more fat, especially saturated fat - without requiring major adjustments elsewhere in the diet.” (FDA Consumer, May 2000)

Much of the rhetoric against soy has focused on the fact that soy is known for having isoflavones that mimic human estrogen in the body (called phyto-estrogen). But wait, this was always considered a good thing.

Low breast, prostate and reproductive organ cancer rates among Asian women and men (who have historically consumed more soy than any other culture in the world) have long been attributed to these isoflavones.

What the mudslingers were counting on is that consumers wouldn’t look into it any further and learn how isoflavones work to prevent cancer. The way the isoflavones work is to attach themselves to estrogen receptors in the human body and actually keep estrogen levels low. But now, there is suddenly rhetoric that isoflavones “flood the body with phyto-estrogen” and the misleading conclusion that it turns men into little girls. It has been a successful negative campaign causing soy sales to drop dramatically in the past 2 years.

One of the best articles on this debacle comes from The American Society of Reproductive Medicine. The ASRM hosts a highly respected medical journal called “Ferility and Sterility”. Recently, they published an article by Mark Messina, PhD, in which he reviewed numerous studies that have been done on soybean isoflavone exposure and whether it has a feminizing effect on men.

Messina discovered a few important things when he looked at these studies. First of all, many of the studies claiming adverse effects of soy were conducted on rats. This data was found to not translate to humans when clinical studies were conducted. There was no evidence from the nine different human clinical studies that isoflavone exposure affects circulating estrogen levels in men. The human clinical evidence also indicates that isoflavones have no effect on sperm or semen parameters. The conclusion is that isoflavones do not exert any feminizing effects on men, even at intake levels equal to and even considerably higher than, what is typical for Asian consumers.

The lesson of this story is that if rhetoric suddenly arises that contradicts long held knowledge from ancient cultures (such as Japanese and Chinese Medicine,) we should take a step back and access the science before we believe everything we hear.

See Messina, M., Fertility and Sterility, Vol 93, Issue 7, Pgs. 2095-2104, 1 May 2010.


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