How do we feel about soy?

Soy. People consume it in tofu, veggie burgers, milk, processed foods, candy, imitation lunch meats, imitation cheeses, imitation butters, imitation eggs, etamame, tempeh, and many more cultural and vege-cultural staples. It is the component of much related to protein in the vegetarian and vegan worlds. Soy is the legume of the modern era. It came out of East Asia, loved by residents of Portland and Boulder, and can produce pretty much the most protein per acre compared to any other veggie. The American Midwest is absolutely covered by it. We actually grow more of it than the stereotypical tofu-eaters the Chinese. It comprised 77.5 million acres of the US in 2009. Americans eat a lot of soy. It’s hard to pick up anything in the middle aisle of an American grocery store without the word “soy” in at least one of the ingredients. It’s abundant, it’s got subsidies, and it’s cheap as a result.

The main concern with soy usually centers around how it affects hormones. On a molecular level, the isoflavones that are found in soy pretend like they are estrogen and can block the real estrogen that your body makes from reaching your receptors which tell the nervous system what to do. A good biological Q & A that goes into more detail can be found here.

So, what’s the science? Let’s take a look.

Soy is really not that okay–
Soy proponents are quick to tell you that it prevents breast cancer or other cancers, especially when it is consumed in the early human years of life, and that some cancers associated with estrogen have not been shown to be aggregated by soy. It has also been shown to kill cancer cells.

Science is not about drawing opinions from individual studies. It is about careful, empirical studies as well as the aggregation of such studies and their comparison to one another. There are so many studies on soy that there are several meta-analyses (aka M-A, or studies of groups of studies trying to find patterns and draw conclusions from aggregate scientific data). These don’t seem so promising for the soy industry or for those that swear that high levels of soy will lead to a better life. One M-A states,

“Our study suggests soy isoflavones intake is associated with a significant reduced risk of breast cancer incidence in Asian populations, but not in Western populations. Further studies are warranted to confirm the finding of an inverse association of soy consumption with risk of breast cancer recurrence.”

Essentially, they are saying that for some reasons these studies are showing that Asian women have reduced breast cancer risk from these soy studies but not Americans, and that we need more information before we can draw any conclusion (read: before we can go around telling everyone to eat more soy). Another M-A from 2009 focusing on breast cancer delivered the conclusion that,

“The findings of the M-A were not deemed credible because of deficient information regarding the target population and outcome variable, lack of confounder control, unclear inclusion and exclusion criteria of the sample, and invalid methods of data abstraction. Because the findings were not credible, they were deemed not to be clinically applicable. Therefore, a high soy diet would not necessarily be recommended.”

…which is just medical-talk for this was inconclusive; don’t go around telling everyone to eat tons of soy.

Walking away from this, what would a vegetarian have to think? Not much. We need to know more. In the meantime, when practicing a vegetarian diet, soy should be taken in moderation, and other proteins given precedent–likely legumes, seeds, and nuts. When in doubt, add some fat to keep you full. Personally, after reading all of these studies, I don’t see eating soy an issue. I see eating a ton of soy an issue–call it the precautionary principle that anti-GMO/Organic food advocates love so much.

The science here isn’t going to change anyone’s mind–just going to have them scratch it. The paleos hate it, the vegans love it. I’ll keep eating my tofu curry and stir fry here and there. May it be so.

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