So What’s the Deal with Soy?

18 10 2013

Soy-Bean-Safe-by-Flickr-kattebelletjeFor as long as I can remember, I’ve had a pretty negative image of soy in my head. I’ve heard that it can cause cancer. I’ve heard that it affects hormones in the body. I’ve heard that it can be detrimental to overall protein absorption. For these reasons, I’ve always kept a solid distance from any product containing soy: tofu, soy milk, miso soup; if it contained soy, I wasn’t interested. All because I’ve heard that soy is the devil, but without ever having looked into the matter. Well, I’ve finally looked into it, and this is what I’ve found…

What is soy?

Soy is derived from soybeans, a plant native to eastern Asia, where it was originally grown for use as a fertilizer. Although not introduced to North America until the 18th century, the US now produces roughly half of the world’s soy crops. Originally grown in the US as a source of animal feed, soy became part of the human diet in the early 1900s, mostly because there was a limit to the amount of soy that could be fed to animals (too much soy caused reproductive issues and other diseases in animals), so they started to market the excess soy as human food; sounds legit. Soy production began to boom during the industrial revolution as technologists experimented with cheap meat alternatives; it was marketed as a “health food” to mask its reputation as a cheap animal feed and the soy industry spent millions of dollars to establish the FDA’s cholesterol-lowering campaign. The crop really took off in the 1990s, especially when genetically modified beans were introduced; upwards of 90% of all soy beans are now genetically modified in some way or shape. This has made the export of US soy crops quite difficult, as most other countries have far stricter regulations on genetically modified foods.

From a nutrition point of view, soy contains roughly 42% protein, 35% carbohydrate (mostly fiber and slow-digesting starches) and 23% fat (mostly polyunsaturated). Soy protein is a complete protein, which is why it has been marketed as a great solution for non-meat eaters. The PDCAAS for soy (a measurement of protein quality) is just under 1.0, which is the highest score. Soy protein isolate has a score of 1.0, making it one of highest quality sources of protein. alongside animal sources.

Fermented vs. Nonfermented

Soy foods can be broken down into two categories: fermented and nonfermented. The fermentation process deactivates some of the anti-nutrients (toxic phytates, etc.) in soy that cause digestive distress and inhibit mineral and protein absorption; the highest-quality fermented soy products are also made with organic soybeans. Popular fermented foods include miso, tempeh, natto, tamari/soy sauce, and fermented versions of tofu and soy milk. Popular nonfermented soy foods include soy milk, tofu, soybean oil, edamame, and processed meat alternatives, supplements, drinks and snacks that contain soy protein isolate, soy protein concentrate, texturized vegetable protein, or other soy additives (soy lethicin is an extremely popular emulsifier and is found in an outrageous number of processed foods. Studies show mixed results, but packaging never indicates if the lecithin has come from a fermented or unfermented source. We have all ingested this product at one point or another, and at such low levels, I don’t imagine it can do much harm, but it’s just another reason to avoid processed food). These nonfermented soy products have been linked to digestive distress, immune system breakdown, reproductive issues, higher risk of heart disease and cancer, and a variety of other issues. Additionally, please do not feed your baby soy-based formulas, as high levels of this low-quality can drastically affect the sexual development and reproductive health of children.

Regarding fermented soy, these foods can be quite beneficial to overall health. Fermented soy products are high in vitamin K, which is one of the most difficult vitamins to get through food, and a vitamin that acts synergistically with vitamin D to help prevent osteoporosis, cardiovascular disease, and other health problems.

In a nutshell, fermented soy is healthy and high levels of unfermented soy is detrimental to overall health.

Makes you think...

Makes you think…

Does soy lower testosterone levels?

Soy contains phytoestrogens (such as isoflavones) which are a group of natural estrogen receptor modulators found in various foods; soy is the most potent food source. Now, when soy protein is extracted from the bean, most of these phytoestrogens are lost; the ones that are left however are similar to the estrogen hormone, estradiol, which can potentially affect our human hormones estrogen and testosterone. At low levels (ie, with unexcessive soy consumption), these phytoestrogens are quite unlikely to affect human hormones. However, at high levels, soy consumption has a far greater chance to affect our sex hormones. To back-up the statement that reasonable soy intake is unlikely to affect our sex hormones, there are several studies that demonstrate that soy protein acts much like any other source of protein when it comes to building lean muscle or improving athletic performance. If soy negatively affected testosterone levels, muscle synthesis and athletic performance would suffer. Unless you are crushing back veggie burgers topped with tofu and edamame on a daily basis, you can probably mix in a bit of soy protein every now and then without any detrimental effects.

On that note, it’s funny that soy gets hammered for its phytoestrogen content, but another staple in the North American diet- dairy- provides 60-80% of the estrogens in the human diet. Drinking milk every day is far more likely to affect sex hormones than moderate amounts of soy. Again, low amounts of these foods are unlikely to cause a problem, but it is interesting how some foods get a free pass and others get demonized.

NOTE: I still love dairy, but I rarely consume it anymore because of this issue. In my opinion, there are simply better products to consume.


Should I avoid soy?

Despite the muddy history and bad reputation, a little bit of soy in the diet appears to be harmless, and if you are only consuming fermented sources, it can likely benefit your health. However, excessive consumption of soy could very well lead to health issues. What is excessive? Consuming soy at every meal is definitely excessive. I’d go as far as to recommend limiting soy consumption to a few times a week, just to be safe; I’d definitely be wary of daily soy consumption. As I mentioned earlier, avoiding soy on a daily basis can be difficult for most people as it is a part of nearly all processed foods, but this is just another reason on the long list of why natural unprocessed food sources should make up the majority of the human diet.

In conclusion…

Soy is not the devil. As a matter of fact, fermented soy products can be quite beneficial. Even unfermented soy products don’t appear to be too harmful if consumption is low, so as usual, moderation and balance reign supreme; it’s all about avoiding the extreme. As a general rule of thumb, don’t fear fermented soy sources and do your best to avoid processed foods, as this is your best defense against harmful unfermented soy. After all my research, I’m not going to change my diet to include more soy, and I’m certainly not going to start using a soy protein supplement, but it’s nice to know which soy products can benefit my health and which soy products I should continue to avoid.

That’s it and that’s all for today- happy Friday!