Tuesday, July 27, 2010

The soy dilemma

At the turn of the century, soy protein was touted as a miracle answer to our protein needs. We could now safely, easily, and conveniently eat all the meat-like product we wanted without ever touching meat. We could even add it to meat products to bulk them up and change the texture. In fact, soy was amazing. It had anti-cancer, anti-inflammatory, and antioxidant properties.

Then, the EVILS of soy were revealed. It is PLANT ESTROGEN. It will give you breast cancer whether you're a boy or a girl. It can turn males into females. I even found this link that claims eating soy can turn male babies homosexual. Suddenly, the wonderfood was the #1 enemy.

So, what is the deal? Well, soy protein is an excellent source of protein for those who choose not to imbibe in meat (can you 'imbibe in meat'. Well, I think you can, so you can!). You should be aware that, with the protein, you get small amounts of isoflavones (a type of small molecule) that act as estrogen (a sex hormone important to development) in our bodies. These are termed 'estrogen mimics' because they aren't actually estrogen, but they can bind estrogen receptors. So, this is estradiol, the active form of estrogen:

And here are the soy isoflavones: Genistein and Daidzein

See how your body could mistake one for the other? I think it's possible.

What do these molecules do? Well, in low doses these can act as antioxidants, anti-inflammatories, and yes, anti-cancers. In 1999, it was recommended that people eat 25 g of soy protein daily to reduce their cholesterol, and they are particularly helpful in male cancers related to testosterone, namely prostate.

However, in larger doses, these can be detrimental to our health. They start to interfere with proper hormonal signalling, and they can lead to hormone-related cancers, usually female breast and reproductive cancers, and sexual dismorphia in males and females. So, the recommended dosage was dropped to 15 g/day and isoflavones less than 100 mg/day. A good review is available here.

At first, I was really skeptical of the data. I mean, the animal studies used a lot of protein every day. It was the equivalent of a 150 lb person eating 48 grams of soy protein everyday. Which is a lot, right? But then I started thinking about how much soy has infiltrated our food chain, and I reconsidered.
 First of all, these isoflavones are not just in soy. They are in quite a few plants in low levels. For instance, they are high in coffee beans as well, and roasted, brewed coffee can have as much as 0.3 mg per 8 oz cup. Cocoa beans have them as well, and they are high in chocolate.

Second, these are fat soluble molecules, meaning that they are swimming in the soybean oil that is used heavily in industrial cooking. Maybe you don't use soybean oil at home, but if you buy processed foods, it can be in there.

Third, soy protein is in a lot of things that you don't think soy protein would be in. Frozen pizza, even Kashi or Amy's, often bulk up their crust with textured soy protein. Cereals have it. Packaged dinners. It's only recently become common to see labels on packaged goods stating the product 'contains soy' or is 'soy free'. How about your healthy granola or protein bars? Do you eat Clif bars or Luna bars? They contain 8-15g of protein, with a considerable amount coming from soy.

So, this can really add up in your diet. Let's just look at three example days and see how much soy protein can add up. Also, consider that there will be small amounts of isoflavones in many vegetables and fruits that I can't account for in these examples.

So, you eat an on-the-go breakfast, a packaged lunch, and some prepared french fries from your freezer for dinner, and you're already over the 15 g of soy protein and 100 mg of isoflavones for the day.

While I totally agree that protein supplemented cereals are the way to go, and I obviously have a love affair with Kashi Go-Lean Crunch, you should be aware that these are often supplemented with soy protein. Why? It's super shelf stable! Finally, while this day was a little extreme in terms of protein intake, a packaged lunch and dinner at a Chinese restaurant aren't really that strange for many people. How about you?

Ok, I chose this particular set of meals because, if you read the blog, you know I eat these meals. I mean, if I'm super busy, fruit & latte are a go-to. If I have a long day, a veggie burger sounds amazing. I don't always eat all of these things on the same day, but I could.

For the record, I used the 3 mg of isoflavones/g of soy protein conversion that is considered low by the USDA.

Ok, so hopefully I've given you some food for thought. I certainly am going to be more careful about my soy protein and soy product consumption, and I would encourage you to do the same.


  1. Do Asian diets consisting of higher plant based materials and specifically soy based products (e.g. Tofo & Tempeh) have higher incedences of reproductive cancers, as well.

  2. No, which is why I think the high use of soy protein and soy oil is linked to the reprodutive cancers in the USA and western nations. I think it also comes down to volume. Eating plant based protein like tofu and tempeh feels like eating a meal. You can stuff an entire brick of tofu worth of protein into a 2-400 calorie protein bar. That is deceptive to your body. You can eat more, and many times you do.