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The Truth About Soy

Soy comes from soybeans. A staple of Asian fare, this little bean is used to make a variety of foods from miso soup to textured vegetable protein. The soybean is unique in many ways. It is the only plant that contains high-quality protein. Soybeans have isoflavones, which are plant-like estrogens that produce health benefits.   

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What are the health benefits of soy? 

  • Decreases menopausal symptoms.
  • Lowers total cholesterol and LDL cholesterol (the bad kind) levels. 
  • Regulates blood sugar levels. 
  • Used as a substitute for animal protein.
  • Is lactose-free and dairy-free. 
  • May enhance kidney function in diabetics.

Can soy stop cancer? 

For a few decades now, research has focused on the connection between soy and cancer. Considerable evidence from population studies suggests that soy offers protection against several kinds of cancer, including breast, prostate, uterine, endometrial, and colorectal cancers.

While the observed cancer protection benefits may be a result of a mixture of dietary and lifestyle factors in certain populations, research clearly indicates that soy foods have promising anticancer potential for established cancers. Most studies have focused on the isoflavone called genistein. In test tubes, genistein halted the growth of human prostate, breast, squamous cell, and bladder cancers. Additionally, human leukemia cells stopped growing when they were treated with a genistein complex. 

Animal studies using soy have produced favorable results as well. Genistein has slowed the growth of melanoma and bladder cancer in laboratory animals. Other cancer-fighting benefits have been linked to genistein. The metastatic properties of cancer cells have decreased with administration of genistein, which has the ability to blunt new blood vessel growth. Genistein has enhanced the effectiveness of Cisplatin and Vincristine treatments on pediatric brain cancers.

What about cancer that is hormone dependent? 

Soy’s impact on hormonally fueled cancer cells has been contradictory and one of the most controversial subjects in oncology and nutrition. This is understandable since estrogens can promote cancer growth, so it would make sense to think that phytoestrogens found in soy might promote growth as well. However, this is very outdated information stemming from rodent studies. Turns out, we metabolize soy differently than mice. In fact, researchers suggest that we would need to eat 58 cups of soybeans per day in order to activate a hormone-driven process. (Am J Clin Nutr, Nov 2011) From this and other findings, we know that large amount of genistein (one of the compounds found in soy) may act more like a human estrogen.

Researchers have found there are two different types of estrogen receptors in the body, alpha and beta. In humans, soy phytoestrogens have an affinity to the beta receptor, creating an anti-estrogenic, protective effect that inhibits the growth of estrogen-fueled cancer cells. (Cancer Res, Jan 2004) One of my favorite analogies of how soy phytoestrogens block estrogen involves a cruise ship. Cruise ships are huge (human estrogen) and go into port at night. But, if the port is blocked by a small sail boat (phytoestrogens), the cruise ship is blocked from entering. In this way, phytoestrogens keep estrogen in the blood from entering receptor sites. We can ensure plant estrogens act like sail boats and not big cruise ships by avoiding concentrated genistein and consuming whole soybean foods. Soy isoflavone powders or pills contain high doses of genistein and daidzein and should be avoided.  

A compilation of research over the last two decades has prompted the American Cancer Society to issue a statement that soy foods are beneficial for cancer survivors. (CA Cancer J Clinical, Jul-Aug 2012) Soy isoflavone powders or pills that contain high doses of genistein and daidzein, however, should be avoided because the plant chemical profile is too concentrated. 

So, there you have it. Soy is good. Isolated soy may not be good. Eat non-GMO whole soy foods for your best protection.

Hungry for some soy?

Moderate consumption, according to the AICR, is 1-2 servings daily of whole soy foods. Your best choices include:

  • Edamame
  • Whole soybeans
  • Miso
  • Soymilk
  • Tofu
  • Tempeh
    Roasted soy nuts

Not soy adventurous or looking for a quick soy fix? If you love smoothies, you will appreciate a whole soybean powder drink mix that is pure, has loads of other health-promoting ingredients, and tastes soy good! Learn more here.

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