Many people approach soy protein with trepidation. They have heard that

• It is dangerous for women with history o breast cancer or with family history of breast cancer
• Men can develop gynecomastia – ‘man boobs’
• Those with thyroid deficiency cannot take soy protein.

 

So let us examine the evidence.

We’ll take the subject of breast cancer first.

There are several studies which show that soy protein is actually protective against breast cancer.

This study found that   Intake of protein containing soy was associated with reduced breast cancer risk . The researchers also found an inverse association between total tofu intake and breast cancer risk among premenopausal women and they concluded that increased regular soy food intake at a level equivalent to traditional Korean consumption levels may be associated with a reduced risk of breast cancer, and this effect is more pronounced in premenopausal women.

In another study, researchers found that soy protein may protect against the development of a more aggressive breast carcinoma.

This study concluded that Isoflavones (phytoestrogens) also possess nonhormonal properties that are associated with reducing cancer cell growth. Thus, there are several possible mechanisms by which soy may reduce the risk of breast cancer.

Yet another study resulted in the conclusion that the existing data should provide some degree of assurance that isoflavone exposure at levels consistent with historical Asian soyfood intake does not result in adverse stimulatory effects on breast tissue.

This study did not show that the adult consumption of soy affects the risk of developing breast cancer or that soy consumption affects the survival of breast cancer patients. Consequently, if breast cancer patients enjoy soy products, it seems reasonable for them to continue to use them.

Now let us determine why this may be so. In other words, where is the conflict?

Soy contains phytoestrogens (plant estrogens) and it is erroneously believed that this can fuel the growth of breast cancer cells. In reality, not all, about 80% of breast cancers respond to the hormone estrogen.This means, 20% don’t even respond to estrogen.

So how is soy protective against breast cancer? It is because the phytoestrogens in soy are weak estrogens compared to the native estrogen in the body. These weak estrogens occupy the estrogen receptors – docking sites – on the cells, blocking the action of the stronger estrogen produced by the body. This means it is like wearing a bulletproof vest, protecting against estrogen ‘bullets’.

 

Gynecomastia – the same argument applies.

 

Thyroid :

This review evaluated 14 studies and concluded that the findings provided little evidence that in normal individuals, soy foods, or isoflavones adversely affect thyroid function   In individuals with compromised thyroid function and/or whose iodine intake is marginal, soy foods may increase risk of developing clinical hypothyroidism. Therefore, it is important for soy food consumers to make sure their intake of iodine is adequate. However, hypothyroid adults need not avoid soy foods.

 

There are other benefits to soy protein:

• It is the only complete protein of vegetable origin.
• This study showed that consumption of soy protein is associated with a lower risk of cardiovascular disease.
• Another study revealed that there is convincing evidence that soybean products have beneficial effects on cardiovascular disease risk factors.
• This study showed that dietary soy protein can lower plasma levels of lipid and improve kidney function in type II diabetes with nephropathy.
• A soy protein diet for 5 weeks improves endothelial (lining of blood vessels) function in renal transplant patients.
• A lower rate of prostate cancer developed in the groups of men given soy compared to the milk casein group.
• Modest amounts of soy consumed during childhood and/or adolescence reduces breast cancer risk. Evidence also suggests that soy reduces prostate cancer risk and inhibits prostate tumor metastasis. Soy protein is reduces cholesterol and lower risk of coronary heart disease. In regard to bone health, soy intake is associated with marked reductions in fracture risk. Soybean isoflavones also modestly alleviate hot flashes in menopausal women. Finally, other than allergic reactions, there is almost no credible evidence to suggest traditional soyfoods exert any harmful effects in healthy individuals when consumed in amounts consistent with Asian intake.

It is quite understandable that, when advised against the use of soy by your health professional, doubts may arise.  However the evidence clearly refutes this belief and one would advise that you take your decision based on credible, recent research. Your body is yours. Not anyone else’s, certainly not your doctor’s. .

 

Now about quality. Are all soy protein powders available in the market equal? Sadly, no. Look for a quality product using quality, certified organic ingredients with high protein content and low carbohydrate content, from a trusted source, for best results.

 

Finally, is soy or whey protein better?

As we have seen, soy is the only complete vegetarian protein. Soy is therefore added to whey to make it complete. Muscle building requires branched chain amino acids found in whey so if that is a priority, go for whey with soy. For all others, either one is good enough.