Soy: The Untold Story

Ever since soy was unveiled as the big ‘wonder-food’ of the 90's the general consensus within many circles has been that eating soy foods has a range of benefits that would almost make it foolish for you NOT to include in your diet.

Super Soy?

Soy is a ‘complete protein’ which is low in saturated fat and cholesterol-free. Soy-foods contain EFA’s (essential fatty acids), dietary fiber and studies suggest soy can help to lower blood cholesterol, raise HDL cholesterol (the good one) and lower blood pressure. In lab studies, soy has also been shown to prevent the growth of some breast cancer cells (Ganry, 2002).

The Plot Thickens:

So ‘what’s the problem then’, you ask? Unfortunately, as is often the case when science is popularized by media, the true depth of the issue is lost in a reductionist attempt to make the topic more marketable to the masses. The reality is that in recent years, scientific evidence has begun to question the benefits of soy and brought to light possible adverse hormonal effects.

Possible Dangers of Soy (Summarized):

Reproductive Health - 

• The isoflavones in soy may lead to decreased fertility in males by lowering sperm concentration (Chavarro, Toth, Sadio & Hauser, 2008). 

• Increased intake of soy has been found to be associated with decreased testosterone levels in men (Dillingham, McVeigh, Lampe & Duncan, 2005). 

• In women, contradicting evidence exists on whether soy isoflavones prevent or stimulate the growth of certain estrogen-sensitive tumors (Messina, McCaskill-Stevens & Lampe, 2006). 

Other Adverse Effects - 

• A recent randomized controlled trial found soy was not effective in improving bone density in post-menopausal women - contradicting the claim that soy products prevent osteoperosis (Kenny, Mangano, Abourizk, Bruno, Anamani, Kleppinger, Walsh, Prestwood & Kerstetter, 2009). 

• The phytic acid in soy hingers the uptake of calcium, magnesium, copper, iron and zinc. 

• Soy contains phytoestrogens that interfere with the functioning of the thyroid. This may cause a range of issues including fatigue, low libido, cramping, depression, hair loss, dry skin and weight gain.

• The way in which soy is processed results in the formation of an unusual amino acid which is toxic. 

• Processed soy also containes nitrosamines, a chemical compound which is highly carcinogenic. 

To Eat or Not to Eat, That is the Question:

Currently, there is a lack of satisfactory clinical findings to support (unequivocally) the benefits of soy or warn against its wide use. I for one steer clear of soy, if only to avoid the ingestion of unnecessary phytoestrogens. However, I believe that like anything the consumption of soy should be subject to moderation. Ultimately -

SOY: SAVIOR OR SATAN

The decision is yours.


References:Ganry, O. (2002). Phytoestrogen and breast cancer prevention. European Journal of Cancer Prevention, 11(6), 519-522.
Chavarro, J.E., Toth, T.L., Sadio, S.M., Hauser, R. (2008). Soy food and isoflavone intake in relation to semen quality parameters among menfrom an infertility clinic. Human Reprocduction, 23(11), 2584-2590.
Dillingham, B.L., McVeigh, B.L., Lampe, J.W., Duncan, A.M. (2005). Soy protein isolates of varying isoflavone content exert minor effects on serum reproductive hormones in healthy young men. Journal of Nutrition, 135(3), 584–91.
Messina, M., McCaskill-Stevens, W., Lampe, J.W. (2006). Addressing the soy and breast cancer relationship: review, commentary, and workshop proceedings. Journal of the National Cancer Institute, 98(18):1275-84.

Weston A. Price Foundation (2006). Soy Alert.

Kenny, A.M., Mangano, K.M., Abourizk, R.H., Bruno, R.S., Anamani, D.E., Kleppinger, A., Walsh, S.J., Prestwood K.M., Kerstetter, J.E. (2009). Soy proteins and isoflavones affect bone mineral density in older women: a randomized controlled trial. American Journal of Clinical Nutrition, 90(1), 234-242.