Oy, Soy--Should You Eat It?

Soy’s meteoric rise began in 1999, when the Food and Drug Administration (FDA) authorized the use of health claims by food manufacturers about the role of soy protein in reducing the risk of coronary heart disease.  Within months the Nutritional Committee of the American Heart Association (AHA) followed suit, officially recommending dietary soy protein containing isoflavones for high-risk populations with elevated LDL and total cholesterol.

But just six years later the AHA’s Nutritional Committee reversed its position, stating the average effect of soy isoflavones on LDL cholesterol and other lipid and heart risk factors is “nil,” After examining reports of soy’s effects on heart disease, cancer and menopause, the AHA concluded, “…earlier research indicating that soy protein has clinically important favorable effects as compared with other proteins has not been confirmed.”

If you are confused, you are not alone.  Although the AHA reversed its position, the FDA continues to approve soy’s ‘heart-healthy’ claims, resulting in mixed messages to the public.

Certain properties render soy protein isolates and isoflavones unsuitable for human consumption. These properties are so well recognized that attempts by food manufacturers to persuade the Food and Drug Administration (FDA) to accept soy protein isolates or soy isoflavones in its “Generally Recognized As Safe” (GRAS) foods list have failed.

Soy binds minerals.  The American Academy of Pediatrics (AAP) reports the very high phytate content of soy binds iron and zinc, making them unavailable to infants. (Phytate is a plant substance that binds certain minerals making them unavailable.)  Modern soy formulas are mineral-fortified to prevent this.  The AAP also reports modern soy formulas contain 9 to 325 times as much aluminum, a common byproduct of soy processing, as in human milk.  The AAP cautions against soy protein-based formula for preterm infants, as aluminum’s competition with calcium causes brittle bones.  Of note, aluminum is also linked to adult neurological diseases, such as Alzheimer’s.

Two recent studies link tofu to accelerated brain aging in adults.  In year 2000 a Hawaii study found, “Poor cognitive test performance, enlargement of ventricles and low brain weight were each significantly and independently associated with higher midlife tofu consumption.” In June this year, a Loughborough University-led study of 719 aging Indonesians reported similar results. Animal studies support findings that soy foods can rapidly age the brain.

Soy is promoted as enhancing bone health. Yet the AAP’s 2006 policy statement, “Optimizing Bone Health and Calcium Intakes in Children and Adolescents,” points out: “calcium in soy products has low bioavailability.” So, as with infants, it is difficult, if not impossible, for children to obtain adequate dietary calcium in the presence of unfortified soy. 

Soy is also promoted as a cancer preventative. Whatever protection may exist is slight, and an emerging area of concern are the effects soy phytoestrogens (plant based sources of the hormone estrogen) may have on existing hormone-sensitive cancers.  After reviewing the data, in January of 2007, the Cancer Council of New South Wales issued a warning about soy to patients with hormone-dependent cancers, stating: "Women with current or past breast cancer should be aware of the risks of potential tumour growth when taking soy products….” 

The hormonal effects of soy phytoestrogens may also impact men.  Studies of rats and monkeys show soy promotes aggression in males, and a recent study found soy decreases sperm counts in humans.

Soy affects the thyroid.  An increase in autoimmune thyroid disease is reported in soy formula fed infants, and in iodine deficient animals and humans, soy is shown to impair thyroid function.  This may or may not affect you; however, you should know the National Health and Nutrition Examination Survey (NHANES) shows that iodine deficiency is on the rise, with about 11 percent of Americans now low in iodine.

As much as 94 percent of all U.S. soy is genetically modified.  Questions as to the human health effects of this genetically modified legume (an ingredient commonly found in processed U.S. foods) is the explanation a number of countries give for rejecting U.S. soybean imports.

Should you eat soy? That’s a personal decision. In my opinion, small amounts of organic, properly prepared and fermented soy sauce, miso, tempeh and natto are a safe bet. Otherwise, I advise you to proceed with caution.


References of interest (if you do not see a working hyperlink, copy and paste the blue address below into your address bar to access the information):

American Heart Association (AHA) comments to the US Food and Drug Administration (FDA), recommending the FDA revoke it's Heart Healthy Claims for Soy :

From the AHA's letter to the FDA:  "...AHA (American Heart Association) strongly recommends that FDA revoke they soy protein and CHD health claim."  (CHD = Coronary Heart Disease)