Soy: What to Eat and What to Avoid

Studies suggest that eating soy can prevent cancer, lower cholesterol, increase bone mineral density and relieve hot flashes. But in some circles, soy has been portrayed as harmful, said to damage the thyroid, disrupt sex hormones and actually cause cancer.

My position is that certain soy foods are a healthy choice for most people. However, exceptions exist and some soy products aren’t good for anyone. Here are my recommendations for what to eat and what to avoid. 

Choose Minimally Processed Products

Look for soy foods that have been minimally processed, like edamame (green soy beans), tempeh (soy beans fermented with whole grains) and tofu. Avoid manufactured foods containing soy extracts, which are often removed with toxic chemical solvents like hexane. Read labels carefully and stay away from ingredients like soy protein isolates or concentrates, textured or hydrolyzed soy protein, soy flour, soy lecithin and soybean oil. Also avoid fake foods like soy meat and soy cheese. 

Find Fermented Forms

Like other legumes, soy contains phytic acid, which can bind to minerals and interfere with their absorption. It can also be difficult for some people to digest. Fermenting soy neutralizes phytic acid and increases digestibility. Fermentation makes nutrients more bioavailable (easier for your body to absorb and utilize) and adds live cultures of healthy microorganisms that promote good digestion.

Look for these fermented soy foods: tempeh, miso (fermented soy bean paste), shoyu (a soy sauce made from fermented soy beans), and tamari (a slightly thicker soy sauce, also made from fermented soy beans).

Choose Organic

According to the Organic Consumers Association, more than ninety percent of soy in the United States is genetically modified. Most soybean crops are also heavily sprayed with pesticides. Always buy soy products that are certified organic to ensure that you aren't ingesting pesticides or genetically modified food. 

Add Sea Foods

It's true that soy can affect thyroid function, but only in people who are iodine deficient. One way to prevent any adverse affect is to consume it with foods high in iodine, like fish, seafood, seaweed and other sea vegetables. But be selective; sea foods can contain toxic compounds like arsenic, mercury and polychlorinated biphenyls (PCBs), absorbed from polluted waters.

Large predatory fish like tuna, shark and marlin are much more likely to have accumulated higher concentrations of toxins than smaller species that live lower on the food chain. Good choices include wild Alaskan salmon, Atlantic mackerel, herring, sardines and anchovies because they are low in contaminants, high in healthy omega-3 fats, and sustainably harvested. For the most up-to-date information on seafood health advisories, check the website of the Environmental Defense Fund or the Monterey Bay Aquarium's Seafood Watch program.

Use Moderation

Soy is one of the top ten most common food allergens. Individuals who eat it too often are more likely to develop a sensitivity or intolerance to it over time. Limit soy consumption to once per day and be sure to incorporate other healthy sources of protein into your diet too, like beans, lentils, nuts, seeds, eggs, cheese, yogurt, keffir, fish, seafood, pasture-raised or grass-fed meats. 

Feed It to Your Daughters

Isoflavones found in soy have been studied for their role in cancer protection. Researchers found that eating soy foods can decrease chances of developing breast cancer, and in breast cancer survivors, soy can reduce the risk of recurrence and death. Eating soy can be beneficial at any age, but studies show that girls who eat it at least once a week during childhood and adolescence get the greatest protection against breast cancer.

Do It Yourself

As an alternative to processed store-bought veggie burgers, learn to make make your own. Use a food processor to combine tofu or tempeh with your favorite flavors, like mushrooms, roasted red peppers and olives. To help hold everything together, add sunflower seeds, walnuts, crumbled feta, crumbled goat cheese, or an egg. Pulse the ingredients until they are well-combined, then form the mixture into patties and sauté them with a little extra virgin olive oil until cooked through for a quick and healthy meal.

Use Caution

Isolated isoflavone supplements are not the same as soy foods. Talk to your doctor before taking any supplements, including isoflavones. Also, women who are taking Taxol should not consume soy for seven days before or after treatment.

References:

Korde LA et al. Childhood soy intake and breast cancer risk in Asian American women. Cancer Epidemiology, Biomarkers and Prevention. 2009 Apr;18(4):1050-9.

Persky VW et al. Effect of soy protein on endogenous hormones in postmenopausal women. American Journal of Clinical Nutrition. 2002 Jan;75(1):145-53.

Shu XO et al. Soy Food Intake and Breast Cancer Survival. Journal of the American Medical Association, 302(22):2437-2443, 9 December 2009.

Trock BJ et al. Meta-analysis of soy intake and breast cancer risk. Journal of the National Cancer Institute, 98(7):459-71, 5 Apr 2006.

Wu AH et al. Adolescent and adult soy intake and risk of breast cancer in Asian-Americans. Carcinogenesis. 2002 Sep;23(9):1491-6.