Is it Risky to Eat Soy?

Kathryn Adel May 22, 2018 Eat Well, Health, Heart Health, Menopause

Menopause and Hot Flashes

Genistein, one of the isoflavones found in soybeans, has been shown to reduce the frequency and severity of hot flashes associated with menopause. For optimal results, it is recommended to consume a minimum of 19 mg/day of genistein. This amount is found in 300 ml of soy milk, 150 g of tofu or 75 g of tempeh.

Male Reproductive System

Some fear that since soy contains isoflavones that mimic the effects of estrogen, its consumption may have adverse effects on male fertility. Various studies have shown that circulating levels of testosterone as well as the number and motility of sperm are not negatively affected by the ingestion of soy isoflavones. Studies show that consumption of up to 150 mg/day of isoflavones has no negative effect on the male reproductive system. This equates to a daily intake of 680 g of tofu, 1.5 L of soy milk or 150 g of soy protein isolate, which is far beyond what people usually consume.

Thyroid Gland

Soy is a potentially goitrogenic food, that is, it can disrupt the functioning of the thyroid gland. However, it is documented that in the absence of abnormalities of the thyroid gland, the risks of soy ingestion impairing thyroid function are minimal, especially if iodine intake is adequate. In the case of medicated hypothyroidism, it is recommended to take thyroid hormone substitution (Synthroid) a few hours apart from consuming soy foods.

In conclusion, soy foods occupy a prominent place in a varied and balanced diet. They can be consumed daily without adverse effects, as long as excess is avoided. To get the maximum benefits, one should focus on its whole form (edamame, dry and canned soybeans) rather than its derivatives and supplements. Fermented products such as tamari sauce, tempeh and miso are also preferred.

Here are some ideas of recipes containing soy foods:

• Soba Noodles Salad with Peanut Sauce
• Red Lentil and Tofu Curry
• Japanese Soup with Noodles and Seaweed
  
• Tempeh, Peppers and Avocado Wrap

References

• Verville et Crépeau (2018) Cancer hormonodépendant : Doit-on manger autrement? Protégez-vous. https://www.protegez-vous.ca/Sante-et-alimentation/manger-autrement-cancer
• Société canadienne du cancer (2018) Bien manger après un cancer du sein. http://www.cancer.ca/fr-ca/cancer-information/cancer-type/breast/supportive-care/eating-well-after-breast-cancer/?region=qc
• Taillefer, Julie (2018) Prise de position sur le soya de l’APSAV, version abrégée. https://apsavorg.files.wordpress.com/2018/03/prise-de-position-soya.pdf

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Author

Kathryn Adel

Kathryn holds a Bachelor Degree in Nutrition as well as a Bachelor and a Master Degree in Kinesiology, all from Laval University. She is a Registered Dietitian and active member of the Ordre professionnel des Diététistes Nutritionnistes du Québec (ODNQ) and of the American Academy of Nutrition and Dietetics. She holds the Monash University's certification for the FODMAP diet and IBS, and has considerable clinical experience in that area. She is also an accomplished athlete, having ran track and cross-country at a national level. Kathryn specializes in sports nutrition, weight loss, diabetes, as well as heart and gastrointestinal health.