Quiz: An ingredient in these meals is affecting your hormones. Can you guess which one?

Alrighty, here are the meal contestants:

1. Sushi (frorm your fave spot) with a miso soup and side of edamame 🍣🍲

2. A heart-happy salad with meatless bacon bits (those are a thing!) 🥗

3. Your morning bowl of cereal and soy milk🥛

Sensing a theme here? Yep, if you guessed soy–you’re right! (Ok... that last one may have been a give-away.) All of these foods contain a significant amount of soy and soy can affect your hormones.

Soy what?!

Soy is a legume that produces phytoestrogens, which are a naturally occurring plant compound. As you might be able to tell from the name, phytoestrogens are structurally similar to estrogens found in mammals (like humans!) and they mimic their effects.

The particular type of phytoestrogren found in high quantities in soy is called an “isoflavone.” Some studies have shown that isoflavones can decrease estradiol (a type of estrogen), progesterone, LH and FSH in premenopausal women.

So should I avoid soy?

It’s important to remember that not all isoflavones will affect everyone in the same way and some soy in the diet is fine. The effects of these compounds depend on a person’s age, gender, ethnicity, diet and even the microbes in their guts!

Additionally, the amount of isoflavones in a food can depend on the crop, the processing of the food and even the year that a plant is harvested. For example, raw Korean soybeans have almost 80% more phytoestrogens than Brazilian soybeans. Btw, If you want to check the isoflavone levels of a certain food, the USDA has a report of isoflavone contents of common foods here.

Soy has also been a hot topic as it relates to reproductive (breast, endometrial, prostate, etc.) cancers. Some studies suggests that it has a protective effect against cancer while others warn that people with a history of reproductive cancers should avoid soy.

And did you know that eating large quantities of soy can actually increase your cycle length (sometimes by up three days every month)? Who knew your daily soy powder shake could do so much?

The bottom line

Soy is powerful but the old adage holds true––everything in moderation. Always remember to consult with your doctor if you have concerns.

References

  • 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), 1275-1284.
  • etchell, K. D., & Cassidy, A. (1999). Dietary isoflavones: biological effects and relevance to human health. The journal of nutrition, 129(3), 758S-767S.
  • Hooper, L., Ryder, J. J., Kurzer, M. S., Lampe, J. W., Messina, M. J., Phipps, W. R., & Cassidy, A. (2009). Effects of soy protein and isoflavones on circulating hormone concentrations in pre-and post-menopausal women: a systematic review and meta-analysis. Human reproduction update, 15(4), 423-440.
  • Kumar, N. B., Cantor, A., Allen, K., Riccardi, D., & Cox, C. E. (2002). The specific role of isoflavones on estrogen metabolism in premenopausal women. Cancer, 94(4), 1166-1174.


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Erin Burke, PhD

Dr. Erin Burke runs research and clinical operations at Modern Fertility. She is a biological anthropologist who received her PhD from Yale University.

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