Debunking Three Myths about Soy
Thursday, February 1, 2018

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Summary

What's fact and what's fiction? Soybeans are nutrient powerhouses, yet conflicting results from research has created fear in the consumption of this wholesome food.
Soybeans growing on plant

As a complete protein, soybeans are a great meat alternative; they are packed with vitamins and minerals, healthy fatty acids and fiber. Clinical evidence shows that consuming soy reduces the risk of osteoporosis, coronary heart disease, and some forms of cancer. However, research has also highlighted the potential health risks of soy, instilling fear and uncertainty in its consumption. To put these fears to rest, here’s the latest research information.   

Myth 1: Soy consumption increases the risk of breast cancer.

The main fear behind soybeans is the isoflavones contained within them. Isoflavones are phytoestrogens, a plant compound that can chemically act like estrogen. Thus, a primary concern is that breast cancer, especially estrogen-positive breast cancer, can grow in the presence of estrogen.

However, multiple research studies suggest that there is no association between consuming soy and breast cancer, and that soy consumption may even lower the risk of breast cancer. Isoflavones have anti-inflammatory and antioxidant properties that have the potential to reduce cancer growth. Although it is true that isoflavones have similar chemical properties to estrogen, the compound also has antiestrogen properties, including the ability to block natural estrogens from binding to estrogen receptors and halting estrogen formation in fat tissue. [1]

Myth 2: Soy imitation meat products are nutritious because they don’t contain meat.

Soybeans are extremely versatile and can be used as an ingredient to create numerous products including soy cheese and soy meat alternatives. These products don’t have meat, so that should make it a healthier and more nutritious option right?

Although soybeans, which indeed are nutrient-packed, have replaced meat in these imitation-meat products, transforming the soybean to a product that resembles a chicken nugget or sausage requires processing. It would also require the addition of other ingredients to mimic the textures and flavors of actual meat, creating a product that could be high in sodium, fat, and chemicals/preservatives. The bottom line: soy meat products are highly processed and far from its original, whole food form. To obtain the most health benefits from soy, stick to the whole or minimally processed forms such as edamame, tofu, tempeh, and miso. Incorporating more whole foods is an important part of a healthy diet.

Myth 3: Men should avoid soy because it reduces testosterone levels.

Another widespread misconception about soy is that it decreases the testosterone levels in men and can lead to prostate cancer. These concerns, however, originate from studies in rodents that showed the impaired ability for male rats to produce offspring when given high doses of phytoestrogens. It’s important to distinguish that rodents metabolize soy isoflavones differently than humans – it has not been shown to have the same effect in humans. Furthermore, a meta-analysis research study (a method of combining data from several selected studies) published in Fertility and Sterility presented that soy protein or isoflavones did not affect the reproductive hormones in men. [2] The American Journal of Clinical Nutrition also published a research study that showed men who actually increased their intake of soy reduced the risk of prostate cancer by 25 percent. [3] 

Based on the overall clinical research, there is no need for fear in the consumption of soy foods. To learn more about the importance of soy and other whole foods and how to incorporate them into your diet, visit http://bastyrcenter.org/services/nutrition to make an appointment with a Bastyr registered dietitian.   

 

References

1.       Thalheimer, Judith C. “The Top 5 Soy Myths.” Today’s Dietitian, vol. 16, no. 4, 2014, p. 52, http://www.todaysdietitian.com/newarchives/040114p52.shtml.

2.       Messina, M. “Soybean isoflavones exposure does not have feminizing effects on men: a critical examination of the clinical evidence.” Fertility Sterility, vol. 93, no. 7, 2010, http://www.fertstert.org/article/S0015-0282(10)00368-7/fulltext.

3.       Yan, Lin, and Spitznagel, Edward L. “Soy consumption and prostate cancer risk in men: a revisit of a meta-analysis.” The American Journal of Clinical Nutrition, vol. 89, no. 4, 2009, http://ajcn.nutrition.org/content/89/4/1155.long.