Soy 101: Is It Healthy?

Ever wonder if soy is healthy? Read on to find out more plus a peek into the foods and products it's in.

And be sure to check out our Plant-Based diet course - if you are a vegan or vegetarian and want a teaser of our Nutrition Certification course.

What is soy?

Soybeans are a type of legume native to East Asia. They are an excellent source of high quality protein, along with being low in saturated fat and high in dietary fiber. Additionly, they are a good source of isoflavones, phytochemicals that promote heart health and the maintenance of bone health in postmenopausal women.

Many of the health properties of soy are due to its nutrient profile. Soybeans contains all of the essential amino acids, as well as a comprehensive list of micronutrients, including: calcium, iron, magnesium, manganese, phosphorus, potassium, vitamins B1, B2, B3, B5, B6, B9, C and zinc. Fiber and essential fatty acids are also present in soy. (Asif, M., & Acharya, M., 2013)

Is Soy Hard to Digest?

One of the drawbacks with soybeans is that they are hard to digest. Fermentation makes them more digestible and adds flavor. It also deactivates soy’s natural phytic acid and enzyme inhibitors, which can affect mineral and protein absorption.

Common Soy Food Products

Edamame
Edamame are green soybeans that are a whole food, commonly found in the frozen food section of grocery stores. The pods are often served boiled in water for a few minutes and then lightly salted. One cup of shelled edamame provides about 23 grams of protein.

Miso
Miso is a fermented soy food that is a strong-tasting, salty condiment often served as soup or in sauces.

Soy Flour
Soy flour is processed from whole ground roasted soybeans. It is used to increase the protein content of breads, cakes, and cookies. Soy flour is naturally gluten free.

Soy Milk
Soy milk is a good source of soy protein. It is made from soybeans that have been finely ground, cooked and strained. Soy milk can be highly processed with numerous additives and flavorings.

Soybean Oil
Soybean oil is a vegetable oil extracted from the seeds of the soybean. It is one of the most widely consumed cooking oils. Soybean oil is also used as a base for printing inks and oil paints.

Soy Protein Powder
To create soy protein powder, soybeans are ground into a meal which contains no hulls or fat. This is then processed into soy protein isolate. Soy protein powder can be used to make protein shakes or to add protein to other meals. Many manufacturers add additional nutrients to commercial soy protein to improve its taste, texture, and nutritional value.

Soy Yogurt
Soy yogurt is made using soy milk by adding yogurt bacteria (Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus), and sometimes sweeteners such as fructose, glucose or sugar.

Tempeh
Tempeh is made from soybeans that have been fermented and then formed into flat blocks. Sometimes grains like brown rice, barley, or millet are added. Tempeh has a meaty taste and is often used as a meat substitute in cooking. It can be marinated and grilled as well as added to stews and pasta sauces. Tempeh is high in protein, fiber and isoflavones. It is one of the healthiest forms of soy.

Tofu
Tofu, also known as bean curd, is made by curdling soy milk (from soybeans) and then pressing the curds into soft, white blocks. Tofu is low in fat and calories, high in protein and a relatively good plant source of iron and calcium.

 Other foods and products that contain or possibly contain soy:

Non-food sources of soy:

Oh No GMO
GMOs are genetically modified organisms. Their safety for human consumption is a hot topic of debate. Many European countries have banned GMOs due to the lack of conclusive data in long term studies regarding the health effects. Some studies have found that glyphosate genetically modified soybeans contain high residues of the pesticide compounds and that organic soybeans showed a more healthy nutritional profile.

Since most of the global soybean crop is genetically modified and much of it ends up in farmed animal feed, my personal preference is to choose organic for both animal and plant products until more studies can confirm long-term safety.

(Bøhn, T., et al., 2014)

Health Benefits

Bone

Consumption of soy with isoflavones may have a beneficial effect on bone health. There was a significant decrease in bone turnover markers of resorption and formation after supplementation with 15 g of soy protein with isoflavones for 6 months.

(Sathyapalan, T., et al., 2017)

Cancer

Breast Cancer
Genistein in soy activates estrogen receptor (ER)-α and ERβ and acts as an estradiol in multiple target tissues. Because estrogens increase breast cancer risk and genistein promotes the growth of ER-positive human breast cancer cells, it has remained unclear whether this isoflavone or soy is safe. Results reviewed in a study by Hilakivi‐Clarke, L., et al. 2010, suggest that women consuming moderate amounts of soy throughout their life have lower breast cancer risk than women who do not consume soy; however, this protective effect may originate from soy intake early in life.

(Hilakivi‐Clarke, L., et al. 2010)

Prostate Cancer
Soy foods and their isoflavones (genistein and daidzein) are associated with lower PSA levels and a lower risk of prostate carcinogenesis. However, some studies show that dietary intake of isoflavones was associated with an elevated risk in advanced prostate cancer.

(Applegate, C. C.,et al., 2018) (Reger, M. K., et al., 2018)

Cardiovascular Disease (CVD)
Soy isoflavones may act as selective estrogen receptor modulators. Supplementation with soy protein isoflavones by women for 6 months significantly improved CVD markers including:

• 27% reduction in 10 year coronary heart disease risk.
• 37% reduction in myocardial infarction risk.
• 24% (p < 0.04) reduction in cardiovascular disease.
• 42% reduction in cardiovascular disease death risk.

(Sathyapalan, T., et al., 2018)

Menopause
Soybean and soy isoflavone supplements have been investigated as a treatment to relieve hot flashes and other menopausal symptoms. Some studies found that soybeans and isoflavones reduced the frequency and severity of hot flashes.

(Ju, Y. H., 2016)

Thyroid
In patients with subclinical hypothyroidism, soy protein and isoflavone combination has been shown to increase the risk of developing overt hypothyroidism; however, it is unclear if soy affects thyroid function in those without existing thyroid compromise.

(Sathyapalan, T., et al., 2015)

Men and Soy
In contrast to the results of some rodent studies, findings from more recent studies show that neither isoflavone supplements nor isoflavone-rich soy affect total or free testosterone levels. Similarly, a number of other clinical studies did not show that isoflavone exposure affects circulating estrogen levels in men or effects sperm and semen parameters.

(Hamilton-Reeves, J. M., et al., 2010) (Messina, M., 2010)

Recipes

Tempeh Stir Fry
Servings: 3-4
Ingredients

• 4 ounces organic soy tempeh or 3-grain tempeh, cut into 1/2-inch pieces
• 1/4 cup reduced sodium organic tamari
• 2 tablespoon rice vinegar
• 3 garlic cloves, minced
• 2 teaspoons minced peeled fresh ginger
• 1/4 teaspoon dried crushed red pepper
• 1/4 teaspoon dried turmeric
• 12 ounces broccoli, stems peeled and cut into 1/2-inch pieces, florets cut into 1-inch pieces
• 2 tablespoons water
• 1 teaspoon honey
• 1 teaspoon cornstarch
• 2 tablespoons avocado oil
• 1/2 cup chopped red bell pepper
• 1/2 cup chopped carrots
• 1 cup diced shiitake mushrooms
• 2 tablespoons thinly sliced green onion

Instructions

1. Stir tempeh, soy sauce, vinegar, garlic, ginger and crushed red pepper in medium bowl to blend. Let marinate 1 hour at room temperature.
2. Steam broccoli until crisp-tender, about 2-4 minutes. Set aside. Strain marinade from tempeh into small bowl; set tempeh aside. Whisk 2 tablespoons water, honey and cornstarch into marinade.
3. Heat oil in large nonstick skillet over high heat. Add marinated tempeh, bell pepper, carrots and mushrooms and sauté 4 minutes. Add broccoli and marinade mixture and sauté until broccoli is heated through and sauce thickens, about 3 minutes. Transfer to bowl. Serve over quinoa or brown rice. Sprinkle with green onion and serve.
4. Optional: Top with Sriracha or your favorite hot sauce.

Silken Tofu Chocolate Mousse
Serves: 3
Ingredients:

• 100 grams (3.5 ounces) roughly chopped organic dark chocolate (70% or greater).
• 1 package (340 grams-12 ounces) organic silken tofu (drained and at room temperature).
• 2 tablespoons maple syrup.

Instructions:

1. Melt the chocolate in a saucepan (low heat) or double boiler, stirring until the chocolate is melted. Set aside to cool at room temperature.
2. Meanwhile, place the silken tofu and maple syrup in a food processor and blend until very smooth. Add the melted chocolate and blend until well combined.
3. Scoop the mixture into 3 ramekins or glasses, and refrigerate for 30 minutes.

Optional Toppings

• Toasted walnuts, pecans or almonds
• Dark chocolate chips
• Fresh mint
• Cayenne pepper

Summary

References

Applegate, C. C., Rowles, J. L., Ranard, K. M., Jeon, S., & Erdman, J. W. (2018). Soy Consumption and the Risk of Prostate Cancer: An Updated Systematic Review and Meta-Analysis. Nutrients, 10(1), 40.

Asif, M., & Acharya, M. (2013). Phytochemicals and nutritional health benefits of soy plant. International Journal of Nutrition, Pharmacology, Neurological Diseases, 3(1), 64.

Bøhn, T., Cuhra, M., Traavik, T., Sanden, M., Fagan, J., & Primicerio, R. (2014). Compositional differences in soybeans on the market: glyphosate accumulates in Roundup Ready GM soybeans. Food chemistry, 153, 207-215.

Hamilton-Reeves, J. M., Vazquez, G., Duval, S. J., Phipps, W. R., Kurzer, M. S., & Messina, M. J. (2010). Clinical studies show no effects of soy protein or isoflavones on reproductive hormones in men: results of a meta-analysis. Fertility and sterility, 94(3), 997-1007.

Hilakivi‐Clarke, L., Andrade, J. E., & Helferich, W. (2010). Is Soy Consumption Good or Bad for the Breast? The Journal of Nutrition, 140(12), 2326S–2334S. http://doi.org/10.3945/jn.110.124230

Ju, Y. H. (2016). To Soy or Not to Soy: Effects of Soybeans on Breast Cancer, Menopause and Heart Disease.

Messina, M. (2010). Soybean isoflavone exposure does not have feminizing effects on men: a critical examination of the clinical evidence. Fertility and sterility, 93(7), 2095-2104.

Reger, M. K., Zollinger, T. W., Liu, Z., Jones, J. F., & Zhang, J. (2018). Dietary intake of isoflavones and coumestrol and the risk of prostate cancer in the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial. International journal of cancer, 142(4), 719-728.

Sathyapalan, T., Aye, M., Rigby, A. S., Thatcher, N. J., Dargham, S. R., Kilpatrick, E. S., & Atkin, S. L. (2018). Soy isoflavones improve cardiovascular disease risk markers in women during the early menopause. Nutrition, Metabolism and Cardiovascular Diseases.

Sathyapalan, T., Aye, M., Rigby, A. S., Fraser, W. D., Thatcher, N. J., Kilpatrick, E. S., & Atkin, S. L. (2017). Soy reduces bone turnover markers in women during early menopause: a randomized controlled trial. Journal of Bone and Mineral Research, 32(1), 157-164.

Sathyapalan, T., Aye, M., Thatcher, N. J., Rigby, A. S., Kilpatrick, E. S., & Atkin, S. L. (2015). Soy protein with isoflavones impairs thyroid function.