What is soy?
Soy, or more accurately, the soybean, is a type of legume that is native to East Asia. Soybeans are used in many different food products. It’s high protein content makes it a great alternative to meat for vegetarians or those wanting to decrease their meat consumption. Soymilk is also a great dairy alternative, and it contains more protein than other choices like almond, oat, and hemp milk.
Nutrient Packed
Soy foods are rich in many beneficial vitamins, nutrients, and plant compounds:
- Protein is essential for many functions in the body, including repairing and building muscle and other tissues. Soy foods like tofu and tempeh contain 10-15 of protein per serving.
- Fiber does a lot in the body, including maintaining the digestive system, lowering cholesterol, and controlling blood sugar levels. Soy foods that utilize the whole soybean, such as tempeh, are high in fiber.
- Vitamins A, B, and E all maintain essential body functions.
- Mono and polyunsaturated fats have been shown to help lower cholesterol levels and reduce cardiovascular disease risk. They give soy foods a healthier fat profile than animal proteins, which tend to be higher in saturated fat.
- Isoflavones are a type of plant chemical, or phytochemical. They protect our cells from damage and prevent diseases such as heart disease and cancer. They also are similar in structure to the hormone estrogen, allowing them to act in similar ways to estrogen in some parts of the body.
- Plant stanols and sterols have been shown to help lower cholesterol.
What the Research Says
Heart Health
A 2015 review described the results of several studies finding that intake of soy products is associated with significant reductions in LDL-cholesterol, the type of cholesterol that contributes to heart disease. Another 2017 research review found that soy-rich diets were associated with a 20% lower risk of stroke and 16% lower risk of heart disease.
Bone Health
There is research suggesting that the isoflavones in soy play a role in enhancing bone formation and reducing bone loss in postmenopausal women. In one 2016 study, the results suggested that consumption of 66mg of isoflavones daily for 6 months was associated with improvements in markers for bone health. In older Asian women, eating more soy is linked to lower rates of bone fracture. Though the current findings are very promising, more research is still needed to confirm the benefits of soy for bone health.
Cancer
Soy consumption is associated with decreased incidence of many cancers. A 2009 meta-analysis found that high intakes of soy was associated with a 26% reduction in prostate cancer risk. Another 2016 review study found that daily soy intake may reduce the risk of endometrial cancer by around 19%.
The American Cancer Society endorses soy foods as safe for women with breast cancer. There is evidence that consuming soy foods may be protective against breast cancer, but only if consumed early in life. Beginning soy consumption later in life does not appear to have any effect on risk of getting breast cancer. However, other research suggests that women with breast cancer who eat soy foods are less likely to see their cancer return and less likely to die from the cancer.
Women’s Health
The isoflavones in soy have no effect on estrogen levels. However, their similarity in structure allows them to provide some of the same health benefits. Results of more than 15 studies have demonstrated that isoflavone supplements, or 2 servings of soy foods per day, can reduce both the number and severity of hot flashes by about 50% in postmenopausal women.
Safety of Soy
There has been some controversy in the past regarding the isoflavones in soy and their potential estrogenic effects on the body. However, human studies support the safety of isoflavone supplements and soy foods, demonstrating that they have no effect on estrogen levels in women or testosterone levels in men. Clinical studies have also shown that they have no effect on sperm or semen. Soy foods have been shown to have no effect on thyroid function in people with normal thyroids. However, people with low thyroid function should not consume soy foods 1 to 3 hours after taking thyroid medication.
References
Messina M. Soy and Health Update: Evaluation of the Clinical and Epidemiologic Literature. Nutrients.2016;8(12):754. Published 2016 Nov 24. doi:10.3390/nu8120754
Messina V. Soy Safety and Health Effects of Isoflavones. Vegetarian Nutrition Dietetics Practice Group.https://higherlogicdownload.s3.amazonaws.com/THEACADEMY/859dd171-3982-43db-8535-56c4fdc42b51/UploadedImages/VN/Documents/Resources/Soy_Safety_Consumer_RDN_Consumer.pdf. Accessed June 8, 2021.
Sathyapalan T, Aye M, Rigby AS, et al. Soy reduces bone turnover markers in women during early menopause: A randomized controlled trial. J Bone Miner Res. 2017;32(1):157-164. doi:10.1002/jbmr.2927.
Tokede OA, Onabanjo TA, Yansane A, et al. Soya products and serum lipids: a meta-analysis of randomised controlled trials. Br J Nutr. 2015;114(6):831-43. doi: 10.1017/S0007114515002603.
Yan Z, Zhang X, Li C, et al. Association between consumption of soy and risk of cardiovascular disease: A meta-analysis of observational studies. Eur J Prev Cardiol. 2017;24(7):735-747. doi:10.1177/2047487316686441.
