Editor’s Note: In “Hey, Health Coach,” Sarah Hays Coomer answers reader questions about the intersection of health and overall well-being. Have a question? Send her a message (and don’t forget to use a sleuthy pseudonym!).
Hey, Health Coach,
We have dairy intolerance in my house, so my son and I have been using soy milk as an alternative. I like it fine, but I’ve heard that soy milk contains estrogen. Is soy bad for us?
— Soy Milk Mom
Dear Soy Milk Mom,
The debate over the benefits and drawbacks of soy has raged on for decades, leaving a lot of people confused about what the science says and what to do about it. There are many misconceptions about how soy interacts with the human body, so I’m glad you asked this question.
Overall, research shows soy isn’t harmful for most people. In fact, it’s a powerful source of nutrients that can be beneficial for health and longevity.
However, there are exceptions. For instance, people with soy allergies can have negative reactions like hives, itching, dizziness or digestive problems. Fortunately, there are lots of alternatives for people who can’t (or prefer not to) eat soy.
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Common Objections to Soy
In my experience, most people who worry about soy are concerned about three things: hormone imbalance in men, cancer in women and consuming processed food.
Does Soy Contain Estrogen, and Is It Bad for Men?
Soy contains estrogen-like compounds called isoflavones. Some people worry that these phytoestrogens (compounds in plants that mimic estrogen in the body) can reduce testosterone levels in men and boys, making them more feminine or affecting their sperm count or quality, but this connection is a myth.
According to a 2020 meta-analysis of 41 studies in Reproductive Toxicology, soy proteins and isoflavones don’t have any significant effect on male reproductive hormones[1]Reed KE, Camargo J, Hamilton-Reeves J, Kurzer M, Messina M. Neither soy nor isoflavone intake affects male reproductive hormones: An expanded and updated meta-analysis of clinical studies. Reprod Toxicol. 2021;100:60-67. .
Can Soy Cause Cancer?
For women, concerns about phytoestrogens often center around cancer risk. Specifically, people worry that eating soy might increase their chances of getting breast cancer.
Evidence shows that eating soy doesn’t increase cancer risk. In fact, a 2022 systematic review of relevant studies found moderate soy consumption can help protect against breast cancer in both pre- and post-menopausal women[2]Boutas I, Kontogeorgi A, Dimitrakakis C, Kalantaridou SN. Soy Isoflavones and Breast Cancer Risk: A Meta-analysis. In Vivo. 2022;36(2):556-562. .
According to Mayo Clinic registered dietician Katherine Zeratsky, the myth that soy causes breast cancer started because high estrogen levels are associated with increased risk of breast cancer, but soy doesn’t contain enough isoflavones to put women at risk. However, she warns that concentrated isoflavone supplements contain much higher levels of estrogen compounds than soy-based foods and could increase the risk for women with a family history of breast cancer or thyroid disease. More research is needed on the potential effects of these supplements.
Is Soy Milk a Processed Food?
Any food that isn’t consumed in its original state is processed, so yes, soy milk is processed. To make soybeans into milk, the beans must be soaked, ground into a pulp (or slurry) and mixed with water. The milk is often fortified with vitamins and minerals as well. Sometimes sugar, salt and other preservatives or thickeners—such as gums or carrageenan, a seaweed derivative that can cause bloating and inflammation in some people—are added to soy milk products, too.
If you enjoy soy milk but would rather avoid those additives, look for unsweetened products and drinks with fewer ingredients. If you’re feeling ambitious, you can make your own soy milk at home, but that extra task can be a stretch for many of us. If making your own soy milk sounds like a hassle, there are plenty of healthy options on grocery store shelves.
The Benefits of Soy
Dan Buettner, National Geographic fellow and bestselling author of The Blue Zones, identified the five places in the world where people live the longest and investigated similarities in their diets and lifestyle behaviors. On his website, he writes that beans (including soybeans) are a “cornerstone” of all five Blue Zone diets that offer myriad health benefits.
Protein
Humans must consume nine essential amino acids to build muscle, support immune function and digestion, as well as maintain many other important functions. Soy contains all nine essential amino acids, making it a complete plant-based protein source.
A cup of soy milk contains about 8 grams of protein. In comparison, a cup of dairy milk contains approximately 8 grams of protein, too.
Vitamins and Minerals
Soy milk and other soy-based products like tofu are naturally high in B vitamins, potassium and magnesium. Soy milk is often fortified with other essential vitamins and minerals, including calcium, vitamin D, B12 and iron, all of which are important for a healthy diet.
Heart Disease
Soy is a reliable source of unsaturated fats, which can help balance cholesterol levels and lower a person’s risk of heart disease. A collection of studies that tracked over 74,000 people for nearly 30 years found higher intake of soy and isoflavones—especially when consumed in the form of tofu—to be associated with lower risk of coronary artery disease[3]Ma L, Liu G, Ding M, et al. Isoflavone Intake and the Risk of Coronary Heart Disease in US Men and Women: Results From 3 Prospective Cohort Studies. Circulation. 2020;141(14):1127-1137. .
Menopause
A small 2021 study in Menopause showed that a plant-based diet including soybeans helped reduce the occurrence of hot flashes in participants by 79%[4]Barnard ND, Kahleova H, Holtz DN, et al. The Women's Study for the Alleviation of Vasomotor Symptoms (WAVS): a randomized, controlled trial of a plant-based diet and whole soybeans for postmenopausal women. Menopause. 2021;28(10):1150-1156. . A larger 2015 meta-analysis also found phytoestrogens helped significantly reduce the occurrence of hot flashes without any significant negative side effects[5]Chen MN, Lin CC, Liu CF. Efficacy of phytoestrogens for menopausal symptoms: a meta-analysis and systematic review. Climacteric. 2015;18(2):260-269. .
Cancers
Eating soy products like soy milk, tofu and edamame may help reduce the risk of certain cancers, including breast, prostate and gastric cancers, according to experts at the Dana-Farber Cancer Institute. Additionally, a study in The American Journal of Clinical Nutrition that followed over 9,500 breast cancer survivors for seven years found soy intake to be associated with a 25% reduction in tumor recurrence[6]Messina M. Soy foods, isoflavones, and the health of postmenopausal women. The American Journal of Clinical Nutrition. 2014;100(1):423S–430S. .
Bone Health
Lastly, a 2022 review of 18 randomized, controlled studies in the Journal of Clinical Medicine concluded that soy isoflavones are effective in slowing down bone loss in postmenopausal women, thereby reducing the risk of osteoporosis[7]Barańska A, Kanadys W, Bogdan M, et al. The Role of Soy Isoflavones in the Prevention of Bone Loss in Postmenopausal Women: A Systematic Review with Meta-Analysis of Randomized Controlled Trials. Journal of Clinical Medicine. 2022;11(16):4676. .
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Alternatives to Soy Milk
If you still have concerns about soy or would like to try other kinds of plant-based milks, you have lots of options. Almond, rice, oat, coconut and cashew milks are all widely available. Like soy milk, many of them are fortified with essential vitamins and minerals, and they all have different flavors and consistencies to suit a range of tastes.
A Healthy Choice
For most people, especially those with lactose intolerance, soy milk can be a wonderful alternative to dairy milk.
The overwhelming consensus in the research is that you can rest easy consuming soy milk and giving it to your son. It’s a healthy option with multiple benefits. Just make sure to choose a brand that’s fortified with essential vitamins and minerals and low in added sugar. Then you two can raise a glass to good health and enjoy.
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