Dear Healing With Plants, What’s the truth about soy as a protein source? …Should it be part of my vegetarian diet? Thx, Ken.
Dear Ken,
Is soy a healthy food or should I stay away from soy? Your question is a common one and many people are confused about whether or not to eat soy. On the one hand we hear about how diets high in soy can protect against cancer and other diseases. On the other hand we hear that soy can cause hormone imbalances putting your health at risk. The truth about soy is simple, thankfully. According to Dr. Neal Barnard, MD, president of the Physicians Committee for Responsible Medicine, there’s “No Debate: Soy is Beneficial to Health.“ Yet there is a small but important caveat here—like most all plant foods today, to determine if soy foods are healthy for you follow this rule:
Whole Plant Foods = GOOD FOR YOUR HEALTH
Processed Foods + and animal foods = HAZARDOUS TO YOUR HEALTH
In general this rule is the best advice I can give you. When it comes to soy, whole soybeans are a great food.
What Science Says About Soy
Science has continually demonstrated the positive health benefits of including soy in your diet. For example:
Soy foods reduce inflammation: Researchers examined inflammation measures and diets among 1,005 Chinese women and found that the more soy the women consumed, the less inflammation they experienced. Inflammation is linked to numerous ailments such as heart disease, cancer, and type 2 diabetes. (Wu, 2012)
Soy protects against heart disease: Research has consistently shown that consuming soy foods is linked to lower overall and bad (LDL) cholesterol and an increase in good (HDL) cholesterol (Pipe, 2009). The evidence is so clear that the FDA allows companies to add a health claim to products with at least 6.25 grams of soy protein per serving which states that a low-fat, low-cholesterol diet including at least 25 grams of soy protein a day may reduce the risk of heart disease. (McDougall, 2005)
Eating soy protects women against ovarian cancer: Researchers analyzed the diets and rates of ovarian cancer among 97,275 women and found those who consumed 3mg of isoflavones from soy foods were at a 44% lower risk of ovarian cancer than women who consumed less than 1 mg. The researchers did not find any other foods or nutrients with a significant link to ovarian cancer risk. (Chang, 2007)
Soy consumption protects men against prostate cancer: A 2009 meta-analysis published in the American Journal of Clinical Nutrition analyzed the results of 24 epidemiological studies on soy and isoflavone (a phytoestrogen found in soy) consumption and prostate cancer risk. After conducting their analysis, the researchers concluded that soy helps protect men against prostate cancer. Eating soy was associated with a reduced risk for this disease. (Yan, 2009)
Soy foods protect against breast cancer: Researchers evaluated the diet and breast cancer incidence rate of 73,223 Chinese women and found “strong evidence” that those who ate more soy foods had a lower risk of breast cancer. (Lee, 2009)
Eating soy is linked to breast cancer survival: A study published in the journal Cancer monitored the diet and mortality rates of 6,235 breast cancer patients over 9.4 years. Those who consumed the highest amounts of isoflavones from soy were at 21% lower risk of dying from cancer during this study period, compared to those who consumed the least amount of soy. (Zhang, 2017).
Eating soy reduces side-effects from breast cancer treatments: A study that followed 365 breast cancer survivors found that those who ate more soy and cruciferous vegetables had fewer negative symptoms after breast cancer treatment than those who consumed little or none of these foods. Eating soy and vegetables such as kale, broccoli, and cauliflower put cancer survivors at a reduced risk for symptoms such as joint pain, fatigue, memory issues, hair loss, and hot flashes. Researchers believe the reduced risk is thanks to reduced inflammation, better regulation of estrogens, and the increased consumption of phytonutrients found in soy and fresh veggies. (Nomura, 2018).
Soy protects our bones: A study published in the American Journal of Epidemiology examined the diets and incidences of hip fractures among 63,257 Chinese living in Singapore. Their analysis found that women who ate the most soy had a 21-36% reduction in hip fracture rates. Eating soy appears to help protect women’s bones. (Koh, 2009)
What About The Estrogen?
Concern over hormones is probably the biggest reason many people choose to avoid soy. Dr. Xiao Ou Shu, MD, MPH, PhD, who established the Shanghai Breast Cancer Survival Study—a study including more than 5,000 breast cancer survivors—has led many studies on soy and breast cancer risk. In an interview with The Physicians Committee for Responsible Medicine Dr. Shu explains that estrogen has a central role in breast cancer development and progression, but that soy foods have an antiestrogen effect. The science shows that eating soy prevents the growth of cancer. Dr. Shu explains that a variety of studies have shown eating soy protects women against breast cancer. He says,
“Evidence is quite consistent that soy food consumption at the level of the traditional Asian diet is associated with a reduced breast cancer risk.” (Barnard, 2016)
But what about the effect of soy on hormones in men? Clinical studies show that eating soy has no effect on testosterone levels or other reproductive hormones in men. A 2010 meta-analysis published in the journal Fertility and Sterility conducted a thorough review of available research examining soy consumption and hormones in men. Their analysis included 15 placebo-controlled treatment groups and an additional 32 reports involving 36 treatment groups. The researchers found that regardless of the statistical model used, no significant effects of soy protein on male hormones was detected. They conclude:
“…neither soy foods nor isoflavone supplements alter measures of bioavailable T (testosterone) concentrations in men.” (Hamilton-Reeves, 2010)
The Good Soy is Whole Soy
Soybeans are seeds and like other seeds they are high in protein and fat compared to other plant foods. Because of this it’s good to eat them in moderation. Seed foods shouldn’t be 100% of your diet or even 50% but whole seeds, including beans, are a healthy part of your diet. Whole soy beans are called edamame and these make an excellent addition to a heart-healthy diet. I like to sprinkle edamame on salads to make the salad more satisfying. They are also great with rice or served with corn. Dr. John McDougall outlines the whole soy foods that are healthy to eat in moderation. He writes:
“In Asian countries, soy is consumed as boiled soybeans (edamame), tofu (soybean curd), natto (fermented soybeans), miso (fermented soybean paste), okara (a by- product of tofu), soybean sprouts, soymilk, yuba (by-product of soy milk), kinako (soy flour), and soy sauce. These foods are made from simple processes like grinding, precipitation, and fermentation – thus, most of soy’s ingredients remain little altered. Less than 5% of daily calories in the typical diet of Japanese or Chinese people comes from soybeans.” (McDougall, 2005)
What About Tofu: Is Tofu Bad for You?
Like the other soy foods Dr. McDougall mentioned, tofu is a pretty natural whole food even though it is processed a bit. Like tempeh, soy milk, and soy sauce, tofu is a traditional food that has undergone a simple process which retains most of the good nutrition found in the whole soy bean. Tofu is good to include in your diet in moderation. Just like with other seeds such as almonds, peanuts, and walnuts, too much soy (seed) consumption can contribute an excess of fat to the diet and could potentially lead to unwanted weight gain. Consider tofu as a delicious and nutritious addition to a meal centered around rice and fresh veggies.
The Bad Soy: Isolated Soy Protein is NOT a Health Food
There is one type of soy that you have to watch out for. Hyper-processed soy foods including isolated soy protein are not health foods. Food companies and special interests are to blame for all the confusion surrounding soy and these foods according to Dr. John McDougall, MD, who writes:
“The truth behind soy is clouded by emotional reactions from the anti-soy movement of hard- core meat-eaters and soy-loving vegetarians – and as usual, money from big businesses, the soy manufacturers. Most of the rhetoric on both sides of the argument is of no real importance – the real issue is whether you are consuming small amounts traditional soy foods or making yourself a diet of synthetic foods.” (McDougall, 2005)
I would not recommend isolated protein in your diet, including isolated soy protein. Dr. McDougall calls these foods “fake foods” and warns that they contain unnaturally high concentrations of protein that may be hazardous to your health. Examples of these foods include soy protein powders and products that mimic the animal foods people are used to. These hyper-processed foods are linked to numerous health problems and can definitely put you on the road to disease.
What’s wrong with soy chicken nuggets, soy burgers, and soy protein shakes? The biggest issue with these foods is that they are not whole foods. They may deliver a lot of protein, but there is such a thing as too much protein. According to one paper published in the journal Nutrition and Cancer, a high intake of protein from animal or soy can increase insulin-like growth factor (IGF-1) which is associated with an increased risk of prostate cancer. They conclude that,
“It may be prudent for men with early stage prostate cancer not to exceed dietary protein recommendations.” (Dewell, 2007)
Numerous other studies have linked excess protein consumption to disease. While whole plant foods contain a perfect cocktail of nutrients including carbohydrates, protein, fat, vitamins, minerals, fiber, water, and phytonutrients, processed foods ultimately fail to match up. No human can match God’s infinite wisdom when creating the perfect cocktail of nutrients in whole plant foods. Man made foods that isolate a specific nutrient are food poisons, toxic to the health because they are out of balance with our natural bodies and natural wisdom of the Creator.
Stick With Whole Soy For Good Health!
People who live in the places where soy is consumed most have some of lowest rates of chronic disease and the longest lifespans of people around the world. These people, and the sum of the scientific research presented here, should help put your soy-scares to rest.
So to summarize the science into practical advice: include whole soy foods in your diet but say no to hyper-processed soy products. In the best interest of your health, avoid soy burgers, soy chicken nuggets, soy protein powders, etc. These are not healthy foods! Say yes to edamame in your salad, with rice, or as a side dish. Enjoy your tofu (not fried though!) with rice and veggies. Go easy on soy milk, soy sauce, and miso. These foods are ok in moderation, just like nuts and avocados.
Science says that whole soy foods including edamame, tofu, tempeh, miso, soy milk, and soy sauce contribute to many positive health benefits. So enjoy some whole soy foods, your body will thank you for it.
Reya Steele is a holistic health writer, educator, and publisher at Healing With Plants. Reya is certified in Plant-based Nutrition and teaches nutrition science and food preparation to students in Southern California. Healing With Plants is empowering people to heal themselves at home, with plants. Explore more nutrition facts, healing whole foods plant-based recipes, and inspiring stories that testify for the amazing healing power of plants.
SOURCES: 1. Barnard, N. "No Debate: Soy is Beneficial to Health." Physicians Committee for Responsible Medicine. March 2, 2016. 2. Chang ET, et al. "Diet and Risk of Ovarian Cancer in the California Teachers Study Cohort." American Journal of Epidemiology. January 8, 2007. 3. Dewell A., et al. "Relationship of dietary protein and soy isoflavones to serum IGF-1 and IGF binding proteins in the Prostate Cancer Lifestyle Trial." Nutrition and Cancer, 2007. 4. Hamilton-Reeves HM. "Clinical studies show no effects of soy protein or isoflavones on reproductive hormones in men: results of a meta-analysis." Fertility and Sterility, 2010. 5. Koh WP., et al. "Gender-specific associations between soy and risk of hip fracture in the Singapore Chinese Health Study." American Journal of Epidemiology, 2009. 6. Lee, SA, et al. "Adolescent and adult soy food intake and breast cancer risk: results from the Shanghai Women's Health Study." American Journal of Clinical Nutrition. 7. McDougall, J. "Soy-Food, Wonder Drug, or Poison?" The McDougall Newsletter. Vol 4, No. 4, April 2005. 8. Normura SJP, et al. "Dietary intake of soy and cruciferous vegetables and treatment-related symptoms in Chinese-American and non-Hispanic White breast cancer survivors." Breast Cancer Research and Treatment. 2018; 168: 467-479. 9. Pipe EA., et al. "Soy protein reduces serum LDL cholesterol and the LDL cholesterol:HDL cholesterol and apolipoprotein B:apolipoprotein A-I ratios in adults with type 2 diabetes" Journal of Nutrition, 2009. 10. Wu SH, et al. "Soy food intake and circulating levels of inflammatory markers in Chinese Women." Journal of the Academy of Nutrition and Dietetics. 2012;112:996-1004. 11. Yan L and Spitznagel EL."Soy consumption and prostate cancer risk in men: a revisit of a meta-analysis." American Journal of Clinical Nutrition, 2009. 12. Zhang FF et al. "Dietary isoflavone intake and all -cause mortality in breast cancer survivors the Breast Cancer Family Registry." Cancer March 6, 2017.
