Have you heard any of the myths passed around on the internet about the dangers of soy? In this article, you will find out how soy protein got became the subject of controversy. Why soy doesn’t deserve the bad rap. We’ll slay the big soy myths. Share the many benefits of soy. Tell you when soy is not good. And finally, share our recommendation for the best soy protein to buy.
The Beginning of the Soy Controversy
In 1999, the FDA took the highly unusual step of allowing a health claim to make soy a food. Not long after this, the food came under attack by a vocal minority of so-called concerned citizens. Unsurprisingly, some of these people represented a small segment of the food industry threatened by soy’s profits.
Economic concerns were clearly one of the main drivers of this controversy.
Sadly, these efforts have led to a considerable amount of misinformation being spread. Instead of enjoying the broad range of benefits, many people are unnecessarily fearful of consuming soy products.
Thankfully, all the noise surrounding soy has resulted in considerable clinical study and research, giving rise to a wealth of scientific literature that validates soy’s health-promoting potential.
The Center of the Soy Controversy
At the center of the controversy is the similarity of soy’s isoflavones to estrogen’s molecular profile and whether they increase the risk of certain hormone-dependent cancers and other adverse effects associated with hormonal imbalance.
But, really, almost all of the negative reports about soy stems from studies that involve rodents. The thing is, rodents metabolize soy much differently than humans , so using these studies as a scientific model for how soy foods affect humans isn’t all that helpful.
And its led to the following soy myths…
Soy Myth 1: Consuming Soy Can Increase the Risk of Breast Cancer.
Breast cancer and the effects of soy is one of the most controversial arguments out there online and real life. Regardless of who is yelling the loudest, the fact of the matter is that for more than 20 years the U.S. National Cancer Institute and laboratories around the world have been rigorously investigating the role of soy in breast cancer prevention Why? Well, Asian populations who traditionally consume soy as a dietary staple typically have far lower breast cancer rates than populations consuming a typical Western diet. And because roughly two-thirds of breast cancer is estrogen-sensitive, the anti-estrogenic effects of soy isoflavones may actually help decrease breast cancer risk. To top it off, studies have found that soy foods and soy isoflavones don’t increase breast tissue density or cause breast cells to multiply , unlike hormone therapy. In fact, consuming soy during the early years of life (the first 20 years, to be specific) may help to reduce the risk of breast cancer later in life .
And, in two recently published studies, soy consumption has also been shown to actually be associated with reduced recurrence rates and improved survival in people with breast cancer [10, 11].
Isoflavones are considered “phytoestrogens” because of their molecular similarity to estrogen, the female sex hormone.
What has led many doctors and scientists to characterize isoflavones as “weak estrogens,” is the ability of isoflavones to “mimic” some of estrogen’s effects.
According to Dr. Mark F. McCarty, an internationally recognized expert in soy isoflavones, this is incorrect.
As our understanding of how the body responds to estrogen has advanced, scientists have discovered that a new estrogen cell receptor exists and actually counteracts the processes associated with some cancer development.
By the way, a cell receptor is simply a molecule that receives chemical signals from outside the cell.
When these chemical signals bind to a receptor, they cause some form of cellular/tissue response.
These new findings actually show isoflavones promote beneficial estrogen-like effects but do not provoke the harmful effects of conventional estrogen replacement therapy in tissues.
For example, soy isoflavones have been shown to exert positive effects in tissues such as bone, vascular endothelium (blood vessel lining), and breast cells without the negative effects in those and other tissues such as liver and uterus, where side effects of estrogen therapy have been observed.
Dozens of studies are emerging which are now giving clear evidence that a diet that includes soy offers a wide array of health benefits.
Soy isoflavones have relaxing effects on blood vessels which explain their potential for the treatment and prevention of hypertension and stroke.
Another interesting benefit is they’ve been shown to increase the body’s antioxidant defense genes. To put it simply, your defense genes help your body cope with environmental stresses like oxidative stress, toxins and other attacks to the body and cells.
Many nations throughout the world have now similarly endorsed soy products based on this data.
Soy Myth #2: Soy Causes Thyroid Problems
If you’re a healthy human, then according to more than 20 studies that have looked at the effects of consuming soy foods (i.e. tofu), soy protein, and soy isoflavones on thyroid function, then you have nothing to worry about . In long-term studies (up to three years!) no effect whatsoever was found in the thyroid functions of subjects who consumed copious amounts of soy . However, it is important to note that people who take synthetic thyroid hormone medication should avoid taking it at the same time as ingesting soy to avoid possible interference with the medication’s absorption. But that doesn’t mean that it’s necessary to avoid it altogether. No, it just comes down to timing and consistency. If thyroid medication is
taken as prescribed (typically on an empty stomach and 30 minutes to an hour before breakfast), and
a consistent amount of soy is consumed in the person’s day-to-day diet, then you’re good to go.
Soy Myth #3: Men Shouldn’t Consume Soy
This myth keeps coming back thanks to two reports published in scientific literature that have described negative effects of excessive soy consumption…in exactly two individuals: men who consumed a massive 14 to 20 servings of soy per day [14, 15].
In contrast, a comprehensive scientific analysis of the research done on more average intakes of soy—more than 30 individual studies, we might add—found that neither soy foods or isoflavones have any effect on male testosterone levels. That’s right, in more than 30 individual studies, it was determined that neither soy foods or isoflavones have any effect on male testosterone levels .
Soy Myth #4: No Evidence of the Health Benefits of Soy, including Protecting Against Heart Disease
It’s actually quite the opposite. Research suggests that incorporating soy foods into a healthful diet has many proven or indicated health benefits for things such as:
- Osteoporosis – helping to reduce bone fractures in postmenopausal women [17, 18]
- Menopause – reducing the severity and frequency of hot flashes (by 50% on average) 
- Prostate health – lowering the risk of cancer 
- Heart disease – including decreasing LDL-cholesterol (the bad cholesterol) . Giving a modest boost to HDL-cholesterolReducing triglyceride levels
Lowering blood pressure . Promoting artery health 
Basically, when soy foods replace conventional sources of protein (usually animal protein) in Western diets, all kinds of good things can and do happen. For instance, saturated fat intake is reduced and polyunsaturated fat intake is increased, which has the comparable cholesterol-lowering effects of the kind of soluble fiber found in oat bran . As early as 1999 the Food and Drug Administration (FDA) awarded a coronary heart disease health claim associated with consuming two servings per day of soy foods.
When Soy Goes Bad
And you thought we were only going to say good things about soy! When soy goes bad, it’s because of the way the soybean is processed. It is true that “overcooked” soy does contain “carcinogenic” compounds. When soy is extruded through high temperature, high-pressure steam nozzles to form what is called “textured vegetable protein – TVP for short”, this form of processing can render the soy “meat substitute” carcinogenic. TVP is what is used in soy dogs and soy burgers, so consider that the next time you’re at the grocery store.
Whole soybeans are high in plant fat. If soybeans are roasted to eat as soy nuts, the heat alters the fat and makes it a trans-fatty acid, which has been shown to cause both cancer and heart disease. As roasted soy nuts sit on the shelf or in the cupboard in storage, the oils are becoming more and more rancid and carcinogenic. For those reasons, we recommend not eating roasted soybeans.
Finally even too much of a good thing like soy can become not a good thing. EXCESSIVE protein can be hard on the kidneys. So if a person consumes more than 2 grams of protein per pound of body weight daily, AND does not consume adequate carbohydrates with it, this could eventually cause kidney damage.
There are other processing errors that can lead to a poor quality soy product. See our article for the seven essential quality controls needed to create a good soy protein.
Some Good Soy Facts
The Benefits of Soy Protein:
Other than those who are allergic to soy (statistics say less than 8%), the vast majority of the medical and scientific communities agree that people can safely consume soy foods. Numerous scientific results obtained from human data, population studies, and clinical research all validate a variety of health benefits as well as the safety of regular consumption of soy foods . In fact, there are strong indications that soy foods offer significant health benefits, including reducing the risk of heart disease .
Here’s a summary of soy’s benefits by Dr. Mark Messina, a noted soy expert at the Department of Nutrition at the Loma Linda University School of Public Health.
- Protection from Cardiovascular Disease
- Combating Metabolic Syndrome
- Strength for Aging Bones
- Strong evidence for cancer prevention
- Shown to slow menopause
According to the Cleveland Clinic eating soy-based food provides a variety of health benefits.
- Eating soy is a great way to increase your plant protein. Research indicates that including more plant protein in your diet, as opposed to more carbohydrate, has clear cardiovascular benefits, such as lowering blood pressure.
- Soy foods are naturally cholesterol-free and low in saturated fat. Animal protein foods high in saturated fat and cholesterol increase your risk of developing cardiovascular disease.
- Substituting them with soy a few times each week can help cut saturated fats and reduce your overall risk for a disease.
- Eating soy-based foods is a great way to boost your fiber intake. Fiber promotes a healthy gastrointestinal system, reduces cholesterol, and is associated with a reduced risk of developing cardiovascular disease. Including fiber-rich soy foods like edamame (green soybeans), black soybeans, soy nuts, soy flour and tempeh in your diet can help you boost your daily dietary fiber.
- Soy foods are a good source of polyunsaturated fat. Polyunsaturated fats have a number of heart health benefits, such as lowering cholesterol. Choosing minimally processed soy foods will help you benefit from these heart-friendly fats.
- Soy foods contain omega-3 fats, essential polyunsaturated fats. Omega-3 fats are linked to a lower risk of cardiovascular disease.
- Soy foods are a great source of vitamins and minerals. B-vitamins, iron, zinc and an array of antioxidants round out the nutritional qualities of soy. In addition, many soy foods are enriched with vitamin B 12, calcium, and vitamin D to help vegetarians get these much-needed nutrients.
- Soy foods are a good source of phytochemicals. The phytochemicals in soy are called isoflavones. Isoflavones are currently being studied for their role in preventing postmenopausal bone loss and certain cancers.
The 2010 U.S. Dietary Guideline calls for increasing the intake of plant protein in the average diet, and soy foods are an excellent way to do that. Based on soy intake in Asians–who have been consuming soy for thousands of years, as well as the amount of soy shown to be beneficial in clinical studies, a good goal is to consume about 15 to 20 grams of soy protein per day or roughly 1 to 3 servings.
However most American get their protein from animal protein, not soy. The problem with animal protein is that it takes too long to digest. Meat also contains too much-saturated fat and cholesterol which brings its own set of problems. And then as we get older it becomes difficult to properly digest meat, which leaves too much residual acid in the body.
Because most animal proteins take too long to digest to maintain the amino acid and protein level, the body then must attack the muscles. This is why we lose muscle mass during our lifetime.
So now that you know the facts about soy. It’s many health benefits. And why its such a great source of protein. We hope you’ll be more comfortable adding it to your diet.
Note: If you just can’t stomach soy-based foods or simply want more information on or more information on other good sources of protein, check out our article Best Sources of Protein.
And if you find it difficult to get 1 to 3 servings of soy into your daily diet, order Shaklee’s new Life Shake. One serving of this delicious breakfast smoothie will provide 20g of healthy soy protein. Find out why Shaklee Protein is the best source of soy protein in our article entitled 7 Reasons Why Shaklee is the Best Source of Protein.
Check out Shaklee’s complete line of Soy Protein products HERE.
1. Oseni T, Patel R, Pyle J, Jordan VC. Selective estrogen receptor modulators and phytoestrogens. Planta Med. 2008. 74, 1656-65.
2. Gu L, House SE, Prior RL, Fang N, Ronis MJ, Clarkson TB, Wilson ME, Badger Tm. Metabolic Phenotype of isoflavones differ among female rates, pigs, monkeys, and women. J. Nutr.2006, 136, 1215-21.
3. Vierk KA, Koehler KM, Fein SB, Street DA. Prevalence of self-reported food allergy in American adults and use of food labels. J. Allergy Clin. Immunol. 2007, 119, 1504-10.
4. Zeitler P, Solberg P. Food and levothyroxine administration in infants and children. J. Pediatr. 2010, 95, 3067-72.
5. Messina M, Watanabe S, Setchell KD. Report on the 8th International Symposium on the Role of Soy in Health Promotion and Chronic Disease Prevention and Treatment. J. Nutr.2009, 139, 796S-802S.
6. Messina M, Barnes S. The role of soy products in reducing risk of cancer. J. Natl. Cancer Inst. 1991, 83, 541-6.
7. Wakai K, Suzuki S, Ohno Y, Kawamura T, Tamakoshi A, Aoki R. Epidemiology of breast cancer in Japan. Int. J. Epidemiol. 1995, 24, 285-91.
8. Hooper L, Madhavan G, Tice JA, Leinster SJ, Cassidy A. Effects of isoflavones on breast density in pre- and post-menopausal women: a systematic review and meta-analysis of randomized controlled trials. Hum. Reprod. Update. 2010, 16, 745-60.
9. Shimizu H, Ross RK, Bernstein L, Yatani R, Henderson BE, Mack TM. Cancers of the prostate and breast among Japanese and white immigrants in Los Angeles County. Br. J. Cancer. 1991, 63, 963-6.
10. Shu XO, Zheng Y, Cai H, Gu K, Chen Z, Zheng W, Lu W. Soy food intake and breast cancer survival. JAMA. 2009, 302, 2437-43.
11. Caan BJ, Natarajan L, Parker BA, Gold EB, Thomson CA, Newman VA, Rock CL, Pu M, Al- Delaimy WK, et al. Soy Food Consumption and Breast Cancer Prognosis. Cancer Epidemiol. Biomarkers Prev. 2011.
12. Messina M, Redmond G. Effects of soy protein and soybean isoflavones on thyroid function in healthy adults and hypothyroid patients: a review of the relevant literature. Thyroid.2006, 16, 249-58.
13. Bitto A, Polito F, Atteritano M, Altavilla D, Mazzaferro S, Marini H, Adamo EB, D’Anna R, Granese R, et al. Genistein aglycone does not affect thyroid function: results from a three- year, randomized, double-blind, placebo-controlled trial. J. Clin. Endocrinol. Metab. 2010, 95, 3067-72.
14. Martinez J, Lewi JE. An unusual case of gynecomastia associated with soy product consumption. Endocr Pract. 2008, 14, 415-8.
15. Siepmann T, Roofeh J, Kiefer FW, Edelson DG. Hypogonadism and erectile dysfunction associated with soy product consumption. Nutrition. 2011.
16. Messina M. Soybean isoflavone exposure does not have feminizing effects on men: a critical examination of the clinical evidence. Fertil. Steril. 2010, 93, 2095-104.
17. Koh WP, Wu AH, Wang R, Ang LW, Heng D, Yuan JM, Yu MC. Gender-specific associations between soy and risk of hip fracture in the Singapore Chinese Health Study. Am. J. Epidemiol. 2009, 170, 901-9.
18. Zhang X, Shu XO, Li H, Yang G, Li Q, Gao YT, Zheng W. Prospective cohort study of soy food consumption and risk of bone fracture among postmenopausal women. Arch. Intern. Med.2005, 165, 1890-5.
19. Messina M, Watanabe S, Setchell KD. Report on the 8th International Symposium on the Role of Soy in Health Promotion and Chronic Disease Prevention and Treatment. J. Nutr.2009, 139, 796S-802S.
20. Yan L, Spitznagel EL. Soy consumption and prostate cancer risk in men: a revisit of a meta-analysis. Am. J. Clin. Nutr. 2009, 89, 1155-63.
21. Jenkins DJ, Mirrahimi A, Srichaikul K, Berryman CE, Wang L, Carleton A, Abdulnour S, Sievenpiper JL, Kendall CW, et al. Soy protein reduces serum cholesterol by both intrinsic and food displacement mechanisms. J. Nutr. 2010, 140, 2302S-2311S.
22. Dong JY, Tong X, Wu ZW, Xun PC, He K, Qin LQ. Effect of soya protein on blood pressure: a meta-analysis of randomised controlled trials. Br. J. Nutr. 2011, 1-10.
23. Li SH, Liu XX, Bai YY, Wang XJ, Sun K, Chen JZ, Hui RT. Effect of oral isoflavone supplementation on vascular endothelial function in postmenopausal women: a metaanalysis of randomized placebo-controlled trials. Am. J. Clin. Nutr. 2010, 91, 480-6.
24. Ramsden CE, Hibbeln JR, Majchrzak SF, Davis JM. n-6 Fatty acid-specific and mixed polyunsaturate dietary interventions have different effects on CHD risk: a meta-analysis of randomised controlled trials. Br. J. Nutr. 2010, 104, 1586-600.
25. Hughes GJ; Ryan DJ; Mukherjea R; Schasteen CS Protein digestibility-corrected amino acid scores (PDCAAS) for soy protein isolates and concentrate: criteria for evaluation. J Agric Food Chem. 2011; 59(23):12707-12.
*NOTE: Results may vary from person to person. All statements in this article have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.