There has been endless confusion in the media about soy and its relationship to breast cancer. Does eating soy promote breast cancer or do soy foods offer a protective effect against this nightmarish and nightmarishly common disease? I for one, loathe confusion and we don’t deserve it. We deserve answers that provide us with accurate, scientifically validated information to make intelligent eating decisions. Only scientific research can provide us with trustworthy answers, not the media. Whereas reading a women’s magazine frequently causes me to cringe due to horrid, inaccurate nutrition advice, an in-depth investigation of intelligently designed studies provides a breath of fresh air for those who desire the truth.
Never has this been more true than in the case of soy. Recent and thoroughly scrutinized meta-analysis reports have provided conclusive evidence in favor of eating soy foods to reduce our risk of breast cancer.[i]
All reports on the dangers of soybean products are simply not founded in science. Study after study supports the benefits of soy foods, and evidence suggests that adding soy to our diets can prevent many types of cancer, reduce the risk of heart disease, promote bone health, keep us mentally sharp in our later years, and do absolutely no harm whatsoever.
One of the reasons soy is powerfully anticancerous is because it contains isoflavones, a type of phytoestrogen. Phytoestrogens are substances found naturally in plants that are chemically similar to estrogen. Because of this similarity in structure, when we ingest them, they bind to estrogen receptors. These suckers are so cool because they can block estrogen’s natural effects or have milder estrogen-like effects on the body. A human biochemistry novice might assume this would be a bad thing. After all, there is evidence that estrogen exposure is linked to an increased risk of breast cancer. But nope, this is a marvelous property for a food to possess. Isoflavones weaken the negative effects of estrogen, and there is conclusive evidence from thousands of studies that phytoestrogens are on our longevity, pro-thrivin’ side.
One study by the American Journal of Clinical Nutrition reports that soy consumption during childhood reduces breast cancer risk in adulthood by 60 percent, and consumption during the teenage years reduces the risk by 40 percent. Soy products are such potent breast cancer fighters that even women who have breast cancer benefit from consuming soy. A recent study of breast cancer survivors has shown that those who consume more soy have a 23 percent reduced risk of recurrence. This myth that soy is toxic and increases our breast cancer risk is hogwash, and we’ve got to dump it like a cheating boyfriend. Because, ladies, when we don’t consume soy, we are cheating ourselves out of some seriously cool anticancer chemicals. Riva Bitrum, the president of research for the American Institute for Cancer Research, has stated, “Studies showing consistently that just one serving a day of soy foods contributes to a reduction in cancer risk are encouraging. Consuming one serving of soy foods is a step most individuals would not find too difficult to take.”
You know who eats a lot of soy? Some of the oldest and healthiest people on Earth. The Okinawans of Japan, who have an overall extremely high life expectancy average and are famed for their population of centenarians, are known to consume large amounts of soy. The Okinawa Centenarian Study observed that high soy consumption was responsible for their amazingly tiny risk of hormone-dependent cancers, like breast, prostate, ovarian, and colon cancers. Okinawans’ rates of breast and prostate cancers are in fact a whopping 80 percent less than rates in the United States. Men would also benefit greatly by including some soy in their diets. A prestigious study called the Health Professionals Follow-Up Study found that men who consume soy milk daily have a 70 percent reduction in prostate cancer risk. Given statistics like these, it seems like a no-brainer that soy not only is not dangerous, but is in fact a rockin’ addition to our diets.
It is a shame that the media, and as a domino effect, word of mouth, has provided nothing but confusion and unjustified worry when in fact, scientific research has provided nothing but clarity and reasons to make unprocessed soy foods a regular part of our diets. Hopefully this blog post will help you see that you don’t have to worry about eating a few servings of soy each day and that unprocessed soy products are actually good for our bodies and offer protective effects against breast cancer.
Don’t just think anticancer when you think of the humble soybean; think anti–heart disease, too! The authors of the Okinawa Centenarian Study announced that the consumption of soy was one of the #1 reasons for the impressively low rates of heart attacks in the Okinawa elderly. Their risk of suffering a heart attack is 80 percent lower—that’s one heck of a risk reduction. One of the researchers was quoted as saying that if North Americans lived like the elder Okinawans and ate similar amounts of soy, we would have to close 80 percent of the coronary care units and one-third of the cancer wards in the United States, and a lot of nursing homes would also be out of business. Whoa. Even the FDA agrees that soy is great for our hearts. In 2000, the Nutrition Committee of the American Heart Association proclaimed that 25 grams per day of soy protein, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease. Of course these benefits assume that we reduce animal products as we eat more soy, but that is the whole point. Yay for soy!
Looking again to the Okinawans, we see that they have much stronger bones than Americans do and less than half the hip fractures. Once again soy can be thanked for playing a role in this health boon. Many studies support a connection between eating soy and a reduced risk of osteoporosis, a skeletal disorder in which one literally loses bone tissue. The reasons behind soy’s impressive bone-strengthening properties are twofold. First, the isoflavones in soy keep our bones strong by inhibiting their breakdown, and a recent meta-analysis demonstrated that soy isoflavones significantly increase bone mineral density in women. Second, soybeans contain many important minerals, like calcium, magnesium, and boron, all of which help our bones stay in tip-top shape.
Our brains benefit from soy just as much as our bones do. The isoflavones in soy help us preserve memory, enhance cognitive functioning, and reduce the risks of dementia and Alzheimer’s in old age. In one study, men and women who consumed a high-soy diet for 10 weeks (which is not even that long!) experienced a substantial enhancement in short-term and long-term memory and flexibility. In other studies, soy has been shown to have protective effects on our brain tissue and improve cognitive function. Like the Okinawans of Japan, the Seventh-Day Adventists, a religious group known for their extreme longevity, consume soy foods all their lives. Both the Okinawans and the Seventh-Day Adventists have paltry rates of dementia compared with the rest of the US population.
So now that we’ve established that soy foods can be pretty hot stuff, let’s be clear that not all soy foods should be consumed with the same gusto. Soy foods come in both highly processed and minimally processed forms. Isolated soy protein, for instance, is the protein isolated from the soybean and is used in absurd amounts in processed goods. Soy-based additives and isolated soy protein don’t have the same health benefits as minimally processed soy foods. Many dairy and meat substitution products, like soy cheeses, soy hot dogs, and soy hamburgers, have soy protein isolate as a main ingredient. We should use these products minimally if at all—they can raise IGF-1 levels similarly, but not as strongly, as animal protein. On the other hand, minimally processed soy foods will help keep us healthy and strong and preserve our precious braininess.
Here are research studies to cement your comfort with consuming soy:
1) Eight different studies were analyzed and found that there is a 16% reduced risk of breast cancer for every 10 mg of soy consumed daily. [iii]
2) Soy intake reduces the risk of type II diabetes! [iv]
3) On a diet? Soy has been shown to double weight loss efforts for those looking to shed pounds. [v]
4) Soy reduces our risks of getting a heart attack. This is pretty fantastic given that heart disease is currently the leading cause of death in America. [vi]
5) Soy strengthens our bones. Research indicates that a compound in soy called genistein can improve bone mineral density. [vii]
Even more studies to check out with even more evidence!
50. X. Zhang, X. Ou Shu, Y. Gao, et al., “Soy Food Consumption Is Associated with
Lower Risk of Coronary Heart Disease in Chinese Women,” Journal of Nutrition
133, no. 9 (2003): 2874–78.
51. X. Zhang, X. Shu, H. Li, et al., “Prospective Cohort Study of Soy Food
Consumption and Risk of Bone Fracture among Postmenopausal Women,” Archives
of Internal Medicine 165 (2005): 1890–95.
52. A. Wu, P. Wan, J. Hankin, et al., “Adolescent and Adult Soy Intake and Risk of
Breast Cancer in Asian-Americans,” Carcinogenesis 23, no. 9 (2002): 1491–96.
53. S. Lee 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 89 (2009): 1920–26.
54. N. Guha et al., “Soy Isoflavones and Risk of Cancer Recurrence in a Cohort of
Breast Cancer Survivors: The Life After Cancer Epidemiology Study,” Breast Cancer
Research and Treatment 118, no. 2 (November 2009): 395–405. Epub 2009 Feb 17.
55. J. M. Chan et al., “Role of Diet in Prostate Cancer Development and
Progression,” Journal of Clinical Oncology 23, no. 32 (2005): 8152–60.
56. A. Atmaca et al., “Soy Isoflavones in the Management of Postmenopausal
Osteoporosis,” Menopause 15, no. 4 (2008): 748–57.
57. P. Wei, M. Liu, Y. Chen, and D. C. Chen, “Systematic Review of Soy Isoflavone
Supplements on Osteoporosis in Women,” Asian Pacific Journal of Tropical
Medicine 5, no. 3 (March 2012): 243–48.
58. H. M. Hsieh, W. M. Wu, and M. L. Hu, “Soy Isoflavones Attenuate Oxidative
Stress and Improve Parameters Related to Aging and Alzheimer’s Disease in
C57BL/6J Mice Treated with D-Galactose,” Food and Chemical Toxicology 47, no. 3
59. S. E. File, N. Jarrett, E. Fluck, R. Duffy, K. Casey, and H. Wiseman, “Eating Soya
Improves Human Memory,” Psychopharmacology (Berlin) 157 (2001): 430–36.
60. M. J. Engelhart, M. I. Geerlings, A. Ruitenberg, et al., “Dietary Intake of
Antioxidants and Risk of Alzheimer Disease,” JAMA 287 (2002): 3223–29.
61. P. Giem, W. L. Beeson, and G. E. Fraser, “The Incidence of Dementia and Intake
of Animal Products: Preliminary Findings from the Adventist Health Study,” Neuroepidemiology 12 (1993): 28–36.
Soy is a super food choice, but remember that we can eat too much of any food (okay well maybe not leafy green vegetables!). It’s not a good idea to rely too heavily on soy foods to meet our protein requirements and the healthiest diet is one that contains an variety of plant foods. One or two servings of soy each day is health promoting, seven or eight servings a day is not. Another note for the wise: soy in the form of soy protein isolate is heavily processed and does not possess the same health benefits of unprocessed soy products.
What are great sources of soy you say? Tofu, tempeh, edamame, and unsweetened soy milk are fantastic!
[i] Trock BJ et al. Meta-analysis of soy intake and breast cancer risk. J Natl Cancer Inst. 2006; 98(7):459-71.
[ii] Sarkar FH, Li Y. Soy isoflavones and cancer prevention. Cancer Invest, 2003; 21: 744 – 57.
[iii] Wu AH et al. Epidemiology of soy exposures and breast cancer risk. British Journal of Cancer, 2008; 98: 9– 14.
[iv] R. Villegas, Y.T. Gao, G. Yang, H.L. Li, T.A. Elasy, W. Zheng, & X.O. Shu. Legume and soy food intake and the incidence of type 2 diabetes in the Shanghai Women’s Health Study. Am J Clin Nutr, 2008; 87(1):162-167.
[v] F.H. Liao, M.J. Shieh, S.C. Yang, S.H. Lin, & Y.W. Chien. Effectiveness of a soy-based compared with a traditional low-calorie diet on weight loss and lipid levels in overweight adults. Nutrition, 2007; 23(7-8): 551-556.
[vi] Goodman-Gruen D, Kritz-Silverstein D. Usual dietary isoflavone intake is associated with cardiovascular disease risk factors in postmenopausal women. J. Nutr, 2001; 131(4): 202-1206.
[vii] Marini H, Minutoli L, Polito F, et al. Effects of the phytoestrogen genistein on bone metabolism on osteopenic postmenopausal women: a randomized trial, 2007; 146(12): 839-847.