Advocates of soybean foods say they are the healthiest food you can put on the table. Critics say they can make you sick, impose a risk of cancer, and might make men infertile.
Ever since 1999 when the U.S. Food and Drug Administration approved food labels that claim soy products can help protect the heart, sales of the wonder bean’s food products have been booming. The accolades have been as fulsome and plentiful as a bushel of beans. But songs of praise have not been without a mounting chorus of Doubting Thomases—and some well-qualified Doubting Thomases.
In addition to reducing the risk of coronary heart disease, soy advocates also suggest other health benefits: reduced blood pressure; reduced risk of colon, breast and prostate cancer; help in managing diabetes (http://soybeanorg/health.html); promoting healthy bones, and alleviating menopausal symptoms. Gloria Tsang, “Powerful Benefits of Soy” in the web site of the Registered Dietitians of Canada. http://www.healthcastle.com/herb_soy.shtml
Some soy food benefits are not disputed. There is reported agreement that soy foods can provide the protein, vitamins, minerals, and fibre found in meat, eggs and diary products, but without the saturated fat and cholesterol from animal food. And too much cholesterol (especially the bad LDL) and too much saturated fat can lead to heart disease and other health problems. http://www.healthcastle.com/herb_soy.shtml
HEALTHY SOY ACCOLADES
It’s hard to imagine stronger accolades than soy foods have garnered during the past couple of decades for their healthy effects. A few of the many:
“Soy foods are the best food you can put on the table. Soy foods lower LDL [low density lipoprotein] cholesterol about 5% to 6%, and raise HDL 2% to 3%. These are all meaningful changes reducing the risk of cardiovascular disease in the range of about 25%.” James Anderson, Virginia Medical Centre and University of Kentucky. Findings of a study headed by Anderson were a key factor in the FDA’s approval of a heart-healthy claim. The Medical News, April 11, 2007 http://www.news-medical.net/news/2007/04/11/23421.aspx
“Ounce for ounce, calorie for calorie, the soybean gets top-billing as a rich source of protein, unsaturated fats, fibre, B vitamins, folic acid, potassium, calcium, zinc and iron—and it’s cholesterol free. There is no other food that supplies so much nutrition in such a tiny package.” William Sears, MD, Associate Professor of Pediatric, University of California, Irvine, School of Medicine http://www.askdrsears.com/
“After lowering your fat intake, the second most important step in a prostate-friendly diet is adding soy.” Trachtenberg, John, et al. “Challenging Prostate Cancer: Nutrition, Exercise and You,” page 14. Prostate Centre, Princess Margaret Hospital, Toronto http://www.prostatecentre.ca/
SOY CLAIMS APPROVED
Probably nothing did as much to boost soy food sales as the FDA’s approval of heart-benefit claims.
An initial step in winning that approval was a 1993 study, which found that “50 grams per day of isolated soy protein is effective in lowering total cholesterol, LDL, and apolipoprotein B while maintaining HDL in mildly hypercholestrolemic men.” Potter, S.M., et al. “Depression of plasma cholesterol in men by consumption of baked products containing soy protein. American Journal of Clinical Nutrition, vol. 58, no. 4, pp. 501-566. http://www.ajcn.org/cgi/content/abstract/58/4/501
More explicit was a 1995 study, which concluded: “The consumption of soy protein rather than animal protein significantly decreased serum concentrations of total cholesterol, LDL cholesterol and triglycerides. Daily consumption of 47 grams of soy protein reduced total cholesterol 9.3%; LDL 12.9%; and triglycerides 10.5%.” Anderson, James W., et al. Meta-Analysis of the Effects of Soy Protein Intake on Serum Lipids. New England Journal of Medicine, August 3, 1995. http://content.nejm.org/cgi/content/abstract/333/5/276
Four years later, after extensive tests, the FDA gave soy food producers approval to include this claim on their product labels: “Diets low in saturated fat and cholesterol that include 25 grams of soy protein a day may reduce the risk of heart disease.”
SOY CLAIMS DISPUTED
Even before it was issued, the claim was disputed—by two of FDA’s own researchers. In an internal letter dated February 18, 1999, researchers Daniel M. Sheen and Daniel R. Doerge wrote that they “oppose this health claim because there is abundant evidence that some of the isoflavones found in soy” pose potential health risks, including breast cancer, Alzheimer’s disease, thyroid abnormalities, and disruption of the endocrine system, the glands that secrete a hormone to regulate the body. http://www.soyonlineservice.co.nz./downloads/nctrpti.pdf
The claim of soy food producers that Chinese have safely eaten soy for 5,000 years is misleading, according to Seth Barrows, a chemical engineer and biochemist and founder of an alternative health firm, The Healing Crow. “The Chinese did not eat unfermented soybeans because the soybeans contain large quantities of natural toxins,” Barrow writes. The soy in soymilk and tofu is unfermented, although in such products as simulated meat it is fermented. The toxins in soybeans, says Barrows, “Can produce serious gastric distress, reduced protein digest and chronic deficiencies in amino acid uptake,” as well as cancer of the pancreas in test animals. Acid washing and other treatment do not completely remove the toxins in unfermented soy products, according to Barrows. Also, “Vegetarians who consume tofu and curd as a substitute for meat and dairy products risk severe mineral deficiencies.” Barrow, Seth. “Soy: For Your Health or Their Wealth?” 2001. http://www.healingcrow.com/incstory/incstory.html
A powerful blow to the claimed cardiovascular benefits of soy came in 2006 from the American Heart Association, which reversed its earlier support. “Earlier research indicating that soy protein has clinically important favourable effects compared with other proteins has not been confirmed,” AHA researchers wrote in the association’s journal Circulation. “In the majority of 22 randomized trials, isolated protein with isoflavones, as compared with milk or other proteins,” the reported reduction in LDL from consuming an average 50 grams of soy protein—“about half the total daily protein intake”—was only 3%. “No significant effects on HDL cholesterol, triglycerides, lipoprotein(a), or blood pressure were evident.”
Other suggested benefits were also questioned, including reduced menopause symptoms and postmenopausal bone loss. “The efficacy and safety of soy’s isoflavones for preventing or treating cancer of the breast, endometrium [inner membrane of the uterus], and prostate are not established; evidence from clinical trials is meager and cautionary with regard to possible adverse effect.”
But the AMA did find some good health effects from soy food, aside from the claims for the controversial isoflavone antioxidants: “Many soy products should be beneficial to cardiovascular and overall health because of their high content of polyunsaturated fats, fibre, vitamins, and minerals and low content of saturated fat.” Sacks, Frank M., et al “Soy Protein, Isoflavones, and Cardiovascular Health.” Circulation. 2006; 113:1034-1044. Abstract. © American Heart Association. http://circ.ahajournals.org/cgi/content/full/113/7/1034
In December 2007, the FDA announced its intention to re-evaluate two previously authorized health claims—dietary fat and cancer; and soy protein and risk of coronary heart disease. Comments were invited. The AHA was quick to respond. The AHA “strongly recommends that the FDA revoke” the cardiovascular claim, AHA president Daniel W. James wrote in a letter dated February 19, 2008. This, despite the fact that, as noted in the Circulation article, soy food can be helpful in replacing animal protein containing saturated fat and cholesterol.
A RISK OF MALE INFERTILITY?
As the FDA re-evaluates, a study by the Harvard School of Public Health and others raises the possibility of another risk from a high intake of soy foods: male infertility. The study suggests that one cup of soy milk or a soy burger or a serving of tofu every day could reduce the sperm content in male semen to a level of between two-thirds and one-half of normal.
The study, reported in the journal Human Reproduction by lead author Dr. Jorge Chavarro, analyzed the soy consumption of 15 soy foods consumed by 99 men who went to a fertility clinic between 2000 and 2006, looking at the relationship between semen quality and isoflavones. Those who consumed the most soy food had a semen concentration that was 41 million sperm per millimetre less than those who ate no soy food. Normal concentration ranges from 80 million to 120 million per millimetre.
The study was prompted by findings from earlier studies that noted a relation between high isoflavone intake and decreased fertility in animals. While the study suggested “that higher intake of soy foods and soy isoflavones is associated with lower sperm concentration,” Dr. Chavarro says that much larger studies will be needed to determine whether this poses a risk of human infertility. Reuters news agency, July 23, 2008. Chavarro, Jorge E. “Soy food and isoflavone intake in relation to semen quality parameters among men from an infertility clinic.” Abstract. Human Reproduction, vol. 23, no. 11, pp 2548-2590. Oxford University Press, on behalf of the European Society of Human Reproduction and Embryology. http://humrep.oxfordjournals.org/cgi/search?fulltext=jorge+chavarro&x=12&y=13
FOR WHAT IT’S WORTH
For what it’s worth, here’s my unprofessional take on what these reports appear to suggest.
Any possible benefits to your blood cholesterol would seem to require substantial daily consumption of soy food. The alleged risks might also require substantial daily consumption. Aside from possible affects on cholesterol—good, bad or nil—there are still good things said about soy food, in moderation.
“One aspect of soy that is not in dispute is that it is a good source of dietary protein,” Camilla Alexander writes in Food Engineering & Ingredients (Vo. 33 No. 2, pp. 13+). And, as already noted, the American Heart Association continues to see soy foods as healthy “because of their high content of polyunsaturated fats, fibre, vitamins, and minerals and low content of saturated fat.” Says Christine Lewis of the FDA’s Office of Nutrition Products Labelling and Dietary Supplements: “Soy by itself is not a magic food, but rather an example of the different kinds of food that together in a complete diet can have a positive effect on health.”
My research for this article has at least resulted in one decision in our house. We had been thinking about switching from dairy skim milk to soy milk and adding tofu to our diet. We’ve scrapped that idea. But we will continue to eat tempeh, the formented mixture of soybeans and grain used as a meat substitute. We won’t be eating it daily; if nothing else, that would be too boring. But we will continue eating it frequently. It’s even higher in protein that the original soy bean, with no saturated fat or cholesterol but lots of fibre, calcium, iron, zinc, B-12 and foliate.
Our favourite tempeh dish is sheperd’s pie. In addition to tempeh in the form of simulated ground round beef, my very easy-to-make shepherd’s pie recipe also includes a rainbow of vegetables and cooked, no-added-salt tomatoes with a little oil, possibly the world’s healthiest food.
TAGS: Soy food. Food and Drug Administration. Protein. Unsaturated fats. Cholesterol. Nutrition. Breast cancer. Alzheimer's disease. Food health risks. Cardiovascular disease. Vitamins. Minerals. Fibre.
TAGS: Soy food. Food and Drug Administration. Protein. Unsaturated fats. Cholesterol. Nutrition. Breast cancer. Alzheimer's disease. Food health risks. Cardiovascular disease. Vitamins. Minerals. Fibre.
