Healthy or Dangerous?
Over the past few years, soy seems to have gone from one of the healthiest foods to one of the least healthy, with some health professionals accusing the bean of causing a wide range of problems, from thyroid damage to pancreatic cancer. Are they right? Should you avoid soy?
My viewpoint: Eating traditional soy foods such as miso, tofu and others in amounts eaten by Asian peoples for thousands of years not only poses no threat to health…but (according to thousands of scientific studies) may help protect you from many chronic diseases, including heart disease, cancer, osteoporosis and kidney disease.
On the other hand, eating some of the recently invented foods that are made from soy—and there are thousands of these—is a different story altogether.
What you need to know…
Soy has many healthful components, including obvious ones such as protein and fiber. But soy’s most distinctive health-giving compounds are soy isoflavones—including genistein, daidzein and glycitein—which have a wide variety of health benefits…
Heart disease. Many studies show that regular intake of soy foods lowers LDL “bad” cholesterol and heart-harming triglycerides (another blood fat) and increases HDL “good” cholesterol—lowering the risk for heart disease.
Kidney disease. Dozens of studies show that soy is a nutritional ally for diabetes patients with kidney disease, slowing the condition.
Cancer. Research shows that soy intake can help prevent breast cancer and improve the chances of survival in women diagnosed with breast cancer. Studies also link soy to a lower risk for prostate, colon and lung cancers.
How it works: Soy isoflavones are phytoestrogens, estrogen-like plant compounds. However, phytoestrogens are only about 1/400th the strength of estrogen—and they have anti-estrogen properties. The American Cancer Society explains that phytoestrogens can block more potent natural estrogens from binding to estrogen receptors in breast cells. (When estrogen binds to estrogen receptors, it can spur on breast cancer.) Phytoestrogens also stimulate production of a protein that binds estrogen in the blood so that it is less able to bind to the receptor.
In addition, factors in soy can slow cancer-cell proliferation (cells dividing and multiplying)…stimulate the death of cancer cells…block the formation of new blood vessels to the tumor…and repair many of the genes linked to the development of cancer.
Osteoporosis. Regular intake of soy can help build bone mass, preventing or slowing this bone-eroding disease.
HOW MUCH TO EAT
I recommend eating (or drinking) three-to-four weekly servings of traditional “good” soy foods (see below). That amount delivers the daily amount of isoflavones eaten in traditional Eastern cultures and the amount that matches the level in studies that show benefits from soy intake.
Important: I don’t endorse the use of soy isoflavone supplements. There are many nutritional and botanical supplements that deliver factors you can’t get from your diet. But you can get the benefits of soy from soy foods—and that’s the best way to get them.
However, certain soy foods are bad for you. Here, the worst and the best…
The worst soy products are margarines and shortenings made from partially hydrogenated soybean oil. These contain trans fat, which hardens and clogs arteries, increasing the risk for heart attack and stroke. And many packaged foods—crackers, cookies, canned food, frozen entrées—contain partially hydrogenated soybean oil. Minimize or eliminate them all from your diet.
Another bad-for-you type of soy is processed soy protein, such as soy protein isolate, soy protein concentrate, texturized vegetable protein and hydrolyzed vegetable protein—ingredients that you will find in many processed foods ranging from nutritional powders to energy bars to veggie burgers.
Traditional soy foods are good choices. When possible, look for foods that are organic and do not contain genetically modified organisms (GMOs). No one really knows what effects GMO foods might have on our health, and animal studies link them to infertility, immune problems, digestive disorders and other issues. Human studies show that they may increase the incidence of food allergies. Traditional soy foods include…
• Miso (fermented soybean paste). Soybeans contain “antinutrients” such as enzyme inhibitors that can interfere with digestion. But Asian cultures discovered thousands of years ago that soaking, sprouting or fermenting soybeans neutralizes the antinutrients. Miso—fermented soybean paste—is such a food. And miso soup—a nourishing broth of fermented soybean paste and seaweed, often with vegetables and tofu—is a dietary mainstay for many Japanese people.
Important scientific evidence: Research from Japan’s National Cancer Center showed that women who ate three or more bowls of miso soup daily had a 54% lower risk for breast cancer than women who ate one bowl.
• Tempeh (fermented soybeans formed into a burgerlike patty). This soy food is a rich source of protein.
New research: In an animal study, rats were protected from drug-induced neurological damage and memory loss when they ate tempeh.
• Natto (boiled soybeans fermented with the bacterium Bacillus subtilis). This soy food is rich in vitamin K-2, a must for healthy bones. It’s also loaded with nattokinase, an enzyme that thins the blood and may help protect against heart attack and stroke.
• Tofu (soybean curd). Tofu is coagulated soy milk pressed into soft white blocks. My favorite way to eat it is to marinate it and make a wrap sandwich with some veggies and plum sauce.
Important scientific research: In one study of more than 1,500 women, published in Cancer Epidemiology, Biomarkers & Prevention, every additional weekly serving of tofu lowered the risk for breast cancer by 15%.
• Soy milk. Look for an organic, non-GMO brand, such as Pacific.
• Tamari. Tamari is made from fermented soybeans and is similar to soy sauce but has more soy and less wheat and is thicker and less salty.
• Edamame (green, immature soybeans, generally steamed and eaten out of the pod). Edamame contains fewer toxins than mature beans.
Allergic to Soy?
Symptoms develop within minutes to hours after eating soy and include mouth tingling, hives or itching, swelling of the tongue, lips or vocal cords, trouble breathing, diarrhea, nausea or vomiting. A severe reaction to soy (anaphylaxis) is rare—symptoms include constriction of airways, rapid pulse and dizziness—and warrants emergency treatment.
You might not be allergic to soy, but you might be sensitive to it. The symptoms of food sensitivity such as nausea, vomiting and diarrhea appear gradually—even days after ingestion—and usually happen when you eat too much or too often. If you have a soy sensitivity, determine the amount you can eat without symptoms and limit your intake.