The Truth About Soy: Healthy or Dangerous?

Reprinted with the permission of Bottom Line/Personal

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 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 its 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 it’s 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 it 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.


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 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 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 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.


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 (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 sensitivity, determine the amount you can eat without symp­toms and limit your intake. Sign up for Bottom Line’s FREE e-letters at

Reprinted with the permission of Bottom Line/Personal. Download the original PDF here.

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4 Replies to “The Truth About Soy: Healthy or Dangerous?”

  1. Thank you for the clarification regarding good snd bad soy products. I also appreciate the advice regarding food sesitivities.

  2. I didn’t know I was allergic to soy and suffered with rashes and low energy until I had a comprehensive food sensitivity test and then found out I am highly allergic to soy. I would not advise eating soy until you are tested for any sensitivity. It can wreak havoc in your digestive system and overall health. This test can save you lot’s of concern for your health down the road because it is in most foods out there organic and everyday processed foods. I suggest eat whole organic foods and prepare the food yourself whenever possible.

    1. Hello Diana – Can you be more specific about how you think soy disrupts the hormones and what type of soy product? Also referencing your research is helpful for me to comment on, as I have written & researched soy extensively. Best – Donnie

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