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Is soy making you sick?

Soy has been lauded as a quality protein that is loaded with nutrients, good for the heart, lowers cholesterol, combats cancer and menopausal symptoms, and oh so versatile. Soybeans can be eaten fresh, dried, in the forms of tofu, fermented as tempeh, and in a number of soy-fortified foods as well as soymilk. Soy has enjoyed a rapidly increasing popularity, but there is a dark side to the soybean. And it is particularly important for women to know the good and bad aspects of soy.

Woman eating Edamame Beans.

If the health food market were high school (and it is like high school, made up of cliques of “in” and “out” crowds and a student body of oft-forgotten or misunderstood lesser nutrients), soy would be head cheerleader. Applauded increasingly over the last decade, the humble soybean and its numerous purported benefits have headlined magazine covers, newspapers, food packaging, supplements and even cosmetics. It has, in short, been very good to be soy.

However, new research is revealing another side of soy – a less positive picture that is of particular concern to women, their health and the health of their children.


  • Source of lean protein. Soybeans are an excellent source of lean protein and the primary source of non-animal protein for vegan and vegetarian populations.
  • High in nutrients and low in calories. Soybeans provide B vitamins, amino acids and heart-friendly fats to the diet – and typically for fewer calories than animal sources.
  • Available in many forms. Soy is available in various forms such as edamame, soy milk, soy yogurt, tofu, natto, miso, tempeh and even soy chips and other soy-fortified foods and supplements.
  • Heart-healthy. Soybeans are rich in saponins, compounds which are thought to lower cholesterol. In 1999, the FDA even approved a health claim stating that soy could help lower cholesterol, allowing companies to tout the healthful properties of soy and leading to a sales boom of almost $4 billion in 2003 – a boom that has continued to increase.
  • Prevents disease and eases menopause. Soybeans are rich in isoflavones, which are plant-based compounds released during digestion. In their active form, isoflavones, also called phtyoestrogens, act as plant-based hormones and have been associated with cancer prevention, combating osteoporosis and easing the symptoms of menopause.

With all these benefits, what could possibly be wrong with soy?


A 2004 study in the Journal of the American Medical Association revealed that isoflavones did not improve cholesterol levels, bone density or other menopausal symptoms in post-menopausal women who supplemented their diets with isoflavones, calling into question previous studies which prompted the FDA’s glowing recommendations. Worse, isoflavones themselves have come under fire as a potential health threat for certain women, and several mainstream medical organizations (including the Mayo Clinic and The Sloan Kettering Cancer Center) now recognize and are monitoring potential risks.


According to Harold McGee, author of On Food and Cooking: The Science and Lore of the Kitchen, the phytoestrogens in soy mimic hormones in the body – and any woman who has experienced PMS or a hot flash will agree that hormones are a powerful aspect of body chemistry. Aside from triggering monthly woes or sexual desires, hormones can directly affect cells by promoting cell-division, leading – in the worst cases – to cell-growth abnormalities such as cancer or goiters. This is not to say that all hormones cause cancer – it simply means that hormone chemistry is not to be tinkered with lightly.

Soy opponents such as Dr. Kaayla Daniel, author of The Whole Soy Story: The Dark Side of America’s Favorite Health Food, says that this is where the trouble begins. The phytoestrogens in soy act as hormones, mimicking estrogen within the body.

According to recent research, this mimicry may actually promote estrogen-dependent cancers, such as breast, endometrial or thyroid cancers, especially in high risk women. Cancer survivors or those who currently have the disease are at higher risk as well. Phytoestrogens may also potentially interfere with breast cancer prevention drugs such as Tamoxifen, an anti-estrogen drug given to high-risk patients.

And while many women take soy supplements to ease the symptoms of menopause, one study conducted at the University of Perugia, Italy, reported that menopausal women who took soy supplements for five years had an increased risk of a specific uterine problem, which can lead to cancer in some instances.


Another controversy lies in baby formula. Nearly 25 percent of bottle-fed infants in the United States receive soy-based formula. Opponents of soy formula accuse its high measures of isoflavones, which raise levels of estrogen in the blood to nearly 15,000 times that of babies given milk-based formulas, of triggering thyroid abnormalities and premature sexual development later in life. Other research also warns that introducing soy into the diet too early in life can increase the risk of allergies later (soy is one of the top 10 food allergens in the country).

While most experts in the United States claim that soy-based formula is safe, the French Food Agency (AFSSA) issued a statement in 2006 that it would “require manufacturers to improve the safety of soy infant formula and to put warning labels on packages of soy foods and milk.” Regulations included removing isoflavones from soy formula altogether, and requiring manufacturers to warn about the dangers of soy for high-risk breast cancer patients and those with hypothyroidism.

The Israeli Health Ministry also advised that babies not be fed soy formula, and encouraged citizens to limit servings of soy to three a week for children under 18 years old.


The research is confusing. Because plant-based or natural treatments and preventatives are, in most cases, safer than their synthetic counterparts, many doctors eagerly leap to the defense of soy – almost as eagerly as others rise to defame it. However, there is a lack of unbiased clinical research on BOTH sides, resulting in more hearsay and less fact on both sides of the issue. So what can you do?
Various Soy Products
1. Monitor your soy intake. Concerned consumers should monitor the overwhelming prevalence of soy in the American diet by reading labels carefully. In addition to the multitude of blatant soy-based foods, soy additives, oils, proteins and emulsifiers can be found hiding in unsuspecting condiments, ice creams, protein bars, processed foods, candies, chocolates, health shakes and beverages, making it easy to consume well over the 35 grams a day recommended by government health agencies. When reading labels, be aware of terms like “lecithin,” “vegetable protein,” and “natural flavoring,” all of which are code for soy. Moderation, as always, is key.

2. Eliminate soy intake if you have a high-risk for cancer. While monitoring soy intake may be enough for some, women at high risk for estrogen-dependent cancers or thyroid disease may want to abstain entirely until more research has been done. Women taking Tamoxifen or similar anti-estrogen drugs should consult with their physician about incorporating soy in their diet.

3. Breastfeed. New mothers may also want to consider milk-based formulas or breastfeeding, if possible, to reduce the risk of hormone-related complications and childhood soy allergies.

There is no reason to swear off soy entirely or panic because you have been consuming soy-based foods or drinks. Low-risk women should also keep in mind that there is a difference between isolated soy compounds and a whole food, so while taking soy supplements such as isoflavones may be dangerous for certain individuals, having the occasional bit of tofu in your pad thai or a moderate amount on a regular basis is unlikely to be detrimental.

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