Soy: A Health Superfood – Or Is It? - Healthy Living Association

Soy: A Health Superfood – Or Is It?

Soy broke onto the American health food scene a relatively few years ago after being eaten by Asians for centuries. Quickly, it gained the enviable status of being a health superfood. Those who don’t eat meat, vegetarians and vegans, touted soy as the best thing since sliced tofu.

So, with this kind of endorsement, soy must be good for you. Right? After all, the Asians who have been eating it have some very good health benefits that seem to come from eating all that soy.

But, have you been sold a bill of goods? There is significant controversy regarding the health benefits of soy. Some say everyone has been fooled by a magnificent marketing effort. After all, the soy market is worth several billion dollars.

Let’s take a look at the good and not-so-good of soy.

Benefits of Eating Soy

1. Effects on Cancer. There are some research findings that suggest eating soy lowers your risk of developing some types of cancer. Most studies that are of sufficiently high scientific quality completed recently show soy does not increase the risk of developing breast cancer. In fact, one meta-analytic report covering 35 studies showed no relationship between consumption of soy and breast cancer in American women. Some research findings have shown eating soy provides some risk lowering for gastrointestinal cancer. The high fiber content of soy foods has been linked to lower risk of colon cancer.

2. Effects on Fertility and Hot Flashes. There may be some benefit from eating soy when you’re trying to get pregnant or if you have hot flashes. Research shows women exposed to BPA toxins and trying to get pregnant through in vitro fertilization were more likely to get pregnant when eating soy. It appears the isoflavones in soy help to neutralize the effects of BPA.

It’s important not to overdo consumption of soy in an effort to get pregnant. Daily consumption of more than 100mg of the isoflavones has been shown to decrease function of the ovaries.

As far as hot flashes are concerned, eating soy may help some women. Among women who produce equol, a metabolite of soy, those who ate the most soy had fewer hot flashes than those who ate the least, according to one study.

3. Soy and the Thyroid. This is a case where a negative finding is positive. Many experts believe soy to have a negative effect on thyroid functioning. But a review of 14 research studies showed no negative effects on thyroid functioning among people with healthy thyroids.

On the other hand, if you have an underactive thyroid, eating soy can lead to problems. But only if you eat too much. Soy has been shown to inhibit the absorption of thyroid medication.

One caveat: Research results aren’t completely conclusive. This means more research needs to be done. In any case, you should wait at least four hours after eating soy to take your thyroid medications.

4. Some Heart Protection. It appears the isoflavones in soy have some heart protective qualities. They also may reduce the risk of osteoporosis and loss of cognitive abilities in older adults. Some of these isoflavones have been found to reduce production of fat cells and thus may provide some protection against obesity. There is some indication that even if the isoflavones are taken out, the protein found in soy may have some heart benefits.

Another possibility is that simply replacing meat with soy in your diet may have health benefits for your heart. Soy has possibly the best protein and amino acid profile of any of the meat-replacing plants available. Lysine is one of those important amino acids found in soy that is not present in other plants.

Negative Effects of Soy

Just as research has shown some health benefits of soy, other research has found some significant negatives in eating soy.

1. Presence of Phytoestrogens. Phytoestrogens act like the body’s natural estrogen. Consuming these substances can lead to infertility, reduced sperm count, out of balance testosterone, and an increased risk of some cancers in men. In women, eating soy and its phytoestrogens can lead to estrogen dominance. This can lead to an increased risk of some cancers, infertility, and some menstrual problems.

The phytoestrogens in soy can be dangerous for babies who are fed soy formula, as well. They are powerful enough to be the equivalent of taking the hormones in 4 birth control pills a day.

These phytoestrogens are found in the isoflavones mentioned above. In men, the imbalance in testosterone brought on by these phytoestrogens can mean loss of energy, lower libido, a buildup of fat around the waist, loss of stamina and virility, and development of larger breasts in men (gynecomastia).

Babies who are fed formula high in soy content may have an imbalance in their hormones, resulting in a failure to develop normally. Too much estrogen in developing baby boys can lead to gynecomastia, failure to thrive, and undeveloped testicles.

Other research has suggested these potential drawbacks may not be as significant as first thought. Some of this research shows the phytoestrogens not to operate in the same way as natural estrogen. They may increase the growth of cancers in woman who have already been diagnosed with breast cancer. However, other research has shown women who eat high amounts of soy in adolescence and early adulthood may actually gain a protective factor against the development of breast cancer before menopause. This protective factor amounts to a 60% lower risk of cancer development.

Another study showed women who drank even a small amount of soy milk daily had lower risk of developing ovarian cancer. Other recent research showed some of the phytoestrogens found in soy to prevent estrogen from attaching to cancer cells, thus inhibiting the growth of the cancer cells.

Other recent research showed these phytoestrogens to have no effect on testosterone levels in men.

2. Inhibition of Digestion and Absorption. Protease inhibitors are found in soy. These compounds interfere with your body’s ability to digest some proteins. Phytic acid in high levels is found in soy. This decreases your body’s ability to absorb nutrients like iron, copper, zinc, calcium, and magnesium. Many people are already deficient in this last mineral.

3. Presence of Goitrogens. These compounds in soy interfere with thyroid functioning and can lead to endocrine disruption. Babies who consume soy-based formula have a higher risk of developing autoimmune thyroid disease. Cruciferous vegetables such as broccoli and cabbage also have these compounds, but they are reduced a large amount by cooking. Unfortunately, cooking does not take them out of soy.

4. Eating Soy Does Not Necessarily Protect Your Heart. In spite of the widely touted beneficial effects on heart health, rigorous research does not support this. In fact, the American Heart Association withdrew its endorsement of soy saying there is not sufficient evidence to make the claim that soy protects your heart. In spite of this, there is a benefit in replacing some meat meals with plant-based food.

5. Leptin Resistance. Just like with other legumes and grains, soy contains lectins. These compounds change your sensitivity to leptins, thus interfering with your brain’s ability to tell you when you’re hungry or when you’re full. This in turn can lead to insulin resistance, potentially causing difficulties with blood sugar and the potential for developing metabolic syndrome.

6. Destructive Crops. Among the monocrops, soy is the most destructive. In addition to taking a great amount of nutrients from the soil and returning none, soy is possibly the most pesticide-soaked crop. Likewise, most soy crops grown in the U.S. are genetically modified in some way. Some sources say 93% of soy is genetically changed in some way. The vast majority of soy produced goes to feed animals. This can pass on the changes brought on by genetic modification to humans who consume meat from these animals. Some experts say the chemical glysophate is so present in soy, that people who eat it can’t avoid the destructive chemical.

Glysophate has been regarded as the largest factor behind the development of chronic diseases and conditions world-wide. These conditions and diseases include autism, obesity, allergies, and cancer.

7. Unknown Effects of Eating Large Amounts of Compounds in Soy. Experts have no knowledge of the effects that may result from consuming large amounts of isolated compounds found in soy. This becomes important when considering the prevalence of soy in products such as supplements and powders.


So, is soy healthy? As with so many products and foods, the research evidence in nutrition regarding soy answers this question both yes and no. It depends on many factors, including the amount of soy you eat, the kind of soy you eat, and whether the research is accurate or not. Any time there are competing opinions from experts and either competing research or insufficient research, health questions regarding nutrition are difficult to answer.

The best thing is for you to read as much information regarding soy as possible and decide for yourself. Be sure the information you read comes from reputable sources. Make the best decision for your health that you possibly can.


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