Is Soy Good or Bad for Your Health?


You’ve probably seen them in supermarkets and have heard them mentioned on the news or some health updates.

But is soy good or bad?

Is it really as healthy as people say it is, or is there something more to it.

We take a closer look at soy and all the products related to it.


What is Soy?

Soybeans are originally from Asia but they are now grown in mass quantities here in the U.S.

Soybeans are used to make many different products including: soybean oil, soy infant formula, soy milk, and tofu. It is also added to many of our processed foods like hot dogs and bologna.

Soy is a Plant Based Complete Protein Source

Soy is one of the few plants that contain protein considered to be the same quality as animal protein. By this we mean that soy is one of the few non-meat complete proteins. Complete proteins contain all the 9 essential amino acids that that body needs but cannot make on its own.

As such, the body can only get these 9 amino acids from food. This makes soy a valuable source of protein for those who choose not to eat meat or dairy, like vegans or certain types of vegetarians.

The FDA says that consuming 25 grams of soy protein daily can lower your risk of heart disease.

Soy Contains Omega 3 Fatty Acids


They are a great source of amino acids as well as omega 3s. Omega 3s are usually found in fish and seafood and studies show that most Americans don’t get enough of this essential nutrient.

Do note however, that there are a different types of Omega-3 fatty acids. These include

  1. EPA (eicosapentaenoic acid),
  2. DHA (docosahexaenoic acid),
  3. and ALA (alpha-linolenic acid).

EPA and DHA are found in animal sources, especially cold water fish like tuna, sardines, mackerel and salmon. They’re also the ones you find bottled in fish oil capsules. Other supplement sources of EPA and DHA are krill oil and cod liver oil.

EPA and DHA omega-3 fats are the ones that are most valuable for us.

ALA meanwhile, are plant based omega-3 fatty acids. This is the type found in soy, as well as nuts and seeds And while ALA is an essential fat the body needs, which it uses for energy. ALA also gets converted into the EPA and DHA in the body.

However ALA gets converted into EPA and DHA at a low ratio.

This means that compared to taking EPA and DHA, if you consume plant based sources of omega-3 which contain ALA, you won’t get as much EPA and DHA, even if you eat the same amount of omega-3 fats to start with.

This is why many health experts recommend going with fish sources of omega-3 compared to plant based sources like flaxseed or soy.

That said, having Omega-3 fats from plant based sources, is still better than not having any at all.

Soybeans Contain A Good Amount of Vitamins & Minerals

Soybeans also contain vitamin c, thiamine, calcium, magnesium, potassium, and iron. These nutrients make soy a good substitute for someone with dairy intolerance issues or someone who is vegan because soy can help replace the protein and nutrients usually found in dairy and meat products.

It’s Loaded with Fiber

Soybeans also contain a high amount of fiber. Each cup of soybeans have over 10 grams of fiber which make them something that can most people since majority of us don’t get enough dietary fiber.

The American Heart Association recommends that adult men get 38 grams of fiber daily while women should target 25 grams of fiber. However, we fall way short of those recommendations, as the average American only gets 15 grams of fiber each day.

One cup of soybeans, at nearly 11 grams, goes a long way to fulfilling the suggested daily fiber intake.

The fiber content in soy, is partially responsible for its ability to help lower cholesterol and blood pressure.


The Darker Side of Soy

tofu avocado salad

So why the controversy?

If you’ve read a bit about soy or followed it, you’ve probably heard that some experts say it isn’t as healthy as the media might be making it sound.

Much of the controversy stems from isoflavones.


Isoflavones are compounds only found in plants. This is why they’re called phytochemicals. Soybeans along with other soy based products, are among the highest food sources of isoflavones.

Isoflavones are also a kind of plant hormone that have qualities like those of estrogen, which is the hormone that gives the female body its distinct properties (relative to the male form).


The Two Faces of Isoflavones

The issue with isoflavones is that it has good and bad sides.

Advocates of soy point out that many of soy’s benefits stem from isoflavones, while detractors say that it is dangerous and harmful to our body.

Estrogen Effects

Isoflavones are phytoestrogens which means they are the plant version of the estrogen our bodies produce, and this is where the controversy comes in.

Opponents of soy argue that these phytoestrogens act like normal estrogen in our bodies. The claim is that this causes either too little estrogen in our bodies because we use the phytoestrogens instead of our body’s own more potent estrogen. Or, that it causes too much estrogen activity by activating the receptors.

Its estrogen like effects also make isfoflavones endocrine disruptors. The body’s endocrine system is responsible for producing hormones that work as signals to help regular almost everything in the body including our metabolism, mood, sleep cycle, and sexual function.

This makes it potentially interfere with the body’s regular functioning.

Breast Cancer

Another claim is the presence of isoflavones in soy leads to increased risk of breast cancer in women.

Studies have shown that women consuming soy have an increase in the cells in the breast most likely to cause cancer, but observational studies have found that women who consume soy have a lower incidence of breast cancer.

At this point, as far as scientific verification goes, there’s nothing conclusive with soy and its effects on breast cancer due to the conflicting research results.

Testosterone and Sperm Count in Men

Men have low levels of estrogen in their bodies naturally. The concern with soy is that raising estrogen levels can affect testosterone and sperm count.

One study followed 99 men at an infertility clinic. The men that had eaten the most soy had the lowest sperm count. Other studies meanwhile, show a slightly lowered sperm count in soy consuming males while others show no change at all.

Isoflavones Suppress Our Thyroid Function


One of the other effects that these compounds have is that they inhibit thyroid peroxidase. Thyroid peroxidase is an enzyme that’s needed for proper functioning of the thyroid. Its presence allows for the proper production on thyroid hormones.

By inhibition the production of our thyroid hormones, the result can lead to hypothyroidism, which affects your energy levels making you feel tired, weak and feel sleepy, as well as experience other symptoms like constipation.

Researchers however have found that getting enough iodine in your diet helps prevent the effects of isoflavones on the thyroid.

So if you regularly eat soy or soy products, you’ll need to make sure that you get sufficient iodine in your diet to counteract the effects of isoflavones on the thyroid enzymes.

It May Prevent Certain Types of Cancer

Proponents of soy say that isoflavones actually lower your risk of hormone related diseases such as breast and prostate cancer.

A number of studies have shown soy to help prevent prostate cancer in men. These studies present the potential of soy for preventing as well as inhibiting the progression of this type of cancer.

However, like the results found in breast cancer studies, soy’s effects on prostate cancer have been inconsistent with some studies showing it helps and other with limited to no effects.

Its Helps Lower Your Risk of Cardiovascular Disease

Isoflavones also prevent the growth of the cells that cause plaque to grow in your arteries and lower your bad cholesterol, decreasing your risk of a heart attack.

Earlier studies showed much larger effects of soy of lowering LDL cholesterol. Lately though, the results have been more modest with smaller decreases in bad cholesterol. Some studies show no effect on cholesterol levels, even.

Isoflavones are Beneficial For Postmenopausal Women

Menopause occurs when menstruation stops in females.

While natural, it does cause some undesirable effects like mood swings and hot flashes. These are caused by the reduction of estrogen levels in the body which occur during menopause.

Soy has been found to help alleviate the symptoms of menopause.

In menopausal women, soy has been shown to have many benefits. Because the isoflavones mimic estrogen they can be a good alternative to hormone replacement therapy. It has been known to reduce hot flashes, mood swings, and reduce the risk of osteoporosis.


So Why All the Inconsistencies

tofu soy products

Going through all the effects of soy, you would have noticed that a lot of them are fairly inconsistent with some research showing good or even significant results while others far less so, with some showing none at all.

One possible reason for this is the isoflavone composition in soy.

Soy is made of mainly 2 types of isoflavones,

daidzein, which makes up around 40%, and
genistein, which is around 50% of the isoflavones in soy.

The remaining 10% is glycitein.

The differences in results comes down to the body’s ability to metabolize these isoflavones and turn them into equol, which is the potent estrogenic metabolite that produces most of the benefits we’ve seen from soy ranging from the cancer preventive effects, to reducing cholesterol and preventing osteoporosis.

The issue arises because only about 1/3 to 1/2 of all people are able to metabolize the isoflavone daidzein to equol. This has to do with the composition of our gut flora. The type of bacteria you have in your gut determines whether or not your body can process this isoflavone.

Those whose bodies can do so, produce equol and gain the extra benefits of soy, compared to those who can’t.

Research has found that Asian populations have higher percentages of individuals who can produce equol compared to westerners, which may also contribute to discrepancies in research results.


Choosing the Right Type of Soy Products

It should be noted that everyone seems to agree that the more processed soy is, the less nutritional value it has.

Some of the best soy products for nutritional value include fermented foods like miso, tempeh and soy sauce, though you’ll want to limit use on the soy sauce because of its sodium content.

Also foods like non-GMO tofu and edamame are great sources of soy if you choose to include it in your diet.

Even proponents of soy say you should try to avoid overly processed soy. Anything that contains soy protein isolate or soy protein concentrate is highly processed and will not give you the same nutrition and benefits as the unprocessed variety.