Soy or Soy Milk: Is it Really Bad or Good for You (Science Based)

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Here is what Happens to Your Body When You Consume Soy

Consuming soy products and soy milk for their health benefits is surrounded by controversy. Many vegans and vegetarians rely on soy because it is a good source of complete protein, amino acids, vitamins, and minerals. However, many people say that consuming more soy is linked to dangers such as cancer, hormonal imbalance, and thyroid disorders.


Are soy foods and soy milk good or bad for you? Does consuming soy pose any health risks for men or women? Scientific research into the health benefits and risks of soy comes up with conflicting answers.

In this article, you will find out what science really says about whether soy milk, soybeans, and soybean-based foods are good for you.

What is Soy?

Soybeans are a type of legume (or, pea) that grow in many countries around the world. The largest producers of soybeans in the world are the United States and Brazil.

The medical journal, American Family Physician, says that soy is a complete source of protein that contains all the essential amino acids needed for good health. Soybeans are one of the few legumes that contain all the essential amino acids needed for good health. The study concludes that overall, soy is well tolerated, and can also help to lower cholesterol. (1)

Soy-based foods come in many shapes and forms. Vegans consume soy milk as an alternative to dairy products. You can also buy tofu, soy flour, soybean infant formula, and soy as a meat substitute.

Fermented soy products such as miso, tempeh, and natto are popular dishes in Asia.

You can also eat cooked immature soybeans which are called edamame.

Nutrients in Soybeans

The rich nutritional value of soybeans means that soy foods and beverages might be a healthy alternative for people who choose a meat and dairy-free diet.

According to the United States Department of Agriculture, 100 g of boiled mature soybeans contain 172 calories. This 100 g portion also provides you with 16 grams of protein which is 33% of your recommended daily intake (RDI) and 6 g of fiber (24% RDI). (2)

100 g of cooked soybeans also contains 5 g of iron (29% RDI), 86 mg of magnesium (21% RDI), 102 mg calcium (10% RDI), and 0.8 mg of manganese (41% RDI).

Soybeans also contain large amounts of vitamin K, vitamin C, and B-group vitamins, as well as trace amounts of vitamins A and E.

So, if soy seems so good for your health, what is all the controversy about?

Is Soy Good or Bad for You – Overview

A medical study about soy says that soy is good for you because it may lower risks of prostate cancer in men and breast cancer in women. The study also claims that increasing dietary whole soy protein lowers levels of total cholesterol, low-density lipoproteins, and triglycerides. Soy may be good for women because it may improve menopausal hot flashes and may also help maintain bone density and decrease fractures in postmenopausal women. (1)

Much of the discussion on whether soy is beneficial for your health or detrimental to it is connected to the large amounts of isoflavones in soybeans.

The journal Mayo Clinic Proceedings reports that isoflavones found in legumes such as soybeans are a class of phytoestrogens. These have an estrogen-like effect on the body. In fact, the effect of soy-based products on estrogen in the body means that soy isoflavones could be an alternative to estrogen for hormone replacement therapy. (3)

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Regarding the potential health risks of consuming soy and soy milk, doctors on WebMD say that one tablespoon of soy powder contains about 25 mg of isoflavones. The estrogen-like effect of isoflavones can affect your thyroid hormone and may speed up cognitive aging. (5)

The journal Alternative Therapies in Health and Medicine reports that soy could be bad for men because it may interfere with male fertility. (6)

However, other studies show that soy isoflavones can have a beneficial effect on your health.

Research published in the journal Biomedical Reports found that soy isoflavones can help protect against heart disease and prevent many complications associated with the menopause. (7)

There is also evidence to suggest that isoflavones from soy legumes can have a protective effect against breast cancer in menopausal women. (8) Some researchers have found that soy isoflavones actually have anti-estrogenic properties and that they alter estrogen metabolism to stop cancerous cells from developing. (39)

It should be noted, that other studies have suggested that soy could actually increase the risk of breast cancer. (6)

At the end of this article, you can find more information on what science says about the link between soy and cancer.

Researchers say that many of the potential health risks of soybeans can be avoided by fermenting soybeans, soaking them, or cooking them. (6)

Obviously, more research into the health benefits/risks of soybeans and soy food products needs to be done before you can definitely say if soy is good or bad for you.

What is Soy Milk?

Soy milk is one of the most popular alternatives to dairy milk for vegans or people who are lactose intolerant.

Soy milk is made by creating a drink by soaking soybeans and then blending them with water until you have a smooth liquid. The liquid is then strained to remove any remaining particles. (9)

Soy milk looks like dairy milk and has a natural savory taste like beans. Most commercial soy milk products are flavored to improve the taste (for example, vanilla soy milk).

Benefits of Soy Milk

There are many benefits of drinking soy milk because it is a rich source of minerals, vitamins, and essential amino acids. Some manufacturers also fortify their soy milk drinks to increase the calcium content to that of dairy milk.

One glass of unfortified and unsweetened soy milk contains 97 calories and 3.5 grams of fat. This amount of soy milk also provides you with 6% of your recommended daily fiber needs (1.6 g). (10)

One glass of unfortified soy milk contains 10.3 g of crabs and 55.1 mg calcium which is 6% of your recommended daily calcium intake (RDI).

Soy milk is also a good source of minerals like manganese, copper, magnesium, iron, and potassium. Soy milk also contains B-group vitamins as well as vitamins C, E, and K.

Let’s look in more detail at the benefits to your health of drinking soy milk.

Soy Milk is a Rich Source of Protein

Soy milk is an important plant-based source of proteins and is classed as a source of complete protein.

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One glass of soy milk contains approximately 6.4 grams of protein which is 13% of your daily protein needs.

The journal American Family Physician says that the reason soybeans and products made from soybeans are so good is that they contain all the 9 essential amino acids. Also, consuming more plant-based protein rather than animal protein helps to lower cholesterol and may reduce the risk of prostate and breast cancer. (11)

Soy milk contains amino acids such as lysine, tryptophan, threonine, phenylalanine, and leucine. These are only obtained through diet and are essential to your body’s metabolic processes.

Soy Milk is Lactose-Free

Drinking soy milk is a healthy alternative to dairy milk if your gastrointestinal system has problems digesting lactose.

The Journal of Food Science and Technology reports that plant-based “milk” products are lactose-free and cholesterol-free. Soy milk is rich in phytosterols which have cholesterol-lowering properties. Soy milk is sold in a variety of flavors, sweetened or unsweetened, and different in formulations. (12)

Some people are allergic to soy and soy-based drinks and therefore lactose-free soy milk isn’t a suitable dairy-alternative for everyone.

Soy Milk is Good for Vegans and Vegetarians

Because soy milk contains no animal-derived ingredients, it is perfect for vegans and others who want to stay away from meat products.

Drinking protein-rich soy milk is a good way to strengthen your body and get your essential amino acids. Some types of soy milk also have added calcium, vitamin A, and vitamin D.

One glass of enriched soy milk (or vanilla soy milk) is cholesterol free and gives you 26% of your vitamin D and 9% of your vitamin A daily requirements. Fortified soy milk also gives you 30% of your calcium requirements as well as all of the other health benefits of soy. (13)

Soy Can Help Lower Cholesterol

One of the benefits of choosing soy milk over dairy milk is that it is cholesterol free. Drinking soy milk can also reduce your total cholesterol, low-density lipoproteins (LDLs), and triglycerides.

Research into soy and soy milk products found that consuming 1 or 2 glasses of soy milk daily is enough to get its health benefits such as lowering cholesterol and protecting your cardiac health. 1-2 cups of soy milk are the equivalent of 25 grams of soy protein. (14)

Find out what else you can do to manage high cholesterol without having to use medication.

Soy May Help Manage Diabetes Symptoms

Consuming soy-based products and soy milk can be good for you if you suffer from diabetes.

One study on the benefits of soybean products found that supplementing the diet with soybean powder. Patients with type 2 diabetes took 23 g of soy powder 3 times a day. After 4 weeks of treatment, researchers noted that blood glucose and lipid (a type of fat in blood) levels were improved. The researchers concluded that soybean can help manage symptoms of type 2 diabetes. (15)

Another study found that soybean products help to prevent fasting and post-load hyperglycemia in overweight men who have diabetes. (16)

Learn about other foods to control type 2 diabetes.

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Soy May Alleviate Complications in Menopause

The effects of soy estrogen could mean that drinking soy milk or consuming soy foods can help to manage symptoms of the menopause.

Scientific research has found that one of the soy isoflavones benefits is increasing estrogen levels in postmenopausal women.

One double-blind study involved 60 postmenopausal women. One group was given 60 mg isoflavones a day to consume. After 3 months of treatment, researchers noted an improvement in menopausal symptoms. (17)

During the menopause, levels of estrogen drop, and this can cause osteoporosis and increase the risk of breast cancer. Research has found that soy isoflavone supplements can prevent the breakdown of bone structure. Soy phytoestrogens can also lower a woman’s risk of breast cancer in later life. (18)

Learn about the best supplements you can take to relieve many symptoms of the menopause.

Is Soy Milk Bad for You?

If there are so many science-based research studies on the benefits of soy, why do so many people say that soy or soy milk is bad for you?

One of the concerns that many people have on consuming soy milk and using soybean oil is that it is high in omega-6 fatty acids. One glass of soy milk contains 232 mg omega-3 fatty acids and 1,731 mg omega-6. (10)

Scientists say that a high ratio between omega-3 and omega-6 fatty acids can increase inflammation in the body that can lead to chronic diseases. (19)

If you regularly drink soy milk, you should make sure and take omega-3 supplements to lower the fatty acid ratio.

What are some of the other reasons why soy milk could be bad for you?

Soy May be Genetically Modified (GMO)

One of the concerns that many people have with adding more soy milk to their diet is the fact that many soybeans are genetically modified.

The Journal of Food and Science Technology reports that soybeans are genetically modified to make them resistant to disease. Some studies indicate that there are differences in levels of isoflavones between modified soybeans and non-modified soybean. (20)

There are also health concerns connected with the herbicide “Roundup” that is used on many soybean plantations. (20, 21)

If you consume soy milk, always choose a non-GMO 100% organic soy milk or soy milk powder.

Soy Contains Isoflavones That May Disrupt Hormones

The high levels of isoflavones in soybeans are one of the reasons why people say that soy or soy milk is dangerous for health.

A report in 2014 on the possible side effects of phytoestrogens found that there is only weak evidence to support the health benefits of isoflavones. There are conflicting reports on the benefit of soy products in preventing cancer. (22)

Researchers point to the fact that phytoestrogens are powerful enough to be used as hormone replacement therapy, and at the same time soy-based infant food is commonly used for pediatric nutrition.

Some scientists are also concerned about the large quantities of soy used for animal fodder and that the estrogen hormones in soy get into the food chain.

Learn how to spot signs that you have a hormonal imbalance in your body.

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Soy May Affect Male Fertility and Testosterone

One of the reasons why some researchers say that soy milk is bad for men is that its estrogen-like phytoestrogens can affect male reproductive health.

One study found that a higher intake of soy isoflavones can affect sperm concentration. (23) However, another study found that taking 40 mg of isoflavones daily had no effect on semen quality. (24)

Other studies have found that regularly consuming soy milk has no effect on testosterone levels in men. (25)

Soy Can Affect Thyroid Function

Soy milk may be bad for your thyroid health because soybean products can inhibit production of the thyroid hormone.

One study found that soy-rich diets could be linked to goiter – an enlarged thyroid gland. (26)

A study from Japan found that eating too many soybean products can suppress the function of your thyroid. The study found that elderly people are especially at risk of thyroid disease if they consume too many soybean products. (27)

The journal Thyroid advised that people who consume many soy foods should make sure they get enough iodine in their diet to prevent hypothyroidism. (28)

Further reading: your complete guide to thyroid hormones.

Soy Infant Formula May Affect Development

There is also increasing concern about soy formula that is used as a replacement for breast milk. The concern revolves around phytoestrogens that act like the hormone estrogen in the body.

One study found that female infants who were fed soy formula had larger breast sizes in the first 2 years of life than those babies who were fed breast milk. (29) Other studies have shown that girl babies who receive soy formula have larger wombs and vaginal cell changes. (30)

However, studies on the long-term effects of feeding infants soy formula have not found any adverse side effects in later life. (31)

Does Soy Increase Risk of Cancer (Such as Breast Cancer)?

One of the most controversial questions when it comes to consuming soy products is if soy causes breast cancer.

One study on the effects of soy protein and the risk of breast cancer found that isoflavones stimulate the increase of cells in the breast. In one study, a group of women received 60 grams of soy a day. After a 2-week period, scientists noticed more epithelial cells in the breast. These are types of cells that are most likely to become cancerous. (32)

However, many studies have shown the opposite results. One observational study found that consuming soy products during adolescence and adulthood actually reduced a woman’s risk of breast cancer. (33)

Regarding the anticancer effect of soy isoflavones, a comprehensive review of studies on soy found that soy isoflavones can protect against breast cancer. For example, numerous studies show that soy isoflavones help to lengthen the menstrual cycle. This has a protective effect against breast cancer in later life. (38)

One long-term prospective study over a 3-year period found that women taking 70 mg isoflavone a day did not increase their risk of breast cancer. (38)

Researchers have concluded that soy isoflavones act differently in animal models than in humans and don’t have an estrogen effect. More studies show that isoflavones have a protective effect against cancer. However, more research needs to be done to examine the long-term effect of soy isoflavone supplementation. (38)

It has also been noted that breast cancer among Asian population is not as great as in Western countries. Asians traditionally consume high amounts of fermented soy products. (33)

Fermented Soy

Many people say that consuming fermented soy products is much healthier for you that non-fermented soy.

The journal Preventative Nutrition and Food Science reported that fermented soy milk has a neuro-protective effect on the brain. Consuming fermented soy milk can help to improve learning and increase memory potential. (34)

Fermented soybean products can also strengthen your immune system and help prevent infection. (35)

Consuming soy milk can also improve your gastrointestinal health. One study found that drinking two glasses a day of fermented soy milk helps to improve your gut’s microbiota and increase the number of probiotics. (36)

Fermented soy products have also been linked to improved cardiac health, lower cholesterol, lower blood pressure, and helping to prevent diabetes. (37)

How Often Can You Eat Soy and How Much?

After learning about the benefits of soy, soy milk, and fermented soy products, you might decide to increase the amount of soy in your diet. Or, you may feel that the potential risks of increasing soy-based food outweigh the possible health benefits.

If you decide to eat more soy, how much soy is safe to eat a day? The U.S. Food and Drug Administration (FDA) recommends not consuming more than 25 g of soy protein daily. (40)

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7 Responses to Soy or Soy Milk: Is it Really Bad or Good for You (Science Based)

  1. Marie Sternhardt says:

    Soy…NO!! The phytoestrogens in soy have a very unique property…….they actually rob the hormone receptor site on the cell. This sealing of the receptor site renders you own secreted hormones as useless since they can no longer get into the cell to their work. Consider the number of hormones your endocrine system produces and the myriad of body functions that are they enable. Doesn’t take much to figure out that those soy phytoestrogens will, over time, cause many dis-eases. Please note that this property of soy phytoestrogens cannot be removed from the soy mush so you are getting this anytime you consume any soy, be it organic or non-GMO. Soy is NOT fit for human consumption! For that matter, I do not give it to my pets either!

  2. .jimmy Hodges says:

    just doesn’t compute when I have thousands of people change their health and improve their life when they switched to a soy based diet. I am now diabetes free, heart disease reversed, have lost 70 lbs of fat , all on my new ntrition plan that consists of lots of soy products. and at 74 years of age I can run 10K

  3. Naomi says:

    What about organic edamame?

    • Jenny says:

      A small quantity once in a while is fine for most people. The problem is that a lot of people munch on edamame like it’s popcorn, consuming it in large quantities and frequently. In this case the quantities of phytoestrogens, phytic acid and goitogens in the edamame add up quickly and these are not good for you.

  4. Linda says:

    interesting reading. I personally need oestrogen so it’s a great way of supplementing my body’s oestrogen levels.
    I think you’ll find that just about every wheat product, cake, biscuit and loaf of bread is made from gmo wheat these days and if Monsanto get their way, everything will be gmo … theirs!

    humans are the only creature that drink milk as adults, let alone another creature’s milk, and that and the meat industry is disgustingly full of antibiotics and gmo breeding.

    I think that the food industry as a whole is in heap big trouble

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