The Negative Effects Of Soy Milk On Men

By Marisa Ramiccio. May 7th 2016

Soy has long been a staple of vegan and vegetarian diets because soy-based products like tofu, miso and tempeh are favorable alternatives to meat-based protein sources. For those who are lactose-intolerant, soy milk is the common choice and is just as nutritious as, if not more than, milk.

But over the years, some men who’ve incorporated soy-based products, particularly soy milk, into their diet have experienced negative side effects that seem to undermine the health benefits that soy has to offer. So is soy milk really as healthy for men as it seems?

What Is Soy?

Soy is a legume that grows in a pod like other beans. The seed is the edible part and comes in a variety of colors including brown, black, yellow and green. Soy is used to make a number of foods including tofu, natto, edamame, miso, tempeh and, of course, soy milk, which is made from whole soy beans, water and oil.

Health Benefits

Soy is an excellent source of protein as well as many other vitamins and minerals, so it’s no surprise that soy milk is just as nutritionally beneficial. Here are just a few of the nutrients that you’d get from drinking one cup of soy milk:

  • 7.9 grams of protein, which is 16 percent of the Daily Value
  • .5 milligrams of manganese, which is 27 percent of the Daily Value
  • 60.7 milligrams of magnesium, which is 15 percent of the Daily Value
  • 11.7 micrograms of selenium, which is 17 percent of the Daily Value
  • .3 milligrams of copper, which is 16 percent of the Daily Value

Soy milk is also low in saturated fat, calories and cholesterol. But soy milk isn’t only good for your diet; it can also impact your health in other ways. For instance, researchers at the Vanderbilt University Medical Center and the Shanghai Cancer Institute found that soy may lower the risk of developing diabetes. Soy is also a good reducer of inflammation and may protect the heart and kidneys from disease. For men, soy can provide other benefits including:

  • Lower blood pressure
  • Lower cholesterol
  • A lower risk of developing cardiovascular disease
  • Protection against prostate cancer

Some research suggests that the isoflavones in soy, particularly genistein and daidzein, are the source of these health benefits. But other research tells a different story.

Negative Effects

While some researchers say genistein and daidzein are beneficial to men’s health, others say those isoflavones do more harm than good. Both genistein and daidzein can act similar to estrogen and are known as phytoestrogens, which are estrogens that are produced by plants. Since these isoflavones act similarly to estrogen, they can interfere with men’s hormones, causing side effects such as:

  • Breast development and nipple tenderness
  • Erectile dysfunction and a decrease in libido
  • A decrease in sperm count
  • Mood swings and heightened emotions

Some researchers have cited daidzein as the specific cause of these side effects as well as of damage to penile tissue and a decrease in testosterone production. Soy itself may also have harmful effects on the brain. A study conducted by researchers from Loughborough University in England showed that people in their late 60s and older who consumed large amounts of tofu had a higher risk of developing dementia and memory impairment than those who consumed a moderate amount of tofu.

The Real Problem With Soy

At this point, the benefits of soy milk outweigh the negative effects it can cause, but one thing to keep in mind is that there are two different types of soy foods: organic soy foods, and purified or processed soy foods. Some studies show that soy foods that are purified or processed do not contain the same amount of nutrients as organic soy foods and may even increase the growth of estrogen-dependent tumors. Because of this, it’s best to stick to organic soy foods such as tofu, tempeh, edamame and miso. Organic soy milk is also recommended since it’s made from whole soybeans.

The other key to consuming soy is moderation. Eating large quantities of soy daily, even if it is whole soy, may not be entirely healthy. Health advisor Andrew Weil, M.D. suggests incorporating one or two cups of whole soy foods into your diet each day.

If you’re concerned about your soy intake or do notice any adverse effects after eating soy-based foods, speak with a doctor immediately. It is possible you’re allergic to soy or are sensitive to the isoflavones. Soy is used in a lot of products and you may not even be aware of its presence in the foods you eat, so check food ingredient labels before purchasing or consuming certain foods if you are soy sensitive.

In the end, soy’s benefits can overcome the negative effects as long as you stick to foods that are made with whole soy and eat them in moderation. Soy has been a staple of vegan and vegetarian diets for years, as well as the Asian diet, and those groups have experienced more positive effects from soy than negative effects.


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