You certainly don’t have to eat soy products, even as a vegetarian or vegan. But for many, options like veggie burgers, soy milk and miso soup make for convenient and tasty meat- or dairy-free dishes. Soy milk is produced from the soybean plant. Although not technically milk, soy milk has provided a dairy alternative for many who cannot or choose not to consume animal’s milk, such as the lactose intolerant and vegans.
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?
Health Benefits
Soy milk contains isoflavones which provide many of the benefits of soy products. Isoflavones, according to the American Cancer Society, can have weak estrogen-like activity, which is the basis for why some men avoid soy milk. The exact amount of nutrients in soy milk depends on the brand and if the milk is fortified.
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. 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.
A diet high in soy might protect men against prostate cancer. A review of studies conducted by the Grand Forks Human Nutrition Research Center and published in the April 2009 issue of “The American Journal of Clinical Nutrition” found that men who ate diets higher in soy had a reduced risk of developing prostate cancer. A Korean review of available studies published in the 2009 “Nutrition and Cancer” found that only tofu, not soy milk, miso or natto, other soy foods frequently consumed in Asian countries, had a protective effect against prostate cancer.
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
A Harvard University cross-sectional study published in “Human Reproduction” found that dietary intake of soy and isoflavones reduced sperm concentration in men. Although the reduction was small, it was considered statistically significant. The research found that including soy in the diet most affected men with normal or high sperm counts. Also, soy food was more related to low sperm in overweight and obese men in the study. Other studies have had conflicting results related to soy milk and sperm production.
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.
Soy may negatively affect behaviors in men, according to research published in “Hormones and Behavior.” Researchers from Wake Forest University Baptist Medical Center divided adult male monkeys into three groups for the 15-month study. One group had approximately 125 mg of isoflavones from soy daily. The second group had half the amount, and the third group’s protein came from milk and animal sources. The monkeys fed the high amount of isoflavones demonstrated more aggressive and submissive behavior than their counterparts. They also spent less time with other monkeys and increased their alone time.
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.
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.