Is Soy Harmful for Men’s Health?

Soy has been making headlines for different reasons. While some nutritionists say it is one of the best options for people on a plant-based diet, others have a totally different opinion. The major concern about soy is the effects it has on males. Some people have opined that this plant-based protein source inhibits male hormones.


Over the years, researchers have delved into this issue and some of the findings have indeed ignited numerous discussions. One research that raised eyebrows was conducted in 2011 and focused on a teenager who consumed large quantities of soya and eventually developed erectile dysfunction. The critics of the study cited the inadequate sample size. Furthermore, the subject was diabetic and therefore the symptoms might have been caused by many other factors.

There have been a number of studies conducted in other animals such as rats. In one of the studies, male rats that were exposed to high levels of soy proteins while in the womb experienced impaired sexual growth. It is however important to note that the metabolism of soy in humans and rats is very different. The anatomy and physiology of the two species is also different. Therefore, the findings in rodents might not be replicated in humans.

An Objective Analysis of Effects of Soy on Men

The criticism of soy stems from the fact that it contains compounds called isoflavones. These are phytoestrogens and they have effects similar to those of estrogen. Estrogen is a hormone that is largely involved in the female reproductive system. Men’s bodies also produce estrogen but at significantly lower levels compared to women. And the big worry is whether taking soy will reduce the testosterone levels in the body of a man.

One meta-analysis of 15 randomized clinical trials revealed that the use of soy supplementation had no significant effect on the levels of testosterone. This applied to men that were consuming a maximum of 70g of soy per day.

70g of soy is equivalent to about 6 cups of soy beans or three scoops of soy protein powder. That’s quite a lot to take in a day. Chances are you are not going to reach these daily levels under normal circumstances. Therefore, it is safe to say that average consumption of soy will not have any effects on the testosterone levels. Consequently, this will not cause the undesirable symptoms of testosterone deficiency. In fact, in this analysis, body builders who took soy were also evaluated and it was found that they gained muscle at the same rate as those who used other forms of protein and supplements.

Another meta-analysis published in 2010 also had similar findings. Researchers in the USA analyzed 47 different studies and found that isoflavones did not affect testosterone levels significantly.

There is an increase in the popularity of vegan diets around the globe and soy tends to feature in most of these diet plans. As a man, you don’t need to be worried about adding soy to your vegan diet. Based on the above studies, you can be sure taking moderate amounts of soy won’t have an impact on your masculinity.

There are risks associated only with consuming very large amounts of soy, which may result in symptoms of testosterone deficiency. Studies have pointed out cases of hypogonadism and erectile dysfunction in people who consumed extremely high amounts of soy. One of the subjects was a guy who drank about 3 liters of soy milk each day. Another one consistently consumed 150 grams of soy every day.

The Benefits of Soy in Men

One of the positive effects of soy is reduced cholesterol. Studies have proved that soy can significantly reduce the levels of LDL, which is also called the bad cholesterol. Conversely, soy causes a rise in HDL, the good cholesterol. Soy has shown to be beneficial among people who are at risk of developing cardiovascular conditions.

Well, testosterone is a steroid hormone which is synthesized from cholesterol. You might think that because soy reduces cholesterol, then it can lower the levels of testosterone. It doesn’t happen that way because the cholesterol used to make testosterone comes from internal body sources.

Besides lowering the levels of cholesterol in blood, soy has been shown to have a host of other benefits. Isoflavones which are contained in soy help to maintain the elasticity of the blood vessels and also reduce inflammation. Moreover, soy plays a role in maintaining endothelial health. Endothelium is the lining of the blood vessels and, when it is intact, there is improved blood flow to all parts of the body.

People on a soy diet have a lower risk of developing stroke and heart disease.

Soy has also been shown to protect against prostate cancer. Men eating soy have the risk of prostate cancer reduced by up to 40%.

Soy has also been shown to lower the blood pressure. One study found that people taking an average of 43 grams of soy per day had their diastolic blood pressures lowered by around 8%.

Finally, soy lowers blood sugar levels and reduces the degree of insulin resistance. This is true even in people with type 2 diabetes. It might therefore prevent the long term complications of diabetes and hyperglycemia, one of which is erectile dysfunction.

In Summary

Soy is a great source of nutrients. Although there have been concerns around the effects it can have on men, it is now clear that moderate ingestion of soy does not affect testosterone levels. Vegan and vegetarian men can have soy without worries because it won’t take away your testosterone unless you go on a soy bingeing craze every day of the week.

You are advised to choose organic soy whenever possible because it is more beneficial. Go for the less processed forms which have more nutrients.

Your plant-based diet should also include other vegan or vegetarian products to get all the nutrients you need. When you combine a diet rich in soy with other healthy practices such as a balanced exercise routine, you will get excellent outcomes.

author: Dr. Marian Davis

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