Long-Term Side Effects of Soy Milk

Drinking soy milk is a healthy choice as long as you're staying within your daily recommendations.
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Soy protein is an excellent alternative for people who can't consume dairy or are looking for meat alternatives. The milk derived from soy, for example, is one of the most popular dairy substitutes. With such a large number of consumers, a vast amount of research has gone into soy side effects.

While often considered a health food product, there's a lot of controversy around this legume and its derivatives. People often worry about the dangers of soy, which are largely related to phytoestrogens. These plant compounds are structurally similar to estrogen and may affect human hormones.



Drinking soy milk is a healthy choice as long as you're staying within your daily recommendations. Of course, not all soy milk brands are made equally. You should read the labels, look for natural or organic sources and avoid added sugars as much as possible.

Background on Soy

The health benefits of soy were first studied because Japanese people had fewer rates of certain chronic illnesses. This difference in diseases among communities was associated with their diets and eventually, soy consumption was believed to be a possible explanation, according to a review from the January 2018 issue of Nutrients.

This line of research was justified by the stark difference in the consumption of soy products between the populations of Japan and America. Most Americans consume about 1 to 3 milligrams of isoflavones, the most abundant antioxidants in soy, per day. Vegetarians, on the other hand, eat 7 to 12 milligrams of these nutrients daily. In contrast, the review found that people in Japan consume 15 to 20 milligrams of isoflavones per day.


Isoflavones are phytochemicals called phytoestrogens. These compounds have a similar structure to estrogen, the hormone your body makes. As mentioned earlier, they are largely responsible for most of the warnings regarding the dangers of soy. However, as the research outlined below demonstrates, these compounds are, for the most part, safe.

What About Soy Milk?

Soy milk was the first form of milk substitute, according to a review from the September 2016 issue of the Journal of Food Science and Technology. They have perfected the production process over the years, and the end product has been subject to numerous studies and reviews. This milk lacks the cholesterol of regular milk and contains phytosterol, which may help lower your cholesterol levels.


Most soy milk brands provide vitamin B, fiber, potassium and magnesium. Furthermore, soy is a complete protein, meaning that it provides all the essential amino acids.

The University of California recommends the consumption of 25 grams of soy protein daily to lower cholesterol levels. Ingesting about 50 grams a day may help prevent diabetes and chronic diseases of the heart. To reap these benefits, you need to be sure that you're getting isoflavone-rich soy milk.

The Association of American Universities found soy milk to be the best milk alternative. But the recommendation was aimed at people who are dairy sensitive.


Read more: The Benefits of Soy Milk — And Some Drawbacks

Soy Side Effects

Most common complaints of soy side effects, apart from allergies, are digestive discomfort and diarrhea. There was some concern that long-term isoflavone supplementation would thicken the endometrial lining, causing uterine cancer. Dietary supplements, however, contain much higher concentrations of isoflavones than soy foods. In fact, soy and its derivatives weren't associated with this risk at all.

Further research on the impact of isoflavone supplements on women with breast cancer or at risk of breast cancer is still needed. But soy products don't have high enough concentrations to be of concern. Also, anecdotal evidence states that men shouldn't consume these products due to their high content of phytoestrogens.

Soy estrogen, or phytoestrogens, have been shown to affect male hormones only statistically in large populations, according to a review from the December 2014 issue of German Medical Science. In males, researchers haven't found a decrease in testosterone levels nor an increase in estrogen levels through regular soy consumption. You'll find that people often overstate the dangers of this food product while overlooking soy isoflavone benefits.

Read more: Is Soy Milk Good or Bad For You?

Does Soy Cause Cancer?

There's a lot of information out there in regards to soy and different types of cancers, with varying results, leading to a need for further research. A review from the September 2014 issue of the Journal of the National Cancer Institute points to evidence that phytoestrogen may both cause and stop breast cancer.

The review found that the critical difference was the age of the women attending these studies. However, the lack of consistency in phytoestrogens' impact on breast cell replication points to a need for further research to be conclusive.

A study published in the_ Journal of Nutrition_ in December 2016 looked at the correlation of phytoestrogens in urine samples and the presence of endometriosis. Researchers have found that there was no association between the two. Furthermore, they concluded that there is no evidence to associate phytoestrogens with this condition.

There was a correlation between soy and a significant decrease in the risk for bladder cancer in men in a study from the November 2018 issue of Cancer Epidemiology, Biomarkers & Prevention. Additionally, a review featured in Molecular and Clinical Oncology in December 2018 has found that soy isoflavones may reduce the risk of prostate cancer.

What these studies and reviews show is that soy does not cause or aggravate most cancers. However, there are some areas where further research is needed to come to a definite conclusion.

Soy Isoflavone Benefits

Soy isn't all scary. Isoflavones actually have benefits you may not know about. First of all, this food is a complete protein source with 16 amino acids, vitamin B and other nutrients like magnesium, potassium and fiber. A study from the June 2016 issue of Nutrients noted that isoflavone benefits also include anti-inflammatory properties. A review published in Phytotherapy Research in November 2017 suggests that it's rich in antioxidants and beneficial for cardiovascular health.

Most of the dangers come from taking soy supplements and not from drinking the milk. If you stick to this healthy milk alternative, you should be able to reap the benefits without having to deal with any adverse effects.

As long as soy is consumed within the normal dietary ranges, it is considered safe. The American population is well below those ranges, so you likely have nothing to worry about. But it's easy to figure out how much soy you're getting in your diet and determine whether or not you're staying within a healthy range. If you find that you are consuming too much soy milk, there are several alternatives available, from almond and coconut milk to rice and oat milk.