Is Soy Milk Healthy? We Asked Experts To Weigh In

July 24, 2023

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While soy milk has actually been around for centuries, it didn’t become popular — at least in the U.S. — until a wealth of research emerged in the ‘80s and ‘90s shedding light on its potential to reduce the risk of cardiovascular disease. Although many studies have pointed to the health benefits of soy milk, others have revealed conflicting findings that suggest some disadvantages as well. Which begs the question: is soy milk healthy after all? Or are you better off cow’s milk or a different plant-based alternative?

Whether you’re an occasional soy milk drinker, or it’s a staple in your fridge, it’s important to know about both the potential perks as well as the drawbacks of this non-dairy milk alternative. Here’s what registered dietitians want you to know.

What is soy milk?

Soy milk is made by soaking soybeans in water overnight to soften them and then grinding the beans with water.

This beverage is lactose-free and safe for people with milk allergies. It’s also naturally gluten-free, but some sweetened and flavored varieties may contain gluten — so, it’s always best to check the label or just opt for plain, unsweetened soy milk.

Some brands fortify their soy milk with vitamin D, calcium, and other vitamins and minerals, making it even more nutritious.

Is soy milk healthy?

One cup of unsweetened, fortified soy milk contains 80 calories, 1 gram of sugar, 4 grams of fat, 4 grams of carbohydrates, and 7 grams of protein. For the sake of comparison, 1 cup of 2% milk contains 120 calories, 12 grams of sugar, 5 grams of fat, 12 grams of carbohydrates, and 8 grams of protein. While soy milk has roughly the same amount of protein, it has significantly less sugar and calories, and slightly less fat, making it a seemingly healthier choice.

Many plant-based milk alternatives — like oat milk, almond milk, and rice milk — are incomplete proteins, which means they don’t contain all nine essential amino acids. But soy milk, like cow’s milk, is considered a complete protein. This makes it an excellent choice for vegans and vegetarians, says Madelyn Larouche, RD.

According to April Bruns, RDN, CPT, founder of Your Fit Fork, soy milk is overall a healthy choice.

“It’s packed with nutrients like protein, B vitamins that give you healthy cells and energy, and important minerals, including calcium and potassium,” she explains. “Even unfortified soy milk tends to be a good source of vitamin B6, magnesium, folate, and zinc. And some brands also deliver vitamin K and iron.”

That said, she notes that not all soy milk is created equal. She advises looking for products that are fortified but contain no added sugar.

The benefits of soy milk

“Soy milk is made from whole soybeans, which contain healthful compounds known as isoflavones,” says Krutika Nanavati, RD, a dietitian and nutritionist with ClinicSpots. “Isoflavones are thought to have antioxidant properties that may reduce the risk of some types of cancer and heart disease.”

In fact, a 2015 meta-analysis conducted by Canada’s Bureau of Nutritional Sciences found a link between soy protein consumption and lower total cholesterol levels — and more specifically, lower levels of low-density lipoprotein (LDL) cholesterol. Because LDL cholesterol can contribute to a buildup of plaque in your arteries — thus increasing your risk of heart disease and stroke — it’s known as the “bad” kind of cholesterol.

“Isoflavones may also play a role in supporting bone health by enhancing bone mineral density,” adds Bruns.

Research has shown that soy isoflavones are especially helpful in preventing bone loss and osteoporosis in postmenopausal women.

But that’s not all these isoflavones can do.

A 2012 review in Nutrition, Metabolism & Cardiovascular Diseases revealed that consuming soy isoflavones can lower blood pressure in people with hypertension.

While there is still limited research on how soy may affect gut health, a 2016 review in the Journal of Agricultural and Food Chemistry showed that consuming soy foods can increase the levels of beneficial bacteria in the gut while also reducing pathogenic bacteria.

The disadvantages of soy milk

There are two main reasons for the controversy around soy milk.

Firstly, as Nanavati points out, some studies have suggested that consuming too much soy can interfere with the body’s absorption of essential minerals, such as zinc and iron. This is because soy milk contains oxalates, natural compounds sometimes referred to as “anti-nutrients” because they bind to certain minerals — like calcium — in the stomach and intestines and inhibit the body from using those nutrients. Soy milk doesn’t have as high an oxalate content as almond milk or cashew milk, but it’s higher than cow’s milk, coconut milk, flax milk, or oat milk. If you have a history of kidney stones, experts advise avoiding oxalate-rich foods like soy products.

Secondly, Nanavati notes that there have been concerns that some soy products contain estrogen-esque compounds that could disrupt hormone balance. Theoretically, that could fuel the development of hormone-dependent cancers, like breast cancer and prostate cancer. But the research shows that isn’t necessarily the case. A 2010 review in the Journal of Nutrition found that moderate consumption of soy can actually reduce your risk of breast cancer, and a 2018 review in Nutrients revealed the same finding for prostate cancer.

That said, if you’ve already been diagnosed with a hormone imbalance, Nanavati recommends consulting your doctor before making soy milk a regular addition to your diet.

“For individuals with thyroid conditions, particularly hypothyroidism, it’s essential to be

mindful of soy intake,” adds Bruns. “Soy contains compounds called goitrogens, which can interfere with thyroid function. Personalized guidance is crucial when managing thyroid health, so don’t hesitate to seek professional advice from a doctor or registered dietitian.”

It’s also worth noting that some — but not all — soy milk contains carrageenan, a common yet somewhat controversial additive extracted from red seaweed that’s used to thicken drinks and foods. Carrageenan is recognized as safe by the Food and Drug Administration and World Health Organization. However, some research suggests that it may cause intestinal inflammation that leads to bowel disorders.

The bottom line

So, is soy milk healthy? Unless you have a history of kidney stones, a thyroid condition, or a hormone imbalance, it’s probably a safe and healthy choice.

“It’s a nutritious choice for many individuals, providing various benefits such as plant-based protein, isoflavones, and heart-healthy fats,” says Bruns.

In order to reap the benefits of soy milk without any risks, try to opt for a product that’s fortified, has no added sugar, and carrageenan-free whenever possible.