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If you’re looking to make your diet more plant-based, chances are you’ve tried one or more plant-based milks, like soy and oat milk.

They’ve become increasingly popular over the past decade. In fact, in 2019 the plant-based milk market was valued at around $14 billion, and it’s projected to become even more profitable by 2029 (1, 2).

Oat and soy milk are among the most popular plant-based milk alternatives. Many people use them on a daily basis in coffee, tea, cereal, and smoothies.

But are these plant-based milks nutritious? Is one better than the other?

This article breaks down the differences between oat and soy milk to help you decide which is a better choice to keep in your kitchen.

Both oat milk and soy milk contain some important nutrients and are among the highest protein plant milks available.

Here’s a nutritional breakdown comparing 1 cup (240 mL) of unsweetened oat milk and unsweetened soy milk (3, 4).

Soy milkOat milk
Calories10079
Fat5 grams1.49 grams
Protein9 grams 4 grams
Carbs5 grams 14 grams
Fiber1 gram 1.92 grams
Iron8% of the Daily Value (DV)6% of the DV
Potassium8% of the DV2% of the DV
Calcium2% of the DV2% of the DV

Compared with plain, unsweetened oat milk, soy milk is slightly higher in calories, higher in fat and protein, and much lower in carbs. It’s also a bit higher in potassium and iron.

They’re both higher in protein than many other plant-based beverages like almond and coconut milk. However, soy milk has more than double the protein of the same volume of oat milk (5, 6).

Oat milk is significantly higher in carbs compared with other plant-based milks, including soy. This is because oat milk is made with whole oats, which are a rich source of carbs (7).

Keep in mind that, unlike many oat and soy milk products, the products above are made with few ingredients.

For example, the soy milk product listed above is made with just water and organic soybeans, while the oat milk is made with just oats, filtered water, and salt.

Many oat and soy milk products contain added sugar and oils and may be fortified with vitamins and minerals. All these added ingredients may significantly change the nutrition content of the product.

Summary

Compared with unsweetened oat milk, unsweetened soy milk is higher in calories, fat, protein, potassium, and iron, while oat milk is higher in carbs.

Neither plant milk will have a significant effect on your health if you’re using it like most people do. That is, occasionally in your coffee drinks, smoothies, or cereal.

However, if either soy or oat milk is a staple in your diet, it could make a significant contribution to your nutrient intake.

For example, soy milk is an excellent source of protein, especially if you’re following a vegan or vegetarian diet.

One cup (240 mL) of soy milk provides 9 grams of high quality plant-based protein, which is a significant amount for a plant-based milk. For comparison, 1 cup (240 mL) of cow’s milk contains 8 grams of protein (3).

Protein is the most filling macronutrient, which means that drinking soy milk will be much more satisfying compared with other types of plant milk, like almond milk (8).

Soy milk is also a decent source of iron and potassium, which many people around the world, including Americans, don’t get enough of (9, 10).

A diet lacking potassium can negatively affect heart health by increasing blood pressure. Meanwhile, not taking in enough dietary iron could lead to iron deficiency anemia (11, 12, 13).

Oat milk contains lower amounts of these nutrients, but is a good source of carbs, which supply the body with energy. Plus, it contains a bit of iron.

Fortified oat and soy milk products contain much higher amounts of a variety of nutrients. This is because the manufacturers add vitamins and minerals to the products during processing — such as iron, vitamin B12, and vitamin D.

A 1-cup (240-mL) serving of Silk fortified soy milk provides 120% and 15% of the DV for vitamin B12 and vitamin D, respectively (14).

For this reason, fortified plant milk products make a good choice if you’re looking to increase your intake of certain vitamins and minerals.

For example, experts recommend that those following vegan diets drink fortified plant milks like soy milk to ensure they’re getting enough of certain nutrients like vitamin B12 in their diet (15).

Summary

Unfortified soy milk contains a good amount of plant-based protein and is a decent source of potassium and iron. Fortified plant milks contain much higher amounts of vitamins and minerals and make a good choice for those following vegan diets.

Even though oat and soy milk may provide a few benefits, both have potential downsides depending on the product.

Some products are high in added sugar

Unless you specifically seek out unsweetened plant milk products, like unsweetened oat or soy milk, chances are the product you’re using contains added sugar.

Companies add sugar to their products to improve taste. Some add a significant amount.

For example, 1 cup (240 mL) serving of Silk vanilla soy milk contains 8 grams or 2 teaspoons of added sugar, while a 1 cup (240 mL) serving of Oatly chocolate oat milk contains a whopping 16 grams or 4 teaspoons of added sugar (16, 17).

If you use these sweetened milks often, they may contribute to consuming excessive amounts of added sugar. A diet high in added sugar negatively affects blood sugar levels and can lead to health issues like fatty liver and high blood pressure (18, 19, 20).

On the same topic, oat milk is relatively high in carbs overall, so if you have prediabetes or diabetes, you may want to choose lower-carb alternatives, like coconut milk or almond milk, which will have less of an effect on blood sugar levels.

Some people are concerned about soy’s effect on health

Some people have voiced concerns about soy because it contains compounds called phytoestrogens and they believe this might lead to harmful effects. However, the research on this is mixed.

Phytoestrogens bind to receptors for the hormone estrogen in your body. They can have either antiestrogenic or estrogenic effects, meaning they can either block estrogen or mimic its activity in the body (21, 22).

For this reason, some people think that eating a lot of soy may increase the risk of certain health conditions, like breast cancer, but research does not support this association.

In fact, studies suggest that consuming soy is associated with a reduced risk of developing breast cancer in Asian women and may reduce breast cancer recurrence in Asian and Western people (23, 24, 25).

Nonetheless, there is some evidence that high soy diets may have a negative effect on the health of the endocrine system and may adversely affect thyroid function (26, 27).

Because a diet high in soy could interfere with thyroid hormone production, healthcare professionals sometimes recommend that those with thyroid conditions limit their intake of soy products, like soy milk (28).

Concerns over pesticide residue in oat milk

Many crops are heavily treated with pesticides and herbicides. Oat crops are often treated with glyphosate, a controversial, broad-spectrum herbicide (29).

Humans can be exposed to glyphosate through food and water, such as eating foods and beverages high in glyphosate residue, like oats and oat-containing cereals (30).

The Environmental Protection Agency (EPA) has stated that glyphosate has no harmful effects on human health when used in appropriate ways (31).

However, some scientists argue that high glyphosate exposure from heavily treated foods may negatively affect many aspects of human health, including reproductive health (32).

Researchers argue that there’s not enough evidence showing that glyphosate is safe to consume, even at low levels, and that more comprehensive research is needed to fully understand how it affects human health (32).

For people who want to minimize their exposure to glyphosate and other pesticide and herbicide residues, a few companies make organic oat milk or offer glyphosate-free products.

For example, Willa’s, Pacific, and Rise oat milks are made with organic oats. Glyphosate is prohibited in organic farming. Additionally, some brands that don’t use organic oats, like Oatly, use third party testing to certify that their products are glyphosate-free (33, 34).

Summary

Some oat and soy products can be high in added sugar and may contain glyphosate residue. Plus, compounds found in soy could affect thyroid function, so those with thyroid conditions may want to limit their soy milk intake.

You can use soy and oat milk in a variety of ways. They are both popular among those who are on plant-based diets or avoiding dairy products.

Both are used in beverages like lattes, cappuccinos, and smoothies and you can use them as a milk alternative in recipes like oatmeal, soups, and chia pudding.

Even though they are used in similar ways, they have some differences in taste and texture.

Oat milk is creamier and a bit sweeter than soy milk, which is why it’s a popular choice for coffee drinks, like lattes.

However, according to online barista forums, soy milk may be a better choice for making foamy coffee drinks due to its higher protein and fat content.

So, if you like a foamier coffee or tea drink, soy milk may be the better option of the two.

Also, oat milk is significantly higher in carbs than soy milk. Some people following lower carb diets or those who are watching their carb intake may want to choose a lower carb plant-based milk, such as soy, almond, or coconut.

Lastly, it’s a good idea to choose unsweetened plant-milk products whenever possible. That’s because sweetened plant-based milks can contain a high amount of added sugar.

Summary

Oat and soy milk are popular plant milks. You can use them in many coffee drinks, but soy may be the better choice for those who like a foamy beverage. Oat milk is a bit higher in carbs and sweetened products can be high in added sugar.

Oat and soy milk are popular plant-based milk alternatives that people often use in coffee drinks, smoothies, and more.

Compared with oat milk, soy milk is higher in calories, fat, protein, potassium, and iron, while oat milk is higher in carbs.

Both can be a healthy and tasty choice, depending on your preferences and health concerns. Whichever you choose, opt for unsweetened products to keep your added sugar intake in check.

Just one thing

Try this today: Try coconut milk in your coffee. I love coffee and I like to make foamy lattes at home. I prefer full-fat coconut milk or cashew milk to create a frothy beverage. Full fat canned coconut milk is my top choice!