Soy Milk vs Oat Milk: What’s Better for You? A Dietitian Spills the Milk

Soy and Oat milk are very popular dairy-free alternatives to dairy milk. Both are widely used for coffee, tea, cereal, smoothies, and baking. Chances are, if you’re vegan or vegetarian, you’ve tried one or both of these options before. 

I’m not here to “spoil” your diet, but I do want to “spill the tea”or milk in this case on which one is better for you in this showdown of soy milk vs oat milk. 

Soy Milk vs Oat Milk: What are they? 

At one time, dairy alternatives were hard to come by. Nowadays, you can find plant-based milk alternatives at almost every grocery store, including soy and oat milk. 

While both oat milk and soy milk can be used as dairy substitutes, they do have different flavors, textures, and nutrient profiles. Let’s take a look at their differences and similarities. 

Soy Milk 

Fortified soy milk is one of the first options for dairy-free alternatives. It is made by removing the outer hull of soybeans, boiling them under high pressure, and then grinding the cooked beans and straining the remaining liquid. 

Flavorings, sweeteners and other ingredients may then be added with soymilk to improve the taste and texture. It’s often sterilized and homogenized (made to have a smooth and consistent mouthfeel similar to milk) to improve shelf-life. 

With about 8.6 g of protein per cup, it’s similar to the protein in dairy milk. Brands often fortify soy milk with vitamins and minerals like Vitamin D, B12, and Calcium to add additional nutrients.. 

The Dietary Guidelines for Americans and MyPlate encourage those who do not consume dairy to use fortified soy alternatives! 

Oat Milk

Oat milk is, well, made from oats. Oats are soaked in fresh water, and then blended and strained. The resulting strained liquid becomes the oat milk. Some companies choose to add flavorings or added sugars to improve taste, but some keep it simple with minimal ingredients. 

With 1.6 g of protein per cup, it's lower in protein than other plant-based milks. Oat milk is often fortified with additional vitamins and minerals like vitamin B12, vitamin D, and calcium to make a source of extra nutrients. 

Oat milk is a popular choice for coffees, lattes, cereal, and smoothies. Plain oatmilk can have a slightly earthy, slightly nutty taste, similar to oats. Some brands offer extra creamy or full-fat varieties that can help add a little frothiness to your morning cup of coffee, but look out for added sugars. 

Soy Milk vs Oat Milk: Nutrition Breakdowns

Soy milk and oat milk are common substitutes for dairy milk, but they have some key differences, primarily in protein, carbohydrates, vitamins, and minerals. Both have similar fat profiles and calories, and their nutrition will vary based on whether they are unsweetened, sweetened, or flavored.

Protein

Depending on your brand, soy milk contains 7-8 grams of protein per cup, comparable to dairy milk, while oat milk is lower, at around 1-2 grams of protein per cup. This isn’t horrible, but if you’re using milk to hit your protein goals, oat milk likely won’t get you there.

Carbohydrates and Sugar

Both oat milk and soy milk contain small amounts of naturally occurring carbohydrates and sugars. Soymilk has around 1-2 grams per cup, less than dairy milks, while oat milk contains 12-13 grams per cup, which is more similar to dairy’s 11-12 grams per cup. 

Remember that total sugars are not the same as added sugars.Added sugars are sweeteners added after processing to improve sweetness. These are products like molasses, table sugar, cane sugar, coconut sugar, vegan honey, sucrose, glucose, and fructose. 

If you’re looking to reduce your added sugars, consider buying unsweetened options or adding smaller amounts of your favorite sweetener or alternative at home.

Fat

Both oat milk and soy milk are lower in overall fat and saturated fats than dairy milk, especially when compared to whole milk. Oat milk and soy milk contain around 5 grams of fat, most of them unsaturated. 

Soy milk and some oat milk brands have a lower amount of saturated fats, less than 0.5 g, compared to milk’s 4.5 grams. Lower amounts of saturated fats in plant-based milks are beneficial for our heart health. Saturated fats have been linked to higher LDL(bad) cholesterol levels.

Vitamins and Minerals 

Both oat milk and soy milk have calcium, B12, and vitamin D. Some brands are fortified with additional vitamins and minerals, like vitamin A, to make them more nutritious, but unfortified versions are also available. 

The Dietary Guidelines for Americans and MyPlate recommend fortified versions to ensure we are getting the nutrition we need throughout the day, specifically for 3 of the primary micronutrients of concern: calcium, protein, and vitamin D.

Soy Milk vs Oat Milk: Answering Common Questions

We’re spilling the milk- again! We’ve gathered the list of top questions most people ask about non-dairy milks right here.

Is soy milk or oat milk better for weight loss?

When used in moderation, soy milk and oat milk can be used as part of a balanced weight loss plan. While soy milk contains higher protein and fewer calories, oat milk has slightly higher calories and lower amounts of protein, but does have fiber that may aid in helping you feel fuller, longer.

Does soy milk mess with hormones?

Soy is an integral part of many vegan and vegetarian diets. It has been linked to potential health benefits like reduction of hot flashes for peri-menopausal women and reduced risk of osteoporosis and cardiovascular disease.

Soy does contain high amounts of phytoestrogens that act similarly to estrogen, a hormone present in both male and female bodies. Because of this, soy’s phytoestrogenic effect has been sensationalized to give the appearance that it will impact testosterone levels, creating the myth of the “Soy Boy.” 

But does soy actually mess with hormones? NO. There is currently no evidence that shows soy has any significant impact on our hormones. 

This expanded and updated meta-analysis of over 38 clinical studies showed no impacts on men’s hormones when they ingested soy or isoflavones (another word for phytoestrogens). At present, there is also no evidence to suggest it negatively impacts women’s hormones, either. 

Soy Milk vs Oat Milk: Best Use Cases

Soy milk is a versatile dairy-free alternative for baking, smoothies, and in coffee. It has similar protein content to dairy milk, although it may not be appropriate for those with soy allergies. Some people may choose sweetened versions when adding to puddings or pies.

Oat milk is a great alternative when you are looking to increase your fiber intake. Unlike soymilk, oatmilk can have 1-2 g of fiber per cup. (Every gram counts when we’re trying to get 25-30g per day!) Oatmilk does have less protein than soy milk, but can be a great alternative for individuals with dairy or soy allergies.

Oatmilk can be used as a 1:1 replacement for dairy in baked goods, but has a lower fat content, which doesn’t make it ideal for things like whipped cream.

Spilling the Milk: Which One Should You Choose? 

Unsweetened oat milk and soymilk are similar in taste and texture. 

Soy milk is most similar to dairy milk in terms of protein and potassium, whereas oat milk is most similar to dairy milk in terms of carbohydrates, but has less protein overall. Both can be fortified with calcium, matching or exceeding the amount in dairy milk.

Oat milk is a good alternative milk for individuals with dairy and soy allergies, while soy milk is a good staple option for those avoiding dairy.

If you’re looking for the milk that’s right for you, try both! Test each one out for one week to see how they compare, while still considering your nutritional needs.