Protein Content Continues to Favor Cow's Milk Over Plant-Based Alternatives

Plant-based milk does not hold up to cow dairy in one key nutritional element, a new study finds.

Over the last few decades, many people have made the shift from cow dairy to plant-based options, generally for perceived environmental or health-related reasons. That, in turn, has resulted in an increase in dairy-free milk available at grocery stores and restaurants.

And, plant-based milk options are often marketed as more nutritious than cow’s milk.

According to a presentation at the American Society for Nutrition’s latest conference, plant-based milk lacks the same percentage of protein as dairy. 

Unless you are taking the time to read every single nutrition label, it can be challenging to know if splashing oat or almond milk on your cereal provides a similar nutrition profile as classic dairy milk. 

“Current US dietary guidelines recommend consuming cow’s milk or soy milk to provide calcium and vitamin D,” Abigail Johnson, PhD, RD, Assistant Professor at the University of Minnesota and lead investigator of the study, told Health.

“We wanted to know if other types of plant-based milk products were similar to cow’s milk and to understand the differences in nutrition content across the plant-based milk types,” she said.

To help answer this question, Johnson and her colleagues assessed the nutritional content of plant-based milk alternatives available in the U.S. market, including almond, cashew, coconut, flax, hazelnut, hemp, oat, pistachio, rice, soy, walnut, and plant blends.

A total of 237 plant-based milk alternatives were analyzed for their level of calcium, vitamin D, and protein. While 72% of the alternatives were fortified with calcium and vitamin D, few plant-based milk alternative products match dairy milk levels of protein.

Johnson used vitamin B12 as an example of the difference between cow dairy and plant-based milks. One serving of cow's milk provides around half of the daily value (DV) of vitamin B12. On the other hand, only 40% of plant-based milks are a good source of vitamin B12.

She emphasized that because of the “wide variation in the nutrient content of plant-based milk products, consumers can't assume that plant-based milks are a 1:1 substitution for cow's milk”.

Keri Hackworth MS, RDN, LD, Director of Nutrition Affairs at the National Dairy Council, agreed. “We need to be thinking quality over quantity when it comes to protein,” she said.

According to the protein rating system, Protein Digestibility-Corrected Amino Acid Scores, milk protein receives a top score of 1.0, while plant-sourced foods like almonds receive 0.39, rice at 0.42, peas at 0.58, and up to 0.98 in soy protein.

“Animal-sourced foods like dairy foods provide high-quality protein and all of the essential amino acids, including glycine, methionine, leucine, and tryptophan,' Hackworth said.

As Toby Amidor, MS, RD, CDN, FAND, award-winning nutrition expert shared, a cup of milk is a great source of many key nutrients.

Amidor, who is also the Wall Street Journal best-selling author of Up Your Veggies: Flexitarian Recipes for the Whole Family explained that “emerging research indicates each dairy food matrix―which is made up of the food’s nutrient and non-nutrient components (i.e., bioactive compounds) and their molecular relationships―may help explain the association seen between consumption of dairy foods and the reduction of chronic disease risk and health benefits.”

Some of the specific chronic diseases that Amidor referred to include insulin resistance, hypertension, and cardiovascular disease. Also, some data suggests that dairy may have anti-inflammatory benefits.

She added that while plant-based milk alternatives may be able to mimic some of dairy’s nutrient composition through fortification, the dairy milk matrix cannot be mimicked. In other words, consumers can't assume that plant-based milk will have the same nutritional makeup as dairy.

The three nutrients that were emphasized in this study—protein, vitamin D, and calcium—are key nutrients that support many aspects of a person's health.

The Dietary Guidelines for Americans advise people to consume three servings of dairy a day to help avoid nutritional gaps.

Based on the study’s results, it is clear that opting for plant-based milk is not a nutritionally equivalent 1:1 swap for dairy, which may result in some people missing out on the amount of nutrients—particularly protein—they need each day.

The true effects of opting for a milk choice that is lower in protein, and not quite equal in calcium and vitamin D, are difficult to assess. Consumers of plant-based milk can maintain these nutrients by including other nutrient-packed foods in their diet.

If a person is avoiding dairy, whether due to an allergy or a lifestyle choice, it’s important to prioritize protein, calcium, and vitamin D in the rest of their diet.

It may also be appropriate to explore a vitamin D and calcium dietary supplement with a healthcare provider.

But Amidor pointed out that a protein supplement may not be indicated for most plant-based milk drinkers, as “there are plenty of animal and plant sources of protein that someone can incorporate in their diet.”