Soy milk and pea milk lead the pack, each delivering 7 to 8 grams of protein per cup. That puts them on par with cow’s milk, which contains about 8 grams per cup. Most other plant-based milks fall far behind, with some providing little to no protein at all.
Soy Milk: The Original High-Protein Option
Soy milk has been the go-to dairy alternative for decades, and it still holds up. A cup of calcium-fortified soy milk provides about 7.4 grams of protein. Beyond the raw number, soy has a significant edge in protein quality. Your body can’t use all protein equally well. It depends on the mix of amino acids and how efficiently you digest them. Soy scores exceptionally high on the DIAAS scale (a measure of how well your body absorbs and uses protein from a food), with values above 100%, putting it closer to animal protein than almost any other plant source.
That said, soy is slightly low in an amino acid called methionine. For most people eating a varied diet, this doesn’t matter at all. Your other meals throughout the day fill in the gap easily.
Pea Milk: The Newer Competitor
Pea milk, made from yellow split peas, matches cow’s milk at 8 grams of protein per cup. Brands like Ripple have built their identity around this number. A cup of unsweetened Ripple milk also delivers 45% of your daily calcium needs and 30% of your vitamin D, with zero carbs and 70 calories. If you’re avoiding soy (whether for allergies or personal preference), pea milk is the strongest alternative for protein.
Pea protein does score lower on digestibility than soy, with a DIAAS value around 62 compared to soy’s 100-plus. It’s rich in lysine (an amino acid many plant proteins lack) but low in methionine, similar to soy. In practical terms, this means pea milk protein is slightly less efficient gram-for-gram than soy milk protein at building and repairing muscle. For most people drinking a glass or two a day alongside regular meals, the difference is negligible.
How Other Milk Alternatives Compare
The drop-off after soy and pea milk is steep. Here’s what you get from a cup of the most common alternatives:
- Oat milk: 3 grams of protein
- Hemp milk: 3 grams of protein
- Almond milk: 1 gram of protein
- Coconut milk: 0 grams of protein
Oat milk has become wildly popular for its creamy texture in lattes, but it’s not a meaningful protein source. Almond and coconut milk are essentially flavored water from a protein standpoint. Hemp milk sits in the middle at 3 grams, and while hemp seeds are a good source of omega-3 fats, the milk form is too diluted to deliver much protein.
Fortified Versions That Close the Gap
Some brands boost lower-protein milks by adding pea protein isolate or soy protein to the formula. Silk makes a protein-fortified almond milk with 8 grams per cup. Good Karma’s Flax Milk + Protein blends cold-pressed flax oil with pea protein to reach 5 grams per serving, along with 1,200 milligrams of plant-based omega-3s. Whole Moon makes an oat milk fortified with roasted soybeans that hits 8 grams per cup.
These products work well if you prefer the taste of oat or almond milk but want more protein. Just check the ingredients list. The added protein typically comes from pea protein isolate or soy protein concentrate, so if you’re avoiding those for allergy reasons, the fortified versions won’t work for you.
Protein Quality Matters, Not Just Grams
A review published in Frontiers in Nutrition found that most plant-based milks made from a single ingredient don’t provide a complete amino acid profile on their own. Soy is the notable exception. Its amino acid balance closely resembles dairy, which is why nutrition researchers consistently rank it as the best plant milk for protein quality.
Pea protein is strong in lysine (5.9% of its amino acid content) but weak in methionine (0.4%). Soy has a similar methionine limitation but scores better overall because your body digests and absorbs it more efficiently. For either one, the practical fix is the same: eat grains, nuts, or seeds at some point during the day, and the amino acids balance out naturally. You don’t need to combine them in the same meal.
Choosing the Right One for You
If protein is your top priority, soy milk gives you the best combination of quantity and quality. Pea milk matches it on grams and works well if soy isn’t an option. Both deliver roughly the same protein as a glass of cow’s milk, which makes them genuine nutritional substitutes rather than just flavor alternatives.
If you’re using plant milk mainly in coffee or cereal and getting your protein from other foods, the protein content of your milk matters less. But if you’re relying on plant milk as a regular part of your diet, especially for children or older adults who need consistent protein intake, the difference between 8 grams from soy and 1 gram from almond milk adds up quickly over the course of a day.