Pea milk has the most protein of any widely available plant milk, with about 8 grams per cup. Soy milk is a close second at 7 grams per cup, which actually matches the roughly 8 grams you’d get from a cup of whole cow’s milk. Every other plant milk falls far behind these two.
How Plant Milks Compare by Protein
The protein gap between the top contenders and the rest of the plant milk aisle is dramatic. Here’s how unflavored, unsweetened varieties stack up per 8-ounce (240 ml) serving:
- Pea milk: 8 grams
- Soy milk: 7 grams
- Oat milk: 3 grams
- Almond milk: 1 gram
- Coconut milk: 0 grams
For reference, whole cow’s milk provides about 7.9 grams of protein per cup. So pea and soy milks are the only plant-based options that come close to dairy as a protein source. Oat milk gives you less than half as much, and almond and coconut milk are essentially protein-free beverages.
Why Soy Protein Is Higher Quality Than Other Plant Sources
Grams per cup only tells part of the story. Protein quality, meaning how well your body can actually use the amino acids it contains, varies significantly between plant sources. Nutritionists measure this with a score called PDCAAS, which ranks proteins on a scale from 0 to 1 based on their amino acid profile and digestibility.
Soy scores a perfect 1.0, placing it alongside whey, casein, and egg as one of the highest-quality proteins available. Pea protein scores 0.82, which is still respectable and well above most plant sources. Hemp seeds, by comparison, score between 0.49 and 0.66 depending on processing. This means that even though pea milk edges out soy in raw grams, soy milk delivers slightly more usable protein per serving.
The practical difference between these two is small enough that either one is a solid choice. But if you’re relying on plant milk as a meaningful protein source in your diet rather than just a splash in coffee, the quality gap between soy or pea and everything else is significant.
How Plant Milk Protein Performs for Muscle
If you’re choosing a plant milk specifically to support exercise or muscle maintenance, soy protein has the most research behind it. Compared to whey (the gold standard for muscle building), soy protein produces similar gains in lean mass over 6 to 12 weeks of resistance training. Over longer periods of 36 weeks or more, whey pulls ahead for muscle growth.
The reason comes down to leucine, an amino acid that acts as a trigger for muscle repair. Whey protein is about 12% leucine, while soy is closer to 8%. Soy protein also digests and absorbs differently, which results in a lower spike in muscle protein synthesis after a meal. That said, soy protein has a unique benefit: it appears to reduce oxidative stress and support antioxidant defenses, something whey doesn’t do as effectively.
None of this means plant milk alone will meaningfully fuel muscle growth. A cup of soy or pea milk gives you 7 to 8 grams of protein, which is a helpful addition to a meal but far less than the 20 to 40 grams typically associated with maximizing muscle repair after a workout.
Factors That Reduce Absorbable Protein
Plant-based proteins contain naturally occurring compounds called antinutrients that can interfere with digestion and mineral absorption. Soy, for example, contains trypsin inhibitors that partially resist breakdown in the stomach, and phytic acid that can bind to minerals. Tannins in some plant proteins can cause proteins to clump together, making them harder to digest.
In practice, commercial plant milks undergo processing (heating, filtering, and fortifying) that reduces many of these compounds. The effect on protein absorption in a finished carton of soy or pea milk is likely modest, but it does mean the protein you absorb is somewhat less than what the label states. This is another reason soy milk’s perfect digestibility score gives it a real-world edge over alternatives with lower scores.
What to Look for on the Label
Protein content varies between brands, sometimes significantly. Some pea milk brands add extra pea protein isolate to hit 10 grams per serving, while others contain less. The same goes for soy milk. Always check the Nutrition Facts panel rather than relying on front-of-package marketing. The FDA recommends comparing plant milks against dairy for protein, vitamin D, calcium, and potassium, and choosing products lower in added sugars and saturated fat.
Flavored and sweetened versions of any plant milk tend to have the same protein content as their unsweetened counterparts, but they add calories from sugar. If protein density is your priority (protein relative to calories), unsweetened versions give you more nutrition per calorie. A cup of unsweetened soy milk typically runs about 80 calories for 7 grams of protein, while sweetened versions can climb above 100 calories with no additional protein benefit.
Newer Options Worth Watching
Lupin-based milk alternatives are beginning to appear in some markets. Lab formulations of lupin milk contain about 3.5% protein by weight, which is comparable to cow’s milk (3.8%) and higher than commercial soy milk alternatives (3.2%) in research settings. Whether these numbers hold up in retail products depends on how manufacturers formulate the final drink, but lupin is a promising legume source with a naturally high protein concentration.
For now, your best bets remain pea milk and soy milk. If you want the highest number on the label, reach for pea. If you care about protein quality and digestibility, soy has a slight advantage. Either way, they’re the only two plant milks that belong in the same conversation as dairy when it comes to protein.