It's The Amino Acids That Matter
When we look at protein itself, it is not the source of the protein that really matters. It is the amino acid profile. Amino acids are the building blocks of protein. When we consume protein like chicken or tofu, our body will breakdown that food into basic units it can use. For protein, we end up with amino acids.
The body is constantly breaking things down and building it back up. Protein is important for this process because we use these amino acids to build things back up. There are 20 amino acids. 9 are essential, meaning our body can’t make them, and 11 are non-essential because our body can make them on their own.
As we digest protein and get free amino acids floating around, out body can now use them to build different things. Depending on the type and amount of amino acids present we can build different things like muscle or connective tissue.
So for protein it is probably less important what the source of the protein is, but more important of the amino acids present in that protein. That is really what makes proteins different like whey or collagen.
Animal Protein
Animal-based proteins such as meat, eggs, dairy, and whey are generally the most efficient at stimulating muscle protein synthesis, and whey is the clearest example of why. Whey is naturally high in leucine and delivers a complete set of essential amino acids, which is why research consistently shows it does a great job of building muscle. This holds up even in populations that are typically harder to build muscle in, like postmenopausal women, where high-quality animal protein has been shown to help overcome some of the anabolic resistance that comes with hormonal changes.
The common thread across animal protein sources whether it’s a chicken breast, eggs, or a scoop of whey is that they naturally provide a complete amino acid profile with a strong leucine content. That’s the actual reason animal protein has earned its reputation, not simply because it comes from an animal.
Plant Based Protein
Plant proteins (pea, soy, rice, hemp, and blends of these) have historically lagged behind animal protein, and the reason comes right back to amino acid profile. Most plant sources are naturally lower in leucine and are often missing one or more essential amino acids.
But here’s the important part: when researchers took a plant-based protein blend and simply added leucine to match the levels found in whey, the muscle protein synthesis response was no longer significantly different. In other words, the “plant protein isn’t as good” idea isn’t really about plants being inferior it’s about whether the leucine and amino acid profile is dialed in. This is exactly why combining multiple plant sources (like rice and pea) is a common and effective strategy. Each one fills in the other’s amino acid gaps. A well-formulated, leucine-rich plant protein can absolutely get the job done.
Collagen Protein
Collagen gets marketed heavily right now, but it’s important to be clear about what it actually does well. Collagen has a very different amino acid profile than animal protein sources like whey, it’s lower in leucine and lower in total essential amino acids. Research directly comparing collagen to whey found collagen was simply less effective for building muscle.
That doesn’t mean collagen is useless. It has a specific job: supporting connective tissue. Studies combining whey and collagen found the blend improved not just muscle protein synthesis, but also connective tissue protein synthesis meaning collagen may have real value for tendons and ligaments, just not as a primary muscle-building protein on its own.
Remember, You Eat Food Not Protein
Here’s something worth remembering when you’re comparing protein sources: most protein-containing foods aren’t pure protein. A steak, a scoop of whey isolate, a handful of nuts, and a serving of Greek yogurt all provide protein, but they come packaged very differently, some with a lot of fat, some with very little, some with carbohydrates attached, some with almost none.
This matters for your overall goals. If you’re watching total calories, a fattier protein source will cost you more calories per gram of protein than a lean one. If you’re trying to hit a fat intake target for hormone health, a very lean protein source might mean you need to get more of your fat from elsewhere. Neither is “better” across the board. It depends on what you’re trying to accomplish with your overall diet, not just your protein target.
What This Means For You
If you’re choosing a protein source based on which category is “best,” you’re asking the wrong question. The real question is whether it has a good leucine and amino acid profile, and whether it fits into the rest of what you’re eating. Animal protein (including whey) remains an efficient, low-fuss option for muscle building. Plant protein can absolutely get the job done as long as it’s leucine-rich or blended well, and you’re not relying on a single, incomplete source. Collagen is worth having in the mix if you want extra connective tissue support, not as your main protein source.
At the end of the day, hitting your daily protein target consistently matters far more than which specific source you use to get there.
Not sure how much protein you actually need, or which sources fit your goals? That’s exactly the kind of thing we help our members figure out at SDPT.