Mushrooms are often thought of as a standout plant-based protein, especially because they contain all essential amino acids. But whether they’re actually the “best” option depends on how you define protein quality and how much you realistically eat

Protein is made up of amino acids, nine of which are considered essential because your body can’t produce them. A “complete protein” contains all nine in adequate amounts. This matters because missing even one essential amino acid can limit how well your body builds and repairs tissue, supports immune function, and maintains muscle mass.

Some research suggests that about 43% of the amino acids in mushrooms are essential, which is comparable to yeast and even slightly higher than soy on a proportional basis.2 That sounds impressive, and it’s one reason mushrooms get labeled as a high-quality plant protein.

But there’s an important caveat: protein quality isn’t just about amino acid presence. It also depends on how much protein you get per serving and how well your body can digest and use it.