Beans, lentils, tofu, nuts, seeds and whole grains all provide plant protein.
But they do not provide exactly the same protein.
Different plant foods contain different amounts of protein, different combinations of amino acids and proteins that are digested differently.
For muscle health, these differences can matter.
What makes one protein different from another?
Proteins are made from amino acids.
Nine amino acids are considered essential because our bodies cannot produce them in sufficient amounts. We therefore need to obtain them from food.
One of these, leucine, has an important role in stimulating the process by which muscle builds new protein.
Animal proteins generally contain all essential amino acids in proportions that support muscle protein synthesis.
Plant proteins also contain essential amino acids, but their amounts and proportions vary between foods.
Soy is particularly well studied
Soy is a useful example of why we should not treat all plant proteins as one group.
In randomized trials comparing soy with milk protein, researchers found no significant difference in muscle mass.
Evidence for several other plant proteins is much smaller.
In the same systematic review, trials involving non-soy proteins such as rice, oat, potato and chia favored animal protein for muscle mass. However, only five trials contributed to this analysis.
That is not enough evidence to conclude that these plant proteins cannot support muscle.
It does show why the term “plant protein” covers many nutritionally different foods.
Variety helps
You do not need to calculate the amino acid composition of every meal.
Eating a varied diet makes it easier to obtain essential amino acids from different sources.
Legumes provide substantial amounts of protein. Soy foods such as tofu, tempeh and edamame are particularly useful plant sources. Whole grains, nuts and seeds can add further protein throughout the day.
Different plant foods can complement one another across the diet.
The total amount of protein also matters. A food may contain good-quality protein but provide relatively little of it in a normal serving.
For healthy aging, both protein quality and adequate protein intake deserve attention.
