Pea protein is broken down into peptides, short chains of amino acids small enough to attach to the hair shaft rather than washing off. Peas are also one of the most sustainable protein crops there is, because the plant fixes nitrogen in the soil rather than consuming it.
The peptides settle as a fine layer on each individual strand and give it slightly more circumference. The effect is not dramatic on one strand, but it is multiplied across hundreds of thousands of hairs and therefore becomes visible as body, particularly if your hair is fine or has thinned over the years.
The layer has two side benefits. It evens out the surface so light reflects back instead of scattering, which gives shine. And it holds on to the hair's own moisture, so the strand does not draw water vapor from the air and turn frizzy.
