A complete
protein is one that contains ample amounts of all 22 amino acids;
an incomplete protein does not.
Because animal proteins (meat, fish, poultry, eggs, and dairy) contain amino
acids combinations similar to humans, they are easily absorbed by our bodies
and are considered “high quality proteins”.
Beans, nuts, legumes, vegetables and fruits often have limited amounts of only
some amino acids (not all 22) and are not as easily absorbed. For this reason,
they are considered inferior or “low quality”
proteins.
It is possible to increase the quality of incomplete proteins by combining certain
foods (i.e. beans + rice).