Protein bioavailability, explained simply: the grams on a nutrition label are what you ate, not what your body actually absorbed and put to use. That gap is real, and it's measured — food scientists score proteins using methods like PDCAAS and DIAAS, which account for both amino acid completeness (see the previous article) and how efficiently the body digests and absorbs a given protein source.
Several things widen or narrow that gap. An incomplete amino acid profile is one, since a missing essential amino acid limits how much of the rest gets used. The structure of the protein itself is another — collagen, for instance, digests and absorbs differently than muscle meat, because its molecular structure and amino acid mix aren't the same. Cooking usually helps rather than hurts: heat unwinds a protein's tightly folded structure, which generally makes it easier for digestive enzymes to break down, not harder. Some plant foods carry fiber and compounds that modestly slow digestion, which is part of why plant and animal proteins don't behave identically even at equal gram counts.
None of this means grams on a label are meaningless — they're the starting point. There's a practical upside here, not just a caveat: bioavailability can be improved with simple choices. Cooking most protein sources rather than eating them raw, combining an incomplete plant protein with a complementary one, and choosing sources with a track record of high digestibility scores all raise the share of labeled protein that actually gets used. The gram count on the label is the ceiling — these choices are what close the distance to it.
But two sauces that each list "20 grams of protein per jar" aren't necessarily delivering the same 20 grams to the body, depending on the source and how complete the amino acid profile is once it's actually absorbed. That's the reasoning behind combining protein sources rather than relying on one — a point the next two articles get into directly.