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Bioavailability
**Bioavailability** is the fraction of an ingested nutrient that is actually absorbed across the gut wall and made available for the body to use. For dietary protein, it describes how much of the amino acid content survives digestion and reaches circulation, rather than the raw protein number printed on a label.
What determines protein bioavailability
Three factors govern how usable a protein is. The first is digestibility — how completely the protein is broken into absorbable amino acids and peptides before it reaches the colon. The second is amino acid composition, since a protein short in one indispensable amino acid limits how much of the rest can be used for synthesis. The third is anti-nutritional factors: compounds that interfere with absorption.
Phytic acid (phytate) is one such factor. A review notes that hemp seeds contain phytic acid, which can chelate minerals and reduce their bioavailability. Plant protein is generally less bioavailable than animal protein, though processing methods such as soaking and sprouting can increase it (Whole Story Nutrition).
How bioavailability is measured
Two scoring systems dominate. The Protein Digestibility-Corrected Amino Acid Score (PDCAAS) and the Digestible Indispensable Amino Acid Score (DIAAS) are the key measures of protein quality, and both tend to be higher for animal than for plant proteins (Foods, 2024, PMID:38890999). Under PDCAAS, egg protein scores 1.00 while wheat gluten scores around 0.25 — a gap that reflects digestibility and a limiting amino acid working together.
Ileal digestibility — measured at the end of the small intestine — offers a more direct read than fecal methods. In a controlled human study, the real ileal digestibility of pea protein averaged 93.6% versus 96.8% for casein, and pea protein isolate scored a DIAAS of 1.00 against 1.45 for casein (American Journal of Clinical Nutrition, 2021, PMID:34665230).
Bioavailability of potato protein
Potato protein isolate performs well on these metrics. Its DIAAS has been reported as high as 100 (Food Science & Nutrition, Herreman et al., 2020, PMID:33133540). A 2020 trial found that 25g of potato protein isolate stimulated muscle protein synthesis in young women, implying high bioavailability and quality (Nutrients, 2020, PMID:32349353). Among plant proteins, that places it favorably — a relevant point for anyone comparing sources, as covered in the guide to what potato protein is. Bioavailability, not the gram count on a tub, is what ultimately determines how much of a protein the body can put to use.
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