The scoop looks precise: one serving, 25g protein, a confident number on the front. But as we explore in our guide on how to read an ingredient list, the source and order matter as much as the headline number. Regulatory standards for these claims also vary globally, which we break down in our food safety regulators comparison. The front of the pack is loud; the back is where the real story lives. DIAAS is the missing score.
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The older protein score is PDCAAS, short for Protein Digestibility-Corrected Amino Acid Score. It adjusts raw protein for amino acid mix and digestion, but it uses whole-gut digestion and caps scores at 1.0. In 2013, an FAO expert group recommended DIAAS, the Digestible Indispensable Amino Acid Score. DIAAS looks at each essential amino acid at the ileum, the end of the small intestine. 1
The difference is not cosmetic, but the evidence needs the right label. A 2017 controlled study in the British Journal of Nutrition used growing pigs, not humans, to compare dairy and plant proteins. Mathai, Liu, and Stein reported that DIAAS split protein sources more clearly than PDCAAS-like scores. In that comparison, PDCAAS-style scoring gave some plant proteins a higher score than DIAAS and compressed the top end of high-scoring dairy proteins.2
The score map below uses published DIAAS examples, not a universal rank for every product. Mathai and colleagues reported young-child-pattern values around 109 for whey protein isolate, 90 for soy protein isolate, and 82 for pea protein concentrate. A 2018 Food Chemistry lentil study reported average DIAAS values of 0.54 for red lentils and 0.49 for green lentils after cooking and processing. These are quality scores, not exact absorption percentages.2, 3
Plant protein is not one single quality category. Many plant proteins are limited by one amino acid: pea is often lower in sulfur amino acids, while rice is often lower in lysine. In the scoring framework, a blend can make those limiting amino acids less dominant, which is why the source list matters.2
This is why single-source vegan protein math needs context, not panic. A pea-rice blend, soy-based product, or mixed meal such as dal with rice can change the amino acid balance compared with a single isolated plant source. The useful label question is simple: does the product show the amino acid profile, or only the headline grams?
India is a useful stress test for this label problem. Protein has moved from gym shelves into daily packaged food: powders, bars, high-protein atta, shakes, yogurts, and dairy upgrades. Grand View Research estimated India's protein supplements market at USD 1.03 billion in 2025 and projected USD 2.71 billion by 2033. Mint reported in February 2026 that whey-cost pressure and import dependence were pushing some Indian companies toward plant-based alternatives.4
That boom brings a label problem. A 2024 Medicine study by Philips and colleagues tested 36 protein supplements sold in India. The team reported gaps between measured protein and label or ad claims, plus concerns about amino spiking, contaminants, and complex herbal blends.
A 2025 Medicine follow-up tested 18 medical whey powders and 16 consumer nutrition whey powders sold in India. The consumer nutrition powders averaged 75.6g protein per 100g, while the medical powders averaged 29.1g per 100g; taurine-based nitrogen spiking was found in 89% of medical products versus 12.5% of consumer nutrition products.5
Protein spiking is possible because common protein tests measure nitrogen. US labelling law allows protein grams to be calculated as 6.25 times nitrogen content, and FDA protein % Daily Value still uses a corrected protein amount rather than DIAAS. Kjeldahl and Dumas methods are useful nitrogen tests. On their own, they cannot tell intact whey or pea protein from added nitrogen-rich compounds such as taurine, glycine, creatine, urea, or other non-protein nitrogen sources. That is one reason a high gram claim is clearer when an amino acid profile is also available.6
DIAAS is not perfect. Many values come from pig or rat models because human ileal testing is hard to do. Scores change with heat, extrusion, isolation, fermentation, and the whole food matrix. A lentil dal, a lentil flour snack, and a lentil protein isolate are not the same biological product. Current reviews treat DIAAS as a better tool than PDCAAS, not a flawless consumer label.1
Lower DIAAS is not a whole-food verdict. Lentils bring fibre, minerals, polyphenols, and slow-digesting carbohydrate. The nutrition value of a mixed meal is not erased by a lower protein-quality score. The label-reading problem starts when a packaged product presents 25g protein as if every source, blend, and nitrogen count were equivalent.
A useful label routine has three steps. Start with the protein source: whey isolate, whey concentrate, soy isolate, pea, rice, lentil, or blend. Then look for a full amino acid profile, especially leucine, lysine, methionine plus cysteine, threonine, tryptophan, and valine. Finally, read the ingredient list for taurine, glycine, creatine, glutamine, or a "proprietary amino blend" sitting beside the protein source. The front says grams. The back shows whether the grams have evidence behind them.