Reference
Whey Protein
**Whey protein** is a fast-digesting dairy protein recovered from the liquid whey separated during cheesemaking, and it serves as the reference benchmark against which other protein sources are measured for quality.
Composition and forms
Whey is a complete protein, supplying all nine essential amino acids. It is sold in two main forms. Whey protein isolate is comprised of 90 to 95% protein and less than 1% lactose, while whey protein concentrate is lower in protein and higher in fat and carbohydrate, including lactose. Monash University notes that isolates undergo more extensive processing to raise protein content, meaning concentrate carries more of the FODMAP lactose than isolate. Leucine content between high-percentage concentrate (80%+ protein) and isolate is nearly identical.
Protein quality
On the Protein Digestibility-Corrected Amino Acid Score (PDCAAS), values are truncated to a maximum of 100% (1.00), and high-quality dairy proteins such as whey reach that ceiling — the reason whey is widely treated as a reference protein (The Journal of Nutrition, 2000, PMID:10867064). On the newer Digestible Indispensable Amino Acid Score (DIAAS), whey isolate falls in the 94–100% range. Whey protein isolate contains 43% essential amino acids, compared with 37% for potato protein isolate (Amino Acids, 2018, PMID:30167963). Its high leucine content is the main reason whey is treated as the quality reference for protein supplements.
Effect on muscle protein synthesis
Whey’s rapid digestion and high leucine content make it effective at stimulating muscle protein synthesis. In older men, whey stimulated postprandial muscle protein accretion more effectively than casein or casein hydrolysate (American Journal of Clinical Nutrition, 2011, PMID:21367943). After resistance exercise in young men, whey stimulated mixed muscle protein synthesis more than casein or soy, attributed to faster absorption kinetics and higher leucine (Journal of Applied Physiology, 2009, PMID:19589961). In a 2024 comparison, whey raised myofibrillar muscle protein synthesis to 0.046%/h versus 0.041%/h for a plant blend — roughly 12.1% higher on average (J Nutr, 2024).
Relevance to potato protein
Whey is the common point of comparison for plant proteins because animal proteins generally score higher on quality metrics. Potato protein isolate is one of the few plant sources approaching that benchmark: soy and potato isolates both reach a DIAAS of at least 100% for children and adults, comparable to whey isolate. For readers weighing options, the broader trade-offs are covered in our complete guide to choosing a protein powder. Unlike whey, potato protein contains no dairy, making it relevant for people avoiding lactose or milk allergens.
Related terms