THE SHORT VERSION
- Two drinks can both list 25 grams of protein. One uses whey; the other uses ultrafiltered milk. The matching number leaves the source and form of that protein to check.
- If all 25 grams come from milk protein with its usual 80:20 casein-to-whey ratio, that is about 20 grams of casein and 5 grams of whey. Added proteins or a different ratio would change the calculation.
- The takeaway: protein grams and quality scores do not describe digestion speed or establish a specific health benefit.
- The question to ask: does the evidence behind a claim match this product, this dose and the outcome I care about?
Imagine comparing two protein drinks. Both list 25 grams of protein and the same percent Daily Value for protein. One names whey protein as its source. The other is made with ultrafiltered milk, which is milk passed through fine filters that concentrate its protein.3
Both can supply complete protein, meaning all nine essential amino acids in adequate proportions. Their matching numbers describe an important nutritional contribution. They leave questions about composition, digestion and particular biological effects open.1,2
Choosing between them starts with knowing which question you want the label to answer.
Identify the protein behind the number
Read the ingredient list for the source supplying those grams. Whey protein concentrate and whey protein isolate come from the whey fraction of milk. Milk protein concentrate and conventional ultrafiltered milk generally retain both casein and whey.1,3
Ultrafiltration describes a filtering process. Whey names a protein fraction. A product made with ultrafiltered milk may also contain added protein ingredients, so read the full ingredient list.3
Take a hypothetical drink whose entire 25 grams of protein comes from milk protein that keeps its usual ratio of about 80 parts casein to 20 parts whey. That serving would supply about 20 grams of casein and 5 grams of whey. A drink with all 25 grams from whey would have a different makeup.3
This is an example, not a way to calculate every drink’s blend from the protein total. Added protein ingredients or a changed ratio would change the calculation.
Both whey and casein supply the essential amino acids, but their proportions and digestive behavior differ. A shared high protein-quality score does not describe every aspect of what happens after consumption.1,2
Protein-quality scoring has limits too. The protein digestibility-corrected amino acid score, or PDCAAS, is capped at 1.0, also written as 100%. Different proteins can reach that ceiling even when their amino acid profiles differ. This 100% is a quality score, not the percent Daily Value on a nutrition label.2
PDCAAS also uses digestibility measured over the whole gut, using stool samples. A newer method looks at the digestibility of individual essential amino acids before they reach the large intestine. It is called the Digestible Indispensable Amino Acid Score, or DIAAS.2,4
In a 2016 paper, an expert group convened by the Food and Agriculture Organization of the United Nations, or FAO, described DIAAS as a preferable approach. The authors also called for more digestibility data on commonly eaten foods. Neither score tells you how quickly a finished drink will be digested.4,5
Compare the portion you will actually consume
Check the serving size attached to the protein amount. A figure per serving, per bottle or per 100 milliliters can describe different quantities of food. Put both products on the same basis, then consider the portion you expect to consume.
Read the rest of the nutrition panel and the allergen information alongside the protein total. Compare calories, sugars, saturated fat and sodium as well. Protein is one part of choosing a food that fits your day.
Look at the protein form and the finished food
The source is a starting point. Micellar casein and sodium caseinate, for example, are different physical forms of casein. Hydrolysis means cutting protein chains into smaller fragments before consumption. Heating, fermentation and other ingredients can also influence how dairy proteins behave during digestion.5
This is why a protein’s name cannot supply an exact digestive timetable for every food containing it. In a study published in 2021, ten older adults consumed eight different dairy products, each providing 25 grams of protein. It was a crossover study, meaning each person tried every product in turn.6
The products included different milks, yogurt, cheese, whey protein concentrate and micellar casein isolate. Whey concentrate and yogurt produced the largest rises in essential amino acids in the blood. Cheese and micellar casein produced more prolonged responses.6
The study examined the combined properties of each food, often called the food matrix. It measured amino acids in the blood for up to five hours. In the milk comparisons, fat delayed the amino acid response. The study found no detectable difference between pasteurized milk and milk given ultra-high-temperature treatment.6
Those findings describe the foods and treatments tested. They do not rank the products by long-term muscle gain, and the study did not test every commercial protein drink.6
A word such as “hydrolyzed” tells you about preparation. Its practical significance depends on the protein, the processing conditions and what you want the finished food to do.5
Decide which outcome matters to you
A convenient way to consume protein is one goal. A claim about fullness, blood sugar or blood pressure asks a more specific question. A protein’s complete amino acid profile establishes something different from evidence for any of those outcomes.1,2
Read the result a study actually measured. Amino acid levels in the blood describe availability and timing. Muscle protein synthesis, the rate at which muscle builds protein, measures a metabolic process. Changes in strength or muscle mass over months require longer-term studies.5,6
A faster rise in blood amino acids does not, by itself, establish greater muscle gains over time. The useful result is one that measures the outcome you care about.5,6
Follow a functional claim to its evidence
When a claim refers to bioactive peptides, it means protein fragments studied for a biological effect. Look for the particular peptide or preparation and the amount tested. A lab test that places a fragment directly onto an enzyme or cultured cells skips questions about digestion and access to its target in the body.1
Human research helps address those questions, but the details still matter. Check whether participants consumed the relevant ingredient or a comparable finished preparation, at a similar dose. Notice who was studied, how long the study lasted and whether the claimed outcome was measured.
Research on a related ingredient can help explain why an effect is plausible. Research using a relevant preparation can test whether it happens under the conditions studied. The closer those conditions are to the product and claim, the more useful the comparison.1,5
A checklist for comparing two products with the same protein number. These questions apply to both.
References
Educational content. The Fountain is written to explain, not to make health claims about any product. This article summarizes published peer-reviewed research. Nothing here is medical advice.
- Auestad N, Layman DK. Dairy bioactive proteins and peptides: a narrative review. Nutrition Reviews. 2021;79(Suppl 2):36–47. https://doi.org/10.1093/nutrit/nuab097
- Schaafsma G. Advantages and limitations of the protein digestibility-corrected amino acid score (PDCAAS) as a method for evaluating protein quality in human diets. British Journal of Nutrition. 2012;108(Suppl 2):S333–S336. https://doi.org/10.1017/S0007114512002541
- McSweeney DJ, Maidannyk V, Montgomery S, O’Mahony JA, McCarthy NA. The influence of composition and manufacturing approach on the physical and rehydration properties of milk protein concentrate powders. Foods. 2020;9(2):236. https://doi.org/10.3390/foods9020236
- Lee WT, Weisell R, Albert J, Tomé D, Kurpad AV, Uauy R. Research approaches and methods for evaluating the protein quality of human foods proposed by an FAO Expert Working Group in 2014. Journal of Nutrition. 2016;146(5):929–932. https://doi.org/10.3945/jn.115.222109
- Horstman AMH, Huppertz T. Milk proteins: processing, gastric coagulation, amino acid availability and muscle protein synthesis. Critical Reviews in Food Science and Nutrition. 2023;63(30):10267–10282. https://doi.org/10.1080/10408398.2022.2078782
- Horstman AMH, Ganzevles RA, Kudla U, Kardinaal AFM, van den Borne JJGC, Huppertz T. Postprandial blood amino acid concentrations in older adults after consumption of dairy products: the role of the dairy matrix. International Dairy Journal. 2021;113:104890. https://doi.org/10.1016/j.idairyj.2020.104890