20–40 g per serving, often before bed.
Like any quality protein, it helps build muscle and strength alongside strength training.
View the study (meta-analysis) →⏱ 3 min read
Casein is the predominant protein fraction of mammalian milk (accounting for about 80 percent of the total protein in cow's milk, versus the 20 percent represented by whey), a protein with distinctive physicochemical properties that make it one of the most studied protein sources in sports and clinical nutrition: in the acidic environment of the stomach, caseins aggregate to form a semi-solid clot that is digested very slowly, releasing amino acids for 6-8 hours after intake, a kinetic pattern markedly different from the rapid, sharp one of whey.
This slow-digestion profile makes casein an ideal "anticatabolic" protein for maintaining a steady supply of amino acids over long periods without protein intake, such as overnight or between widely spaced meals; compared with whey, which produces a sharp, brief peak of plasma amino acids with intense but short-lived activation of muscle protein synthesis, casein produces a more sustained profile with moderate but prolonged activation, a functional difference with practical implications for the supplementation schedule in different clinical and sports contexts.
The indication with the strongest clinical support is casein intake before bed to sustain muscle protein synthesis overnight: several trials from the van Loon group published over the past ten years have documented that 30-40 grams of micellar casein taken 30 minutes before sleep increase overnight muscle protein synthesis by approximately 22 percent compared with placebo, without altering subjective sleep quality or producing relevant adverse effects.
This strategy has clinical application beyond sport: in older adults with sarcopenia, in patients recovering from surgery or convalescing, and in other situations of increased protein requirements, nighttime casein can improve daily protein balance and help preserve muscle mass when daytime meals are not enough to reach total protein targets.
In the context of weight loss with a calorie deficit, several studies have shown that dairy proteins (whey and casein) preserve lean mass better than isolated plant proteins at equal protein intake; casein specifically has shown superiority over whey in some long-term weight-loss studies, possibly because of its sustained satiety profile that helps control appetite between meals.
Casein has a notable and sustained satiating effect, attributed mainly to its slow digestion and the prolonged release of amino acids that keep peripheral satiety signals active (cholecystokinin, GLP-1, peptide YY); this profile makes it an interesting option for people seeking to control appetite between meals or for meal-replacement shakes where lasting fullness is a priority.
There are two main commercial forms with slightly different profiles: micellar casein (the "natural" form present in milk, obtained by gentle ultrafiltration) and calcium or sodium caseinate (obtained by acid precipitation and then solubilization with salts), which is digested a little faster than micellar casein and is usually cheaper; for indications requiring slow, sustained digestion (overnight recovery, prolonged satiety), micellar casein is clearly preferable.
The doses studied in sport and body composition range from 20 to 40 grams per serving, depending on goal and body size; for overnight support, 30-40 g of micellar casein 30 minutes before bed; for satiety between meals, 20-30 g as part of a snack; typical commercial products contain 70-85 percent protein by dry weight; formulations that combine it with whey (whey + casein) offer the sharp peak of whey and the sustainability of casein, a common strategy for long-duration post-workout use.
Generally very well tolerated in people without allergy or intolerance to milk proteins; the most frequent adverse effects are mild digestive discomfort (flatulence, fullness, occasionally diarrhea with high doses in people with partial lactose intolerance or with sensitivity to caseins), although most commercial products are low in lactose because of processing; people with a cow's milk protein allergy should avoid it completely (this is not the same as lactose intolerance); those with sensitivity specifically to A1 casein (with the BCM-7 polymorphism associated in some studies with digestive discomfort and inflammatory responses) may tolerate products derived from A2 milk or goat's milk better; in people with seriously impaired kidney function, total protein intake should be moderated; in pregnancy and breastfeeding casein is perfectly safe and is a natural part of the usual dairy diet.
Information, not medical advice. Scientific evidence reflects the quality of the studies.