20–40 g per serving to stimulate muscle synthesis; adjust to your total daily protein (1.6–2.2 g/kg).
Increases lean mass and strength when total dietary protein falls short.
View the study (meta-analysis) →Increases fullness and helps preserve muscle when losing weight.
View the study (meta-analysis) →⏱ 4 min read
Whey protein is the soluble protein fraction separated from milk during cheesemaking (it is the liquid that drains off when casein is coagulated with rennet, and which was traditionally discarded as an industrial by-product until sports nutrition turned it into one of the most widely consumed protein supplements in the world); it contains a mixture of soluble globular proteins (beta-lactoglobulin, alpha-lactalbumin, immunoglobulins, lactoferrin, serum albumin) with an exceptionally favorable amino acid profile, a high concentration of branched-chain amino acids (especially leucine, the most potent activator of the mTOR pathway responsible for initiating muscle protein synthesis), and rapid digestion that produces a sharp, high peak of plasma amino acids after ingestion.
This kinetic profile makes it the protein of choice for the post-workout period and for situations where the goal is to maximize the acute anabolic response; compared with casein (slow digestion), whey produces a higher but briefer "peak," whereas casein keeps plasma amino acids elevated for hours: both profiles have complementary applications in different sports nutrition contexts, and many commercial formulations combine the two to pair a fast onset with a prolonged duration of amino acid availability.
The indication with the strongest clinical support is maximizing post-workout muscle protein synthesis and muscle mass gain in people doing strength training: multiple trials and meta-analyses have confirmed that providing 20-40 grams of whey protein around training significantly improves strength and muscle mass gains compared with placebo or with lower protein intakes.
A meta-analysis published in the British Journal of Sports Medicine in 2018 with 49 trials confirmed that protein supplementation (predominantly with whey) significantly increases strength and muscle mass in people doing resistance training, with an effect that plateaus at approximately 1.6 g/kg/day of total dietary protein (including the supplement), above which no additional benefits are observed in most people.
In older adults with sarcopenia or at risk of sarcopenia, several trials have shown significant improvements in muscle mass, strength, and function with whey protein supplementation combined with strength training over months; older adults have muscular "anabolic resistance" (they need more leucine per dose to reach the same level of protein synthesis as younger people), and whey, with its high leucine content, is particularly appropriate for this population.
In the context of weight loss with a calorie deficit, whey supplementation helps preserve lean mass while adipose tissue is lost; several trials have documented significant improvements in body composition with high protein intakes (1.8-2.4 g/kg/day) supplemented with whey, compared with hypocaloric diets with lower protein intake.
Whey has notable satiating effects compared with other protein sources, attributed to the rapid release of amino acids and the stimulation of satiety hormones (cholecystokinin, GLP-1, peptide YY); this characteristic makes it useful as a component of weight-control strategies to reduce hunger between meals.
The main commercial forms are: whey concentrate (80 percent protein by weight, with some residual lactose and fat, the cheapest and the most studied), whey isolate (90-95 percent protein, virtually lactose-free, more expensive but suitable for people with partial lactose intolerance), and whey hydrolysate (enzymatically predigested whey for faster absorption, the most expensive and with a slightly superior absorption profile, especially useful in contexts of maximum acute post-workout utilization).
The doses studied are 20-40 grams per serving, typically 1-2 servings daily depending on goals and total needs; the "post-workout" timing has a clear mechanistic basis, but the anabolic window is wider than was believed a decade ago (several hours), so the total distribution of protein throughout the day (4-5 meals/servings with 25-40 g of protein each) is more important than the exact timing; commercial powders are mixed in water or milk; in people with partial lactose intolerance, prefer isolate or hydrolysate.
Generally very well tolerated in people without a milk protein allergy or intolerance; the most common adverse effects are mild digestive discomfort (flatulence, fullness, diarrhea at high doses), which typically lessen when the dose is adjusted or when switching to isolate/hydrolysate; people with a cow's milk protein allergy should avoid it completely (an allergy distinct from lactose intolerance); those with lactose intolerance should prefer isolate or hydrolysate; people with seriously compromised kidney function should moderate their total protein intake; in pregnancy and breastfeeding it is perfectly safe as part of an adequate protein intake; cheap products may be adulterated or have a lower protein content than declared (the practice known as "amino spiking," adding cheap amino acids such as glycine or taurine to the product to inflate the total nitrogen content measured in standard analyses); it is advisable to choose products from manufacturers with a good reputation and, ideally, with third-party verification (Informed Sport, NSF Certified for Sport, etc.).
Information, not medical advice. Scientific evidence reflects the quality of the studies.