Benefits
Muscle protein synthesis similar to whey at a matched 20 g dose
In 16 healthy middle-aged men, 20 g of milk protein concentrate or 20 g of whey protein concentrate raised muscle protein synthesis to a similar degree in the first 90 minutes, and both returned to baseline by 210 minutes. Whey was digested faster, yet the muscle response did not differ. The drinks were supplied by a dairy company that employed one author.
Higher muscle protein synthesis after exercise at larger doses
In 48 healthy older men given 0, 15, 30 or 45 g of milk protein concentrate after resistance exercise, whole-body protein balance rose with each dose. Muscle protein synthesis was significantly higher with 45 g than with none, and 30 g showed a similar trend that did not reach significance.
Longer-lasting muscle protein synthesis after a meal-sized dose
In 7 young men, 38 g of labelled milk protein concentrate released its amino acids gradually, about 27% within 2 hours and another 31% over the next 3 hours, and muscle protein synthesis stayed raised throughout the 5-hour period. This study had no whey or placebo comparison.
Lean mass gains with resistance training
In a 12-week study of 56 novice male weightlifters, drinking fat-free milk after each workout led to greater gains in lean mass and muscle fiber size than an equal-energy soy or carbohydrate drink; strength gains did not differ. In a related study, milk after exercise produced higher muscle protein synthesis than soy. These studies used fluid milk rather than powder.
Strength recovery between football matches
In a crossover trial of 20 football players over a week with two matches, milk protein concentrate after games and training shortened the dip in knee strength compared with a carbohydrate placebo. Speed and jump height fell in both trials, and muscle soreness and creatine kinase did not differ.
Mechanism of action
Fast whey plus slow casein
Milk protein is about 20% whey, which is digested quickly, and 80% micellar casein, which releases amino acids more slowly. After 38 g of milk protein, dietary amino acids entered the blood over about 5 hours rather than in a single short peak, and muscle protein synthesis stayed raised for that whole time.
Growth signalling in muscle
Milk protein increased activity of mTORC1, a key switch for building muscle protein, for several hours after a meal-sized dose. After resistance exercise, as little as 9 g of milk protein boosted some of these signals compared with carbohydrate, though it did not change amino acid transporter levels.
Peak amino acid level is not decisive
In 30 young men, a mineral-modified milk protein concentrate that raised blood essential amino acids 19% to 27% higher than standard concentrate or casein did not increase muscle protein synthesis after exercise more than either. So a higher, faster amino acid peak did not translate into more muscle building in this study.
Clinical trials
Randomized comparison with stable-isotope tracer infusion and muscle biopsies after 20 g of milk protein concentrate or whey protein concentrate supplied by Fonterra (Mitchell et al. 2015, Nutrients)
16 healthy middle-aged men aged 45 to 60 (8 per group).
Muscle protein synthesis rose from about 0.02% per hour to 0.057% with milk protein and 0.052% with whey in the first 90 minutes, with no difference between groups, and returned to baseline in both by 210 minutes.
Single-group stable-isotope study using intrinsically labelled milk protein concentrate with repeated blood and muscle sampling for 5 hours (van Vliet et al. 2019, J Appl Physiol)
7 healthy young men (average age 22).
About 27% of the dietary amino acids appeared in blood in the first 2 hours and another 31% from 2 to 5 hours. Muscle protein synthesis and mTORC1 signalling stayed raised throughout the 5 hours. There was no comparison group.
Randomized trial of 0, 15, 30 or 45 g of milk protein concentrate after a single resistance exercise session, with stable-isotope tracers (Holwerda et al. 2019, J Nutr)
48 healthy older men (average age 66).
Whole-body net protein balance and incorporation of dietary amino acids into muscle rose with each dose. Muscle protein synthesis was higher after 45 g than after 0 g (P < 0.05); the difference for 30 g was a trend (P = 0.07).
Double-blind randomized trial of a drink with 9 g of milk protein or an equal-energy carbohydrate drink after one-leg resistance exercise (Mitchell et al. 2017, J Int Soc Sports Nutr)
20 healthy middle-aged men (average age 46).
Some markers of muscle growth signalling (P70S6K and rpS6 sites) rose more with milk protein than with carbohydrate, but amino acid transporter expression did not differ. Muscle protein synthesis itself was not measured.
Randomized parallel trial of fat-free milk, an equal-protein soy drink or a carbohydrate drink taken after workouts during 12 weeks of resistance training, 5 days a week (Hartman et al. 2007, Am J Clin Nutr)
56 healthy young novice male weightlifters.
Lean mass and type II muscle fiber area increased more with milk than with soy or carbohydrate. Strength gains did not differ between groups.
Randomized, double-blind, placebo-controlled crossover trial of milk protein concentrate (1.15 g/kg on game days, 0.26 g/kg on training days) or an energy-matched carbohydrate placebo (Poulios et al. 2018, Nutrients)
20 football players.
Knee extensor strength declined for fewer days with milk protein after both games, and high-intensity running late in the second game fell less. Speed, jump height and knee flexor strength fell in both trials, and muscle soreness, leukocytes and creatine kinase did not differ.