When to take protein powder

Is the anabolic window real?

The “anabolic window” is the idea that most of the muscle gain is lost if protein is not taken within a short period after training. The meta-analysis by Schoenfeld and colleagues tested this idea: the hypertrophy analysis included 23 studies and 525 people; the strength analysis included 20 studies and 478 people. In the simple analysis without controlling for covariates, a small-to-moderate effect on hypertrophy was seen and there was no significant effect on strength. In the full model controlling for all covariates, no significant difference between treatment and control was found for strength and hypertrophy; the strongest determinant of effect size for hypertrophy was total protein intake. The authors interpreted the result as refuting the belief that protein timing around training is critical. ^[2]

There is a published criticism of this meta-analysis. Beale states that 20 of the 23 studies compared protein supplementation with placebo and that in none of these 20 studies was total daily protein intake equalized between groups, so total protein is a confounder; he adds that only 3 studies (77 people in total) were suitable for the timing question. ^[3] So the meta-analysis does not conclusively show that “timing has no effect”; rather, no strong and direct benefit has been shown for timing, and well-designed direct comparisons are few.

The narrative review by Aragon and Schoenfeld, published the same year, states that the existence and width of the “window” depend on many factors; in particular, in training done in a fasted state, muscle breakdown increases and this may make urgent feeding more meaningful. As a practical framework, the authors write that pre- and post-workout meals should not be separated by more than about 3–4 hours; they also state that findings are inconsistent and systematic studies are few, so practical recommendations have had to fill gaps in the literature with “field observations and experience.” ^[4] The ISSN, on the other hand, says that intake both before and after training can be beneficial, that the anabolic effect of exercise lasts at least 24 hours but declines over time, and that the optimal time frame most likely depends on personal tolerance. ^[1]

How much protein in one meal benefits muscle?

Moore and colleagues gave 6 healthy young men 0, 5, 10, 20, and 40 g of egg protein after leg resistance exercise. Muscle protein synthesis responded to dose and peaked at 20 g; at 20 and 40 g, leucine oxidation increased, meaning that excess protein was irreversibly burned rather than incorporated into tissue. ^[5] This is a measurement in a very small sample, in young men, with egg protein, and after a single exercise session; it does not show the same limit for every person and every protein.

The ISSN says that recommendations on the amount of protein per meal are mixed and depend on age and recent resistance exercise; as a general recommendation it reports that high-quality protein be 0.25 g/kg or an absolute 20–40 g, with doses distributed equally through the day about every 3–4 hours. ^[1] This is the general framework of a position stand; it is not a personal dose.

Should protein be distributed equally across the day?

Mamerow and colleagues conducted a crossover feeding study in 8 healthy adults (5 men, 3 women; mean age 36.9), 7 days each, separated by a 30-day washout. Two patterns containing the same energy and the same nitrogen were compared: about 31.5 / 29.9 / 32.7 g of protein at breakfast, lunch, and dinner (even) or 10.7 / 16.0 / 63.4 g (evening-skewed). Mixed muscle protein synthesis over 24 hours was 25% higher with the even distribution than with the evening-skewed pattern (0.075 versus 0.056 %/hour). ^[6] This finding is a protein synthesis measurement; it is not a result for muscle mass or strength over weeks, and the number of participants is small. The study was partly supported by research funding from the beef industry, and two authors reported receiving speaking fees from an organization of the same industry.

Does drinking casein before sleep work?

Res and colleagues compared a drink containing 40 g of casein with placebo 30 minutes before sleep in 16 healthy young men after evening resistance exercise and standard post-exercise recovery nutrition. Casein was digested and absorbed overnight; whole-body protein synthesis and net protein balance increased. Mixed muscle protein synthesis was about 22% higher, but statistical significance was borderline (P = 0.05). ^[7]

Snijders and colleagues randomized 44 young men to a 12-week resistance training program. One group received a supplement containing 27.5 g of protein, 15 g of carbohydrate, and 0.1 g of fat before sleep every night, the other a calorie-free placebo. Strength (+164 kg in the 1-repetition maximum tests as reported, +130 kg in the placebo group) and quadriceps cross-sectional area (+8.4 cm², +4.8 cm² in the placebo group) increased more in the supplement group; the increase in type II muscle fiber size was also greater in the protein group. ^[8] This is a single randomized study (evidence grade at most C) and was conducted only in young men. Because the comparison was with a calorie-free placebo, the result cannot separate the effect of night timing from the effect of extra protein intake.

Summarizing this group of studies, the ISSN states that 30–40 g of casein taken orally 30 minutes before sleep increased overnight muscle protein synthesis, and that in older men the same result was seen with casein given by nasogastric tube. ^[1] The long-term outcome of night intake in women, older adults, or people who do not train was not measured in these studies.

What about rest days and days without training?

A timing strategy specific to rest days was not tested separately in any of the studies on this page. The available data point to two things: the ISSN reports that the anabolic effect of training lasts at least 24 hours ^[1]; and in the Schoenfeld meta-analysis, the strongest determinant for hypertrophy was total daily protein intake. ^[2]

What is known about timing?

This guide does not recommend a personal dose or time. Total daily protein, needs calculation, and label reading are described on the how to use page, and the types of powder on the whey protein page.

Is 20 grams an absorption limit?

No. A 2023 experiment found a larger and longer anabolic response over 12 hours after 100 g of post-exercise protein than after 25 g. This challenges the claim that protein above 20–25 g is automatically “wasted.” Acute protein synthesis is not the same outcome as muscle gained over months, and the study does not recommend 100 g at a meal for everyone. Daily adequacy, meal patterns and tolerance remain relevant. ^[9]