Nighttime Casein Supplementation

It is well established that total daily protein intake is critical for maximizing the work we do in the gym and optimizing the training adaptations we’re looking for. Once paired with resistance training, ensuring that our total protein intake is sufficient is easily the most impactful variable in seeing positive body composition changes.

As we nail down our baseline habits (sleep, nutrition, training, stress) and get more specific, it’s understandable that we can come across some confusion regarding how we can best approach our day to day. Every client and athlete will operate under different circumstances and lifestyles, so molding each nutrition- or training-related variable to suit the individual’s life, while also being used effectively, is the main goal.

Protein timing, for example, is one of these variables that is definitely beneficial, but also leaves room for approaches that may simply be insignificant for the athlete if we look at the big picture. Nighttime casein supplementation in particular is a popular approach that we get asked about often regarding protein timing and maximizing muscle protein synthesis.

Whey vs. Casein

While whey and casein protein powders are, well… both protein powders, they are definitely not the same thing. They have a couple of main differences that will be important to point out which will also provide us with some background about why casein is commonly used at night/before bed.

Both whey and casein are the two types of proteins found in cow’s milk, making up about 20% and 80% of milk protein, respectively. The primary difference between these two proteins is how fast our bodies are able to digest and absorb them; they both digest at different rates.

To sum up this process, once we digest protein they are broken down into amino acids, which then circulate in the blood stream until they are absorbed. When we ingest whey protein, these amino acids stay elevated in the bloodstream for about 90 minutes. In contrast, casein protein can take up to 4-5 hours to absorb, making it take much longer to digest compared to whey.

This is a great example of why whey protein is so efficient post-workout and highly recommended, but we’re not here to talk about whey. They question remains if nighttime casein supplementation can make substantial differences in markers like body composition and muscle growth.

Daytime vs. Nighttime

This study sought to compare daytime (DT) and nighttime (NT) casein supplementation on the muscular adaptations and body composition changes of men following a 10-week resistance training program.

Calorie goals were established using the Mifflin St. Jeor equation (a 1.6x adjustment was made for activity level) in conjunction with protein targets being set at 1.8 grams/kg/bodyweight inclusive of the provided casein supplement.

Each serving of casein consisted of 35 grams of protein and less than 0.5 gram each of fat and carbohydrates. In addition to this study being diet- and exercise-controlled this was also a double blind and placebo-controlled design, so the placebo being used was a serving of maltodextrin containing 35 grams of carbohydrates and less than 0.5 gram each of fat and protein.

As you can probably guess, the nighttime group was supplemented with their casein supplement immediately before going to bed; the 35g of maltodextrin was supplemented with earlier in the day. The daytime group, in contrast, supplemented with casein earlier in the day and took the 35g of maltodextrin at night before going to bed.

Which Timing Wins?

After completing 10 weeks of resistance training, results found that subjects in both daytime and nighttime supplemental protocols experienced similar changes in body composition. Regardless of the time of day their casein was consumed, subjects were able to similarly increase muscle mass and strength while decreasing body fat percentage over the study period.

Training volume didn’t differ between the groups either, so given an effective training stimulus and an adequate total protein intake we can expect to see positive body composition changes and improvements in muscle size and strength.

There’s no special or superior timing for protein feedings, so being intentional with our diets regarding physique enhancement should be considered on a larger scale – looking at total protein intake, staying in a positive net muscle protein balance, and supplementing accordingly where the individual needs it. It does no harm, of course, but it’s won’t provide an added benefit if your protein intake is already where it should be to meet your specific goals.

While specific times aren’t critical when looking at the big picture, appropriately spacing out your meals is still an important habit to maintain. We generally recommend having 3-5 protein feedings per day. Of course, the amount of meals will differ based on your schedule and preference, but having a few meals spread out will be most ideal for maximizing muscle protein synthesis.


Joy, J.M., Vogel, R.M., Broughton, K.S., et al. Daytime and nighttime casein supplements similarly increase muscle size and strength in response to resistance training earlier in the day: a preliminary investigation. Journal of the International Society of Sports Nutrition. 2018 15:24.

Be the first to know

Get exclusive, no bullshit content from our coaches that is scientifically based and experience driven.