Workout Supplements: Whey vs. Casein Protein

Medically Reviewed by Christine Mikstas, RD, LD on July 11, 2023
3 min read

Adding a protein supplement/powder to your health and fitness routine can help you maximize your gains. Whether you want to show off your muscles at the beach or just replace your junk-food snacks with a healthier alternative, either whey or casein protein may be a good option.

Here, we'll take a deep dive into the differences between casein and whey, so you can decide which works best for you and your workout routine. 

To best promote muscle growth, you should feed your muscles more protein than they need. Between whey and casein, whey is the "faster" protein supplement because its amino acids are absorbed quickly by your body. While casein is the "slower" supplement — since it’s digested more slowly — both proteins can help your muscles grow when you work out. That’s because they re-form fatigued muscles after exercise

Regardless of which type you choose, the most important factor is how much total protein you eat throughout the day.

The main benefit of whey protein is that it allows you to quickly reap the results of the work you put in at the gym. That's because your body can break it down and absorb it in only 20 minutes. So your body can more quickly rebuild and grow the muscle that was broken down during your workout.

Just like whey protein, casein protein provides all the essential amino acids your body needs.  As opposed to whey, casein can be thought of as a "time-release" protein since it’s digested more slowly.  After you consume casein, your body’s absorption of amino acids and creation or synthesis of proteins will peak after roughly 3 to 4 hours.

Depending on what your fitness goals are, casein protein may be a better option. For example, if you’re getting ready to go to bed and won’t be eating for a while, casein can provide your body with a slow-release source of protein over several hours.

Casein protein doesn't boost your amino acid levels as high or as quickly as whey protein does. But it slows the speed at which proteins are broken down in your body. This protects your muscle mass and makes you feel full longer, which is great for curbing your late-night hunger.

The fast-acting quality of whey protein makes it the clear choice before or after a workout. On the other hand, the slower-acting casein is the best option for days when you're not exercising or before bed.

Other things to consider:

  • Casein protein powder tends to have a higher price per gram than whey protein powder, meaning you get more protein for your buck 
  • Whey protein powder is easy to mix with liquids, while casein protein powder may form clumps
  • Whey protein powder tends to have a better taste and texture than casein protein powder

If your fitness routine involves daily strength training with few days off and you don’t have late-night cravings, whey protein is probably the best option for you. If your workouts tend to be less strenuous, and you tend to go longer between meals, maybe you should go with casein. Or, use both in your daily routine: take whey protein after a workout and take casein protein before bed.

Both whey and casein provide plenty of the essential amino acids your body needs for protein synthesis and muscle growth, so it ultimately comes down to personal preference. Despite their differences, both are healthy for your body's muscle growth. 

Remember, the most important thing for muscle growth or gain is consuming more protein than your muscles use up, regardless of whether you get it from whey, casein, or some other protein source. Whatever your fitness goals are, your progress depends more on your workout and dietary habits than on your choice of protein supplements.