What’s the Difference Between Whey and Casein Protein?

updated May 1, 2019
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(Image credit: Emma Christensen)

The amount of protein powders on the market is staggering. And while you don’t necessarily need to invest in one to add to your smoothies, they’re another great way to add a nutritious boost to them. But if you do decide to try one, what kind of protein powder should you choose?

Whey and casein protein are two of the most popular options. The only thing that makes them similar is that they’re both dairy proteins found in milk. Otherwise, they are quite different. Here’s what you need to know to make the right choice for you.

Whey Protein

Like the name implies, this form of dairy protein comes from none other than whey. When you heat milk and add an acid like vinegar or lemon juice, the milk separates into two components: solid curds and liquid whey. Whey protein is contained in this liquid portion. The body breaks down and digests this kind of protein faster than casein protein, so it’s absorbed much more efficiently. This type of protein is best used right after a heavy workout, so try adding some to your next post-exercise smoothie. Why? First, it provides a quick energy boost. Second, intense exercise causes your muscles to break down, and the faster your body receives and digests protein, the faster these muscles can get repaired.

Casein Protein

Think of this type of protein as whey’s slower, steadier sibling. Casein protein is found in the curd portion of milk and is actually the most abundant form of protein in milk — it accounts for about 80 percent of the protein content, while whey protein makes up the remaining 20 percent. It takes much longer for the body to digest casein protein, meaning it lingers in your system for an extended period of time. Since it’s more slow-acting, it’s not the best choice for a post-workout boost, but instead for those times when you need to stay full and focused for hours at a time. A little in your morning smoothie will help keep your stomach from rumbling until lunchtime.