Many athletes, and nearly all bodybuilders, supplement with some type of protein powder. Getting all of your macronutrients solely from food (your diet) isn't the easiest thing to do when you have and are building considerable muscle mass. Sometimes you go over your daily calorie limit trying to get enough protein, or maybe you end up taking in too much fat.
With a protein powder like whey or casein, you're able to get a huge boost of protein without doing those things. You also spend much less time eating, since a shake in a blender bottle takes very little time out of your day.
What Are Whey and Casein Protein?
Whey is considered to be a fast digesting protein. It's what people will recommend one takes directly before or after resistance training, as your body will metabolize it more quickly than casein.
Casein, on the other hand, is considered a slow digesting protein. Most proteins will be considered slow, especially when taken with a mixed meal as many people tend to do (think steak and potatoes with a side of veggies).
How Whey (Powder) is Made
It's essentially what's left over after milk has been curdled and strained when producing cheese. The milk curdles (casein), and the leftover liquid (whey) is then dried into a powder by separating the water from it.
How Casein (Powder) is Made
Like whey, casein comes from milk as well and it's the predominant protein in milk. Once the milk curdles, those curdles are then dehydrated into casein powder.
Casein and Whey Protein (Milk) Promote Lean Mass
In a study conducted on 56 healthy, untrained males over 12 weeks, skim milk was overall superior to that of soy milk and an isocaloric carbohydrate drink. Those drinking the milk saw the biggest decrease in body fat and the biggest increase in muscle mass (hypertrophy).
We conclude that chronic postexercise consumption of milk promotes greater hypertrophy during the early stages of resistance training in novice weightlifters when compared with isoenergetic soy or carbohydrate consumption.
One thing that we can take away from this study is that a mixture of whey and casein are great for building mass and increasing strength. So the question still remains unanswered: which of the two is superior in that respect?
Whey Stimulates Protein Synthesis
Since whey protein is a much faster digesting protein compared to casein, it's able to more rapidly augment protein synthesis. One reason is due to its higher level of leucine — an amino acid that stimulates such synthesis.
- The digestion rate of protein is an independent regulating factor of postprandial protein retention: https://www.ncbi.nlm.nih.gov/pubmed/11158939
The acute and abundant amounts of amino acids that enter your blood from whey is what's doing the heavy lifting when it comes to protein synthesis. With whey, you're able to metabolize the protein quickly, resulting in a spike of amino acids in your blood.
Casein Helps Prevent Muscle Breakdown
Because of casein's slower digestion rate, it can help to create a positive protein balance that prevents the catabolism of muscle by prolonging the duration that amino acids stay in your blood.
- Slow and fast dietary proteins differently modulate postprandial protein accretion: https://www.ncbi.nlm.nih.gov/pubmed/9405716
Whey. Casein is much easier to come by in your regular diet; you can drink milk, and you can eat cheeses or meats.
If you're going to buy a supplement in powdered form, whey just seems like the most appropriate choice. Take it before or after a workout (or both), and you'll be be metabolizing that protein much quicker than if you bought the casein variation.
There's definitely efficacy to those that answer this with "use both," but purely in terms of a powdered form that you spend your hard-earned money on... whey is the way.
To summarize and avoid confusion: both of these are important and we certainly recommend getting both types of protein everyday. Casein you'll simply have through meals, and whey you can pick up as a supplement to take before and after your workout and first thing in the morning.