Question: “The Ultimate Starters Guide suggests Optimum Nutrition 100% Gold Standard Whey and Casein. Does it matter what type of protein I take?” –Brian S., via Twitter

Answer: When it comes to protein powders, it definitely matters which protein you take. 

Whey and casein have different amino acid profiles and digestion rates and, as a result, have distinct metabolic effects on the body.

Whey for instance has the highest branched-chain amino acid (BCAA) content out of any protein at 23-25 percent. Whey is also digested the fastest at 8-10 g per hour. Casein, on the other hand, has 18 percent BCAA but more glutamine than whey and is digested at a slower rate than whey at 6.1 g per hour. All of this means whey is better for muscle building (protein synthesis) because of its high amount of BCAA plus fast absorption. However, casein is better at preventing muscle break down because of its slower rate of digestion.

Research has shown that whey is best consumed 30 minutes before weight training. Subjects had higher testosterone levels compared to taking whey immediately after because of its fast digestion rate and high BCAA content. A university of Baylor study showed a combination of whey and casein is best after workout, providing greater muscle gain than casein or whey alone, because their strengths offset each other’s weaknesses.

Kelechi Opara is a lifetime natural athlete with over 15 years experience in the fitness field. He’s the creator of the iPhone/Android app Nutritionist, the revolutionary app that’s transforming lives around the world. He’s also an Optimum Nutrition athlete where he helps in the formulation of their supplements. In addition, he’s an internationally published cover model and a former United States Marine.