Not all protein is created equal, says a new study.

By Julia Malacoff
October 27, 2016

If you scoop protein powder into your morning or post-workout smoothie, you're probably aware that there are many different kinds available, in terms of both flavors and ingredients. The most popular type is whey protein, but there are also a whole host of other options like casein, pea, rice, and hemp protein. Protein helps your body recover post-workout, builds new muscle, and minimizes soreness. Many avid exercisers make it protein shakes a habit-especially those who lift weights. (BTW, it is possible to overdo it on protein powder.)

In order to figure out which of the many options available is the most efficient for building strength and lean muscle mass, researchers decided to study protein quality based on two components: the presence of key amino acids (aka the building blocks of protein) and digestibility. In the Nutrition and Metabolism study, researchers measured the level of leucine in various types of protein powder. Leucine is a super-common amino acid that has been shown to be very effective at getting muscles to process protein. They also did a comprehensive review of past studies to see how different types of protein affected lean muscle mass. When all was said and done, the winning protein powder was clear: Whey, which has the highest concentration of important aminos (like leucine) and is easily digested into your system. The study ranked soy, pea, and rice protein after whey (in that order), with rice protein being significantly lower-ranked in "quality." (Vegan? Scope these three clean vegan protein powders we love.)

"The amount of leucine in a protein supplement has the greatest impact on muscle protein synthesis," said the lead author of the study, Stuart M. Phillips, Ph.D., of McMaster University, in a press release. In other words, out of all the amino acids, it makes the most impact on your muscles' ability to actually use the protein you're ingesting. The amino also acts as a kind of trigger for your muscles to process a higher amount of protein. The researchers explain it's like a light switch for working muscles to absorb and use more protein, leading to "greater gains in lean body mass and strength, and subsequently, body composition improvements." Essentially, that means less fat, more muscle-which is pretty much the reason you consume extra protein in the first place, right?

Phillips also explains that while this study is very relevant to those who do any kind of strength or resistance training, it's also applicable to people who don't do a ton of resistance training. They can still benefit from eating higher-quality proteins and improve their lean muscle mass, although those who lift weights do see much better and faster results. At the moment, more research is needed to evaluate how other amino acids affect resistance training. But for now, Phillips recommends choosing a protein powder that is high in leucine content (like whey) in order to see maximum benefits from your sweat sessions.