Branched-chain amino acid (BCAA) supplements have long held a special place in the hearts of bodybuilders and endurance athletes alike. But recently, essential amino acid (EAA) supplements have started cropping up everywhere, threatening to edge out BCAAs as fitness enthusiasts’ go-to sports supplement.

Is one really better than the other? Which supplement is right for you? Here’s everything you need to know about the two popular sports supplements.

Amino Acid Basics

The proteins that make up our muscles are in a constant state of turnover; as old proteins degrade, we produce new proteins to take their place. When the number of proteins being created exceeds the number of proteins breaking down, your body ‘grows,’ and you build muscle mass (this is called an anabolic state). When the number of proteins breaking down exceeds the number of proteins being created, though, the entire body enters a state of breakdown and you may lose muscle mass (this is called a catabolic state).

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If you’re working out to build muscle and perform at your absolute best, you want your body to spend as much time as possible in ‘grow’ mode. Thing is, exercise typically shifts it into ‘breakdown’ mode. That’s where amino acids come in. To repair proteins and produce new ones—and ultimately boost your ability to pack on muscle—after exercising, your body needs an adequate amount of protein building blocks, molecules called amino acids.

There are 20 different amino acids total. Nine of them are considered ‘essential,’ which means our bodies can’t produce enough of them on its own and we have to get them via food and/or supplements. These essential amino acids (EAAs) include isoleucine, leucine, valine, lysine, methionine, phenylalanine, threonine, histidine, and tryptophan.

Of those nine EAAs, three are known as the branched-chain amino acids (BCAAs) and play unique roles in muscle protein synthesis (the process of repairing and building muscle). The three BCAAs are isoleucine, leucine, and valine.

In addition to supporting the muscle-building process, two of these amino acids (isoleucine and valine) can also be used as energy sources during endurance exercise, when muscle glycogen (one of our bodies’ main sources of fuel) gets used up, says Kelly Pritchett, Ph.D., R.D., C.S.S.D., assistant professor of sports nutrition at Central Washington University and national media spokesperson for the Academy of Nutrition and Dietetics.

BCAAs vs. EAAs

According to the Essentials of Strength Training and Conditioning, 4th ed., our muscles are especially receptive to amino acids for up to 48 hours after we exercise—hence why amino acid supplements have become intra- and post-workout staples of so many fitness enthusiasts.

A recent study published in Frontiers in Physiology found that ingesting 5.6 grams of BCAAs after a strength-training session lead to 22 percent greater muscle protein synthesis. However, a review published in the Journal of the International Society of Sports Nutrition purports that you need an abundant supply of all the EAAs—not just BCAAs—to stimulate muscle protein synthesis.

A number of research studies, in fact, support the idea that all of the EAAs play key roles in repairing and building muscle, and that supplementing with EAAs may stimulate muscle protein  just as much as supplementing with a whole protein source that contains the same amount of those EAAs (like whey protein or chicken breast).

So, Which Supplement Should You Take?

EAAs and BCAAs both impact your ability to be strong and fit. In a perfect world, you’d get all your EAAs and BCAAs from whole foods. (Animal-based proteins like meat and dairy are the richest sources, while plant proteins—with a few exceptions—may be lacking in one or more EAA, making it critical for herbivores to mix up their protein sources.) That said, many of us struggle with eating enough healthy, whole foods to meet our amino acid needs—and it’s even more difficult if we exercise a lot. “If we are talking about people who train at a high level, meeting your requirement for protein and EAAs on a daily basis may be challenging,” says Brian Tanzer, M.S., C.N.S., Manager of Scientific Affairs at The Vitamin Shoppe. That’s where a BCAA or EAA supplement comes in.

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According to Tanzer, both BCAA and EAA supplements can support muscle growth and recovery from training. However, BCAAs are better suited for people who meet their total daily protein needs, while EAAs are best for those who typically fall short.

The International Society of Sports Nutrition recommends active adults aim for 1.4 to two grams of protein per kilogram of body weight (your weight in pounds divided by 2.2) per day. That’s between about 95 and 136 grams of protein per day for someone who weighs 150 pounds. If you get the proper amount of protein but want to support your muscles after working out, go for a BCAA supplement. If you eat less than 1.4 grams of protein per kilogram of your body weight, try EAAs.

Pin this handy infographic to keep your amino acid facts straight:

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