First, a quick refresher on amino acids: They are the building blocks of protein, which helps your body build muscle, repair muscle damage, and regulate immune function, among other things. While there are 20 amino acids in total, nine are essential—essential, because your body can’t produce them, but you need them to live.
BCAAs are three specific essential amino acids that inhibit muscle protein breakdown and aid in glycogen storage: leucine, isoleucine, and valine. Because BCAAs are essential, you have to get them from your diet.
“Any complete protein will contain all amino acids, and therefore BCAAs,” Monica Auslander Moreno, R.D.N., founder of Essence Nutrition tells Runner’s World. These include animal-sourced products such as eggs, meat, poultry, fish, and dairy. “You can also find [BCAAs] in other plant-based protein sources,” Moreno adds, including peanuts, chickpeas, lentils, quinoa, and whole grains. When grains and legumes are eaten together (think: rice and beans or peanut butter on whole grain bread), they make up a complete protein.