When you purchase through links on our site, we may earn an affiliate commission. Protein protein fat carbs calories per gram a macronutrient that is essential to building muscle mass. It is commonly found in animal products, though is also present in other sources, such as nuts and legumes.

Meat, seafood, poultry, grains, beans and dairy products are good sources of protein. The word protein comes from the Greek “protos,” which “reflects protein’s top- shelf status in human nutrition,” Harvard Health reported. When protein is broken down in the body it helps to fuel muscle mass, which helps metabolism,” said Jessica Crandall, a registered dietitian nutritionist, certified diabetes educator and national spokesperson for the Academy of Nutrition and Dietetics. It also helps the immune system stay strong. Proteins are complex structures in the body.

Here, the brightly colored and twisty blobs represent different immune system proteins on the outer layer of a T-cell, a type of white blood cell that helps the body to identify foreign invaders. For example, research has shown that satiety, or feeling full after a meal, improved after consuming a high-protein snack. A similar study published in 2015 in the Journal of Nutrition found that adolescents who consumed high-protein afternoon snacks showed reduced appetite, satiety and diet quality. The teens also had improved moods and better cognition.