Protein

What Is Protein?

Protein is found throughout the body—in muscle, bone, skin, hair, and virtually every other body part or tissue. It makes up the enzymes that power many chemical reactions and the hemoglobin that carries oxygen in your blood. At least 10,000 different proteins make you what you are and keep you that way.

Protein is made from twenty-plus basic building blocks called amino acids. Because we don’t store amino acids, our bodies make them in two different ways: either from scratch, or by modifying others. Nine amino acids—histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine—known as the essential amino acids, must come from food.

The National Academy of Medicine recommends that adults get a minimum of 0.8 grams of protein for every kilogram of body weight per day, or just over 7 grams for every 20 pounds of body weight. The National Academy of Medicine also sets a wide range for acceptable protein intake—anywhere from 10% to 35% of calories each day. Beyond that, there’s relatively little solid information on the ideal amount of protein in the diet or the healthiest target for calories contributed by protein. In an analysis conducted at Harvard among more than 130,000 men and women who were followed for up to 32 years, the percentage of calories from total protein intake was not related to overall mortality or to specific causes of death. However, the source of protein was important.

It’s important to note that millions of people worldwide, especially young children, don’t get enough protein due to food insecurity. The effects of protein deficiency and malnutrition range in severity from growth failure and loss of muscle mass to decreased immunity, weakening of the heart and respiratory system, and death. However, it’s uncommon for healthy adults in the U.S. and most other developed countries to have a deficiency, because there’s an abundance of plant and animal-based foods full of protein. In fact, many in the U.S. are consuming more than enough protein, especially from animal-based foods.