Proteins

Proteins are part of every cell in the body. They build and repair tissues, and they make up many of the enzymes, hormones and antibodies the body depends on. Here is what protein does, how much you need and where to find it.

Tissue structure and repair

Muscles, bones, skin, hair and organs are all built largely from protein. The body constantly breaks down and rebuilds these tissues using amino acids, the building blocks of protein, so a steady supply matters at every age, and especially for growing children and teens and during pregnancy.

Enzymes and hormones

Many enzymes and hormones are proteins. They drive digestion, energy production and countless other processes, including the signals that regulate growth and blood sugar.

Immune defense

Antibodies, which help the body fight infection, are proteins too. Getting enough protein supports a normal immune system, and people who are seriously short of protein are more prone to infections. Eating more protein than you need, however, doesn't boost immunity further.

Transport, fluid balance and energy

Proteins carry oxygen, iron and other substances in the blood and help keep fluids in balance. The body can also burn protein for energy when it needs to.

Complete and incomplete proteins

Proteins are made from 20 amino acids, nine of which the body can't make and must get from food. Animal proteins and soy contain all nine in useful amounts. Most other plant proteins are low in one or more, but eating a variety of plant foods over the day, such as beans with grains, provides them all.

How much protein do you need?

The long-standing Recommended Dietary Allowance for adults is 0.8 grams of protein per kilogram of body weight a day, or about 0.36 grams per pound: roughly 46 grams for an average woman and 56 grams for an average man. Needs are higher during pregnancy and breastfeeding, and many experts suggest older adults aim higher too, to help preserve muscle.

The 2025–2030 Dietary Guidelines for Americans set a higher target of 1.2 to 1.6 grams per kilogram for adults, about 80 to 110 grams a day for someone who weighs 150 pounds. Some nutrition scientists have questioned the higher figure for the general population and point out that the source of protein matters: diets rich in plant protein and fish are linked to better health than diets high in red and processed meat. The right amount depends on your age, size, activity and health, and a doctor or registered dietitian can help you set a target.

Sources of protein

Some everyday foods and their approximate protein content:

• 3 ounces cooked chicken breast: about 26 g
• 3 ounces cooked salmon: about 22 g
• ¾ cup plain Greek yogurt: about 15 to 17 g
• ½ cup cooked lentils: about 9 g
• 1 cup milk: about 8 g
• 1 cup cooked quinoa: about 8 g
• ½ cup cooked beans: about 7 to 8 g
• 1 ounce of almonds: about 6 g
• 1 large egg: about 6 g

Animal sources: meat and poultry, fish and seafood, eggs, and dairy products such as milk, cheese and yogurt.

Plant sources: beans, lentils and peas, soybeans, tofu and tempeh, nuts and seeds, and whole grains such as quinoa, oats and brown rice.

Lean proteins

Lean proteins are lower in saturated fat. Good examples:

• skinless chicken or turkey breast
• fish and seafood, such as salmon, tuna and cod
• beans and lentils
• low-fat dairy products
• tofu and tempeh
• nuts and seeds, in moderate portions

Including a variety of protein sources in your diet gives you the full range of amino acids, along with the different vitamins, minerals and fats each food brings.

A few cautions

People with chronic kidney disease may need to limit protein, so follow your doctor's advice. Most people can get enough protein from food, so protein powders and bars aren't necessary; if you use them, remember they are sold as dietary supplements, which the FDA doesn't approve before sale. Very high-protein diets built on red and processed meat can be high in saturated fat and salt.

Sources

• Dietary Guidelines for Americans, 2025–2030 (US Department of Health and Human Services and US Department of Agriculture)
• Dietary Guidelines for Americans 2025–2030: what changed (Harvard T.H. Chan School of Public Health)
• Dietary Reference Intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein and amino acids (National Academies)

Last reviewed November 2026. This article is general information, not medical advice.