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Protein in diet

Definition

Proteins are the building blocks of life. Every cell in the human body contains protein. The basic structure of protein is a chain of amino acids.

You need protein in your diet to help your body repair cells and make new ones. Protein is also important for growth and development in children, teens, and pregnant women.

Alternative Names

Diet - protein

Food Sources

The protein in food is broken down into parts called amino acids during digestion. The human body needs a number of amino acids in large enough amounts to maintain good health.

Amino acids are found in animal sources such as meats, milk, fish, and eggs. They are also found in plant sources such as soy, beans, legumes, nut butters, and some grains (such as wheat germ and quinoa). You do not need to eat animal products to get all the protein you need in your diet.

Amino acids are classified into three groups:

• Essential
• Nonessential
• Conditional

Essential amino acids cannot be made by the body. They must be supplied by food. They do not need to be eaten at every meal. The balance over the whole day is more important.

Nonessential amino acids are made by the body from essential amino acids or in the normal breakdown of proteins.

Conditional amino acids are needed in times of illness and stress.

Recommendations

The amount of protein you need in your diet will depend on your overall calorie needs. The daily recommended intake of protein for healthy adults is 10% to 35% of your total calorie needs. One gram of protein supplies 4 calories. Therefore, a person on a 2000 calorie diet could eat 100 grams of protein, or 400 calories from protein, which would supply 20% of their total daily calories.

One ounce (30 grams) of most protein-rich foods contains 7 grams of protein. An ounce (30 grams) equals:

• 1 oz (30 g) of meat fish or poultry
• 1 large egg
• ¼ cup (60 milliliters) tofu
• ½ cup (65 grams) cooked beans or lentils

Low fat dairy is also a good source of protein.

Whole grains contain more protein than refined or "white" products.

Children and teens may need different amounts, depending on their age. Some healthy sources of animal protein include:

• Turkey or chicken with the skin removed, or bison (also called buffalo meat)
• Lean cuts of beef or pork, such as round, top sirloin, or tenderloin (trim away any visible fat)
• Fish or shellfish

Other good sources of protein include:

• Pinto beans, black beans, kidney beans, lentils, split peas, or garbanzo beans
• Nuts and seeds, including almonds, hazelnuts, mixed nuts, peanuts, peanut butter, sunflower seeds, or walnuts (Nuts are high in fat so be mindful of portion sizes. Eating calories in excess of your needs may lead to weight gain.)
• Tofu, tempeh, and other soy protein products
• Low-fat dairy products

The US Department of Agriculture's newest food guide, called MyPlate, can help you make healthy eating choices.

References

Cooney J, Neild P. Diet and nutrition. In: Syndercombe Court D, Kadri A, Xiu P, eds. Medical Sciences. 4th ed. Philadelphia, PA: Elsevier Limited; 2025:chap 16.

Hensrud DD. Diet and nutrition. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 13.

National Academy of Sciences, Institute of Medicine, Food and Nutrition Board. Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids. National Academy Press. Washington, DC, 2005. nap.nationalacademies.org/catalog/10490/dietary-reference-intakes-for-energy-carbohydrate-fiber-fat-fatty-acids-cholesterol-protein-and-amino-acids. Updated 2005. Accessed April 9, 2025.

Snetselaar LG, de Jesus JM, DeSilva DM, Stoody EE. Dietary guidelines for Americans, 2020-2025: understanding the scientific process, guidelines, and key recommendations. Nutr Today. 2021;56(6):287-295. PMID: 34987271 pubmed.ncbi.nlm.nih.gov/34987271/.

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