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Facts about Protein1

Nicole C. Agro and Wendy J. Dahl2

Protein Basics

Our bodies are made of many proteins. Proteins are made from amino acids, and each protein has its own unique amino acid sequence that determines its shape and function. There are twenty different amino acids. Our bodies can make 11 of the amino acids that are needed to make protein but cannot make the other nine, so we must get them from our diet. These amino acids are considered “essential.” Foods that provide high levels of all of the essential amino acids are meat, poultry, eggs, fish, milk, cheese, and yogurt. Proteins low in one or more of the essential amino acids include those from plant foods: vegetables, fruits, grains, legumes, nuts, and seeds. Although it is not necessary to eat foods containing all of the essential amino acids at every meal, it is important for good health to ensure that what you eat over the course of the day provides enough of all of the essential amino acids and total protein. This is especially true for those who eat only plant sources of protein, such as vegans. As long as vegans eat a varied diet containing vegetables, legumes, grains, nuts, and seeds, they should have no problem getting enough of each of the essential amino acids and meeting their protein needs.

Figure 1. 
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Role of Proteins in the Body

Proteins have many functions in the body. For example, proteins help with digestion. They also help with the formation of red blood cells that deliver oxygen to our cells. They provide the framework and support for muscles, bones, skin, cartilage, hair, nails, teeth, and skin. Proteins also help the body fight infections.

Recommended Intake

The Recommended Dietary Allowance (RDA) for protein is 0.8 grams of protein for every 2.2 pounds (1 kilogram) of body weight for adult men and women who are not pregnant or breastfeeding. Table 1 lists estimated RDAs for protein based on reference body weights. Protein needs vary with age and sex. Use this equation to calculate your daily protein requirement, in grams: (Your Weight in Pounds/2.2) x 0.8.

Table 1. 

Recommended dietary allowance for protein based on reference body weights.

Age

Protein (grams/day)

Children ages 1–3

13

Children ages 4–8

19

Children ages 9–13

34

Girls ages 14–18

46

Boys ages 14–18

52

Women ages 19–70+

46

Men ages 19–70+

56

Source: Centers for Disease Control and Prevention 2012.

Sources of Protein

Sources of protein include meats, poultry, nuts, seeds, seafood, eggs, legumes (beans, peas, and lentils), soy products, dairy foods, and grains. Table 2 lists examples of protein sources and the amount of protein they provide in a given serving size (Choose My Plate 2014c).

Table 2. 

Protein sources.

Source

Foods

Serving Size

Amount of Protein

(grams)

Meat

beef, pork, lean luncheon or deli meats

3 ounces, cooked

23

Poultry

chicken and turkey

3 ounces, cooked

26

Nuts and Seeds

almonds, cashews, peanuts, pistachios, pumpkin seeds, sunflower seeds

1 ounce

6

Seafood

salmon, tuna, trout, snapper, herring, cod

3 ounces, cooked

17

Legumes

black beans, chickpea,

kidney beans

lentils

½ cup

½ cup

7

9

Soy Products

tofu, firm

veggie burger

tempeh

½ cup

1 patty

½ cup

10

11

15

Milk

whole, 2%, 1%, skim

1 cup

8

Grains

grits, yellow

brown rice

oatmeal

quinoa

½ cup, cooked

½ cup, cooked

½ cup, cooked

½ cup, cooked

1

2

3

4

Source: USDA Nutrient Data Laboratory 2011.

Protein Intake and Your Health

Most people eat more protein than they need without harmful side effects. However, some protein choices can be less healthy than others because they contain saturated fat. Saturated fat raises low-density lipoprotein (LDL) cholesterol levels, increasing the risk of heart disease and stroke. Fatty meats, poultry with the skin, sausage, hot dogs, and bacon are examples of sources of protein that are high in saturated fat. Replacing these options with healthier sources of protein has been shown to lower the risk of several diseases (Harvard School of Public Health 2014).

Figure 2. 
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How to Make Healthier Protein Choices

For healthier eating, choose lean or low-fat meat and poultry. Lean beef cuts include top sirloin and chuck shoulders. Lean pork includes pork loin, tenderloin, and ham. Extra-lean ground beef should say “90% lean/10% fat” on the package. When buying chicken and turkey, look for the skinless options. Avoid deli meats because they are high in sodium and some are high in fat.

Vary your protein choices. Make it a goal to have seafood at least twice a week. Fish containing omega-3 fatty acids have been shown to help reduce the risk of heart disease. Choose fish high in omega-3 fatty acids such as salmon, lake trout, mackerel, and herring. Choose unsalted nuts and seeds, such as pecans, almonds, or pumpkin seeds. Using visual cues for portion control will help to control the amount you eat. The “divided plate” method is a great way to determine the proper amount of protein that should be served. Protein foods should take up a little less than ¼ of your plate (Choose My Plate 2014a). Dairy food such as milk, yogurt, and low-fat cheeses are also good sources of protein.

Summary

There are many sources of dietary protein. Meat, poultry, eggs, fish, and dairy products are sources that provide a high level of essential amino acids that our bodies need. Plant foods such as grains, legumes, nuts, and seeds are also sources of protein. It is best to eat a variety of sources throughout the day to meet your needs. The Recommended Dietary Allowance (RDA) is 0.8 grams of protein for every 2.2 pounds (1 kilogram) of body weight. It is vital to consume the recommended amount of protein daily because proteins have many different roles in the body. Choosing protein sources such as lean meat, skinless poultry, fish, eggs, legumes, and unsalted nuts and seeds is an excellent way to get the protein you need in a healthier way.

References

Centers for Disease Control and Prevention. 2012. “Nutrition for Everyone: Protein.” http://www.cdc.gov/nutrition/everyone/basics/protein.html

Choose My Plate. 2014a. “Daily Food Plan.” http://www.choosemyplate.gov/myplate/index.aspx

Choose My Plate. 2014b. “What Foods Are in the Protein Foods Group?” http://www.choosemyplate.gov/food-groups/protein-foods.html

Choose My Plate. 2014c. “Why is it Important to Make Lean or Low-Fat Choices from the Protein Foods Group?” http://www.choosemyplate.gov/food-groups/protein-foods-why.html

Harvard School of Public Health. 2014. “The Nutrition Source: Protein.” http://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/protein/

Institute of Medicine, Food and Nutrition Board. 2005. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids,” pp. 339–421. Washington, DC: The National Academies Press.

Kids Health. 2011. “The Truth about Serving Sizes.” http://kidshealth.org/parent/nutrition_center/healthy_eating/portions.html#

USDA Nutrient Data Laboratory. 2011. National Nutrient Database for Standard Reference. http://ndb.nal.usda.gov/

Footnotes

1.

This document is FSHN15-01, one of a series of the Food Science and Human Nutrition Department, UF/IFAS Extension. Original publication date January 2015. Reviewed August 2018. Visit the EDIS website at http://edis.ifas.ufl.edu.

2.

Nicole C. Agro, former graduate student; and Wendy J. Dahl, associate professor; Food Science and Human Nutrition Department; UF/IFAS Extension, Gainesville, FL 32611.


The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county's UF/IFAS Extension office.

U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.