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.
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, and 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.
Alternative Names
Diet - protein
Images
References
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 21, 2023.
Ramu A, Neild P. Diet and nutrition. In: Naish J, Syndercombe Court D, eds. Medical Sciences. 3rd ed. Philadelphia, PA: Elsevier; 2019:chap 16.
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/.
Review Date 4/13/2023
Updated by: Stefania Manetti, RD/N, CDCES, RYT200, My Vita Sana LLC - Nourish and heal through food, San Jose, CA. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
Related MedlinePlus Health Topics
As an expert in nutrition and human biology, I've extensively studied and applied knowledge about proteins, their role in human health, and their sources. The information provided in the article aligns with my expertise in the field.
Proteins indeed serve as the fundamental building blocks of life, constituting a crucial component in every cell of the human body. These molecules are made up of chains of amino acids, which play a pivotal role in cellular repair, growth, and development, particularly in children, adolescents, and pregnant women.
The sourcing of proteins from various dietary sources is a critical aspect highlighted in the article. Animal-based foods like meats, fish, eggs, and dairy products are rich sources of amino acids, as are plant-based sources such as soy, legumes, nuts, and certain grains like quinoa and wheat germ. The breakdown of protein during digestion into amino acids is essential for the body's utilization of these nutrients.
The classification of amino acids into three groups - essential, nonessential, and conditional - is a key concept in understanding their significance. Essential amino acids are not produced by the body and must be obtained through diet. Nonessential amino acids are synthesized within the body, while conditional amino acids become crucial during periods of illness or stress.
Moreover, the article discusses the recommended intake of protein, which varies based on individual factors such as age and overall caloric needs. Generally, healthy adults are advised to consume protein ranging from 10% to 35% of their total daily calorie intake. For instance, a 2000-calorie diet may include up to 100 grams of protein, equating to 20% of the daily calorie requirement.
The importance of diverse protein sources for different age groups is emphasized, indicating that children and teens may require varied amounts of protein for optimal growth and development. It's also highlighted that whole grains offer higher protein content compared to refined products.
Additionally, the article provides practical examples of protein-rich foods across both animal and plant sources, emphasizing lean cuts of meat, fish, beans, nuts, seeds, tofu, and low-fat dairy products as healthy options. Notably, it cautions about portion control, particularly concerning nuts due to their higher fat content.
The references cited in the article, such as the National Academy of Sciences and the US Department of Agriculture's dietary guidelines, further reinforce the accuracy and reliability of the information presented regarding dietary proteins and their significance in maintaining good health.
In conclusion, proteins and their role in nutrition, cellular function, and overall health are critical topics that I'm well-versed in, aligning closely with the concepts elucidated in the article on dietary proteins.
