What Are the Essential Amino Acids and How Much Protein Do I Need?

Patient Presentation
A 14-year-old male came to clinic for his health supervision visit. He was a runner and had become more interested in eating healthier to improve his running. “I’m drinking more milk and eating more vegetables lately,” he said. “I’m thinking about eating vegetarian, but I’m not sure that I can get enough protein. I don’t like seeds, nuts, or tofu, so I’m not sure that I can do it,” he explained. The past medical history showed no athletic injuries. The family history was positive for heart disease and stroke in family members > 60 years of age. The review of systems was negative.

The pertinent physical exam revealed a thin male with height at the 75% percentile and weight at the 25%. Vital signs were normal as was the rest of his physical examination. The diagnosis of a healthy male was made. He was counseled to continue to eat a variety of foods including calcium-rich foods. The pediatrician told him that he still could get enough protein in his diet using a variety of foods if he chose to eat a vegetarian diet. “It’s important to eat a wide variety of foods in your diet and in general as long as you are eating enough calories from good foods, and a combination of foods you probably should get enough protein. Some people try to make the change to eating vegetarian all at once, but others do it in more steps. You also have to consider who is going to buy the food and cook it, so you need to think about the rest of your family too and how they eat. You might want to try to make some changes to your breakfast, lunch and snacks first since you control those foods more. Then maybe try adding in meatless dinner more often,” the pediatrician offered. “You may also find out that you like some nuts or tofu when you cook them differently.”

Vegetarians have a diet pattern that emphasizes consuming plant foods (i.e. vegetables, grains and nuts) and avoiding flesh food (i.e. red meat, poultry, fish). Some vegetarians include milk and egg products in their diets and would be more accurately described as lacto-ova-vegetarians. Vegans are vegetarians who avoid all animal products including foods such as dairy products, eggs, butter, honey and gelatin.

One of the most common questions that vegetarian are asked is about how they obtain enough protein from their diets. In general, a mixed diet of a variety of foods with appropriate calories should provide anyone, vegetarian or not, with enough protein. Vegetarians like anyone who is restricting or avoiding certain foods, just need to pay a little more attention to the mixture of foods they are consuming. Vegetarians like everyone need to pay attention to the calories from fat in their foods also because nuts, seeds, some plants such as avocados, eggs, and some dairy products contain a higher amount of fat and calories. They are healthy foods but like any food, these need to be consumed as part of an overall healthy diet. To review what types of foods vegetarians should eat to maintain proper nutrition, click here.

Learning Point
Amino acids are categorized as essential and non-essential. Essential amino acids are those which cannot be synthesized by the body and must be obtained from food. These include 9 amino acids: histadine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. Non-essential amino acids can be synthesized by the body or occur in the normal breakdown of protein.

Complete proteins are those which contain all the essential amino acids in the proper proportion. Usually these are from animal protein such as meat, poultry, fish, eggs, milk, cheese and yogurt, but also soy and quinoa are complete proteins. Incomplete proteins are those which may contain all the essential amino acids but are low in 1 or more of them. For example grains have lower lysine, isoleucine and threonine and legumes have lower methionine and trptophan. Nuts and seeds are lower in lysine and isoleucine. Proteins from plants, legumes, grains, nuts, seeds and vegetables are usually incomplete proteins. Complete proteins can be made by eating a variety of different foods that “compliment” each other. There’s a reason that people have been mixing beans and rice (i.e. red beans and rice, dal and rice), beans and corn (i.e. tacos, chili beans and cornbread), beans and bread (i.e. hummus on pita bread) for a long time. The complimentary foods do not need to be eaten in the same meal but should be consumed over the day. It is possible to eat enough of an incomplete protein food to get enough amino acids to make a complete protein but most people would not choose to eat 8 large potatoes, 15.5 cups of rice, or almost 13 cups of corn to get enough protein in their diet.

There is also protein in fruits and vegetables themselves but in much smaller amounts.

The recommended daily allowance of protein is about ~0.8 grams/kg/day of protein. This is about 45-55 g/day for teens and adults. Total amounts for children obviously is lower. One cup of milk or yogurt is 8 and 11 grams of protein respectively. Three ounces of meat is about 21 grams of protein and 1 cup of dried beans is about 16 grams.

Most people don’t think about their diets this way, they think about amounts. The USDA recommends 5 ounce equivalents of protein a day for girls and women > age 9 years. For boys or men it ranges from 5-6.5 ounce equivalents depending on age. Boys 9-13 years should have 5 ounce equivalents/day, those boys and men 14-30 years should have 6.5 ounce equivalents/day, those 31-50 years should have 6 ounce equivalents/day, and those men > 51+ years should have 5.5 ounce equivalents/day. An ounce equivalent is 1 ounce of an animal protein such as 1 ounce of lean beef, ham, pork, chicken or fish or 1 egg. Nuts and seeds butters (i.e. peanut butter) are 1 tablespoon = 1 ounce equivalent. Nuts and seeds are 1/2 ounce = 1 ounce equivalent. Beans, peas, and tofu are 1/4 cup of cooked item = 1 ounce equivalent.

Questions for Further Discussion
1. What are tofu, tempeh and seitan?
2. Which types of foods are anti-oxidant rich?

Related Cases

To Learn More

To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at SearchingPediatrics.com, the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.

Information prescriptions for patients can be found at MedlinePlus for this topic: Vegetarian Diet

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

To view videos related to this topic check YouTube Videos.

Knutson P. Your Vegan Guide to Foods With Protein. Vegan Coach.
Available from the Internet at http://www.vegancoach.com/foods-with-protein.html (rev. 2014, cited 8/26/14).

Savvy Vegetarian. How to Get Enough Protein In Vegetarian\Vegan Diets.
Available from the Internet at http://www.savvyvegetarian.com/articles/get-enough-protein-veg-diet.php (rev. 2014, cited 8/26/14).

Centers for Disease Control. Protein.
Available from the Internet at http://www.cdc.gov/nutrition/everyone/basics/protein.html (rev. 10/4/12, cited 8/26/14).

Mangels R. Protein in the Vegan Diet. Vegetarian Resource Group.
(rev. 2014, cited 8/26/14).

United States Department of Agriculture. What Counts as an Ounce Equivalent in the Protein Foods Group? ChooseMyPlate.gov.

United States Department of Agriculture. How Much Food from the Protein Foods Group is Needed Daily? ChooseMyPlate.gov.
http://www.choosemyplate.gov/printpages/MyPlateFoodGroups/ProteinFoods/food-groups.protein-foods-amount.pdf (cited 8/26/14)

ACGME Competencies Highlighted by Case

  • Patient Care
    1. When interacting with patients and their families, the health care professional communicates effectively and demonstrates caring and respectful behaviors.
    2. Essential and accurate information about the patients’ is gathered.
    4. Patient management plans are developed and carried out.
    5. Patients and their families are counseled and educated.
    8. Health care services aimed at preventing health problems or maintaining health are provided.

  • Medical Knowledge
    10. An investigatory and analytic thinking approach to the clinical situation is demonstrated.
    11. Basic and clinically supportive sciences appropriate to their discipline are known and applied.

  • Practice Based Learning and Improvement
    13. Information about other populations of patients, especially the larger population from which this patient is drawn, is obtained and used.


    Donna M. D’Alessandro, MD
    Professor of Pediatrics, University of Iowa Children’s Hospital