A complete protein or whole protein is a food source of protein that contains an adequate proportion of each of the nine essential amino acids necessary in the human diet. Examples of single-source complete proteins are red meat, poultry, fish, eggs, milk, cheese, yogurt, soybeans and quinoa. The concept does not include whether or not the food source is high in total protein, or any other information about that food's nutritious value.
It was once thought that plant sources of protein are deficient in one or more amino acids, and so vegetarian diets had to specifically combine foods during meals, which would create a complete protein. However, the most recent position of the Academy of Nutrition and Dietetics is that protein from a variety of plant foods eaten during the course of a day supplies enough essential amino acids when caloric requirements are met. Normal physiological functioning of the body is possible if one obtains enough protein and sufficient amounts of each amino acid from a plant-based diet. In fact, the highest PDCAAS scores are not given to commonly eaten meat products, but rather to animal-derived vegetarian foods like milk and eggs and the vegan food soy protein isolate.
Optimal amino acid profile
The following table lists the optimal profile of the nine essential amino acids in the human diet, which comprises complete protein, as recommended by the Institute of Medicine's Food and Nutrition Board:(note that the examples have not been corrected for digestibility)
|Essential amino acid||mg/g of protein||percentage of total protein||raw, whole chicken egg||quinoa||raw spinach|
Total adult daily intake
The second column in the following table shows the amino acid requirements of adults as recommended by the World Health Organization calculated for a 62 kg (137 lb) adult. Recommended Daily Intake is based on 2,000 kilocalories (8,400 kJ) per day, which could be appropriate for a 70 kg (150 lb) adult.
|Essential amino acid||Required mg/day for a 62 kg (137 lb) adult|
|Total||11,408 milligrams (11.408 g)|
|Total Protein||46 to 56 grams (46,000 to 56,000 mg)|
Sources of complete protein
- Proteins derived from animal foods (meats, fish, poultry, milk, eggs) are generally complete.
- Foods that also obtain the highest possible Protein Digestibility Corrected Amino Acid Score (PDCAAS) score of 1.0 are certain dairy products (including whey), cooked egg whites, and soy protein isolate.
- Other foods, such as amaranth, buckwheat, hempseed, meat, poultry, Salvia hispanica, soybeans, quinoa, seafood, seaweed, and spirulina are complete proteins, but may not obtain a PDCAAS score of 1.0.
- "Protein in diet". Medline Plus Medical Encyclopedia. U.S. National Library of Medicine and National Institute of Health. September 2, 2003. Retrieved 2006-10-28.
In the published meta-analysis of nitrogen balance studies by Rand and coworkers (2003), there were no significant differences in the intakes of dietary nitrogen required to meet nitrogen equilibrium between those studies that supplied dietary protein predominantly from animal, vegetable, or mixed protein sources. It is important to realize, however, that this aggregate analysis does not suggest that dietary protein quality is of no importance in adult protein nutrition. ... the quality of well-processed soy proteins was equivalent to animal protein ... while wheat proteins were used in significantly lower efficiency ... while lysine is likely to be the most limiting of the indispensable amino acids in diets based predominantly on cereal proteins, the risk of a lysine inadequacy is essentially removed by inclusion of relatively modest amounts of animal or other vegetable proteins, such as those from legumes and oilseeds, or through lysine fortification in cereal flour.
- Food and Nutrition Board of Institute of Medicine (2005) Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids , page 691, from National Academies Press
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- World Health Organization, Protein and Amino Acid Requirements in Human Nutrition http://whqlibdoc.who.int/trs/WHO_TRS_935_eng.pdf, p. 245
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