Complete protein
A complete protein (or whole protein) is a source of protein that contains an adequate proportion of all nine of the essential amino acids necessary for the dietary needs of humans or other animals.[1] Some incomplete protein sources may contain all essential amino acids, but a complete protein contains them in correct proportions for supporting biological functions in the human body.
The following table lists the optimal profile of the essential amino acids, which comprises a complete protein:[2]
| Essential Amino Acid | mg/g of Protein |
|---|---|
| Tryptophan | 7 |
| Threonine | 27 |
| Isoleucine | 25 |
| Leucine | 55 |
| Lysine | 51 |
| Methionine+Cystine | 25 |
| Phenylalanine+Tyrosine | 47 |
| Valine | 32 |
| Histidine | 18 |
Nearly all foods contain all twenty amino acids in some quantity. However, proportions vary, and some foods are deficient in one or more of the essential amino acids. Apart from some exceptions such as quinoa or soybeans, vegetable sources of protein are more often lower in one or more essential amino acids than animal sources, especially lysine, and to a lesser extent methionine and threonine.[3]
Consuming a mixture of plant based protein sources can increase the biological value of food. For example, to obtain 25 grams of complete protein from canned pinto beans requires consuming 492 grams (423 kcal), however if combined with 12 grams of Brazil nuts, requires only 364 g of pinto beans (391 kcal).[4]. These complementary protein sources do not need to be consumed in the same meal (see Protein combining).
[edit] Sources of complete protein
- Generally, proteins derived from animal foods (meats, fish, poultry, cheese, eggs, yogurt, and milk) are complete, though gelatin is an exception.[1] Proteins derived from plant foods (legumes, grains, and vegetables) tend to be limited in essential amino acids. Some are notably low, such as corn protein, which is low in lysine and tryptophan.[5]
- Some foods contain all the essential amino acids on their own in a sufficient amount to qualify as a "complete protein". Complete protein foods that also obtain the highest possible PDCAAS score of 1.0 are certain dairy products (including whey), egg whites, and soy protein isolate. Other foods, such as amaranth, Aphanizomenon flos-aquae[citation needed], buckwheat, hempseed, meat, poultry, Salvia hispanica, soybeans, quinoa, seafood, and spirulina also are complete protein foods, but may not obtain a PDCAAS score of 1.0.
[edit] Notes
- ^ a b c "Protein in diet". Medline Plus Medical Encyclopedia. U.S. National Library of Medicine and National Institute of Health. September 2, 2003. http://www.nlm.nih.gov/medlineplus/ency/article/002467.htm. Retrieved 2006-10-28.
- ^ Recommended by the Institute of Medicine's Food and Nutrition Board http://www.iom.edu/CMS/3788/4576/4340.aspx http://www.nutritiondata.com/help/analysis-help#protein-quality
- ^ Young VR, Pellett PL (1994). "Plant proteins in relation to human protein and amino acid nutrition" (PDF). AMERICAN JOURNAL OF CLINICAL NUTRITION 59 (5 Suppl): 1203S-1212S. PMID 8172124. http://www.ajcn.org/content/59/5/1203S.long.
- ^ Woolf, P. J.; Fu, L. L.; Basu, A. (2011). Haslam, Niall James. ed. "VProtein: Identifying Optimal Amino Acid Complements from Plant-Based Foods". PLoS ONE 6 (4): e18836. doi:10.1371/journal.pone.0018836. PMC 3081312. PMID 21526128. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3081312.
- ^ http://www.faqs.org/nutrition/Ca-De/Corn-or-Maize-Based-Diets.html Retrieved 23 June 2010
- ^ "Quinoa: An emerging "new" crop with potential for CELSS (NASA Technical Paper 3422)" (PDF document). NASA. November 2003. http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940015664_1994015664.pdf. Retrieved 2006-10-28.
