complete protein
{{short description|Protein source containing all nine essential amino acids}}
{{Main|protein (nutrient)|protein combining}}
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.{{cite encyclopedia | encyclopedia = Medline Plus Medical Encyclopedia | title = Protein in diet | url = https://www.nlm.nih.gov/medlineplus/ency/article/002467.htm | accessdate = 2006-10-28 | date= September 2, 2003 | publisher = U.S. National Library of Medicine and National Institute of Health}}{{cite book|publisher=Food and Nutrition Board of Institute of Medicine, National Academies Press|date=2005|title=Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids|url=https://www.nap.edu/read/10490/chapter/12#691|page=691|doi=10.17226/10490|isbn=978-0-309-08525-0}}{{cite web|title=All About the Protein Foods Group|url=https://www.choosemyplate.gov/eathealthy/protein-foods|publisher=US Department of Agriculture|accessdate=20 May 2018|date=3 November 2017}}{{cite journal |last1=Mariotti |first1=François |last2=Gardner |first2=Christopher D. |title=Dietary Protein and Amino Acids in Vegetarian Diets—A Review |journal=Nutrients |date=Nov 2019 |volume=11 |issue=11 |page=2661 |doi=10.3390/nu11112661 |pmid=31690027 |pmc=6893534 |doi-access=free }}{{cite journal |last1=Young |first1=VR |last2=Pellett |first2=PL |title=Plant proteins in relation to human protein and amino acid nutrition. |journal=The American Journal of Clinical Nutrition |date=May 1994 |volume=59 |issue=5 Suppl |pages=1203S–1212S |doi=10.1093/ajcn/59.5.1203S |pmid=8172124 |doi-access=free }}
Concept
Protein nutrition is complex because any proteinogenic amino acid may be the limiting factor in metabolism. Mixing livestock feeds can optimize for growth, or minimize cost while maintaining adequate growth. Similarly, human nutrition is subject to Liebig's law of the minimum: The lowest level of one of the essential amino acids will be the limiting factor in metabolism.
:If the content of a single indispensable amino acid in the diet is less than the individual's requirement, then it will limit the utilization of other amino acids and thus prevent the normal rates of synthesis even when the total nitrogen intake level is adequate. Thus the "limiting amino acid" will determine the nutritional value of the total nitrogen or protein in the diet.Food and Nutrition Board of Institute of Medicine (2005) Dietary Reference Intakes for [http://www.nap.edu/read/10490/chapter/12 Protein and Amino Acids], page 685, from National Academies Press
Protein sources are thus rated by their limiting amino acids.{{cite journal | author=Young VR, Pellett PL | title=Plant proteins in relation to human protein and amino acid nutrition | journal=American Journal of Clinical Nutrition | volume=59 | issue=5 Suppl | year=1994 | pages=1203S–1212S | url = http://www.ajcn.org/content/59/5/1203S.long | format = PDF | pmid=8172124 | doi=10.1093/ajcn/59.5.1203s| doi-access=free }}
Most people eat a varied diet with multiple sources of protein. Incomplete sources can complement each other and become complete when combined.{{Cite web |title=What's a Complete Protein and Should You Care? |url=https://health.clevelandclinic.org/do-i-need-to-worry-about-eating-complete-proteins |access-date=2024-04-19 |website=Cleveland Clinic |language=en}} Combining does not need to happen for every single meal: so long as the diet is varied and meets caloric needs, even vegans and vegetarians – people who tend to have more "incomplete protein" in their diet – can easily meet their amino acid needs. In other words, most people do not need to consider the completeness of proteins of single foods.{{Cite journal |last1=Melina |first1=Vesanto |last2=Craig |first2=Winston |last3=Levin |first3=Susan |date=2016-12-01 |title=Position of the Academy of Nutrition and Dietetics: Vegetarian Diets |url=http://jandonline.org/article/S2212-2672(16)31192-3/fulltext |journal=Journal of the Academy of Nutrition and Dietetics |language=en |volume=116 |issue=12 |pages=1971 |doi=10.1016/j.jand.2016.09.025 |issn=2212-2672 |pmid=27886704 |s2cid=4984228 |url-access=subscription |via=}} [https://web.archive.org/web/20161202165753/http://www.eatrightpro.org/~/media/eatrightpro%20files/practice/position%20and%20practice%20papers/position%20papers/vegetarian-diet.ashx PDF]
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 US Institute of Medicine's Food and Nutrition Board. The foodstuffs listed for comparison show the essential amino acid content per unit of the total protein of the food; 100g of spinach, for example, only contains 2.9g of protein (6% Daily Value), and of that protein 1.36% is tryptophan.{{cite web|url=http://www.nutritiondata.com/help/analysis-help#protein-quality|title=Protein quality|publisher=Conde Nast, Nutritiondata.com|date=2018|access-date=13 April 2020}}(note that the examples have not been corrected for digestibility)
| class="wikitable sortable" | |
| Essential amino acid | mg/g of protein
!percentage of total protein |
|---|---|
| Tryptophan | 7
|0.7% |1.33% |1% |1.36% |
| Threonine | 27
|2.7% |4.42% |3.2% |4.27% |
| Isoleucine | 25
|2.5% |5.34% |4.2% |5.14% |
| Leucine | 55
|5.5% |8.65% |7.3% |7.8% |
| Lysine | 51
|5.1% |7.27% |6.1% |6.08% |
| Methionine+Cystine | 25
|2.5% |5.18% |2.7%+1.3% |1.85%+1.22% |
| Phenylalanine+Tyrosine | 47
|4.7% |9.39% |4.3%+3.6% |4.51%+3.78% |
| Valine | 32
|3.2% |6.83% |5% |5.63% |
| Histidine | 18
|1.8% |2.45% |3.1% |2.24% |
| Total
|287 |28.7% |50.86% |41.8% |43.88% |
= 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{{Cite web|last=|first=|date=2007|title=Protein and Amino Acid Requirements in Human Nutrition|url=https://apps.who.int/iris/bitstream/handle/10665/43411/WHO_TRS_935_eng.pdf|access-date=January 21, 2021|website=World Health Organization}} calculated for a {{convert|62|kg|lb|abbr=on}} adult. Recommended Daily Intake is based on {{convert|2000|kcal|}} per day,{{cite web|title=Guidance for Industry: A Food Labeling Guide|url=https://www.fda.gov/Food/GuidanceRegulation/GuidanceDocumentsRegulatoryInformation/LabelingNutrition/ucm2006828.htm|archive-url=https://wayback.archive-it.org/7993/20171031143107/https://www.fda.gov/Food/GuidanceRegulation/GuidanceDocumentsRegulatoryInformation/LabelingNutrition/ucm2006828.htm|url-status=dead|archive-date=2017-10-31|website=U.S. Food & Drug Administration|publisher=US FDA|accessdate=14 January 2017}} which could be appropriate for a {{convert|70|kg|lb|abbr=on}} adult.
| class="wikitable sortable" | |
| Essential amino acid | Required mg/day for a {{convert|62|kg|lb|abbr=on}} adult |
|---|---|
| Tryptophan | 248 |
| Threonine | 930 |
| Isoleucine | 1240 |
| Leucine | 2418 |
| Lysine | 1860 |
| Methionine+Cystine | 930 |
| Phenylalanine+Tyrosine | 1550 |
| Valine | 1612 |
| Histidine | 620 |
| Total
|{{convert|11408|mg|g}} | |
| Total Protein
|{{convert|46|to|56|g|mg}} |