Complete protein
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.
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.Protein sources are thus rated by their limiting amino acids.
Most people eat a varied diet with multiple sources of protein. Incomplete sources can complement each other and become complete when combined. 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.
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, and of that protein 1.36% is tryptophan.| Essential amino acid | mg/g of protein | percentage of total protein | raw, whole chicken egg | quinoa | raw spinach |
| 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 calculated for a adult. Recommended Daily Intake is based on per day, which could be appropriate for a adult.| Essential amino acid | Required mg/day for a adult |
| Tryptophan | 248 |
| Threonine | 930 |
| Isoleucine | 1240 |
| Leucine | 2418 |
| Lysine | 1860 |
| Methionine+Cystine | 930 |
| Phenylalanine+Tyrosine | 1550 |
| Valine | 1612 |
| Histidine | 620 |
| Total | |
| Total Protein |