Goodness of dairy 3Proteins are bio-molecules that are made up of smaller building blocks called amino acids. There are twenty different amino acids in total, nine of which are essential. Milk has a high protein quality, as it contains all nine essential amino acids in relatively high quantities.

Essential and non-essential amino acids

Essential and non-essential amino acids form the basic material of all proteins found in the diet. The liver can make non-essential or dispensable amino acids if dietary intake is insufficient, but it cannot produce the nine essential amino acids. A sufficient dietary intake is therefore necessary to meet the body’s requirements.

Amino acid profile dairy versus other sources

All essential amino acids are present in milk proteins in relatively high amounts. Table 2 provides the amino acid profile of various animal and plant proteins, in comparison with the FAO requirement.  Methionine and cysteine, the sulphur-containing amino acids, are often grouped together as they are metabolically close. The same is true for aromatic amino acids phenylalanine and tyrosine. This is reflected in the recommendations below.

mg /g protein milk egg beef soy wheat rice FAO requirements
Lysine

 

83 72 89 60 23 34 45
Histidine 28 23 44 25 21 21 15
Isoleucine 64 69 50 42 34 40 30
Leucine 93 82 79 77 69 77 59
Valine 68 74 53 47 38 54 39
SAA

 

32 51 36 24 36 42 22
Aromatics

 

105 104 91 88 77 94 38
Threonine 51 50 47 40 28 34 23
Tryptophan

 

14 16 14 12 10 11 6
Total EAA 538 541 503 423 336 407 277
SAA = methionine + cystein ; Aromatics = phenylalanine + tyrosine

Protein and amino acid requirements

The FAO has defined amino acid requirements per age group. The amino acid requirements for children above the age of three, adolescents and adults are similar. However higher protein and amino acid recommendations are for instance given to pregnant and lactating women – together with the advice to obtain additional proteins from food sources rather than from supplements. There are currently ongoing discussions about higher protein requirements for the elderly.

Reference

FAO/WHO/UNU Expert Consultation (2007). Expert consultation on protein and energy requirements. Protein and amino acid requirements in human nutrition. WHO Technical Report Series nr. 935.