Alpha-protein

Alpha-protein (Alpha-lactalbumin)

Alpha-protein (or α-protein) is the main whey protein found in human milk. It is rich in essential amino acids, especially tryptophan and cysteine. Clinical evidence on α-protein and other milk proteins is summarised below.

α Protein is a good source of essential amino acids

Essential amino acids are important for infant growth and development and must be consumed in the appropriate proportions for optimal health.¹ α-protein is a good source of essential amino acids.² In particular, α-protein has a high content of tryptophan and cysteine, which are thought to have important roles beyond protein synthesis.^3,⁴

Tryptophan³

A precursor of serotonin, a neurotransmitter

Levels may influence conscious behaviour and sleep patterns

Cysteine³

A component of glutathione, an important element of the antioxidant system

A precursor of taurine, an amino acid which may be involved in brain development

Human milk and cows’ milk differ in protein content and composition

The protein content and composition of human milk differs from that of cows’ milk in several important aspects. In human milk, whey proteins are the predominant form of protein, of which α-protein is the most abundant. In cows’ milk, casein is the predominant form of protein, with beta-lactoglobulin (ß-protein) being the most abundant whey protein.^2,^3,⁵

Typical whey-dominant formulae

In typical whey-dominant infant milk, ß-protein is the predominant whey protein (human milk usually has none) and levels of α-protein are less than half those present in human breast milk.² The protein profiles in typical infant formulae supply an excess of amino acids in order to meet the infant’s growth and development. The excess amino acids must be broken down and the nitrogen excreted, potentially placing a strain on the infant’s developing kidneys.²

Formula enriched with alpha-lactalbumin offers advantages

Infant milks enriched with α-protein are another step closer to the composition of human milk. Such formulae have increased levels of α-protein and decreased levels of ß-protein, resulting in an improved essential amino acid profile.²

The advantages of α-protein-enriched formula over standard formula include:

Closer to breast milk protein profile.²
Improved essential amino acids profile.^1,^2,⁶
Reduction in total protein content.²
Reduction in renal solute load.³
Tolerated similar to breast milk.⁶

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References:
1. Jackson JG, Hanszen DB, Lonnerdal B, et al. A multinational study of alpha-lactalbumin concentrations in human milk. J Nutrit Biochem 2004; 15: 517-521.

2. Lien EL, Davis AM, Euler AR, et al. Growth and safety in term infants fed reduced-protein formula with added bovine alpha-lactalbumin. J Ped Gastro Nutr 2004; 38: 170–176. Abstract

3. Lien EL. Infant formulas with increased concentrations of alpha-lactalbumin. Am J Clin Nutr 2003; 77: 1555S–1558S. Full text

4. Heine WE, Klein PD, Reeds PJ. The importance of alpha-lactalbumin in infant nutrition. J Nutr 1002; 121: 277–283..

5. Fomon SJ. Nutrition of normal infants. St Louis; MO:Mosby;1993

6. Davis AM, Harris BJ. Increased alpha-lactalbumin infant formula fed to healthy term infants in a multi-center plasma essential amino acid study. Abstract presented at the 38th Annual Meeting of the European Society for Pediatric Gastroenterology, Hepatology and Nutrition: Porto, Portugal, June 1-4, 2005. J Ped Gastro Nutr 2005; 40: 630 Abstract N-04. Abstract.

IMPORTANT NOTICE: Breast feeding is best for babies. Infant milks are intended to replace breast milk when mothers do not breast feed. Good maternal nutrition is important for the preparation and maintenance of breast feeding. Introducing partial bottle feeding may have a negative effect on breast feeding and reversing a decision not to breast feed is difficult. You should always seek the advice of a doctor, midwife, health visitor, public health nurse, dietitian or pharmacist on the need for and proper method of use of infant milks and on all matters of infant feeding. Infant milk should always be prepared and used as directed. Unnecessary or improper use of infant milk may present a health hazard. Social and financial implications should be considered when selecting a method of infant feeding.

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