α-Lactalbumin: Functional properties and potential health benefits

α-Lactalbumin (α-LA) is an active protein with multiple biological functions, which can provide the body with abundant essential amino acids, such as Trp and Lys. It is the main whey protein in human milk, accounting for about 22% of its total protein, and provides energy and nutrition for infants' body and brain development. However, the α-LA in bovine milk is relatively low, so bovine α-LA is often added as a supplement to improve α-LA content and the balance of amino acids in infant formula. In addition, more studies have focused on the health benefits of α-LA in humans, proposing novel physiological roles or supplementing more substantial research evidence, including improving metabolism-related chronic diseases, promoting intestinal health, strengthening bone and muscle health, reducing oxidative stress, delaying aging, and enhancing sleep and cognitive performance. Nonetheless, a considerable proportion of the research remains confined to the realm of cells and animals, and it remains uncertain whether these findings will be replicated in humans, and at what dosage. This review describes the basic properties and the structural characteristics focusing on α-LA and specifically discusses its digestion and absorption in infants, adults, and the elderly. Further, the review summarizes the beneficial effects and mechanisms of action of α-LA supplementation in infants and adults, as well as the future applications of α-LA are also discussed.