In vitro digestibility of commercial whey protein supplements

Abstract

Amongst the sport dietary supplements, those manufactured with whey protein (WP) represent an important amino acid source. However, as a result of product lack of uniformity, the nutritional quality of this type of product is uncertain. Thus, the aim of this study was to investigate the protein quality of WP supplements produced by U.S. (WP-USA), and Brazilian companies (WP-BRA), evaluating the in vitro protein digestibility, and the essential amino acid (EEA) composition. In addition, the amino acid (AAS) and protein digestibility-corrected amino acid (PDCAAS) scores were calculated. Although WP-USA supplement exhibited greater (P < 0.05) digestibility than WP-BRA counterparts, both WP supplements exhibited greater (P < 0.05) digestibility than soy and caseinate isolate supplements, which were used as reference. Considering the WHO/FAO/UNU protein standard for non-athletic adult, the WP-USA and WP-BRA supplements scored high AAS. In addition, the PDCAAS values on both supplement groups were >1.0, with exception of threonine and valine in WP-USA, and isoleucine and leucine in WP-BRA. However, when the calculated AAS and PDCAAS based on the suggestion for adult athletes were considered, both supplements exhibited suboptimal score values for several EAA. In addition, both WP-USA and WP-BRA supplements were unable to supply the suggested adult athlete EAA requirement.