The impact of whey protein on plasma branched-chain amino acids and glycaemic control in humans. A narrative review.

Abstract

Impaired glycaemic control is a major risk factor for developing type 2 diabetes (T2D), a worldwide health epidemic intrinsically linked to diet and obesity. Whey proteins (WP) are increasingly popular supplements that are a rich source of branched-chain amino acids (BCAA), essential for muscle protein synthesis and metabolic regulation. In humans, fasting plasma concentrations of BCAA are maintained around 350 µM but become chronically elevated by 10-25% in persons with T2D. Little is known about whether BCAA from WP impacts circulating BCAA concentrations and contributes to this phenomenon. This narrative review used a systematic search approach with relevant keywords to identify evidence from randomised controlled trials in normoglycaemic humans and those with insulin resistance or T2D, on the effects of WP intake on plasma BCAA and glycaemic control. This review is, to the authors' knowledge, the first to specifically examine the effects of WP intake on plasma BCAA concentrations in relation to glycaemic control. Whilst the majority of acute studies identified (n=6) reported that WP consumption between 10 to 50 g significantly elevates postprandial BCAA and insulin responses (as evidenced by peak concentration and/or area under the curve), evidence from chronic studies (n=3) report inconsistent findings on the impact of 9 to 51g of WP per day on fasting BCAA and glycaemic control (e.g., fasting glucose and insulin, insulin clearance). Findings from this literature review highlight the need for further studies that investigate the relationship between WP consumption with BCAA and glycaemic control, and to determine underlying mechanisms of action.