Introduction

The global rise in impaired glucose tolerance, insulin resistance, and type 2 diabetes underscores the urgent need for effective nutritional strategies to improve postprandial glycaemic control (1). Palmaria palmata (dulse), a red seaweed rich in bioactive peptides, offers a novel marine-derived alternative and sustainable protein with potential glycaemic benefits. Such hydrolysates have been demonstrated to increase incretin secretion and β-cell function in vitro, and attenuate postprandial glycaemia in mice, thus warranting further investigation in humans (2).

Aim

To investigate the effect of a dulse protein hydrolysate on postprandial blood glucose, insulin and incretin concentrations, and β-cell function in healthy adults.

Methodologies

Six healthy adults (age 44±7 y; height 170±3 cm; body mass 72.4±4.9 kg; body fat 24.0±3.1%) participated in a randomised, double blind, crossover feeding study. Written informed consent was obtained from all participants, the study was approved by the local Ethics Committee (2022_12_14_EHS) and registered at ClinicalTrials.gov (NCT05850429).

Following a >10 h overnight fast, participants consumed a beverage containing 0.6 g·kg body mass (BM)^-1 maltodextrin, with either 0.150 g·kg BM^-1 (High), 0.075 g·kg BM^-1 (Low) or no (CON) dulse protein hydrolysate, in randomised order. Blood samples were taken prior to and 15, 30, 45, 60, 90, and 120 minutes post ingestion. Glucose, insulin, C-peptide, glucagon, GIP and GLP-1 concentrations were measured in plasma and expressed as incremental Area Under the Curve (iAUC) and across time. β-cell function parameters derived from mathematical modelling of glucose and C-peptide data were assessed, including insulin secretion rate, glucose sensitivity (insulin response to glucose) and rate sensitivity (early insulin response).  Differences in iAUC and time-course data were tested for using one-way and two-way repeated measures ANOVAs, respectively, with post-hoc Dunnett’s to compare differences between protein and control conditions. Effect sizes were calculated using Hedge’s g. The alpha level was set at p<0.05. Data are Mean±SD.

Results

The 2-hour Glucose iAUC was significantly different between conditions (High: 265±135; Low: 228±108; CON: 380±203) (P<0.05), with post-hoc testing indicating a significant difference between Low and CON conditions only (P<0.05), with a large effect size (g=-0.9, 95% CI (-1.8, -0.1)). Concentrations of all analytes increased significantly after consumption of each beverage (main effect of time: P<0.05), with no between beverage differences observed (P>0.05). Time course of insulin secretion rate (ISR) was affected by condition (P<0.01). High augmented ISR by 81±125 and 86±114 pmol⋅min^-1⋅m^-2 at 15 and 20 min, respectively, versus CON (P<0.01). Conversely, Low decreased ISR by 62±62, 62±62 and 64±59 pmol⋅min^-1⋅m^-2 at 75, 80 and 85 min, respectively (P<0.05).

Conclusions

This study demonstrated the potential of a novel dulse protein hydrolysate to reduce postprandial blood glucose concentrations in a cohort of healthy individuals, though we did not observe a dose-response. These data are consistent with the literature on co-ingestion of other protein sources, which have been previously observed to attenuate postprandial glycemia (3). While this study is limited by a small sample size, large effect sizes were observed for potential enhancements in glucose and ISR in protein conditions. These findings suggest palmaria palmata as a potential alternative and sustainable bioactive protein for regulation of glucose control.