The prevalence of Type 2 diabetes (T2D) is increasing, which creates a large economic burden. Diet is a critical factor in the treatment and management of T2D; however, there are a large number of dietary approaches and a general lack of consensus regarding the efficacy of each. Therefore, the purpose of this narrative review is twofold: (1) to critically evaluate the effects of various dietary strategies on diabetes management and treatment, such as Mediterranean diet, plant-based diet, low-calorie and very low-calorie diets, intermittent fasting, low-carbohydrate and very low-carbohydrate diets, and low glycemic diets and (2) to examine several purported supplements, such as protein, branched-chain amino acids, creatine, and vitamin D to improve glucose control and body composition. This review can serve as a resource for those wanting to evaluate the evidence supporting the various dietary strategies and supplements that may help manage T2D.

The primary protein source of a diet may impact skeletal muscle maintenance with advancing age. The impact of the animal and plant protein content of a typical protein-containing diet on muscle anabolism in middle-to-older aged adults is unknown. To determine muscle adaptive remodelling response to a 10-day dietary intervention containing divergent protein sources, with and without resistance exercise training (RET) in middle-to-older aged adults. In a single-blind randomized control trial, twenty-seven 50-70-year-old participants consumed 1.0g·kg BM^-1·day^-1 of protein from an animal-focused whey protein-supplemented diet (AW-D) or plant-focused pea protein-supplemented diet (PP-D). Throughout the 10-day diet intervention, unilateral knee extensor RET was performed every other day. Deuterated water ingestion and skeletal muscle biopsies enabled measurement of daily integrated myofibrillar protein synthesis (iMyoPS) rates in the trained, and untrained legs. Changes in metabolic rate, body composition, lipid profiles, renal function, whole-body nitrogen balance (WBNB), strength and muscle architecture were also determined. Daily iMyoPS rates were significantly greater (P<0.001) in the trained compared to the untrained leg for AW-D (1.44 ± 0.26 vs 1.29 ± 0.27 %⋅day^-1) and PP-D (1.50 ± 0.17 vs 1.34 ± 0.21 %⋅day^-1) with no differences between groups, within leg. Training and diet did not affect intracellular anabolic signalling, muscle architecture, strength, metabolic rate, renal function or WBNB. Serum non-HDL cholesterol was significantly (P=0.014) lower following the intervention for PP-D only (pre: 3.89 ± 0.84, post 3.37 ± 0.78 mmol⋅L) with no other changes in lipid profiles. The 10-day provision of 1.0g·kg BM^-1·day^-1 from predominantly plant-derived or animal-derived protein does not influence daily iMyoPS rates in middle-to-older aged adults and has little impact on metabolic and renal health parameters. RET enhances rates of daily iMyoPS in middle-to-older aged adults consuming a typical protein-containing diet, with no influence of protein source. ClinicalTrials.gov NCT05574205 https://clinicaltrials.gov/study/NCT05574205.

The addition of low-dose protein to low protein-containing meals in middle-to-older aged adults may promote greater postprandial plasma aminoacidemia and mitigate declines in muscle health but may be dependent on the source and quality of protein consumed. This single-blind randomised study investigated postprandial plasma aminoacidemia and appetite regulatory responses to a typical lower protein-containing (∼0.07 g·kg body mass[BM]⁻¹) mixed breakfast supplemented with ∼0.13 g·kg BM^− 1 of whey protein concentrate (MB + WPC) or pea protein isolate (MB + PPI) in middle-to-older aged adults. Venous blood samples were collected whilst fasted and over a 180-min postprandial period to determine plasma amino acid and appetite hormone concentrations. Perceived appetite ratings were measured using Visual Analogue Scales. Plasma total amino acids and essential amino acids increased over time (both P < 0.05) with no between-group differences or overall availability over 180 min (incremental area under the curve (iAUC)). Plasma leucine concentrations increased over time (both P < 0.05) with greater peak concentrations (P = 0.032) and iAUC (P = 0.012) in MB + WPC compared with MB + PPI. Plasma total-ghrelin and total-GLP-1 concentrations and perceived ratings of hunger, fullness, and satiety were transiently altered following MB + WPC and MB + PPI (P < 0.05 for all), with no differences between groups. In middle-to-older aged adults, co-ingesting a small bolus of whey protein alongside a typical lower protein-containing breakfast elicits greater plasma leucinemia than co-ingestion of pea protein, with no differential impact on appetite regulation. Whether the addition of low-dose whey protein to typical meals of middle-to-older aged adults can enhance muscle anabolism without adversely affecting appetite remains to be determined.

Reductions in musculoskeletal mass and function can occur with ageing and disuse. While resistance exercise training is known to minimise these detriments, it is not always feasible. Vortex wave stimulation (VWS) may mitigate skeletal muscle decline in such scenarios. The aim of the present study was to explore the acute physiological and metabolic effects of VWS in healthy older adults. Fourteen participants consumed deuterium oxide (D ₂ O) stable oral isotope tracer for 7 days. Serial skeletal muscle biopsies were obtained to measure integrated rates of myofibrillar (iMyoPS) and sarcoplasmic (iSarcPS) muscle protein synthesis and regulatory signalling over ∼48 h before (habitual) and after two consecutive‐day bouts of VWS. Myoelectrical activity and muscle oxygenation during VWS, and pre‐post changes in peripheral blood flow and concentrations of inflammatory and bone turnover markers were also measured. There was an increase in iMyoPS (0.23% day ⁻¹ , P = 0.025), but not iSarcPS (0.07% day ⁻¹ , P = 0.582) above habitual rates following VWS. There was no difference in the expression of anabolic signalling proteins, nor peripheral blood flow following VWS. Myoelectrical activity increased during VWS (9.47 µV, P = 0.010), while muscle oxygenation decreased at the gastrocnemius ( P = 0.001) and quadriceps ( P = 0.017). There was a reduction in P1NP (8.27 µg L ⁻¹ ) and lactate (0.84 mmol L ⁻¹ ) concentration post‐VWS (both P < 0.001), while there was no difference in other biomarkers. This is the first study to demonstrate that VWS elicits acute physiological responses congruent with musculoskeletal adaptive remodelling, which warrants further exploration. image Key points: Resistance exercise is known to mitigate skeletal muscle atrophy associated with ageing and/or disuse but is not always feasible. We investigated, for the first time, the effects of a novel mechanical stimulus – vortex wave stimulation (VWS) – on integrated rates of myofibrillar and sarcoplasmic muscle protein synthesis, alongside other musculoskeletal and physiological outcomes, in healthy older adults. We demonstrated that VWS elevated myofibrillar, but not sarcoplasmic muscle protein synthesis compared to baseline, while increasing myoelectrical activity and reducing muscle oxygen saturation, lactate and bone turnover markers. These findings suggest VWS elicits acute physiological responses congruent with musculoskeletal adaptive remodelling.

Exercise-induced muscle damage (EIMD) impairs muscle function and subsequent performance. While research investigating the protective role of animal-derived protein is widespread, investigations into sustainable alternatives are lacking. The present study examined the effects of a novel, salmon-derived protein peptide (SPP) on muscle recovery. In a single-blind, parallel-design, 33 recreationally active adults (age: 23.9 ± 4.0 years, body mass index: 23.7 ± 4.0) were randomly assigned to one of three groups: (a) SPP, (b) whey protein, or (c) carbohydrate control. In addition to a controlled 1.0 g·kg body mass ⁻¹ ·day ⁻¹ dietary protein intake, participants consumed either 0.9 g·kg body mass ⁻¹ ·day ⁻¹ supplemental protein or isoenergetic carbohydrate for 4 days following EIMD (10 × 10 unilateral eccentric knee extensions). Maximal voluntary contraction, countermovement jump height, muscle soreness, thigh circumference, creatine kinase, and lactate dehydrogenase were assessed at baseline and +1, +4, +24, +48, and +72 hr post EIMD. Significant time effects were observed for all variables. Countermovement jump height was greater in the SPP versus carbohydrate groups at +72 hr and across all time points when pooling the two protein groups, creating a higher protein versus normal protein group comparison. There were no significant group effects for all remaining outcomes. High-quality protein supplementation >1.0 g·kg body mass ⁻¹ ·day ⁻¹ appears to have only a modest effect on the rate of recovery following EIMD, with a potential role in alleviating muscle damage, particularly in the later stage of recovery. Furthermore, the SPP supplement was not inferior to a high-quality protein source (whey protein), indicating that it may represent a sustainable and effective alternative for muscle recovery.