Dr Tracey Robertson
Previous work has shown increased insulin sensitivity, increased hepatic insulin clearance and lower postprandial insulin responses following treatment with resistant starch, a type of dietary fibre. The objective of this study was to further explore the effects of resistant starch on insulin secretion. Twelve overweight (BMI 28.2±0.4 kg/m(2)) individuals participated in this randomized, subject-blind crossover study. Participants consumed either 40 g type 2 resistant starch or the energy and carbohydrate-matched placebo daily for four weeks. Assessment of the effect on insulin secretion was made at the end of each intervention using an insulin-modified frequently sampled intravenous glucose tolerance test (FSIVGTT). Insulin and C-peptide concentrations were significantly higher during the FSIVGTT following the resistant starch compared with the placebo. Modelling of the data showed significantly improved first-phase insulin secretion with resistant starch. These effects were observed without any changes to either body weight or habitual food intake. This study showed that just four weeks of resistant starch intake significantly increased the first-phase insulin secretion in individuals at risk of developing type 2 diabetes. Further studies exploring this effect in individuals with type 2 diabetes are required.
There is much epidemiological evidence suggesting a reduced risk of development of type 2 diabetes (T2D) in habitual coffee drinkers, however to date there have been few longer term interventions, directly examining the effects of coffee intake on glucose and lipid metabolism. Previous studies may be confounded by inter-individual variation in caffeine metabolism. Specifically, the rs762551 single nucleotide polymorphism (SNP) in the CYP1A2 gene has been demonstrated to influence caffeine metabolism, with carriers of the C allele considered to be of a “slow” metaboliser phenotype. This study investigated the effects of regular coffee intake on markers of glucose and lipid metabolism in coffee-naïve individuals, with novel analysis by rs762551 genotype. Participants were randomised to either a coffee group (n=19) who consumed 4 cups/day instant coffee for 12 weeks or a control group (n=8) who remained coffee/caffeine free. Venous blood samples were taken pre- and post13 intervention. Primary analysis revealed no significant differences between groups. Analysis of the coffee group by genotype revealed several differences. Prior to coffee intake, the AC genotype (“slow” caffeine metabolisers, n=9) displayed higher baseline glucose and non esterified fatty acids (NEFA) than the AA genotype (“fast” caffeine metabolisers, n=10, p
Potatoes have been an affordable, staple part of the diet for many hundreds of years. Recently however, there has been a decline in consumption, perhaps influenced by erroneous reports of being an unhealthy food. This review provides an overview of the nutritional value of potatoes and examines the evidence for associations between potato consumption and non-communicable diseases. Potatoes are an important source of micronutrients, such as vitamin C, vitamin B6, potassium, folate, and iron and contribute a significant amount of fibre to the diet. However, nutrient content is affected by cooking method; boiling causes leaching of water-soluble nutrients, whereas frying can increase the resistant starch content of the cooked potato. Epidemiological studies have reported associations between potato intake and obesity, type 2 diabetes and cardiovascular disease. However, results are contradictory and confounded by lack of detail on cooking methods. Indeed, potatoes have been reported to be more satiating than other starchy carbohydrates, such as pasta and rice, which may aid weight maintenance. Future research should consider cooking methods in the study design in order to reduce confounding factors and further explore the health impact of this food.
This pilot study investigated the effects of chilling and reheating a pasta-based meal on the postprandial glycaemic response. In this single-blind crossover study, 10 healthy volunteers consumed identical pasta meals (pasta, olive oil and tomato sauce), served either freshly prepared, chilled or chilled/reheated, on three separate randomised occasions. Capillary blood samples were taken for two hours postprandially. A significant difference in glucose Incremental Area Under the Curve (IAUC) was observed (p = 0.006), with the greatest difference observed between the freshly cooked and chilled/reheated meals (p = 0.041). Significant differences in incremental peak glucose were also observed (p = 0.018). These results suggest that making simple changes to domestic food processing methods can reduce the glycaemic excursion following a pasta meal, with the potential for health benefit.
This pilot study explored the feasibility of a moderate time-restricted feeding (TRF) intervention and its effects on adiposity and metabolism. For ten weeks, a free-living TRF group (n=9) delayed breakfast and advanced dinner by 1.5-hours each. Changes in dietary intake, adiposity and fasting biochemistry (glucose, insulin, lipids) were compared to controls (n=7) who maintained habitual feeding patterns. Thirteen participants (29±2kg/m2) completed. The average daily feeding interval was successfully reduced in the TRF group (743±32 to 517±22 mins/day (p