Type 2 diabetes mellitus (T2DM) is the most common form of DM and its prevalence is increasing worldwide. Because it is a progressive disease, prevention, early detection and disease course modification are possible. Diet plays a critical role in reducing T2DM risk. Therapeutic dietary approaches routinely recommend diets high in plant foods (i.e., vegetables, fruits, whole-grains). In addition to essential micronutrients and fiber, plant-based diets contain a wide-variety of polyphenols, specifically flavonoid compounds. Evidence suggests that flavonoids may confer specific benefits for T2DM risk reduction through pathways influencing glucose absorption and insulin sensitivity and/or secretion. The present review assesses the relationship between dietary flavonoids and diabetes risk reduction reviewing current epidemiology and clinical research. Collectively, the research indicates that certain flavonoids, explicitly anthocyanins and flavan-3-ols and foods rich in these compounds, may have an important role in dietary algorithms aimed to address diabetes risk factors and the development of T2DM.

Strawberries are a dietary source of anthocyanins, particularly pelargonidin glycosides. Dietary anthocyanins have received increasing attention among researchers and consumers due to their health benefits. The oral bioavailability of anthocyanins is reported to be low and various dietary factors may influence their oral bioavailability further. Milk is suggested to reduce (poly)phenols’ oral bioavailability. However, the effect of milk on anthocyanin oral bioavailability remains uncertain. Likewise, mixed nutrient meals may influence the oral bioavailability of anthocyanins. Therefore, the purpose of this study was to assess the effect of milk on the oral bioavailability and other pharmacokinetic (PK) variables of strawberry anthocyanins consumed with and without a meal. Nine healthy participants consumed a strawberry beverage prepared in milk or water with a standard meal on two occasions. On two additional occasions, the beverages were given to a subset (n = 4) of participants to determine the impact of the meal on anthocyanin PK variables, including oral bioavailability. Independent of the meal, beverages prepared in milk significantly reduced the peak plasma concentrations (C_max) of pelargonidin-3-O-glucoside (P-3-G), pelargonidin-glucuronide (PG) and pelargonidin-3-O-rutinoside (P-3-R), as well as the PG and P-3-R area under the curve (AUC) (p < 0.05) compared to beverages prepared in water. Milk did not influence the oral relative bioavailability of pelargonidin anthocyanins under meal conditions; however, the oral relative bioavailability of pelargonidin anthocyanins was reduced by ∼50% by milk under without meal conditions (p < 0.05). Consuming strawberry beverages made with milk and consuming those made with water with and without a meal influenced different aspects of strawberry anthocyanin PKs. The significance of this effect on clinical efficacy requires additional research.

Diets emphasizing unsaturated fat and high fiber are associated with reducing cardio-metabolic risk factors. Avocados are rich in mono- and poly-unsaturated fats and fiber. Assess replacement of carbohydrate energy with avocado energy for 12 weeks on glucose homeostasis and cardio-metabolic risk factors in self-selecting free-living adults with overweight or obesity and insulin resistance. In a single-center, randomized, 2-arm, controlled, 12-week parallel trial, adults [n = 93, male: female 39:54, mean ± SD age 42 ± 12 years, BMI 32.6 ± 3.9 kg/m2, homeostatic assessment for insulin resistance, 2.7 ± 1.7] were counseled to exchange avocado (AV) or control food (C, low-fat low-fiber energy-matched) for carbohydrate food in their usual diet for 12 weeks. The primary outcome was the change in Matsuda Insulin Sensitivity Index (MISI) after 12-week interventions. Secondary outcomes were changes in fasting and post-oral glucose tolerance test glycemic variables, fasting lipids, endothelial activation and inflammation markers. ASA24 dietary assessment tool captured weekly dietary intake. Intervention effects were mainly determined by analysis of covariance using PC-SAS, 9.4. Dietary total, mono- and poly-unsaturated fat, fiber, and vegetable intake were higher in the AV group compared to C group (P < 0.05), and no change in body weight or composition was observed (P > 0.05). Differences between the changes in MISI after AV compared to C were not different (Δ0–12 week, P = 0.1092). Differences in fasting insulin (Δ0–12 week, P = 0.0855) and improved HbA1c (Δ0–12 week P = 0.0632) after AV vs C were suggested. C-reactive protein was significantly lower after AV vs C at 12 weeks (P = 0.0418). Select biomarkers of endothelial activation and lipoproteins by NMR were also influenced by AV vs C food intake. Avocado intake was associated with a healthier dietary pattern and trends favoring improved glucose control and reduced biomarkers of cardiometabolic risk when replacing avocado energy for carbohydrate energy in free-living adults with overweight or obesity and insulin resistance.

Pharmacokinetic (PK) evaluation of polyphenolic metabolites over 24 h was conducted in human subjects (n = 13, BMI = 22.7 ± 0.4 kg/m²) after acute mango pulp (MP), vitamin C (VC) or MP + VC test beverage intake and after 14 days of MP beverage intake. Plasma and urine samples were collected at different time intervals and analyzed using targeted and non-targeted mass spectrometry. The maximum concentrations (C_max) of gallotannin metabolites were significantly increased (p < 0.05) after acute MP beverage intake compared to VC beverage alone. MP + VC beverage non-significantly enhanced the C_max of gallic acid metabolites compared to MP beverage alone. Pyrogallol (microbial-derived metabolite) derivatives increased (3.6%) after the 14 days of MP beverage intake compared to 24 h acute MP beverage intake (p < 0.05). These results indicate extensive absorption and breakdown of gallotannins to galloyl and other (poly)phenolic metabolites after MP consumption, suggesting modulation and/or acclimation of gut microbiota to daily MP intake.

Resistant starch (RS) is a variant of starch that is indigestible by human enzymes and has been acknowledged for multiple physiological benefits including attenuation of postprandial glycemia when incorporated into foods. Distarch phosphate is a RS type 4 (RS4) containing phosphodiester cross-links within and between starch molecules. Considering the importance of RS to human health, the present study aimed to investigate the dose response effect of a novel RS4 (potato-derived distarch phosphate – (VERSAFIBE 1490™) on acute postprandial glycemic responses compared with energy/available carbohydrate and sugar-matched control. The study was designed as a controlled, single-center randomized, single-blinded, cross-over trial, in which 31 healthy adults consumed a baked breakfast cereal bar containing 0, 10 or 20 g RS4 followed by serial blood samples over two hours to determine glucose and insulin concentrations and calculate the incremental area under the curve (iAUC). Results suggest that the addition of RS4 did not reduce iAUC glucose or insulin responses significantly (P > 0.05) at the doses provided. No significant changes in the glucose or insulin maximum concentration (C_max) and time to reach maximal glucose and insulin concentrations (T_max) were observed (P > 0.05). Overall, this particular RS4 did not affect measures of glycemia in healthy individuals at doses provided in ready-to-eat baked-good.