Strawberries Improve Insulin Resistance and Related Cardiometabolic Markers in Adults with Prediabetes: A Randomized...

Prediabetes, as a risk factor for type 2 diabetes, as well as cardiovascular disease, is a burgeoning public health concern in the United States and worldwide. Dietary supplementation of polyphenol-rich berries has been demonstrated to be a feasible nutritional intervention in improving multiple cardiometabolic risk factors in adults. However, reported clinical trials are quite heterogeneous in study findings, and focus on prediabetes is lacking.

We examined the effects of a feasible dietary dose of strawberries (32 g freeze-dried strawberries ∼2.5 servings fresh strawberries) on glycemic control (primary) and cardiometabolic markers in adults with prediabetes in a 28-wk randomized controlled (no strawberry) crossover single-blinded study (12 wk/period).

A total of 25 adults were recruited in each period of the study, and anthropometric, clinical, and dietary data and blood samples were collected at baseline, 6 wk, 12 wk, 16 wk (washout), 22 wk, and 28 wk of the crossover study. A mixed-model analysis of variance was used to examine treatment effects accounting for the fixed effects of treatment, time, order of randomization, age, sex, ethnicity, body mass index (in kg/m²), dietary calories, and physical activity over time, as well as the baseline value for each outcome.

Strawberry period significantly improved glycemic control (serum insulin, insulin resistance, fasting glucose and glycated hemoglobin) and serum total cholesterol in an adjusted model compared with control; [adjusted mean difference 95% confidence interval (CI): -6.9 μIU/mL (-3.2, -10.7) μIU/mL, -2.3 (-1.3, -3.4), -8.9 mg/dL (-4.7, -13.2) mg/dL, and -0.2% (-0.1, -0.3)%, and -7.0 mg/dL (-2.0, -12.0) mg/dL, respectively, all P < 0.05]. Strawberry period also decreased body weight, high sensitivity C-reactive protein, and interleukin-6 in the adjusted model (all P < 0.05).

These findings show that a 2.5-serving dose of strawberries consumed daily for 12 wk can improve prediabetes status and overall cardiometabolic profile in adults.