Strawberries and Risk of Diabetes in Adults

Strawberries can be categorized as a functional food based on results from several clinical trials in improving cardiometabolic health beyond providing nutrition. Recent studies identify the role of strawberries in improving insulin resistance and risks of type 2 diabetes which urgently warrants further investigation, keeping in view the huge public health burden of diabetes in the US. In this study, the investigators propose to investigate the effects of a dietary achievable dose of strawberries on glycemic control, insulin resistance, and HbA1c (primary variables) and biomarkers of inflammation and endothelial function in a 28- week controlled crossover study.

Strawberries are popularly consumed fruits in the US and are a rich source of several bioactive compounds with demonstrated health benefits in T2D and cardiovascular disease (CVD). Based on previously reported studies, strawberries have been shown to improve elevated lipid profiles/dyslipidemia, oxidative stress and inflammation in adults with the metabolic syndrome or prediabetes. In a recently reported study, strawberries at a dose of two-and-a-half servings per day for four weeks was shown to significantly reduce insulin resistance and serum adipokines in obese adults. These results conform to only a few reported trials using strawberries in adults with cardiometabolic risks. While these study findings are clinically meaningful, these warrant urgent investigation in trials of longer duration specifically targeting adults with impaired fasting glucose (vs. other features of the metabolic syndrome) as well as adults with diagnosed T2D with poor glycemic control despite taking medications. Furthermore, to the best of our knowledge, only one clinical trial has been reported on the role of strawberries in improving glycemic control, oxidative stress, and inflammation in adults with T2D. While these results are encouraging, they lack generalizability due to the short duration of the study (six weeks) that precludes accurate changes in glycated hemoglobin (HbA1c) as a stable biomarker of glucose control. Based on these gaps in the existing literature, the investigators will examine the effects of strawberry supplementation at a dose of 2.5 servings/day for 12 weeks on glycemic control and related cardiometabolic profiles in prediabetes in a randomized controlled crossover trial.

Whole strawberries are freeze-dried to form a powder with improved shelf life that will be used in this research study. Strawberry powder will be provided by the California Strawberry Commission (Watsonville, CA)

Inclusion Criteria: At least 18 years of age Waist size greater than 40 inches in men or 35 inches in women Blood glucose greater than 100mg/dL but less than 126 mg/dL or glycated hemoglobin less than 6.5% Not on diabetes medications Normal liver and kidney function tests Exclusion Criteria: Allergy to strawberries Smoke or drink alcohol on a regular basis Pregnant or lactating.