Can strawberries help prevent diabetes? New trial shows promising results in prediabetic adults

By Priyanjana Pramanik, MSc.Reviewed by Susha Cheriyedath, M.Sc.Oct 21 2025

Researchers found that daily freeze-dried strawberry intake enhanced antioxidant biomarkers, lowered inflammation, and improved fasting glucose, suggesting a delicious way to support metabolic health and prevent diabetes progression.

Study: Dietary Strawberries Improve Serum Antioxidant Profiles in Adults with Prediabetes: A 28-Week Randomized Controlled Crossover Trial. Image Credit: Vidic Bojan / Shutterstock

In a recent study published in the journal Antioxidants, researchers evaluated the impacts of consuming freeze-dried strawberries (FDS) on antioxidant status, fasting blood glucose, and vascular inflammation indicators in prediabetic adults.

They found that consuming FDS daily for 12 weeks reduced inflammation markers and fasting glucose; multiple antioxidant biomarkers also improved significantly, highlighting strawberries as a practical dietary intervention that improved fasting glucose in this trial to strengthen antioxidant defense in prediabetic adults.

Background

Prediabetes represents a crucial stage between normal glucose metabolism and type 2 diabetes (T2DM), characterized by mild hyperglycemia that contributes to oxidative stress and inflammation.

Elevated blood glucose increases reactive oxygen species (ROS), which impair insulin function and damage pancreatic β-cells. Proinflammatory cytokines such as TNF-α also aggravate insulin resistance by disrupting glucose uptake and promoting inflammatory signaling pathways. These processes contribute to vascular dysfunction and atherosclerosis through increased endothelial adhesion molecules and decreased antioxidant enzyme activity.

Dietary antioxidants, including vitamins, polyphenols, and carotenoids, can counteract oxidative stress, though supplementation studies’ results are inconsistent due to differences in absorption and bioavailability. However, meta-analyses and clinical studies indicate that plant-based antioxidants improve total antioxidant capacity and glycemic outcomes in individuals with prediabetes or T2DM. Berries, including strawberries, are particularly rich in polyphenols like anthocyanins and ellagic acid that enhance antioxidant enzyme activity and insulin sensitivity.

Previous trials with FDS have shown improved antioxidant capacity and reduced inflammation in people with metabolic disorders. Building on this evidence, the present study aimed to test whether FDS supplementation could improve antioxidant defenses and reduce vascular inflammation in adults with prediabetes.

About the Study

Researchers conducted a randomized controlled crossover trial over 28 weeks at the University of Nevada, Las Vegas. Twenty-five adults meeting the American Diabetes Association’s criteria for prediabetes participated. Each participant completed both study phases, including 12 weeks of daily FDS intake and 12 weeks of control (no strawberries), separated by a 4-week washout period.

Participants were randomly assigned to begin with either FDS or the control condition. The intervention provided 32 g/day of FDS powder (equivalent to 2.5 servings of fresh strawberries), containing dietary fiber, polyphenols, flavonols, and anthocyanins.

Participants maintained their usual diet and physical activity throughout. Compliance was assessed by dietary logs, return of unused powder, and plasma ellagic acid levels. Blood samples were collected at baseline, 12, 16, and 28 weeks to measure fasting glucose, antioxidant enzymes, total antioxidant capacity, and vascular adhesion molecules using standardized assays. Carotenoid levels were analyzed via high-performance liquid chromatography (HPLC).

Statistical analyses used a mixed-model analysis of variance (ANOVA) adjusting for treatment, period, randomization order, age, sex, fasting glucose, and baseline values, providing a robust assessment of treatment effects. Power analysis indicated a sufficient sample size to detect significant changes in antioxidant and vascular markers.

Key Findings

The analysis showed that FDS supplementation significantly improved antioxidant and metabolic markers in adults with prediabetes. Compliance was high (> 85%), confirmed by plasma ellagic acid detection during the FDS phase.

Compared to the control period, FDS intake led to notable increases in antioxidant biomarkers, including superoxide dismutase, glutathione (GSH), antioxidant capacity (AC), and β-carotene, while no changes were seen in catalase, glutathione reductase, glutathione peroxidase, or α-carotene.

Fasting glucose levels also decreased significantly during the FDS period, showing improved fasting glycemic control. Additionally, FDS supplementation reduced vascular inflammation, evidenced by lower intercellular adhesion molecule (ICAM) and vascular cell adhesion molecule (VCAM) levels, whereas P-selectin and E-selectin were unaffected.

Correlation analyses revealed small, inverse relationships between ICAM and GSH, AC, and β-carotene, and between VCAM and AC, suggesting that better antioxidant status is linked to lower vascular inflammation. Only minor side effects, such as mild gastrointestinal discomfort and headaches, were reported.

Overall, the findings indicate that daily consumption of a realistic dietary dose of FDS can enhance antioxidant defense, reduce inflammation, and improve fasting glucose regulation in individuals with prediabetes.

Conclusions

This study shows that 12 weeks of FDS intake was associated with improvements in antioxidant capacity, fasting glucose, and vascular inflammation in adults with prediabetes.

These findings suggest that strawberries may be a practical, food-based dietary strategy with potential to help prevent progression to T2DM in clinical and everyday contexts. These improvements may result from polyphenols enhancing glutathione synthesis and superoxide dismutase activity, along with carotenoids and anthocyanins reducing oxidative stress and endothelial dysfunction.

Strengths of this analysis include the randomized crossover design, 12-week duration per phase, objective biomarker analyses, and use of a dietary-achievable FDS dose. However, limitations include the small, predominantly female sample, lack of a placebo drink and participant blinding, and recruitment from a single site, which may affect generalizability.

The trial was funded by the California Strawberry Commission. In summary, incorporating FDS into the daily diet may offer an accessible approach to improve antioxidant status, lower inflammation, and support glycemic health in adults with prediabetes.