Strawberries May Support Glucose Control and Reduce Inflammation in Prediabetes, Study Finds
Key Takeaways:
- Daily intake of freeze-dried strawberries for 12 weeks improved fasting glucose and reduced inflammation in adults with prediabetes.
- Antioxidant biomarkers including superoxide dismutase, glutathione, and β-carotene significantly increased during strawberry supplementation.
- Findings suggest strawberries could serve as a practical, food-based intervention to prevent progression to type 2 diabetes.
Strawberries and prediabetes: A promising link
A new randomised controlled trial published in Antioxidants has found that consuming freeze-dried strawberries (FDS) daily may help reduce fasting blood glucose and vascular inflammation in adults with prediabetes. The research also showed marked improvements in antioxidant status, highlighting the potential of strawberries as a simple dietary intervention for metabolic health.
The authors concluded that “strawberries may represent a practical dietary intervention that improves fasting glucose and strengthens antioxidant defence in adults with prediabetes.”
Understanding prediabetes and oxidative stress
Prediabetes represents a critical stage between normal glucose metabolism and type 2 diabetes mellitus (T2DM). It is characterised by mildly elevated blood glucose levels, which contribute to oxidative stress and low-grade inflammation.
High glucose levels increase reactive oxygen species (ROS), impairing insulin function and damaging pancreatic β-cells. Proinflammatory cytokines such as tumour necrosis factor-alpha (TNF-α) further aggravate insulin resistance by interfering with glucose uptake and triggering inflammatory pathways. Over time, these effects contribute to vascular dysfunction and atherosclerosis through increased endothelial adhesion molecules and reduced antioxidant enzyme activity.
Dietary antioxidants – including vitamins, polyphenols, and carotenoids – can neutralise oxidative stress. However, studies using supplements have produced inconsistent results due to differences in absorption and bioavailability. Evidence from clinical trials and meta-analyses indicates that plant-based antioxidants can improve total antioxidant capacity and glycaemic outcomes in people with prediabetes or T2DM.
Berries, particularly strawberries, are rich in polyphenols such as anthocyanins and ellagic acid, which are known to enhance antioxidant enzyme activity and improve insulin sensitivity. Previous studies using FDS have already shown benefits for inflammation and oxidative stress in metabolic disorders, providing a foundation for this new research.
Study design and methodology
Researchers at the University of Nevada, Las Vegas, conducted a 28-week randomised controlled crossover trial involving 25 adults who met the American Diabetes Association’s diagnostic criteria for prediabetes.
Each participant completed two 12-week phases: one with daily FDS intake and another control period without strawberries, separated by a four-week washout. Participants were randomly assigned to begin with either the FDS or control phase.
During the intervention, participants consumed 32 grams of FDS powder per day – equivalent to roughly 2.5 servings of fresh strawberries – containing dietary fibre, polyphenols, flavonols, and anthocyanins. They were instructed to maintain their usual diet and physical activity throughout the trial.
Compliance was carefully monitored using dietary logs, returned powder packets, and plasma ellagic acid levels. Blood samples were collected at baseline, 12, 16, and 28 weeks to measure fasting glucose, antioxidant enzyme activity, total antioxidant capacity, and vascular adhesion molecules using standardised assays. Carotenoid levels were analysed via high-performance liquid chromatography (HPLC).
A mixed-model analysis of variance (ANOVA) was used to evaluate treatment effects while accounting for treatment period, randomisation order, age, sex, fasting glucose, and baseline values. Power analysis confirmed the study was adequately powered to detect meaningful changes in metabolic and antioxidant markers.
Improvements in antioxidant and metabolic markers
Results showed high adherence rates, with more than 85% compliance confirmed by elevated plasma ellagic acid during the FDS phase.
Compared with the control period, strawberry supplementation produced significant improvements in several antioxidant biomarkers, including superoxide dismutase, glutathione (GSH), total antioxidant capacity (AC), and β-carotene. No significant changes were observed in catalase, glutathione reductase, glutathione peroxidase, or α-carotene.
Fasting blood glucose levels also decreased significantly during the FDS period, indicating better glycaemic control. Moreover, markers of vascular inflammation – particularly intercellular adhesion molecule (ICAM) and vascular cell adhesion molecule (VCAM) – were notably reduced. Levels of P-selectin and E-selectin remained unchanged.
Correlation analyses revealed modest inverse relationships between ICAM and GSH, AC, and β-carotene, and between VCAM and AC, suggesting that stronger antioxidant status was associated with reduced vascular inflammation.
Only minor side effects were reported, such as mild gastrointestinal discomfort and headaches.
Implications and limitations
The findings suggest that incorporating strawberries into the diet could help strengthen antioxidant defences, lower inflammation, and improve fasting glucose regulation in people with prediabetes. These benefits may be linked to polyphenols enhancing glutathione synthesis and superoxide dismutase activity, alongside carotenoids and anthocyanins reducing oxidative stress and endothelial dysfunction.
The study’s strengths include its randomised crossover design, objective biomarker measurements, and the use of a realistic dietary dose of strawberries. However, the relatively small and predominantly female sample, the absence of a placebo control drink, lack of participant blinding, and single-site recruitment limit the generalisability of results.
The study was funded by the California Strawberry Commission.
A food-based approach to diabetes prevention
In summary, consuming a daily portion of freeze-dried strawberries for 12 weeks led to measurable improvements in antioxidant capacity, fasting glucose, and vascular inflammation among adults with prediabetes.
While further research in larger, more diverse populations is needed, these results point to strawberries as a simple, accessible dietary strategy that could help prevent the progression from prediabetes to type 2 diabetes in everyday clinical and public health settings.
CCH insights
It is great to have research that shows health benefits from eating strawberries, because nearly everyone loves strawberries and there aren’t many foods that are extremely popular and good for us. However, the amount of freeze-dried strawberries consumed in this study would set you back about £20 per week – not a huge amount, but during a cost-of-living crisis might not be feasible for many people. This study was, unsurprisingly, funded by the California Strawberry Commission, and it begs the question whether eating other berries or certain other foods might not have a similar effect – but credit to the strawberry industry for making the effort to do the research.
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Green Tea Shows Significant Benefits for Glucose Metabolism and Muscle Health in Mice with Obesity
Key Takeaways:
- Green tea extract significantly improved insulin sensitivity, glucose tolerance, and muscle preservation in mice with obesity, even when they continued consuming a high-calorie diet.
- The study controlled for temperature effects, providing clearer evidence that green tea’s metabolic benefits are independent of cold-induced energy expenditure.
- Findings suggest a potential role for green tea as a safe, accessible adjunct to obesity treatment in humans, though exact dosing for people remains to be established.
Ancient beverage, modern research
Green tea, long valued for its medicinal and antioxidant properties, continues to attract scientific interest for its impact on metabolic diseases such as obesity and type 2 diabetes. A recent study led by Professor Rosemari Otton from the Interdisciplinary Graduate Programme in Health Sciences at Cruzeiro do Sul University in São Paulo, Brazil, offers new insights into how green tea affects metabolism.
Otton, who has dedicated over 15 years to the study of green tea, explained that her initial curiosity stemmed from the popular belief that green tea promotes weight loss. The findings of her latest research, published in Cell Biochemistry & Function, reinforce the potential of green tea as a therapeutic adjunct in managing obesity.
Study design and green tea administration
The research team first fed mice a high-calorie diet for four weeks, including both a fat-rich diet and a “cafeteria diet” to replicate a Western-style eating pattern. “We give them chocolate, filled cookies, dulce de leche, condensed milk… In other words, the same type of food that many people consume on a daily basis,” said Otton.
After this induction phase, the mice continued on the high-calorie diet for 12 weeks, with some receiving a standardised green tea extract at 500mg per kilogram of body weight via intragastric gavage. This method ensured precise dosing. “If we put it in water, for example, we’d have no way of knowing how much the animal actually ingested,” Otton explained.
For humans, this dose would equate to approximately 3 grams of green tea daily — roughly three cups. However, Otton cautioned that not all commercial products meet required standards:
“Ready-made tea bags do not always guarantee the quantity or quality of the compounds. The ideal for consumption would be to use standardised green tea extract, like those found in compounding pharmacies. This is a concentrated way of using the plant, with a guarantee of the presence of flavonoids, which are the health-beneficial compounds present in the green tea plant.”
Controlled conditions for reliable results
A distinctive feature of the study was the use of a thermoneutral environment at 28°C, eliminating confounding effects caused by chronic cold exposure. Mice are typically kept at around 22°C in animal facilities, a temperature that triggers energy expenditure to maintain body heat.
“Excessive cold activates compensatory regulatory mechanisms in the animals’ bodies, causing them to expend more energy to stay warm. This can mask the real effects of any substance,” Otton explained. “By maintaining thermoneutrality, we were able to see the effects of green tea in a ‘clean’ way, without environmental interference.”
A previous study published in European Journal of Nutrition (August 2022) found that obese mice treated with green tea lost up to 30% of their body weight — a reduction Otton described as highly significant:
“If a person loses 5% to 10% of their body weight, that’s already a lot. So this result in animals is very significant.”
Preservation of muscle health
One of the most striking findings of the latest study was the preservation of muscle fibre morphology. Obesity often leads to a reduction in muscle fibre diameter, but green tea helped maintain muscle structure.
“One way to assess muscle function is to look at fibre diameter. If it increases, we have more active muscle components. Green tea managed to maintain this diameter, showing that it protects muscle against the harmful effects of obesity,” Otton said.
Genetic and metabolic insights
The study also explored gene expression related to glucose metabolism. Green tea treatment enhanced the expression of genes such as Insr, Irs1, Glut4, Hk1, and Pi3k, all of which play a role in glucose uptake and utilisation in muscle tissue. Additionally, the activity of lactate dehydrogenase (LDH), an enzyme vital for glucose metabolism, was restored.
Otton noted that green tea appeared to have a selective effect:
“It makes obese animals lose weight but keeps lean animals at a balanced weight. This shows that the tea seems to need an environment with excess nutrients to act, which supports the hypothesis that it acts directly on fat cells.”
Synergy of bioactive compounds
Green tea contains dozens of bioactive compounds, and attempts to isolate them have proven less effective than using the whole extract.
“We’ve tried to separate these compounds and study their effects individually, but the whole extract is always more effective. There’s a synergy between the compounds that we can’t reproduce when they’re isolated,” Otton explained.
One mechanism under investigation involves adiponectin, a protein secreted by fat cells that regulates inflammation and metabolism. In mice genetically modified to lack adiponectin, green tea showed no effect — pointing to adiponectin as a key mediator of its benefits.
Translating findings to human health
Despite these promising findings, Otton cautioned that safe and effective doses for humans have yet to be established, owing to variability in extracts and individual responses. She stressed the importance of long-term, habitual consumption rather than expecting rapid results:
“The ideal is chronic consumption, as we see in Asian countries. In Japan, for example, people consume green tea every day, throughout their lives, and obesity rates are low. But this is different from drinking tea for five months and expecting a miraculous weight loss effect.”
Otton also emphasised the importance of accessible and safe treatment options:
“The idea is to have safe, natural, effective, and high-quality compounds. The Camellia sinensis plant offers this. We’re still studying all the compounds involved, but there’s no doubt that green tea, as a plant matrix rich in flavonoids, has important therapeutic potential.”
The road ahead
Finally, Otton underscored the need for caution when translating animal research to clinical practice:
“What we see in animals doesn’t always reproduce in humans. But if we want to make this translation to real life, we need to think about all the details, such as ambient temperature. It’s these precautions that increase the validity of our data. We’re far from having all the answers, but we’re getting closer and closer.”
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