Bilberry fruit, blood fats and brain insulin receptors in diabetic rats
What it found
In diabetic rats, bilberry fruit raised the number of insulin receptors on brain nerve cells but did not lower blood sugar.
In healthy rats, it lowered one type of bad cholesterol.
What they found
Animal and lab studies
Brain insulin receptors in rats
Diabetic rats that ate bilberry had more insulin receptors on their brain nerve cells than diabetic rats on normal feed. These receptors help nerve cells respond to insulin. The effect was seen only in the cell fluid, not the cell nucleus.
Blood sugar in diabetic rats
Eating bilberry did not lower blood sugar or fructosamine levels in the diabetic rats. Blood sugar actually rose after 6 weeks, which the authors link to severe pancreas damage from the chemical used to cause diabetes.
Cholesterol in healthy rats
Healthy rats fed bilberry saw a large drop in LDL-cholesterol over 6 weeks, falling from 27.0 mg per 100 mL to 7.3 mg per 100 mL. This level was also much lower than in healthy rats eating normal feed.
Good cholesterol across groups
HDL-cholesterol rose in all rat groups after 6 weeks, whether they ate bilberry or not. The authors suggest the standard rodent feed, which contains 5% fibre, likely caused this rise rather than the fruit.
Other findings
Antioxidant content measured
Lab tests confirmed the bilberries were rich in polyphenols, measuring 611.45 mg per 100 g fresh weight. The fruit also showed strong ability to neutralise free radicals in two different lab assays.
What the authors conclude
- They conclude that adding bilberry fruit to the diet during diabetes can change brain nerve cells by increasing the number of insulin receptors.
- They note that blood test results were mixed, and bilberry did not clearly improve blood markers in the diabetic rats.
- They advise that more research is needed to find out whether these brain changes actually protect nerve cells from diabetes-related damage.
How it was done
Long-term high blood sugar can damage the brain and change how nerve cells respond to insulin. Bilberry is rich in antioxidant plant compounds and has long been used in traditional medicine for diabetes, so the authors wanted to see if it could protect brain cells in diabetic animals.
The researchers studied 36 male Wistar rats over 6 weeks. Some rats were made diabetic with a chemical injection, while others stayed healthy. Half of each group ate standard feed, and half had some feed replaced with mashed bilberry pulp at 16 g per kg of body weight daily.
What it can’t tell you
- These findings come from rats, so they cannot show what happens in people who eat bilberries.
- The study lasted only 6 weeks, so scientists do not yet know if longer use would have different effects.
- Because the rats were made diabetic with a chemical injection, the results may not match how diabetes develops naturally.
Who paid
- Authors work at
- University of Life Sciences, Poland
The paper
- Title
- Insulin receptors in the CA1 field of hippocampus and selected blood parameters in diabetic rats fed with bilberry fruit
- Type
- Study
- Evidence
- Animals and lab studies
- Summarised from
- Full text
- Cite
- Matysek M, Borowiec K, Szwajgier D, Szalak R, Arciszewski MB (2021). Insulin receptors in the CA1 field of hippocampus and selected blood parameters in diabetic rats fed with bilberry fruit. Annals of agricultural and environmental medicine. doi:10.26444/aaem/128879Free full textPubMed 34558266DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error