Vitamin C could help reduce some of the complications associated with diabetes, research suggests.
Vitamin C, found in citrus fruit, could help diabetic patients
However, a University of Warwick team found the blood pressure-lowering drug Telmisarten had the same effect - and might be a safer alternative.
Both help "mop-up" tissue-damaging molecules called free radicals which are over-produced in diabetes patients.
Experts warned the work, published in two diabetes journals, was no reason to start taking vitamin C supplements.
High blood-sugar levels associated with type-1 diabetes can cause changes to mitochondria - the energy-producing boiler rooms of cells.
These changes trigger an increase in the amounts of free radicals produced by the mitochondria.
The Warwick team found these effects persisted long even after blood-sugar levels were normalised.
This suggests free radicals continue to be produced in diabetic patients, and can damage tissues leading to possible amputations, heart disease or blindness.
Lead researcher Professor Antonio Ceriello said the finding confirmed the importance of identifying and treating high blood sugar levels - hyperglycaemia - as soon possible.
In a second study, the Warwick team found that it was possible to normalise free radical levels by first treating people with type 1 diabetes with insulin, and then with vitam C or Telmisarten.
Vitamin C neutralises free radicals, while Telmisarten stimulates the natural removal of the molecules by cells.
However the treatments are only effective if continued in the long-term.
Professor Ceriello said this was important because long-term treatment with vitamin C could be dangerous, making the blood-pressure lowering drug potentially more useful.
The team are now looking for other drugs to try to permanently stop the free radical production.
Matt Hunt, Science Information manager at Diabetes UK said: "This was a fairly small study and based on a theory that there is a molecular memory of diabetes, a theory which is interesting but relatively new and as yet, not established.
"At this early stage we would view these results cautiously and call for further research.
"We would certainly not encourage people to start taking vitamin C supplements based on the findings of this research."