Diabetes UK advised against seeking vitamin supplements at this stage
Doses of vitamin B1 (thiamine) can reverse early kidney disease in people with type 2 diabetes, research shows.
The team from Warwick University tested the effect of vitamin B1, which is found in meat, yeast and grain, on 40 patients from Pakistan.
The treatment stopped the loss of a key protein in the urine, the journal Diabetologia reports.
Charity Diabetes UK called the results "very promising" - but said it was too early for any firm conclusions.
The latest findings build on earlier work by the Warwick University team, showing that many diabetes patients have a deficiency of thiamine.
According to the researchers, this cheap and readily available supplement could benefit most people with diabetes - both type 1 and type 2 - as between 70% and 90% of people with diabetes are thiamine deficient.
In diabetes the small blood vessels in the body can become damaged.
When the blood vessels that supply blood to the kidneys are involved, the kidneys stop working correctly and important proteins, such as albumin, are lost from the blood into the urine.
A third of the patients in the study saw a return to normal urinary albumin excretion after being treated with high dose (300mg) thiamine taken orally each day for three months.
The experts say thiamine works by helping protect cells against the harmful effects of the high blood sugar levels found in diabetes.
Lead researcher Professor Paul Thornalley said: "This is the first study of its kind and suggests that correcting thiamine deficiency in people with diabetes with thiamine supplements may provide improved therapy for early-stage kidney disease."
They plan more work to confirm their findings.
Dr Iain Frame of Diabetes UK said: "Diabetes UK hopes a large clinical trial will be possible as results so far are very promising.
"However, we would like to stress that it's still too early to come to any firm conclusions about the role of vitamin B1 and we would not advise that people look to vitamin supplements to reduce their risk of kidney complications at this stage."
A person should be able to get all the thiamine they need from a normal healthy diet.