A simple vitamin deficiency may be the cause of many of the side effects of diabetes, a study suggests.
Researchers found people with the disease expelled thiamine - vitamin B1 - from their bodies at 15 times the normal rate in a study of 94 people.
The Warwick University team said thiamine helped ward off complications such as heart disease and eye problems, the Diabetologia journal said.
Experts said diet supplements could potentially help people with diabetes.
It is the first time a deficiency of the vitamin, which is found in meat, yeast and grains, has been identified in people with diabetes.
It has been missed in the past because of the way thiamine levels were measured.
Traditionally, the activity of an enzyme called transketolase in red blood cells has been used to indicate thiamine levels.
But the researchers found that increased activity - usually a sign of high thiamine levels - was also associated with the body's response to deficiency.
Instead, the team measured thiamine levels in blood plasma and found concentrations were 76% lower in people with type 1 diabetes and 75% lower in people with type 2.
Thiamine is key to warding off vascular problems such as kidney, retina and nerve damage as well as heart disease and stroke.
It works by helping protect cells against the effect of high glucose levels.
Trials are now being carried out to see if supplementing diet with thiamine could return levels to normal.
Lead researcher Professor Paul Thornalley said: "It is early days, but it could have a huge difference.
"Supplementing diets could be an effective way of minimising the risk of these complications."
Matt Hunt, of Diabetes UK, which helped to fund the study, said more research was needed.
But he added: "The study could potentially have very exciting outcomes.
"Around 80% of people with diabetes die of cardiovascular disease and diabetes is the leading cause of blindness in the UK's working age population.
"Therefore, any research that could help must be looked at seriously."