Women with high blood sugar levels are at an increased risk of developing cancer, a major European study finds.
Junk food contains high levels of sugar
Diabetes causes high blood sugar, as does eating too much sugary food.
The Swedish research, which looked at 64,500 people, linked raised blood sugar with pancreas, skin, womb, and urinary tract cancers in women.
Diabetes experts said more evidence was needed to confirm the link. The study comes as other work links a high fat diet to increased breast cancer risk.
In this study, carried out by a team at the University of Umea, high blood sugar was also linked to breast cancer risk - for women under 49.
Overall, the research found women in the top 25% range of blood sugar readings after fasting had a 26% higher chance of developing cancer than those in the bottom quarter.
The research was part of the Vasterbotten Intervention Project, a major health investigation in Sweden.
Participants were invited into the study at the ages of 40, 50 or 60 in the mid-1980s.
Fasting blood sugar levels were measured, as well as the amount of sugar in the blood after an infusion of glucose. Overall, the study spanned 13 years.
During the course of the research, 2,478 cases of cancer were identified.
The research also found clear evidence of higher rates of hyperglycaemia - unusually high blood sugar levels - with increasing age.
The researchers, led by Dr Par Stattin, said: "Abnormal glucose metabolism was associated with a statistically significantly increased risk of cancer overall in women but not in men."
In men, raised blood sugar levels in men appeared to protect against prostate cancer, though not to a significant degree.
The research was partly paid for by the World Cancer Research Fund (WCRF).
Dr Greg Martin, science and research manager for WCRF UK, said: "The results of this research are concerning.
"However, they are important because if women are aware of the facts, they are likely to be more motivated to change their lifestyle if their blood sugar levels are too high.
"And the good news is that it is possible to reduce your blood sugar levels by eating a healthy balanced diet with lots of fruit and vegetables and maintaining a healthy weight.
"We know that up to 40% of cancer cases can be prevented by this type of healthy lifestyle, so this is just another reason for people to make those small changes that could make a big difference."
Previous research has shown an increased risk of cancer in patients with type 2 diabetes.
However, this new research shows that even when people do not have the condition, rising blood sugar levels are associated with increased cancer risk in women.
Natasha Marsland, care manager at the charity Diabetes UK, said: "This is an interesting study.
"However, much more research needs to be done before we can conclude if there is a link between high blood glucose levels and cancer.
"A simple blood test at your doctor's is the best way to find out if you have a high blood glucose level.
"Having a high blood glucose level can indicate diabetes but this is not always the case.
"If someone is white and over 40, or over 25 from a black or South Asian background, and has either a family history of Type 2 diabetes or is overweight, they should consider asking their doctor for the simple blood test to determine whether or not they have diabetes."