Does high blood sugar increase cancer risk?

A Swedish study suggests links between blood sugar levels and some cancers in women. Sanjay Tanday reports

What is the story?
Women who eat a diet rich in sugary foods are at an increased risk of developing cancer, according to media reports.

Swedish researchers found that women with elevated blood sugar levels were at greater risk of cancers of the pancreas, breast, skin, womb and urinary tract.

Women in the top 25 per cent range of blood sugar readings after fasting had a 26 per cent higher chance of developing cancer than those in the bottom quarter, say the papers.

Women with high blood sugar levels who had not yet gone through the menopause were also found to be at an increased risk of breast cancer.

No link between sugary foods and cancer was found in men.

Previous research has shown an increased risk of cancer in patients with type-2 diabetes. But the new findings demonstrate that, even without diabetes, rising blood sugar levels are associated with increased cancer risk in women.

The researchers advised that women should avoid eating processed foods, which are high in sugar, in favour of a diet full of fruit and vegetables.

What is the research?
The reports are based on a Swedish cohort study, which examined the association between hyperglycaemia and cancer risk in 65,000 men and women aged between 29 and 61.

Participants had their fasting and post-glucose load blood sugar levels measured at the start and end of the 13-year study.

Over the course of the study, an increase in blood glucose levels was observed, rising by an average of 17 per cent for fasting glucose and 6 per cent for post-load glucose, say the researchers.

Information from national and regional cancer registers identified 2,478 cases of cancer in the cohort during follow-up.

In women, the risk of developing cancer increased with elevated plasma glucose concentrations. Women in the highest quartile of fasting glucose — greater than 6.9mmol/l — had a 26 per cent higher risk of pancreatic and urinary tract cancers than those from the lowest quartile, with a level less than 6.1mmol/l.

Among women younger than 49 — presumed by researchers to be premenopausal — an increase in breast cancer risk with elevated fasting glucose levels was also observed. The exact reasoning behind the link was unclear.

No statistically significant link was observed between glucose levels and cancer risk in men. Although raised glucose levels in men appeared to protect against prostate cancer, the association was not statistically significant.

The researchers concluded that the findings of the study were in accordance with observations from other large-cohort studies, suggesting abnormal glucose metabolism is a general risk factor for cancer development.

What do the researchers say?
Lead researcher Dr Par Stattin, from the Umea University Hospital in Sweden, said: ‘The increase in risk of cancer associated with high blood glucose levels is caused by the concomitant high insulin levels.

‘But an increased risk of cancer was not seen in men because of the effect of high glucose levels on testosterone, believed to be a stimulating factor for prostate cancer initiation and early growth.’ High blood glucose levels are known to lower testosterone levels, he explained.

‘Regular exercise, a higher intake of vegetables and fruit, and less refined carbohydrates and saturated fats can decrease the risk not only of cardiovascular disease but also of cancer,’ said Dr Stattin.

What do other experts say?
Natasha Marsland, care manager at the charity Diabetes UK, said the study was interesting but more research was needed before a conclusion could be made on a link between blood glucose levels and cancer.

Dr Greg Martin, science and research manager at the World Cancer Research Fund UK, said: ‘The results are concerning but 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.’

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