Artificial light linked to obesity, diabetes and cancer – study

Streetlights can make you fat, according to a recent study.

Artificial light - such as the bright streetlamp outside your window – is one of the factors that can lead to health risks caused when your body-clock is interrupted, according to the latest research from the University of Otago.

Jetlag, shift-work, or anything else that interferes with the circadian rhythm has a strong negative effect on blood-sugar levels, according to Alexander Tups, an associate professor of endocrinology who oversaw the research.

In the study, one group of mice had their circadian rhythm disrupted repeatedly, and a second group were fed a high-fat diet. After 12 disruptions, the blood-sugar levels were found to be “much higher” in the first group than the second.

“Even these extremely obese mice had lower blood-glucose levels than the ones with disrupted circadian rhythms,” said Mr Tups.

He said the increase in exposure to artificial light in daily life from laptop screens to electronic billboards was harming a person’s ability to produce the sleep hormone, melatonin.

“It’s secreted at night. If we’re exposed to bright light at night then melatonin is not secreted and the body-clock gets out of sync,” said Mr Tups.

“That is bad for our bodies; obesity and type-two diabetes may emerge, and cancer risk might be increased.”

While the Otago study did not analyse cancer risk resulting from disrupted sleep patterns, more research is emerging linking the two.

A study completed last year by the University of Texas found that 50% of liver tumours lacked proteins which regulated circadian rhythms. Once these proteins were introduced, the tumour cells died.

The report stated that the researchers were able to minimise the growth of liver cancer by manipulating the circadian clock.

“Shift work is classified as a carcinogen in Denmark,” said Mr Tups.

New Zealand should follow the lead of countries that recognise the ill-effects of sleep cycle interference, he said.