Girls who frequently drink fizzy sugary drinks are putting themselves at risk of breast cancer, research warns.
Drinking just one-and-a-half cans a day causes early puberty and that increases their cancer risk. For each year they mature earlier, it is estimated breast cancer risk increases by five per cent.
The Harvard Medical School study of 5,583 girls aged nine to 14 found those who drank more than 1.5 servings of sugary drinks a day had their first period 2.7 months earlier than those who drank two or fewer drinks a week.
Drinks with added sugar are said to ramp up insulin concentration in the body, which in turn results in higher concentrations of sex hormones, normally associated with periods starting earlier.
Associate Professor Karin Michels said: “Our study adds to increasing concern about the widespread consumption of sugar-sweetened drinks among children and adolescents.
“The main concern is about childhood obesity, but our study suggests that age of first menstruation (menarche) occurred earlier, independently of body mass index, among girls with the highest consumption of drinks sweetened with added sugar.
“These findings are important in the context of earlier puberty onset among girls, which has been observed in developed countries and for which the reason is largely unknown.
“Our findings suggest that frequent consumption of sugar-sweetened beverages may be associated with earlier menarche.
“A one-year decrease in age at menarche is estimated to increase the risk of breast cancer by five per cent… thus, a 2.7 month-decrease in age at menarche likely has a modest impact on breast cancer risk.
“Most importantly, the public health significance of sugar-sweetened beverages consumption at age at menarche, and possibly breast cancer, should not be overlooked, since, unlike most other predictors of menarche, sugar-sweetened beverages consumption can be modified”
The study published in the journal Human Reproduction found those who drank more than 1.5 servings of sugar-sweetened drinks a day were 24 per cent more likely to start their first period a month earlier.
The average age of the first period among girls consuming the most sugary drinks was 12.8 years, compared to 13 years for those drinking the least.
At the time of joining the study none of the girls had started their periods.
When researchers adjusted results to take account of BMI, the effect of sugary drink consumption on the age of onset of menstruation was still significant.
Girls consuming the most were 22 per cent more likely to start their first period in the next month compared to girls consuming the least.
Although greater caffeine intake has also been associated with earlier periods, the researchers found that total sugar or caffeine intake did not explain their results, and that it was the added sugar in drinks that was the culprit.
Dr Michels added: “This research shows that it’s even more important that children switch to water.
“We have recently linked early menstruation with childhood obesity, but this study shows that it’s also associated with other disorders as well.”