Do sugary drinks trigger early puberty in girls?
点击量： 时间：2017-10-03 05:01:05
By Linda Geddes (Image: Getty) Girls who drink more sugary beverages start their periods earlier than girls who consume fewer. That’s the finding of a new study, and it suggests that this consumption is somehow linked to the onset of puberty. The association remained even once the girls’ weight and height had been controlled for. But how robust is the link? So, are girls really entering puberty earlier? It seems that way. Girls usually enter puberty somewhere between the ages of 8 and 14, although some start sooner. The average age that girls start their periods is 12. A 2010 study found that 10 per cent of white 7-year-olds had breast development consistent with the onset of puberty; twice as many as in 1997. Why is it a problem if girls are starting earlier? Early puberty can be psychologically traumatic for girls if they are developing faster than their peers. There is also some evidence linking early puberty to increased risk of breast cancer. However, there is currently no evidence linking childhood consumption of sugary drinks to breast cancer in later life. Ok, so what is driving the earlier onset? It is unclear. Many of the changes girls experience at puberty are driven by the hormone oestrogen. Exposure to oestrogen-containing shampoos, and other chemicals that mimic the hormone’s effects – including those found in some plastics – have been blamed. But probably the most convincing argument is that rising rates of childhood obesity are the culprit, because body fat can produce oestrogen. Ah, so that’s why the study found an association with sugary drinks? Possibly. The study found that girls who drink more than 1.5 sugar-sweetened beverages a day started their periods 2.7 months earlier on average than girls who consumed them twice a week or less. The finding didn’t apply to fruit juice – which contains a sugar called fructose – only to drinks sweetened with sucrose. The study followed 5583 girls who had not begun their periods at the start of the study. They were given questionnaires to fill out about their health, diet and lifestyle, and then followed up annually with a similar questionnaire, which also recorded whether or not they had started menstruating. Girls who drank a lot of sugary drinks also tended to do less exercise, consumed more calories overall, and ate less protein, but the researchers say that the association remained even after they controlled for these factors. It also remained once the girls’ weight and height in the form of their body mass index (BMI) was controlled for. This suggests the mechanism is not as simple as sugary drinks lead to weight gain and more body fat, in turn leading to earlier puberty. What is the mechanism then? That’s one of the problems: we simply don’t know. Karin Michels at the Harvard T. H. Chan School of Public Health, who supervised the study, says that sucrose in sugary drinks causes a spike in the hormone insulin, which controls blood sugar levels. Over time this may make the body’s tissues less sensitive to the hormone, with consequences for metabolism. Quite why this would lower the age of menstruation isn’t understood, but a drug called metformin, which makes the body more sensitive to insulin, has been shown to reverse early puberty in clinical trials. What’s now needed are larger studies to see if these results can be replicated, as well as studies that measure hormone levels in girls after they drink sweetened drinks, to see if a plausible mechanism can be established. So what message should parents take from this study? The observed differences between girls are population averages, so even if the association is proven, it doesn’t necessarily follow that an individual girl who consumes a lot of sweetened drinks will start puberty earlier. The difference in starting time isn’t huge so not something to worry too much about in itself. However, given the known links between sugary drinks and childhood obesity, it would be wise to limit their consumption to an occasional treat. Journal reference: Human Reproduction, DOI: 10.1093/humrep/deu349 More on these topics: