Colas and other sweetened drinks have been under flak for making children overweight, hyperactive, gappy-toothed and osteoporotic — largely because fizzy drinks have replaced milk as the drink of choice in many homes — but new findings are now linking them to early puberty (maturation) in girls.
Drinking half-a-litre a day of cola, lemonade, iced tea or other sugar-sweetened drinks cause early puberty and increases breast cancer risks in girls by 5% for each year they mature earlier, shows new research from the Harvard Medical School in the journal Human Reproduction.
The study, which followed 5,583 girls aged 9 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. Girls who drank a lot of sugary drinks also tended to exercise less, eat more fats and carbohydrates and less proteins, but the researchers say that the association remained even after they controlled for these factors. It also held irrespective of their weight and body size (obesity is an established risk for early puberty).
The finding didn’t apply to fruit juice — which contains a sugar called fructose — but only to drinks sweetened with sucrose. Researchers recommend children switch to unsweetened milk or water and have sweetened drinks occasionally as a treat.
Added sugar spikes insulin levels in the blood, which over time makes tissues less sensitive to insulin and affects how the body converts sugar into energy. Scientists have still not identified the mechanics of how exactly this causes early puberty, but clinical trials show that the diabetes drug metformin, which helps the body regulate insulin, reverse early puberty.
Growing up too soon
Puberty normally starts between ages 9 and 13 in girls and between ages 11 and 14 in boys. Doctors diagnose ‘early’ or ‘precocious’ puberty when this natural biological process — hormonal changes, physical growth spurts and bone maturation — begins before age 8 in girls and before age 10 in boys.
Experts say that on average, children are hitting puberty earlier than they did two decades ago. In the US, twice as many girls reach puberty aged 7 as a decade ago, reported a study in the journal Paediatrics in 2011. The study found that of the 1,200 girls tracked for seven years in three US cities — the San Francisco Bay Area, Greater Cincinnati, and New York City — 10.4% of seven-year-olds had breast development consistent with the onset of puberty, compared with 5% in a 1997 study. The median age of breast development was 8.8 for African-American girls, 9.3 for Hispanic girls, 9.7 for Caucasian girls, and 9.7 for Asian girls. But more than ethnicity, being overweight was a stronger indicator of early maturation. Overweight and obese girls developed breasts about a year earlier than normal-weight girls.
In India, while the average age of starting menstruation has dropped by a few months to a year over the past two decades, other early signs of maturation — like breast development — are happening more than a year earlier, largely because of environmental triggers.
Exposure to chemicals that mimic the properties of the female hormone oestrogen is one of the reasons for fast-tracked puberty, the other is rising obesity. Oestrogen-like chemicals in pesticides, plastics and shampoos and growth hormones found in meat and milk are contaminating the environment and triggering early sexual development in girls. Pesticides and their byproducts — such as DDE (a breakdown product of DDT) and PCBs (polychlorinated biphenyls) — work like oestrogen and cause maturity in girls as young as eight.
If a child is showing early signs of puberty, an evaluation by an endocrinologist is recommended to rule out other risks. In a few cases, early puberty can be indicative of a tumour of the reproductive organs or that the brain has erroneously triggered the production of oestrogen. But a maturity spurt is accompanied by headaches, abdominal pain, or weight loss, or if there isn’t the growth spurt associated with puberty, there may be trouble.
There’s little you can do about environmental triggers, but you can protect your children by ensuring they are active and have a diet low in fat and sugar. It will not only lower their chances of maturing early but also protect them from several chronic health problems, such as high blood pressure, heart disease, diabetes and certain cancers.