Skip the soft drinks, period

There are plenty of reasons to shun soft drinks and sugary beverages. Studies have shown they can promote cavities, foster weight gain and even weaken bones. Research now suggests that downing sweet drinks daily also can speed up puberty in girls.

The findings come from a five-year study of more than 5,000 girls from across the United States. Those who drank a sugar-sweetened beverage each day had their first menstrual cycle almost three months earlier than did girls who consumed far fewer sugary drinks. The start of menstruation is a key sign that a girl’s body is maturing into womanhood.

About a century ago, most girls didn’t have their first period until well into their teens. No longer. Many girls reach this milestone before turning 13.

Researchers have wondered why. And they’ve looked to a hormone called estrogen. During the two- to three-year period of development known as puberty, a girl’s reproductive organs rev up their production of this hormone. That surge causes her to grow physically. Her body also changes, such as developing breasts. Eventually she’ll contend with monthly cycles and their accompanying mood swings.

The body’s fat cells also produce estrogen. So it made sense when some research pointed to body weight and diet as factors that might affect when a girl gets her first period. Still, scientists hadn’t homed in on the possible impacts of specific foods. Or drinks.

At least they didn’t until researchers at the Harvard School of Public Health in Boston, Mass., mined some dietary information on 9- to 14-year-old U.S. girls. Their new analysis finds that sugary drinks may play a role. Karin Michels and her team reported their findings early online January 27 in the journal Human Reproduction.

What the surveys showed

In 1996, questionnaires were mailed to a cross-section of American girls whose mothers were participating in a larger study of female nurses. The National Institutes of Health funded that study to investigate factors that influence weight change. The written survey asked each girl how often, in the past year, she had eaten certain foods. It asked about French fries, bananas, milk, meat, peanut butter — 132 items in all. For each food, the girls marked one of seven frequencies. The options ranged from never to six times a day.

The girls reported their height and weight. They answered questions about their physical activity — such as how much time they spent exercising, playing sports, watching TV or reading. Finally, each girl indicated whether she had gotten her first period that year, and if so, at what age. Participants were asked to fill out follow-up questionnaires each year until they got their first period.

As an epidemiologist, Michels works as a sort of data detective. Her job is to sleuth out clues to health issues. In this instance, she and her team mined those questionnaires for information on what girls who got their periods early did differently, if anything, from those who developed somewhat later.

Girls who guzzled 12 ounces (or more) of sugary soft drinks each day were, on average, 2.7 months younger when they had their first period, the researchers found. That’s compared to girls who drank fewer than two servings of these sweet beverages per week. The link held even after the researchers adjusted for a girl’s height, weight and the total number of calories she consumed each day.

Other sugar-sweetened beverages — Hawaiian Punch, for example, or Kool-aid — showed the same effect as soda. Fruit juice and diet soda did not.

What sugar may be doing

Michels speculates that the links she sees may trace to another hormone: insulin. The body secretes this hormone into the blood during digestion. It helps cells absorb and use any sugar that gets released. But if a lot of sugar floods the body all at once, such as when downing a soda or other sweetened drink, blood levels of insulin may spike. And those spikes could affect other hormones.

For instance, Michels notes, “High levels of insulin can translate to high estrogen levels.”

She’s not totally surprised that fruit juice didn’t provoke the same response as sugary soft drinks. The reason: Fructose, the type of sugar in fruit juice, does not produce insulin spikes nearly as strongly as does sucrose (also known as table sugar). High-fructose corn syrup, the sweetener used to flavor many sodas and processed foods, has a chemical structure similar to that of sucrose, Michels says. “It raises insulin levels and increases diabetes risk.”

Diet sodas don’t have sugar. So they also don’t trigger big surges of insulin. (Diet sodas are loaded with fake sugars, though, which some studies have suggested might provoke other risks. For instance, recent research has suggested artificial sweeteners may make it easier to overeat or to disrupt the good microbes in our gut.)

Pediatricians have long recommended that teens limit their intake of sugary beverages to prevent obesity and tooth decay. The new study suggests that sugar-sweetened drinks “may further influence growth and development, specifically the age at which girls get their first period,” says Maida Galvez. She’s a pediatrician at Mount Sinai School of Medicine in New York City. “The bottom line for teens is to choose water over sugar-sweetened beverages when possible,” she says.

And if water seems “boring,” adds Michels, “there are ways to add taste without adding sugar” — such as putting in a squirt of fresh lemon juice.

Michels notes, though, that soda and sugary drinks might not have been the only culprits in this study. Girls who load up on sweetened beverages might also choose other foods that are quite different from what’s eaten by girls who shun sugary drinks. So it’s possible that another food or nutrient could explain why those who regularly drank sugary beverages got their period at a younger age.

Power Words

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digest  (noun: digestion) To break down food into simple compounds that the body can absorb and use for growth.

epidemiologist  Like health detectives, these researchers figure out what causes a particular illness and how to limit its spread.

estrogen   The primary female sex hormone in most higher vertebrates, including mammals and birds. Early in development, it helps an organism develop the features typical of a female. Later, it helps a female’s body prepare to mate and reproduce.

fructose    A simple sugar, which (along with glucose) makes up half of each molecule of sucrose, also known as table sugar.

hormone   A chemical produced in a gland and then carried in the bloodstream to another part of the body. Hormones control many important body activities, such as growth. Hormones act by triggering or regulating chemical reactions in the body. 

insulin  A hormone produced in the pancreas (an organ that is part of the digestive system) that helps the body use glucose as fuel.

obesity  Extremely overweight. Obesity is associated with a wide range of health problems, including type 2 diabetes and high blood pressure.

menstruation  Monthly flow of blood from the uterus. It begins at puberty in girls and other female primates. People generally refer to each monthly episode as a woman’s period.

microorganism (or “microbe”)  A living thing that is too small to see with the unaided eye, including bacteria, some fungi and many other organisms such as amoebas. Most consist of a single cell.

pediatrics  Relating to children and especially child health.

puberty    A developmental period in humans and other primates when the body undergoes hormonal changes that will result in the maturation of reproductive organs.

questionnaire  A list of identical questions administered to a group of people to collect related information on each of them. The questions may be delivered by voice, online or in writing. Questionnaires may elicit opinions, health information (like sleep times, weight or items in the last day’s meals), descriptions of daily habits (how much exercise you get or how much TV do you watch) and demographic data (such as age, ethnic background, income and political affiliation).

sucrose   Better known as table sugar, it’s a plant-derived sugar made from equal parts of fructose and glucose.

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