By Markham Heid
September 5, 2019

Spend an afternoon hanging out in a Starbucks or Dunkin, and you’ll probably see a handful of teens—and maybe even some younger kids—stopping in for a cup of coffee. A 2017 industry report from the National Coffee Association found that the percentage of Americans aged 13 to 18 who drink coffee every day had risen to 37%, marking a 14-percentage-point increase since 2014.

The image of a 13-year-old drinking coffee seems somehow wrong—a child enjoying an adult’s habit. But there’s actually a lot of good in it. Recent studies have found that coffee consumption may lower a person’s risk for heart disease and early death. While coffee was once vilified, the prevailing wisdom these days is that if it isn’t messing with your sleep, it’s pretty much all upside. Research has also found that coffee contains several antioxidant compounds, including polyphenols, that seem to have healthy anti-inflammatory effects.

But some of today’s most-popular coffee drinks contain a lot more than just coffee. Sugar is a featured ingredient in many of the proprietary latte and cappuccino offerings at popular coffee chains. Starbucks sells a “Double Chocolaty Chip Crème Frappuccino” that contains 52g of sugar, which is the amount of sugar in a 16-oz Coca Cola. Dunkin, meanwhile, sells a “Cinnamon Sugar Pumpkin” latte that contains 55g of sugar. At some point the ostensible coffee becomes caffeinated candy.

Those quantities of sugar far exceed the 25g-per-day maximum that the American Heart Association suggests for people 18 and younger. And doctors who’ve studied the health effects of sugar say that, not surprisingly, it raises a young person’s risks for obesity and diabetes, and maybe also for cognitive development issues.

And then there’s the stimulating effect of the caffeine. The American Academy of Pediatrics (AAP) recommends that kids aged 12 to 18 consume no more than 100 mg of caffeine per day, which is about the amount in a single 8 oz. cup of brewed coffee. But the impact even this moderate amount of caffeine has on young people is less clear than it is for adults.

“We did research on kids and caffeine for a decade, and we found that within the range of what is normally consumed—anything from between one can of soda to a couple cups of coffee—[caffeine] doesn’t seem to have adverse effects on physiology or mood,” says Jennifer Temple, an associate professor and director of the Nutrition and Health Research Laboratory at the University at Buffalo.

Temple is quick to add that caffeine consumed in the afternoon or evening may disrupt a young person’s sleep. “A child’s sleep requirements are greater than an adult’s,” she says. “And they need sleep for healthy growth and academic performance.” Some recent reports have found that adolescents today are sleeping less than they used to. But it’s not clear that caffeine is a major driver of the problem. (Much of the research on kids and sleep implicates social media and nighttime screen use, not caffeine, as the likeliest culprits.)

“Kids don’t need caffeine,” Temple says. “But is it dangerous? If a young person is sleeping well, probably not.”

Not all the research on kids concludes that the caffeine is harmless, however. “Caffeine is a stimulant that affects the nervous system, and our studies have looked at how those effects might impact the developing brain,” says Ryan Bachtell, an associate professor of psychology and neuroscience at the University of Colorado.

For a study published in 2016, Bachtell and his colleagues administered caffeine to adolescent rats. They found regular caffeine consumption changed the way genes were expressed in the rats’ brains, and that those changes could be associated with an increase in symptoms of anxiety-related behaviors during the rats’ adulthood. Similar changes to similar genes in humans could have similar effects. More of Bachtell’s research has found that young rats exposed to caffeine showed a greater sensitivity to other stimulants they were given later, including illicit drugs such as cocaine.

Rat studies don’t always translate to people. And there’s a need for more research on real-world kids and coffee consumption. But a 2014 study did seem to confirm Bachtell’s rat findings, showing that kids who consume energy drinks, which are also a major source of caffeine, may be at greater risk for anxiety during adulthood. “The takeaway from all these studies is that adolescent caffeine use may make the brain more vulnerable later in life,” Bachtell says. “The adverse consequences aren’t definitive, but I think caution is warranted.”

So should parents deny their teens coffee? Bachtell says he wouldn’t go that far. “As with most things, I think moderation is key,” he says. While the amount of caffeine can vary widely in coffee, one 8-oz. cup shouldn’t contain much more than the 100-mg limit the AAP recommends. As long as a young person is drinking coffee early in the day—and not loading it up with sugar or other unhealthy additives—parents probably needn’t worry.

It’s also worth noting that many of the studies linking coffee to health benefits have found these benefits hold whether a person is drinking decaf or regular, since it’s the other components in coffee that pay those dividends. For the parents of teens who are intent on drinking coffee, guiding them toward decaf of “half-caf” may mitigate any risks while potentially providing some benefits.

Contact us at editors@time.com.

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