Why don't most parents let their kids drink coffee? The first, most obvious answer is that caffeine is addictive. Overcaffeinated kids will be bouncing off the walls and staying awake at night, and letting them drink coffee is a likely way for them to get hooked. Soda, though, is also caffeinated, and a common beverage for kids in the US. Smithsonian Mag offers a different theory about why coffee's off limits: a persistent belief that coffee stunts the growth of children.
Smithsonian Mag writes: “'It’s ‘common knowledge,’ so to speak—but a lot of common knowledge doesn’t turn out to be true,' says Mark Pendergrast, the author of Uncommon Grounds: The History of Coffee and How It Transformed Our World. 'To my knowledge, no one has ever turned up evidence that drinking coffee has any effect on how much children grow.' "
No study has ever lent credence to the theory that coffee harms the development of children, though Smithsonian Mag points out that no study has ever exposed children to years worth' of coffee, either. "There has, however, been research into the long-term effects of caffeine on children, and no damning evidence has turned up," they add. "One study followed 81 adolescents for a six-year period, and found no correlation between daily caffeine intake and bone growth or density. Theoretically, the closest thing we do have to evidence that caffeine affects growth is a series of studies on adults, which show that increased consumption of caffeinated beverages lead to the body absorbing slightly less calcium, which is necessary for bone growth. However, the effect is negligible: The calcium in a mere tablespoon of milk, it’s estimated, is enough to offset the caffeine in eight ounces of coffee."
So where did this idea come from? What spawned the belief that coffee will stunt the growth of children, while it's perfectly fine for adults? The idea may have originated with advertising created by C.W. Post, who founded Post Foods in the late 1800s. The company is still a popular cereal maker. Post created a grain-based drink, called Postum, that was popular until the 1960s. It was only discontinued in 1967, but some longtime fans have brought the drink back, billing it as "a healthy coffee alternative for those who have dietary and health restrictions. Postum is caffeine free and won’t cause the sleeplessness, high blood pressure or digestive problems that are often linked to coffee and tea."
To push people to drink Postum with their breakfast instead of coffee, Post created a series of ad campaigns talking about coffee's harmful effects. Some ads called it "nerve poison." Other specifically discussed children, claiming it made them sluggards and robs them of the milk they need in their diet. One ad credited a "world famous Research Institute" for a study that conclusively proved coffee made children stupid. "Less than 16% of those who drank coffee attained good marks!" it exclaimed.
Somehow, Postum didn't stick around, but its ads must have worked their way into the public consciousness. Coffee doesn't stunt growth or make kids fail school. Still, you may not want them to drink it; there's still the no sleeping, bouncing off the walls issue to consider.