Does Coffee Stunt Your Growth?

No. There's no scientific evidence that coffee stunts growth. The idea comes from an old worry that caffeine drains calcium from bones, but its effect on calcium is tiny and easy to offset. A six-year study of teenagers found caffeine intake had no link to how much bone they built. Sleep is the bigger thing caffeine can affect.

That doesn't mean caffeine is a free-for-all for kids and teens. Below is where the myth started, what the bone research actually measured, how much caffeine is considered reasonable for younger people, and the one way coffee really can get in the way of growing and training: lost sleep.

Where Did the Idea That Coffee Stunts Growth Come From?

From concerns about calcium and bones. Caffeine slightly increases how much calcium the body loses, so people reasoned that coffee might weaken growing bones and limit height. Early studies linking coffee to weaker bones reinforced the idea, but those studies had a problem: the coffee drinkers in them also drank less milk.

Harvard Health states it plainly: "There is no scientifically valid evidence to suggest that coffee can stunt a person's growth." It explains that when researchers re-examined the studies suggesting a link, the people who drank more coffee were also getting less calcium from milk and other drinks.

That points to diet, not coffee, as the real issue. Low calcium is bad for bones whether or not you drink coffee, so that's the part of your diet worth checking first.

Does Caffeine Weaken Your Bones?

Not in people who get enough calcium. Caffeine slightly reduces how much calcium your gut absorbs, but the effect is so small that one to two tablespoons of milk cancels it out. Controlled studies found no change in how much calcium people lose in their urine over a full day.

A 2002 review of caffeine, bone and calcium in Food and Chemical Toxicology looked at both physiology studies and population research. It found "a clear but only a very small" effect on calcium absorption and concluded there's no evidence caffeine harms bone in people meeting recommended calcium intakes.

The review also noted that high caffeine intake is often a marker for low calcium intake, which matches what Harvard Health describes. A latte, with its milk, may actually add calcium to your day rather than taking it away.

What Does Research on Teenagers Show?

It found no link between caffeine and bone growth. A study that followed teenagers from age 12 to 18 tracked their diets and measured their bones. Those who had the most caffeine built just as much bone as those who had the least, and their hip bone density at 18 was the same.

That 1998 study in the Journal of the American College of Nutrition followed 81 teenage girls through the Penn State Young Women's Health Study, using six years of food diaries. Their caffeine intake ranged from under 25 mg a day to more than 50 mg a day.

The study has limits worth knowing. It included only girls, the highest intake group averaged just 77 mg a day, which is less than a typical cup of coffee, and only 11 people were in that group. Larger long-term studies in teens are scarce.

How Much Caffeine Can Teenagers Have?

A common guide is up to 2.5 mg of caffeine per kilogram of body weight per day. For a teen who weighs 60 kg (about 130 pounds), that's around 150 mg, roughly one cup of brewed coffee. Healthy adults can have more: the FDA cites up to 400 mg a day for most adults.

A 2017 systematic review of caffeine safety in Food and Chemical Toxicology reviewed hundreds of studies and concluded that 2.5 mg/kg a day "remains an appropriate recommendation" for children and teens. It also noted there's limited research in younger people, so the guide is cautious by design. For healthy adults, the same review supported up to 400 mg a day, finding no adverse effects on bone status at that level.

Here's what that works out to by body weight:

Body weight	Daily caffeine guide (2.5 mg/kg)
45 kg (about 100 lb)	About 110 mg
60 kg (about 130 lb)	About 150 mg
70 kg (about 155 lb)	About 175 mg
80 kg (about 175 lb)	About 200 mg

For comparison, the FDA lists 113 to 247 mg in 12 ounces of brewed coffee. Energy drinks can push teens over the guide quickly: the FDA lists anywhere from 41 to 246 mg in a 12-ounce energy drink, and pre-workouts can be just as strong.

Can Coffee Affect Growth Through Sleep?

Indirectly, it can hurt the sleep that growing and training bodies need. Caffeine taken even six hours before bed disrupted sleep in a controlled study. For teens, who often go to bed late and get up early for school, an afternoon coffee or energy drink can cut into sleep that's already short.

In that 2013 study in the Journal of Clinical Sleep Medicine, 400 mg of caffeine taken at bedtime, three hours before or six hours before all significantly disrupted sleep compared with a placebo. The authors recommended avoiding substantial caffeine for at least six hours before bed.

Sleep matters for anyone who trains, at any age. Our guide on how long caffeine lasts explains why a midday cup can still be in your system at night.

Does Coffee Affect Height After You Stop Growing?

No. Once you've finished growing, your height is set, and nothing you drink will change it. Most of a person's growth happens long before they start drinking coffee regularly, which is another reason the stunting idea doesn't hold up.

Harvard Health makes the same point: by the teen years, most people have almost reached their full adult height, and bone growth can't be "undone" once it's complete. For adults, the bone question is about keeping bones strong, which comes down to calcium, vitamin D and strength training, not avoiding coffee. And no, lifting doesn't stunt growth either; does lifting weights stunt growth covers the youth training research.