How much caffeine is safe for you and your child?

We are a nation obsessed with caffeine: Cans of caffeinated energy drinks with flashy names line beverage shelves. New coffee shops seem to open every day. Caffeine is added to gum, jelly beans, oatmeal and the soap in our bathtub. You can even inhale it through a caffeine vaporizer.  

Eighty-five percent of Americans consume at least one caffeinated beverage each day. And unfortunately, it’s not just adults. About 73 percent of children consume caffeine on a given day. Caffeine in high amounts can be dangerous for anyone, but children especially can fall victim.  

A 16-year-old South Carolina student collapsed during class in April 2017 after drinking a latte, a large Diet Mountain Dew and an energy drink in a two-hour period. The coroner said the previously healthy teen died from a caffeine-induced cardiac event that likely caused arrhythmia, or abnormal heartbeat. Unfortunately, these stories are becoming all too common.  

Caffeine is a stimulant that can give you a boost of energy and make you feel more awake. But it also can increase your blood pressure, cause shaky hands, insomnia and an upset stomach, and in extreme cases can cause abnormal heart rhythm and seizures.

And although it’s legal and widely consumed, make no mistake: Caffeine is a drug. More than 20,000 people visited emergency rooms in 2011 for health problems involving caffeinated drinks, particularly energy drinks. That was double the number in 2007. I’ve seen this increase firsthand at MedStar Health, particularly among college students during finals. The reporting for such visits isn’t great, and I think this number is just the tip of the iceberg of the true number of people who are negatively affected by caffeine.  

To turn this disturbing trend around, we must examine the risk caffeine poses and what we need to do as individuals, as parents and as a country to keep our hearts safe.  

How much caffeine should adults and children have in a day?

The U.S. hasn’t developed guidelines for caffeine intake, but medical organizations generally recommend the following:

  • Adults: Less than 400 mg of caffeine a day
  • Age 12-18: Less than 100 mg  
  • Age 10-11: Less than 85 mg
  • Age 7-9: Less than 60 mg
  • Age 4-6: Less than 45 mg
  • Younger than 4: No caffeine  

These recommendations are based on a 24-hour period, not all at once in two or three hours. But these numbers may not be perfect for everyone. Other details must be considered. People with a heart condition such as a cardiac arrhythmia may need to be careful when consuming caffeine.  

The American Academy of Pediatrics advises that children and adolescents not consume energy drinks of any kind. Not long ago, I saw a man in a gas station about to buy a 20-ounce energy drink for a 7- or 8-year-old. I stepped in and said while I didn’t want to tell him what to do, I was worried about the effect the drink could have on the boy. The man replied, “Are you kidding me? I didn’t know that. I’m not buying this for him.”  

Body size also affects the amount of caffeine you can safely consume. A 240-pound man may be able to tolerate more caffeine than a 155-pound man. Genetics affects how your body reacts to caffeine. People who have a specific variation of a certain gene metabolize caffeine more slowly, which means they experience side effects from less caffeine than others.  

How much caffeine are you drinking?

The amount of caffeine varies dramatically between types of drinks and brands. And for coffee, it also depends on how it was prepared:

  • Brewed, drip coffee (8 ounces): 75-165 mg
  • Espresso (1 shot): 45-75 mg
  • Latte or mocha (8 ounces): 63-126 mg
  • Soft drinks (12 ounces): 30-60 mg
  • Energy drink (8 ounces): 27-164 mg  

Based on these amounts, a teen could have two 12-ounce soft drinks a day to stay within recommended guidelines while an adult could have about four 8-ounce cups of coffee or two to three 8-ounce energy drinks.

Don’t forget to check your drink size. Is that cup of coffee in front of you really only 8 ounces? Or did you order a large and it’s actually 20 ounces? How about that energy drink? Is it 8 ounces, 16 ounces or more? If so, double, triple or even quadruple the above caffeine amounts to determine how much you’re really consuming.  

How caffeine affects the heart

Caffeine affects the heart in a few ways. 

  • It stimulates the synthetic nervous system, which activates the body’s fight or flight response and causes an increased level of adrenaline in the blood. This in turn can raise your blood pressure and heart rate.  
  • It also can interfere with the heart’s conduction system, the process by which electrical impulses sent from the heart muscle cause the heart to beat.  

Both of these have the potential to trigger an abnormal heart rhythm.  

While most people develop a tolerance to caffeine over time and the effects on the heart are lessened, the risk never disappears entirely.  

When it comes to energy drinks, the amount of caffeine isn’t the only concern. These drinks tout “natural energy-boosting effects” gained from a mix of other ingredients including stimulants and additives. Unfortunately, we don’t know a lot about the safety of such ingredients, especially when paired with caffeine.  

An April 2017 study found that consuming an energy drink was associated with potentially harmful changes in blood pressure and heart function beyond those seen with caffeine alone. The researchers measured participants’ blood pressure and used an electrocardiogram (ECG or EKG) to monitor the heart’s electrical activity twice for 24 hours: once after consuming an energy drink and once after drinking another beverage with the same amount of caffeine but none of the other ingredients.  

They found blood pressure increased by five points after drinking the energy drink but less than one point after the caffeine beverage. Blood pressure also remained elevated six hours later with the energy drink. An ECG change known as QTc prolongation, which is sometimes associated with irregular heart rhythms, also was seen after drinking the energy drink but not with the caffeine beverage.  

What can we do to prevent future tragedies?

Every time I read a story in the media about a caffeine-related death, especially when it’s a child, I wonder when we as a country will wake up to the real risks caffeine poses – especially energy drinks. How many deaths will it take before we stop selling drinks containing toxic levels of caffeine over the counter to our children?  

Energy drinks are primarily marketed to kids and adolescents. The bright colors, flashy labels and names such as “Monster” and “Rockstar” seem designed to appeal to our nation’s youth. It’s reminiscent of how Joe Camel ads were used by the tobacco industry.  

The Food and Drug Administration (FDA) regulates the amount of caffeine in soda, but not energy drinks because they are considered a dietary supplement and not a food. Other countries are moving to increasingly regulate energy drinks, and I think it’s time the U.S. does so as well.  

While regulating the amount of caffeine in such drinks or requiring warning labels may take time and considerable debate, I think we can find common ground on other regulations, such as restricting their sale to minors.  

Until the FDA acts, it’s up to us to keep ourselves and our children safe. I think the biggest challenge is that too many people simply don’t know how dangerous high amounts of caffeine can be – especially for children.  

We need to talk to our children about caffeine the same way we discuss alcohol, tobacco and other drugs. Caffeine is a drug and it’s addictive. By recognizing the potential risks that large amounts of caffeine can pose, we can prevent more people from consuming dangerous amounts of it.  

Allen J. Taylor, MD, FACC, FAHA, is chief of cardiology at MedStar Heart & Vascular Institute, including MedStar Georgetown University Hospital and MedStar Washington Hospital Center in Washington, D.C. In his 20-year United States Army career at Walter Reed, Dr. Taylor served as director of cardiovascular research, director of the Cardiovascular Disease Training Program and chief of the cardiology service. He retired from military service in 2008 at the rank of Colonel, held the Army’s “A” proficiency designator and was decorated with the Legion of Merit. He is professor of medicine at the Uniformed University of the Health Sciences, and Georgetown University.

Dr. Taylor’s major research accomplishments include defining the role of lipid lowering therapy on carotid atherosclerosis, focusing on HDL cholesterol and the use of niacin. His pioneering work in the field of cardiac CT includes conducting long-term prospective outcomes trials, randomized clinical trials on the utility of the technique, and methods to enhance the safety and appropriateness of cardiovascular imaging. He has published four books and more than 180 manuscripts in journals such as Circulation, Journal of the American Medical Association and New England Journal of Medicine.

Dr. Taylor serves as founding editor-in-chief of the Journal of Cardiovascular CT, and as editor of the Braunwald’s Heart Disease companion text atlas on cardiac CT. He is president of the Society of Atherosclerosis Imaging and Prevention, immediate past chair of the Imaging Council, current chair of the FOCUS campaign of the American College of Cardiology, and incoming president of the Certification Council of Cardiovascular Imaging.