HOUSTON -

A chain of convenience stores in Missouri is refusing to sell some energy drinks to minors.

Energy drinks, gums and candy are everywhere and they're especially popular with teens and young adults.

Next week, experts from around the country will meet in Washington D.C. to focus on the dangers of consuming high levels of caffeine. A Houston cardiologist will be there to share his own personal experiment.

Caffeine toxicity: that's the cause of death listed for 14-year-old Anais Fournier who died after drinking two cans of Monster Energy in two days. Her family is now suing the manufacturer.

Her mother, Wendy Crossland, told NBC News, "So we just need to get the word out there, so this never happens to anyone else."

UTHealth and Harris Health System sports cardiologist Dr. John Higgins said more kids are coming into the emergency room because of complication from energy drinks.

Dr. Higgins added, "Often times they'll drink not just one. They'll have two or three and also sometimes they're mixing them with alcohol as well and we know that alcohol causes the caffeine concentration to go up higher and stay up higher longer."

To understand how these beverages and the blend of stimulants in them affect the body, Higgins himself chugged a 24 ounce can of Monster, then measured how his body reacted. The EKG showed and increase in heart rate and blood pressure.

Even more surprising was the before and after images of his artery.

Dr. Higgins explained, "Normally it's nice and flexible and it opens and closes really nicely. But then after the energy beverage, we've seen it opens and closes a little bit more sluggishly and that means there's not as much blood flow."

Higgins said the results of his self test were so surprising, he's issuing this warning to families: "Particularly in the kids, we want them to avoid the energy beverages right now under all circumstances."

Dr. Higgins said other groups that should stay away from high levels of caffeine include pregnant women and people with cardiac issues or known caffeine sensitivities.

If you're concerned, check with your doctor.