At 35, chest pains are the last thing Clint Harris expected. That's exactly what landed him in his doctor's office this summer, however.

“It felt like tightness and pressure. It felt like you were pushing on it from inside out,” Harris recalled recently.

His doctor gave him a stress test that was completely clear. So he began looking to other possible sources of the problem. One of the first questions that his doctor asked him was if he drinks energy drinks.

“I started drinking them last summer as a replacement to coffee,” he said.

Since coffee never bothered him, Harris assumed the energy drinks would be fine too but, after encouragement from his doctor, he gave them up. Just days later, the pain went away.

“I have no doubt there was correlation because I was having them daily. I stopped drinking them and four days later I had the last one (pain) and haven't had single one,” he said.

Dr. David Cochran, who is not Harris's doctor, isn't surprised.

“It has a direct effect on blood pressure and heart rate. Even in 20-year-olds with no other medical problems, it can have that effect,” he said.

At 80 to 100 milligram per 8 ounces, energy drinks don't have a whole lot more caffeine than what is in coffee. The problem, say some doctors, is the quantity many people consume.

Most cans include caffeine content on the can but that's for one serving. Some cans have three servings and three times the caffeine of coffee.

That could be what caused Harris's sensitivity, since he replaced about two 8-ounce cups of coffee each day with at least two supersized 16-ounce cans of an energy drink.

“We really have to step back and evaluate what we're putting in our bodies,” said Dr. Ken Sharlin of Ozarks Community Hospital.

Sharlin says not everyone has to swear off energy drinks but agrees there are much better ways to get a boost.

“If the person drinking an energy drink is only sleeping five hours a night, then they need to get seven to eight hours a night," he said.

In addition to caffeine, most of the drinks contain B vitamins. Sharlin says this is also something of which you should be wary. Vitamin B contains niacin which, in large doses, can cause dizziness, nausea and even passing out.

As with most things, both doctors agree that energy drinks, in moderation, are perfectly fine for most people. They say people should just pay attention to the quantities that they're consuming.