Energy drinks may not be the healthiest thirst quenchers in the hot summer months.
Summer heat increases the risk of dehydration, and many people try to relieve thirst and fatigue with one of the many energy drinks on the market.
Dr. David Katz, ABC News' medical consultant, warns that they may not always be the best thing to drink, especially when it is hot.
Considering energy drinks' popularity, it is important for people to understand exactly what they are drinking.
Katz said that heat could put stress on the metabolism, which could lead to dehydration. Energy drinks, he said, are designed to be stimulants and can give people a little edge when playing sports. They can also be dangerous because stimulants can increase body temperature and pose a hypothermia threat.
They can lead to collapse or heat stroke when people who engage in strenuous physical activity use them on a very hot day. They can also be dangerous for people with heart abnormalities and high blood pressure.
"We should distinguish between a sports drink and an energy drink, which is usually designed as a rehydration formula," said Katz, who is also director of the Yale Prevention Research Center. "If you are riding your bike and sweating and it's inconvenient to eat, it makes good sense."
"But if you are doing the average amount most people do, you don't need it. You can get all the fluid you need from water and food. The idea that the energy you turn to for hydration needs to be full of sugar is false. Water is the way to go for the way most of us exercise."
Part of the problem, Katz said, is that some energy drinks contain stimulants like caffeine or natural stimulants like guarana, which is derived from a South American plant and bitter orange, which contain synephrine, a newly popular alternative to ephedrine.
Bio-Engineered Supplements & Nutrition Inc., which makes the energy drink EndoRush, warns consumers to "seek advice from a health care practitioner if you are unaware of your current health condition or have any pre-existing medical condition."
Consumers, Katz said, should pay attention to how their bodies react to energy drinks, especially after exercise during hot weather.
"If you're overdoing it, your pulse will pound, you'll get sweaty, feel flushed, lightheaded, dizzy. A headache could be indicative of a change in blood pressure," Katz said.
"Stop drinking it. Get to a cool place. If you are feeling lightheaded or have a cold sweat, recline, put your feet up higher than your head. And of course replace the fluid with water," he said.
The popular Red Bull energy drink has a relatively high concentration of caffeine. An 8-ounce can has 80 milligrams of caffeine, 20 milligrams fewer than the same amount of coffee.
"Athletes have to consider that Red Bull is a functional drink and not a thirst quencher," the makers of Red Bull said in a statement. "It is recommended that the daily consumption of Red Bull should conform to a person's intake of caffeine, and this varies from person to person."
Katz said that people should try to consume less than 500 milligrams of caffeine a day. He also said that people should avoid consuming bitter orange.
"It contains synephrine, a stimulant similar to ephedra, which was banned by the FDA in 2004," he said.
Because energy drinks often contain natural supplements that are not regulated by the FDA, they can have effects that the consumer does not anticipate or know about, Katz said.
"Most people who are prescribed a drug ask about the side effects, yet people happily consume a beverage with ingredients they can't pronounce," he said. "I mean, do you really know what guarana is? Things you haven't heard of are cause for concern. There is a tendency to use the names of plants because they sound natural, but they aren't necessarily."