Dangers of Energy Drinks for Exercise

High Caffeine Drinks Not Meant for Exercise

Ian Stewart of Colorado Rockies Drinks Red Bull at Game
Energy Drinks and Exercise. Doug Pensinger/Getty Images Sports

High-caffeine energy drinks have become increasingly popular, but these drinks don't mix well with exercise. While most sports drinks are non-caffeinated and meant to replenish fluids lost in exercise, energy drinks have a large dose of caffeine and caffeine-like stimulants (such as guarana). These can lead to dehydration, according to Dee Rollins, R.D., Ph.D., a dietitian with Baylor Regional Medical Center at Grapevine, Texas.

Sports Drinks vs. Energy Drinks

Traditional sports drinks such as Gatorade and Powerade include water, salt, and sugars in proportions that help the body absorb fluids and salts lost in sweat and in the breath while exercising. The sugars not only help the body take in the water, but also provide fuel for muscles that need sugars to keep performing well during long walks, runs, or bikes. A small amount of salt helps protect the body from hyponatremia, (also known as water intoxication), which can happen if you drink a large amount of water without any salt.

Energy drinks are formulated to deliver caffeine and other stimulants, such as guarana or ginseng, to give the drinker a rush of energy. They are not designed to replace lost fluids during exercise. Some come in small cans that deliver a large amount of caffeine in a small amount of fluid. Many are carbonated, which can lead exercisers to experience burping, nausea and a bloated feeling.

Marketing at Athletic Events

The energy drink Red Bull is often handed out at running and walking events by marketers, which might lead people to think it is a sports drink. "Most people assume that if you stick something in their hand while they are exercising, that it is good for them," says Rollins. But Red Bull comes in small cans that pack as much caffeine as a cup of coffee (80 milligrams) and more than a can of cola (40 milligrams). While replacing less fluid, it delivers a punch of caffeine that stimulates the kidneys to produce more urine and lose more fluid.

Dangers of Too Much Caffeine and Exercise

Rollins notes that if you have already had a cup or two of coffee in the morning, adding a can of energy drink can put you over the amount of caffeine most dietitians think is a reasonable limit for the day. "You are losing body fluids through perspiration when walking. Caffeine compounds dehydration further," said Rollins.

Losing Track of Caffeine

If exercisers rely on energy drinks, they may drink two to three small cans thinking they haven't had enough fluids. If they drink a larger can, it may contain two servings. Many pain medications, sinus medications, and other beverages also contain caffeine. "People may be in more trouble than they realize," said Rollins. She says a general consensus is that 250 milligrams per day of caffeine should be the limit. Drinking more than 400 milligrams a day -- two cups of coffee and an energy drink -- can lead to jitters, nausea, or even heart palpitations.

Effects of Caffeine When Exercising

Caffeine stimulates urine production, which removes water from the body. If you are already losing water in sweat, losing more in the urine means needing to drink more during exercise. Caffeine can also have a laxative effect. "When you walk, you make your whole GI tract move from mouth to rectum," noted Rollins. This can lead to needing a restroom more often, or with more urgency (runners trots).

Preventing Dehydration

There is no magic formula for determining how much water and sports drink you need to prevent dehydration while exercising. Everyone reacts a little differently. The recommended rule of thumb for walkers and runners is to carry water or sports drink with you so you can drink as soon as you are thirsty. Don't ignore hunger pangs, either. Rollins notes that some people will feel hungry rather than thirsty when they need water.

Weighing yourself before and after a workout can tell you whether you are drinking correctly. You should neither gain nor lose any weight over the course of a workout. If you lose weight, you are dehydrated. If you gained weight, you are drinking too much and may put yourself at risk of hyponatremia.

Drinking Recommendations for Distance Walkers

The International Marathon Medical Director's Association revised guidelines for drinking and fluid intake for walkers and runners at endurance events in May 2006. For a workout of 30 minutes or more, they recommend drinking a sports drink, and not diluting the sports drink with extra water or switching back and forth between sports drink and water. Evidence says that thirst is the best protection for athletes when it comes to drinking the correct amount.​

  • Drink when you are thirsty.
  • Don't drink if you aren't thirsty.
  • Don't drink at every water stop at an event just because it is there or your companions are drinking.
  • Rely on your thirst unless you discover it is leading you wrong, from weighing yourself before and after a workout.
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