End-of-term exams, marathon Christmas shopping, the hamster wheel of everyday life: what wouldn’t you give for a little extra energy? But chugging down cans of it may not be the best solution.

Red Bull, Full Throttle and Rockstar number among the numerous energy drinks jostling for our attention on store shelves. Boasting that they were developed for periods of increased mental and physical exertion and promising to heighten wakefulness, they are packed with sugar and caffeine. Both ingredients are good at briefly re-igniting your get-up-and-go, but can have serious health effects.

With obesity and diabetes surging across North America, downing even more sugar isn’t the healthiest choice. The high levels of caffeine in energy drinks, meanwhile, have been associated with a cavalcade of adverse reactions — from anxiety and nausea to seizures and cardiac irregularities — following heavy consumption.

Health Canada says healthy adults shouldn’t consume more than 400 milligrams of caffeine a day. Children, 10 to 12, should be limited to 85 mg a day, and younger children even less.

A 250-mL bottle of Coca-Cola has 26 mg of caffeine, and a cup of coffee between 80 and 150 mg. The energy drink, Rockstar Burner, contains 160 mg of caffeine per 500 mL, while a 75-mL bottle of Rockstar Energy Shot packs 200 mg of caffeine. Some drinks contain much less caffeine.

Labels on energy drinks warn that children and pregnant or breast-feeding women should avoid them, while others should consume no more than one or two cans a day.

Dr. Ahmed El-Sohemy, a professor in the University of Toronto’s department of nutritional sciences and an expert on the body’s processing of caffeine, says insufficient evidence makes it difficult to pinpoint the dangers of over-consuming energy drinks.

"There’s anecdotal evidence linked to death in some teens who consumed it and engaged in rigorous physical activity shortly after, but that’s just anecdotal. There is evidence that caffeine may trigger a heart attack in . . . individuals who have an impaired caffeine metabolism (so-called "slow" caffeine metabolizers) based on their genetics."

El-Sohemy says that the long-term effects of heavy caffeine consumption are unknown, but that caffeine withdrawal effects such as headaches are common. When combined with sugar, that could lead to "a form of dependency."

He also points out that in Canada, energy drinks fall under Natural Health Product regulations. But he adds that there is no limit to caffeine content, which companies must list on the can.

Ontario’s Ministry of Health, meanwhile, says that while moderate use of energy drinks by adults is safe, the long-term effects of taurine, a common ingredient said to enhance alertness, is unknown. Moreover, there’s no scientific evidence to support claims that herbal ingredients, like ginseng and gingko biloba, improve performance.

Experts say to avoid energy drinks when exercising because caffeine, a mild diuretic, can heighten dehydration. Also don’t drink them on an empty stomach and never mix them with alcohol because the caffeine can create a false sense of awareness and self-control.

Other popular beverages

Sports drinks

According to Health Canada, beverages, like Gatorade G2 and Powerade, rehydrate the body, provide energy-creating sugars and replenish electrolytes to maintain salt and potassium balances.

Protein drinks

Marketed as a way to build muscle, shed weight and stay healthy, protein drinks, like Myoplex and Muscle Milk, could lead to overexposure to arsenic and other heavy metals if consumed in excess, says Consumer Reports.

Vitamin drinks

Dieticians generally agree that vitamins and minerals should come from a balanced diet. Vitamin drinks may contain elevated levels of sugar.