Energy Drinks: Caffeine + Calories = ???

The market for caffeinated products is growing. [1] It started simply with a cup of coffee then expanded to caffeinated beverages and now to other caffeinated products, like gum and even waffles!

It’s not surprising then that nearly 1 in 4 adults drink at least one sports or energy drink every week.[2] But the FDA doesn’t have a way to regulate or evaluate caffeinated products. Energy drinks, which have been on the market long enough for health officials to gather data on their safety, have come under scrutiny recently because they’ve been linked to several deaths and other serious problems. So do the benefits of energy drinks outweigh the risks?

Most energy drinks have the same basic ingredients.[3] They are high in sugar and caffeine, and vitamins and herbal supplements that are supposed to strengthen immunity, help combat fatigue, and rev up metabolism.[4] These drinks are not, however, regulated by the FDA, so do they really do what they claim?

The ingredients in the drinks are all considered safe, by themselves, but not necessarily all together. Some of the ingredients, like guarana, are hidden sources for additional caffeine (the caffeine doesn’t have to be listed on the label) that last much longer than the caffeine in a cup of coffee. This means that the drink can have much more caffeine than the label says.[1] The FDA doesn’t inspect the finished products to see if the ingredient information on the label is accurate.  It was only after several people died after consuming these drinks that the FDA started testing the combination of ingredients used in energy drinks to see if there is anything harmful or beneficial about consuming the ingredients together.[5]

What exactly is in an energy drink? While each energy drink has its own special formula, these are some common ingredients.

Caffeine- Caffeine stimulates the nervous system, making people feel more alert and energetic. The high level of caffeine in energy drinks may give the boost that most drinkers are looking for.  However, adults should consume less than 400 mg of caffeine per day. Youth and teens (under age 19) should consume less than 100 mg per day. Having more caffeine than these recommended amounts is dangerous. Most hospital ER visits from energy drinks have been caused by a reaction to too much caffeine, such as a fast or irregular heartbeat. Energy drinks have 80-400 mg of caffeine, depending on the size of the drink and mix of ingredients. Large bottles (16-24 oz) contain even more caffeine. A regular 8oz coffee has 70-100 mg of caffeine.

Glucose (sugar)- Glucose is another name for sugar. Sugars are a source of carbohydrates, which provide energy for your cells but can also be turned into fat if the energy is not used up. In an energy drink, sugar does not provide an added benefit. Sugar-free energy drinks do not have added glucose but have other sources of carbohydrates.

Taurine- Taurine is naturally found in meat, fish, and dairy products. Taurine is included in energy drinks to promote the functioning of your immune system, muscle, and brain. Taurine may help improve stamina when taken consistently on a long-term basis, but not from occasional energy drink consumption.

Glucuronolactone- By adding this to energy drinks, manufacturers avoid putting in more sugar, while still providing a source of energy for your cells. It may help combat sleepiness and improve stamina, or it might not.  No studies have been performed to test these effects.

B Vitamins (mainly B6 and B12)- These vitamins are important for the normal function of cells in your body, like making DNA and proteins. B vitamins help cells break down carbohydrates into energy. There are many natural sources for B vitamins, such as cereals and vegetables. In energy drinks, these vitamins are included in very high amounts, up to 10-times the recommended daily amount! Your body will only use a small portion and then gets rid of the rest. It is easy to get B vitamins in a balanced daily diet, or in vitamin pills. The high level of B vitamins in energy drinks has also not been studied.

Niacin (Vitamin B3)- Niacin is another B vitamin that helps cells turn carbohydrates into energy. Niacin is found in many different natural food sources: meat, vegetables, dairy, grains, and nuts, to name a few. Some people are very sensitive to niacin. Niacin sensitivity usually produces feelings of anxiety or nervousness and flushing of the skin. Since it is easy to get your daily recommended amount of niacin through normal diet, an energy drink can put your intake above the recommended upper limit.

Guarana- Guarana is an herbal supplement that can provide additional caffeine, depending on how it is processed. Research suggests that guarana may help improve memory when taken regularly in low doses, but it is unclear if this is just due to the caffeine or the herb itself. The amount of guarana in energy drinks (and the additional caffeine provided by guarana) is not monitored by the FDA.

If energy drinks deliver on their promise at all, it’s mostly from the caffeine.[2], [6] It’s a similar jolt to drinking coffee and it isn’t necessarily any healthier. Drinking one energy drink will provide the amount of caffeine needed to be alert and have better cognitive function.[5] Drinking one or two before or during exercise may provide enough caffeine to improve physical performance.[7] Unfortunately, there aren’t any good studies that compare the effects of drinking energy drinks to the effects from drinking some other form of caffeine.

Can these drinks kill you if you are otherwise healthy?  Can they kill you if you aren’t getting enough sleep?  It seems likely that they could, but research is still underway. Ever feel jittery after drinking coffee or energy drink? What you were feeling was mild caffeine toxicity.  After drinking an energy drink, the sharp increase in the level of caffeine and some of the ingredients can be very harmful.  Someone who usually avoids caffeine may experience caffeine toxicity from drinking a whole energy drink, but even regular caffeine drinkers can have the same problem. Caffeine toxicity can cause a fast heart rate, headache, insomnia, tingling or numbness in hands and feet, and a jittery, nervous sensation.[end Clauson, K.A., et al. Saftey issues associated with commercially available energy drinks. Journal of the American Pharmacists Association 2008.] Usually these side effects will fade over time but they can be life threatening, by causing a heart attack or seizure.[7], [8] Regular energy drinkers often have to drink more than the recommended amount of an energy drink to feel a boost. By drinking more than one energy drink on a regular basis, they are putting themselves at high risk for caffeine toxicity.

Severe reactions can occur when caffeine or herbal supplements are added to some medications or other stimulants, like alcohol. Several companies made alcoholic energy drinks, but they were essentially banned because of so many reports of hospitalizations and deaths. The high levels of caffeine with the alcohol seem to have made a lethal combination of a fast, irregular heart rate and dehydration. Scientific research has not been able to conclude if mixing alcohol and energy drinks yourself has the same risks.  Another claim is that the energy boost makes someone a more alert drunk, so that they drive or do other activities that they would otherwise avoid when drunk and sleepy but there is no data connecting the energy drinks, rather than alcohol, to more risky behavior.

Age and weight influence the impact of energy drinks. In a double blind study, adults who were given 200mg of caffeine performed better in tasks that tested memory and alertness.[5] In another study, adults had better endurance exercising after drinking caffeinated beverages.[6] Youth and teens drinking the same amount can end up with serious complications. Simply put, a child drinking one energy drink will have much higher blood caffeine levels than an adult. This puts them at higher risk.

Bottom Line

Energy drinks provide large amounts of caffeine and sugar in a short amount of time. Caffeine and sugar are known to temporarily boost energy, mental function, and, when taken at the right time, physical performance, but they can also increase anxiety, cause weight gain, and have serious risks that send you to the hospital or can even be fatal. Energy drinks contain many ingredients that do not have a known benefit, and the drinks themselves have not been monitored by the FDA or other agencies so we don’t know for sure how much are in each energy drink. Anyone who is sensitive to caffeine, such as young children, teens, or anyone with heart problems, should drink less than a full serving or avoid energy drinks entirely. Energy drinks can have a different impact on different people, or even have a different impact on the same person depending on how much sleep, alcohol, caffeine, or other drugs he or she has had.  If your performance is important, an energy drink may not provide the safe boost you crave.


1. Dennis, B. Slew of caffeinated food products has FDA jittery. Washington Post. June 1, 2013. Accessed June 3, 2013.

2. Park, S., et al. Characteristics associated with consumption of sports and energy drinks among US adults: National Health Interview Survey, 2010. Journal of the Academy of Nutrition and Dietetics 2013.

3.  McLellan, T.M. and Lieberman, H.R. Do energy drinks contain active components other than caffeine? Nutrition Reviews 2012.

4. Seifert, S.M., et al. Health effects of energy drinks on children, adolescents, and young adults. Pediatrics 2011.

5. FDA letter to Senator Durbin. November 21, 2012. Accessed January 10, 2013

6. Giles, G.E., et al. Differential cognitive effects of energy drink ingredients: caffeine, taurine, and glucose. Pharmacology, Biochemistry and Behavior 2012.

7.  Ballard, S.L., Wellbork-Kim, J.J., and Clauson, K.A. Effects of commercial energy drink consumption on athletic performance and body composition. The Physician and Sportsmedicine 2010.

8. Cannon, M.E, Cooke, C.T., and McCarthy, J.S. Caffeine-induced cardiac arrhythmia: an unrecognized danger of healthfood products. Medical Journal of Australia 2001.