With the darker days upon us, it may be tempting to try to fight fatigue with energy drinks.

Ever wonder what’s really in them and what they might be doing to you? I just came across an article in the November issue of the Mayo Clinic Proceedings that broke it down nicely.

Here’s the summary.

Caffeine.  No brainer. Interestingly, it is on the list of substances banned by the International Olympic Committee (which is just another reason you won’t see me in the Olympics). Most energy beverages (EB) contain 70-200 mg of caffeine per 16-oz serving. There is 65-125 mg in percolated coffee. Caffeine increases heart rate and blood pressure. If you drink more than 200 mg at a time, you may experience insomnia, nervousness, headache, abnormal rhythms in your heart, and nausea. Absorption is very rapid and the half-life is quite variable (from 2.7 to 9.9 hours). That morning coffee could still be “in your system” in the late afternoon. Whether it really dehydrates you is controversial and it seems that this not as likely if you are a regular caffeine drinker.

Taurine.  An amino acid (which is a building block of protein). We have tons of it and it is already in our diet. It helps the function of our muscles, among numerous other benefits on a cellular level. The amounts that are in EBs are not enough to be particularly helpful or harmful.

Glucuronolactone. Don’t try to say or remember this one. This is made in small amounts within the body. Not much is known about its effect in humans.

B vitamins. Thiamine, riboflavin, niacin, pantothenic acid, pyridoxine hydrochloride, biotin, inositol, and cyanocobalamin. These are important for proper cell function and energy production. Cyanocobalamin, in particular, is important in formation of red blood cells and helps maintain nerve cell function. A common deficiency we see is cyanocobalamin (B12) deficiency. When a patient has been fatigued, we take a look at the red blood cells to see evidence of B12 deficiency.

Guarana. This is a rainforest vine and guarana fruit seeds contain more caffeine than any other plant. The Amazonians used it to increase awareness and energy. Guarana overdose has been known to occur and has sent some people to the ER.

Ginseng. There are a fair amount of adverse effects with Ginseng, but the amounts in EBs are not significant.

Gingko biloba. So far, there is no evidence that it has any particular health benefits.

L-carnitine. This is also an amino acid. This is made by the liver and kidneys to increase metabolism.  But there does not appear to be any benefit to taking more than a certain amount because we can only absorb so much at once.

Sugars. Yikes. There is a lot. One typical EB (500mL) can has 13 teaspoons of sugar. I don’t think I have to say more about why this is not good.

Antioxidants. There haven’t been any significant effects in well-trained athletes when they took antioxidants.

Remember that these drinks are unregulated and often the amount of every ingredient is not known.  No more than 1 can a day is recommended (if that).

Other notable precautions:

• EBs can cause seizures, cardiac arrest.
• In one case report, a healthy 18-year-old died playing basketball after drinking 2 cans of Red Bull
• Red Bull has been banned in Norway, Denmark, and France
• Energy drinks can reduce symptoms of intoxication, increasing the probability of accidents and alcohol dependence

So, if you are going to drink energy drinks,

• DO NOT drink energy beverages while exercising
• DO NOT mix EBs with alcohol
• DO NOT use energy drinks if you have high blood pressure or other heart condition

And remember to let your doctor know if you are drinking energy beverages or taking other herbal medications. Always ask your own doctor for advice.

Linda Pourmassina is an internal medicine physician who blogs at Pulsus.

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