CAPT. STEVEN BROWN, DO
Flight Surgeon
School of Army Aviation Medicine
Fort Rucker, Alabama

I had just opened an energy drink to make it through the after-lunch lull when I started feeling strange. Inside my chest was a bizarre, panicky feeling. I was jittery, as if I had just run several miles. Of course I hadn’t. Otherwise I wouldn’t have been so sleepy that afternoon. My fingers were also trembling slightly. It was a normal day with nothing to worry about — nothing out of the ordinary anyway. What was going on?

I checked my calendar to ensure I wasn’t forgetting anything important that might have me overly anxious, but there was nothing. I knew energy drinks could cause symptoms like this, but this was my first one of the day. While I don’t drink energy drinks every day, I’m certainly not naïve to the effects of caffeine. I have coffee most mornings. On this day I’d had two. I didn’t sleep well the previous night and had a slight headache that morning, so I’d taken some Excedrin. That got rid of my headache quickly. Tylenol never works for me. I believe it’s the caffeine in the Excedrin that does the trick. Actually, when I stopped to think about it, I’d had a good bit of caffeine. Between the coffee, Excedrin and that energy drink, I was going on … 585 milligrams! Was that too much?

Caffeine is the most frequently used drug in the world. It’s been around for millennia in the form of coffee, cocoa, tea, kola nuts, guarana and other natural sources. More recently it has been added synthetically to soda, energy drinks and even candy and food products. At relatively low doses, caffeine gives people the benefits that have kept it popular all these years. It helps fight fatigue, improves concentration, energizes and staves off sleep.

Caffeine is widely available around the world, and that includes within the U.S. military. In fact, it has even been added to first strike ration MREs in the form of energy gum, mints, beef jerky and other foods. Athletes and Soldiers have begun using caffeine in energy gels and workout supplements to improve performance. It has appeared in many medications, diet pills and even as a stand-alone caffeine pill. People can’t seem to get enough.

Caffeine isn’t all good, though. Some particular groups of people are especially susceptible to its adverse effects. That panicky feeling I experienced can happen to anyone with a high enough dose. To people with anxiety disorders — including post-traumatic stress disorder, or PTSD — it can trigger anxiety or panic attacks at otherwise normal doses. People with heart conditions would also be wise to avoid caffeine as it can elicit certain irregular heart rhythms.

Caffeine also increases urine output. While this effect is usually quite inconsequential, to someone who is already dehydrated or who rarely drinks anything other than caffeinated beverages, it can induce muscle spasms, lead to kidney injury or cause seizures. Such dehydration is not uncommon for Soldiers in the desert or after a long ruck march.

Research continually shows that children and adolescents are particularly vulnerable to these negative effects, and pediatricians warn that they should not consume caffeine at all. Caffeine has also been associated with miscarriages and pre-term labor in pregnant women. In addition, breastfeeding mothers can pass caffeine to their infants in breast milk, thereby causing restlessness, reflux and agitation.

Fortunately, most healthy adults can benefit from caffeinated products quite safely. If the above risks don’t apply to you, the real question is how much is too much? It seems our society at large lacks a good, working knowledge of caffeine limits. Curious about the general awareness of this, I recently asked an aviator how much he considers to be too much caffeine. He replied, “When my hands start shaking.” Luckily, we can be a little more deliberate than this with our current understanding.

Experts agree 400 mg per day can be safely tolerated by most healthy adults. Of course, 400 mg at once would likely cause problems in just about anyone. In fact, caffeine intoxication is a medical diagnosis that consists of multiple adverse effects and is typically caused by doses of 250 mg or more. Keep in mind that everyone responds to caffeine slightly differently. Some people simply experience a sensitivity to comparatively small doses. Pay attention to how your own body responds to caffeine and set that bar a little lower if nature tells you.

A potentially increasing problem as caffeine spreads to a wider variety of delivery methods is keeping track of your total intake in a given day. The source of the caffeine is irrelevant and each serving has a cumulative effect. This problem is worsened by the fact that some products don’t list their caffeine content on the label. This makes it all-the-more important you arm yourself with knowledge and keep your body safe and healthy.

The internet is a great resource, especially for those products whose labels are lacking. Below is a graphic reference for caffeine content in a variety of sources. Pay special attention to the quantities listed at the bottom, as some sizable doses come in very small packages. You will also see that many products have wide ranges of caffeine content. Depending on your preference, you may surpass the 400 mg mark in two servings or less.

This is far from a comprehensive list, so do your homework on your favorite caffeine delivery products. When used appropriately, caffeine is a beneficial additive to our busy modern lives. If you choose to use it, keep it safe and stay healthy.