You love your morning coffee. You count on your afternoon latte. You enjoy your post-dinner espresso and yes, you drink a caffeinated pre-workout because it gives you a nice kick in the butt. And you’re not alone; caffeine is the most commonly consumed drug in the world. But it’s also commonly misunderstood. With the help of nutritionist Mike Roussell, PhD, we offer some clarity on some of the common conundrums surrounding caffeine.

There is no real difference between caffeine from natural and synthetic sources

Natural caffeine is extracted from plants, including tea leaves, guarana berries and the seeds of coffee beans, Kola nuts, and cacao beans. Synthetic caffeine is derived from urea and chloroacetic acid, and has become the norm in energy drinks and sodas because it’s cheaper to produce. While virtually the same on a molecular level, synthetic caffeine is often more quickly absorbed, providing a faster spike and subsequently a faster crash. For some perspective, a 12-ounce coffee contains 135 mg of caffeine, while a 12-ounce energy drink contains 110 mg. By contrast, a tablet caffeine supplement typically contains over 200 mg. “The levels of caffeine you get from a cup of coffee versus a supplement will be a lot different,” Roussell says. “You have to be careful, because you may be consuming a lot more than you think.”

It's Genetic

Some people drink one cup of coffee and become jittery, sweaty, and anxious. Others become laser-focused, while still others can drink four cups of coffee and immediately take a nap. This is because how you metabolize coffee is genetic. There is a gene that controls an enzyme that determines how quickly our bodies break down caffeine. Fast metabolizers tolerate caffeine well and clear it from their systems four times more quickly than slow metabolizers, who feel the effects of caffeine more and for a longer period of time. Also keep in mind that the half-life of caffeine, while variable based on factors like age, weight and liver health, is between four and six hours. That means if you’re not a fast metabolizer, the coffee you drink at noon can still be in your system at 10 p.m. and can cause a disruption in your sleep.

Dark roast coffee often has less caffeine than light roast coffee

As coffee beans roast, they lose water, and the longer the roast time, the more water the beans will lose. When the ground beans are measured by volume, the the light roast grounds are denser and weigh more than the darker roasted beans, which means per unit volume, there is more caffeine in light roast coffee than dark roast. “People assume that because dark roast coffee has a stronger, more bitter taste, it has more caffeine,” Roussell says. “The smell of it may make you go, ‘whoa,’ but sniffing coffee doesn’t give you caffeine.”

Like anything else, you get used to it

“Your body habituates to caffeine within five days,” says Roussell. “99 percent of the effects of caffeine consumption are purely placebo.” That means with each consecutive day you consume caffeine, the effect on your body diminishes. And by the fifth day, the alertness and energy you feel from your daily cup of Joe are purely perceived. To feel a real effect, the dose of caffeine would have to be increased each day. However, that is not a directive! Placebo effects are just as good as the real thing.

Caffeine won’t make you dehydrated

Caffeine has been thought to have a dehydrating effect on those who consume it since a 1928 study documented increased urination in those who drank caffeinated beverages. However, it has since been proven that drinking caffeinated beverages does not cause fluid loss in excess of the volume ingested. “Caffeine can certainly increase the frequency in which you urinate, but it doesn’t lead to dehydration,” Roussell says. “Peeing more often just makes you feel like you’re losing more liquid.” So yes, caffeine is a diuretic, but it won’t actually make you dehydrated, and a higher dose of caffeine is no more likely to cause dehydration than a lower dose. However, that’s not to say it’s a good idea to choose caffeinated beverages for hydration. Too much caffeine can cause headaches and insomnia, so water is still your best bet!

Caffeine may make you more alert, but …

Caffeine consumption has been associated with increased alertness, an increase in reaction time and a decrease in perceived muscle pain and fatigue, which are all good things for athletes. However, a 2019 study showed that while caffeine improved reaction times, it did not improve the accuracy of those reactions. “The benefit of caffeine from an athletic performance standpoint is shown more clearly with endurance exercise, but if you’re in a sport where a millimeter or an inch make a difference, that’s a total negative for caffeine.”

Caffeine may help you burn some fat, but it’s not as effective as you think

Yes, caffeine does increase your body’s ability to oxidize fat, but according to Roussell, these effects are minor in the grand scheme of pounds lost. And while green tea and green tea extracts, which contain the antioxidant EGCG, are often touted for their fat-burning effects, Roussell says caffeine is a key component. One way caffeine can help you drop pounds, however, is that it decreases the rate of perceived exertion during exercise. “Caffeine makes you think you aren’t working as hard as you really are,” Roussell explains. “That, coupled with a decrease in fatigue from exercise will allow you to work harder and thus burn more calories when you exercise.”



Freelance Sports Journalist -

Lindsay Berra is a New Jersey-based freelance sports journalist who contributes regularly to the Sports Business Journal, Baseball America, ESPNW, Fast Company, Men’s Health, and other outlets. At and MLB Network from 2013 through 2018, she established herself as an authority on baseball fitness and injuries. As a senior writer for ESPN Magazine from 1999 through 2012, she covered primarily ice hockey, tennis, baseball and the Olympics. Lindsay graduated from the University of North Carolina at Chapel Hill, where she played varsity softball and men’s club ice hockey. She is a Level 1 CrossFit coach, triathlete, avid hiker and yogi.