Thankfully for millions of athletes around the globe, coffee can be enjoyed guilt-free as part of a healthy sports diet. Coffee contains nutrient-dense plant compounds called phytochemicals that promote health and offer strong anti-oxidant and anti-inflammatory properties. Studies suggest coffee can actually improve heart-health. That said, high coffee/caffeine intakes can trigger pre-existing cardiovascular conditions such as atrial fibrillation. And, needless to say, coffee brimming with sugar, flavorings, cream, and coffee whitener is not a part of this conversation!

Scientifically speaking, coffee and caffeine are two different substances. Caffeine is pure and comes in standardized doses (such as NoDoz, caffeinated chewing gum, caffeinated sports gels,). The average American consumes 165 to 230 mg. caffeine per day—that's more-or-less the amount in two small (8-oz) cups coffee or a 16-oz Starbucks Grande. The caffeine content of coffee varies according to the type of bean, how it is roasted, ground, and brewed. Analysis of 20 commercial espressos reported the caffeine content was inconsistent and ranged between 50 to 320 mg per 8-ounce serving. FDA's recommended daily limit is 400 mg caffeine per day.

Although coffee is the most popular form of caffeine, other sources include:

Caffeine appears quickly in the blood (within 5 to 45 minutes after ingestion). Its impact generally peaks within 15 to 120 minutes and the boost can last for ~4 to 6 hours. By that time, half of the caffeine has been metabolized by the liver. By 10 hours, caffeine generally will have been completely cleared from the bloodstream. Caffeine's impact varies widely person to person, depending on genes that influence the breakdown of caffeine. Athletes who are fast metabolizers of caffeine get an immediate boost. Others are slow metabolizers. Learn your body's response!

For athletes who already feel anxious before a competitive event, pre-exercise caffeine can put them over the edge by increasing jitters and anxiety levels. A better time to consume caffeine to enhance performance can be when the athlete starts to feel tired (as opposed to taking it an hour pre-exercise). Delaying caffeine use until the onset of fatigue gives a welcomed boost. Caffeinated gels, sports drinks or sports chewing gums are popular energizers during endurance exercise!

Given most athletes know that coffee/caffeine can make a workout seem easier, this article addresses other questions asked about this beloved morning wake-me-up-er and idolized afternoon energizer.

Do habitual coffee drinkers get the same performance benefits as non-users? 

Yes. If you habitually drink coffee every day, you may need a higher dose of performance-enhancing caffeine than a coffee-abstainer. A proposed dose is about:

For a 150-lb athlete, this ranges widely between 150-450 mg. per dose.

The days before your event, there's no need to stop drinking coffee. You'll simply suffer through withdrawal symptoms like headaches. You won't get an added boost from abstinence followed by an event-day jolt of caffeine.

How much is too much coffee/caffeine?

The FDA's suggested 400-milligrams of caffeine per day is a safe dose for most adults. That's the amount in about four 8-oz cups (32 oz.) of coffee, 10 cans of cola, or four 12-ounce cans of Red Bull. If you are pregnant, abstaining from coffee will minimize the risk of miscarriage or other negative outcomes. A toxic amount is 1,200 mg caffeine taken in one dose. Unlikely to happen, but not impossible...

Does coffee/caffeine "work" for every type of athlete?

Yes, caffeine can effectively—and equally—help males and females, sprinters and endurance athletes, power athletes and teams. Athletes have sought-out caffeine for more than 100 years. It improves  both physical and mental performance. Caffeine increases arousal, alertness, vigilance, and mood. It reduces perception of pain and can make a tough workout seem a lot easier! That said, caffeine's effectiveness is variable. The response is weaker for some athletes and stronger for others, depending on  their genetic predisposition.

The suggested performance-enhancing dose is between 1.5-3 mg/lb (3 - 6 mg/ kg). That equates to roughly 200 to 400 mg for a 150-lb (68 kg) athlete. That said, each athlete needs to experiment during training to learn the right dose, timing, and source of caffeine for their body. Perhaps a sip of morning coffee does the job? Or maybe you benefit from an hourly caffeinated gel during the marathon? Whatever you do, don't over-do it! More is not better, and you want to be able to sleep that night...

Is coffee dehydrating when taken during exercise? When consumed throughout the day?

No. Caffeine is not a diuretic. Drinking coffee does not lead to dehydration. A study with 50 habitual male coffee drinkers who consumed coffee with ~300 mg. caffeine four times a day indicated no difference in urine output compared to when they drank the same amount of plain water. That means you can count coffee as water, even when exercising in the heat. It replaces sweat losses and contributes to the daily recommended 8 glasses water a day.

Many athletes believe coffee has a diuretic effect because, after having consumed a mugful of coffee, they need to visit the bathroom. While they might need to pee quicker than if they had consumed plain water, in 24-hours, they won't pee more than they consumed. (That is, unless they consume very high doses of caffeine (>6 mg/kg or >500 mg/dose). By that point, they would likely feel yucky and jittery.

The bottom line:

If you are a coffee drinker, please enjoy your morning brew guilt-free (as long as it is not loaded with cream, sugar, and excess calories). As an athlete, you may want to learn how to best use coffee/caffeine as a potential performance enhancer. That said, no amount of caffeine will compensate for inadequate sleep and an irresponsible sport diet. Fuel wisely, sleep well, train appropriately, and then add some caffeine, if desired.

Nancy Clark MS RD CSSD  counsels both fitness exercisers and competitive athletes in the Boston-area (617-795-1875). Her best-selling Sports Nutrition Guidebook is a popular resource, as is her online workshop. Visit NancyClarkRD.comfor more information.

For more information:
Antonio J. et al. (2023) Common questions and misconceptions about caffeine supplementation: what does the scientific evidence really show? J Int'l Soc Sports Nutr 21:1, 2323919

Lowery L et al. (2023) International society of sports nutrition position stand: coffee and sports performance. J Int'l Soc Sports Nutr 20:1,2237952