What You Need to Know About Caffeine

Caffeine is a stimulant that affects the central nervous system. It can offset many of the hindering effects of fatigue and improve mental alertness. Caffeine is one of the most widely accepted performance enhancing substances out there with evidence to support its use. Whether or not caffeine will work for you will depend on the amount you consume, the form, and the timing relative to training or competition.

What Does It Do?

Caffeine can enhance endurance performance and improve reaction time, concentration, and your self-perceived energy levels. It delays the feelings of exhaustion and decreases the perception of effort and pain. Due to these properties, you may find you are able to train at higher intensities or for longer periods of time.

Where’s It Found?

Caffeine is found naturally in food and can also be synthetically made and added to products. Either way, the caffeine is identical.

Caffeine is found in products such as coffee, tea, soda, and chocolate. Caffeine is also commonly found in energy drinks, bars, and gels. Cacao, guarana, guayusa, kola nut, and yerba mate are other ingredients that are commonly included in energy drinks and may be added to other products that are also a source of caffeine. The amount of caffeine found in medications, energy gels, and bars tends to be consistent, while the amount in coffee and tea can vary considerably due to preparation methods.

Here’s the approximate caffeine content of some common items.

• 2 fluid ounces energy shot: 200 milligrams
• 8 fluid ounces coffee: 100 to 200 milligrams (home-brewed coffee will usually come in at the lower end of this range, while coffee from places like Starbucks will have more)
• 1 fluid ounce shot of espresso: 75 milligrams
• 8 fluid ounces black tea: 50 to 100 milligrams
• 8 fluid ounces green tea: 20 to 50 milligrams
• 8.4 fluid ounces energy drink: 80 milligrams (will vary depending on brand)
• 12 fluid ounces diet cola: 46 milligrams
• 12 fluid ounces regular cola: 35 milligrams
• Energy gels and gummies: 20 to 150 milligrams per serving
• 1.5 fluid ounces dark chocolate: 35 milligrams
• 8 fluid ounces hot cocoa: 5 milligrams
• 8 fluid ounces chocolate milk: 2 milligrams

Sources include the U.S. Department of Agriculture and product websites.

Caffeine pills that can be purchased over the counter generally contain 100 to 200 milligrams and migraine headache medications have around 65 milligrams per pill.

Be cautious with energy drinks, pills, and other “preworkout” mixes as stimulants such as synephrine, ma huang, or geranium may be present and may or may not be listed on the label. When these substances are combined with caffeine, serious health consequences can result. It’s important to read labels to verify how much caffeine you’re consuming and obtain supplements from reputable sources.

How Much to Consume?

So, how much is enough to reap the benefits? Generally, a dose of 2-3 milligrams per kilogram of body weight 1 hour before activity is recommended. You may consider starting with a lower dose and increasing gradually to gauge your body's reaction. So, if you’re 150 pounds then you might consider a dose of 70 to 200 milligrams.  The effects of caffeine will likely last 3 to 4 hours.  

For longer events, it may be beneficial to consume another dose of caffeine a few hours into the event, depending on its length. Some athletes may prolong the effects of caffeine during a lengthy event by consuming a low dose of caffeine during the event in addition to taking caffeine before the event. Every athlete will respond differently to various amounts of caffeine, so it’s important to experiment. You should experiment during training, not right before a swim meet. You’ll want to try different doses gradually to understand how much provides you with a performance-enhancing benefit. Lower doses have been shown to be effective and are also less likely to cause side effects.

Is It Safe?

It’s possible to experience side effects such as jitteriness, an inability to focus, anxiety, insomnia or disrupted sleep, gastrointestinal distress, or an elevated heart rate.

More is not necessarily better. Caffeine consumed in very high doses (6 to 9 milligrams per kilogram of body weight) can actually have negative impacts on training, performance, and sleep. It’s usually helpful to avoid caffeine in the late afternoon and evening hours to avoid disruptions in sleep.

For healthy adults, it’s safe to consume 400 milligrams of caffeine throughout the day (except pregnant and nursing women, who should consume only up to 200 milligrams of caffeine daily).

Should You Try It?