The Downsides of Caffeine For Athletes

by Lori Russell, MS RD CSSD
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The Downsides of Caffeine For Athletes

Caffeine is a substance that many start the day with to feel awake and focused. Others use it for special occasions like long drives or late-night engagements to stay alert. Athletes use it to boost performance. It is the most well-studied, legal performance aid.

Since caffeine was removed from the World Anti-Doping Agency’s list of banned substances, roughly 75% of athletes use caffeine strategically for performance. While it is popular and known to improve results, the supplement has downsides that might not be right for everyone.


The brain can increase receptors for caffeine with long term, high intake which means you need more to feel the same effects. Consuming a little bit each day can easily lead to consuming a moderate and then a large amount because you build a tolerance to it. This could happen without you even being aware, due to the prevalence of caffeine in food, drinks and supplements — caffeine is in waters, gums, sport gels; even a standard cup of coffee or tea can vary greatly in caffeine content.

The fix: Tracking your eating and drinking habits can be a great tool to figure out how much you are taking in each day.


Caffeine’s main job is to keep you alert, which is great — unless you need to get some shut-eye. How quickly or slowly you process caffeine varies from person to person based on factors such as age, gender, diet, disease and genetics. The stimulant typically stays in the body for 4–6 hours. Athletes who consume high amounts of caffeine for late-day training or to combat feeling exhausted after early morning training, might be hindering their sleep and ultimately their performances.

The fix: Try consuming caffeine before noon to increase your odds of getting adequate rest.


Those concerned with their fitness routine are typically also invested in healthy eating habits. Unfortunately, consuming caffeine can interfere with the absorption of key nutrients needed to keep an active body healthy such as B vitamins, iron, calcium, and magnesium. In fact, consuming caffeine with a meal can reduce the absorption of heme iron by 50% and non-heme iron by more than 60%.

The fix: To ensure you’re still getting enough nutrients everyday, consume caffeine away from meals, eat nutrient-rich foods and take a daily vitamin to cover your bases.


The scientific literature available does not come to a clear conclusion on whether caffeine is good or bad for your heart. In general, using up to 600mg (roughly 6 cups of coffee) per day is considered safe, but limited research is available for those consuming over that amount. About 25% of adults consume more than 600mg, making it a legitimate concern. While those involved in ongoing physical fitness generally have better heart health than sedentary people, there is a known increase in the risk of experiencing cardiac events during serious performances, such as during a marathon. Consuming excessive pre-race caffeine could heighten this risk.

The fix: Wear a heart rate monitor during workouts to get a better idea of your caffeine response — tracking if and how much caffeine was consumed. Reducing caffeine content before/ during workouts might be key if you are a high consumer.


Caffeine can negatively interact with many medications by either blocking or exacerbating their absorption. One study found taking thyroid medication with coffee reduced absorption of the medication by roughly 50%. Some antibiotics, osteoporosis drugs and antidepressants can also be affected by caffeine consumption.

The fix: If you take medication, speak to your doctor or pharmacist and act accordingly.


Many of these issues are personal and vary highly from individual to individual, making specific guidelines difficult to advise. If you suspect caffeine is causing your body or mind stress, start reducing the amount you consume each day. Once the substance is eliminated, you can evaluate how you feel and whether or not you wish to return to using caffeine daily, for performances only or not at all.

About the Author

Lori Russell, MS RD CSSD

Lori, MS RD CSSD is an accomplished sports dietitian; she holds a Master’s Degree in Human Nutrition and Certification as a Specialist in Sports Nutrition. As a current professional road cyclist and previous elite marathoner and ultra-runner, Lori knows firsthand that food can enhance or diminish performance gains. She understands the importance of balancing a quality whole food based diet with science-backed performance nutrition and strives to share this message with others. Learn more about her @HungryForResults.


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