Athletic training: How much caffeine is too much?

Many elite and recreational athletes turn to the world’s most popular drug — caffeine — to boost their performance in training or in a race.

But can you take too much before or during a workout or competition?

“Well, yes — as with anything, too much can be harmful, and not everyone responds to caffeine the same way,” Susan Kitchen, a dietician, triathlon coach and endurance athlete, wrote in Outside magazine.

Natural caffeine is in found in foods like coffee, tea and chocolate. It is also synthetically produced and added to sports gels, chews, energy drinks, sports drinks, chewing gum and dietary supplements. It stimulates the central nervous system by blocking adenosine receptors in the brain, reducing perceived effort, delaying fatigue, reducing pain, and improving mental focus, attention and motivation, per Kitchen.

Boosting athletic performance

The drug enhances various aspects of exercise performance in many but not all studies, according to the National Institutes of Health . Benefits include muscular endurance, movement velocity and muscular strength, sprinting, jumping and throwing performance, as well as a wide range of aerobic and anaerobic sport-specific actions.

Aerobic endurance appears to be the form of exercise with the most consistent moderate-to-large benefits from caffeine use, although the magnitude of its effects differs among people, according to NIH.

Kitchen notes that the physiological response to caffeine is highly individual, adding some are caffeine-sensitive due to genetic variations that affect the breakdown rate. “These variations explain why some people experience adverse side effects at very low doses and cannot tolerate caffeine, while others can drink coffee late in the day and still sleep well,” she wrote.

How much caffeine should I take?

So, what is the proper dose of caffeine to enhance performance but avoid side effects?

“The recommended dose for a performance boost while minimizing side effects is a moderate 2-3 mg/kg of body weight. Higher doses of 5-6 mg/kg of body weight do not further enhance performance, but increase the risk of side effects. Those side effects include headaches, increased anxiety, irritability, rapid heart rate, dizziness, nausea, tremors, elevated blood pressure, insomnia, and gastrointestinal distress. Overconsumption or improper use can lead to severe consequences, including arrhythmias and potentially death,” according to Kitchen.

The best way to determine your effective dose is through repeated and careful experimentation during workouts and race-intensity training, Kitchen said. The NIH suggests that 2 milligram/kilogram body weight is a reasonable starting dose for most athletes.

Know what you’re ingesting

Kitchen said it’s important to know what you’re taking and how much caffeine it contains. The FDA does not regulate beverages and supplements containing synthetic caffeine, such as energy drinks and powdered caffeine, so they’re not required to disclose the amount of caffeine or list ingredients on the label.

Caffeine peaks in the bloodstream 60 minutes after consumption and has a half-life of approximately five hours, the time it takes the body to break down 50% of it.

The body absorbs synthetic caffeine faster and it takes effect faster than natural caffeine. After a person ingests caffeine, say in their morning coffee or a sports energy drink , it’s absorbed through the stomach and travels through the bloodstream, readily moving throughout the body in water to the brain, where it binds to adenosine receptors. The body, however, absorbs caffeine from chewing gum directly through the lining of the cheeks inside the mouth, bypasses the liver and enters the bloodstream within five to 15 minutes.