By Danielle Fryer, RDN, CSCS
Caffeine is a 15-year, well-researched, performance-enhancing aid! In numerous scientific studies, the conclusion is clear that caffeine enhances mental functioning, especially after sleep loss and long bouts of exercise. While active, caffeine reduces the feeling of perceived exertion (how hard you feel you’re working). Also, caffeine improves exercise endurance performance (how long you are active in one session) by one to eight percent.
Caffeine affects the brain by binding to adenosine receptors, preventing adenosine from binding to its receptors. Adenosine is a central nervous system neurotransmitter created in the brain. When adenosine binds to its own receptors, it makes you feel sleepy. Therefore, when caffeine binds to adenosine receptors, instead, it decreases the sleepiness effect of adenosine and you feel alert. Genetics play a role on how you adapt to caffeine and sleep. Long term caffeine users alter the expression of adenosine receptors in the body. This explains why some people say caffeine doesn’t affect them. These people can consume caffeine then go to sleep with no trouble, because they have altered their adenosine receptors with habitual use of caffeine. A tolerance to caffeine occurs when it is consumed daily. The more you consume, the more you need to feel the stimulus response. The greater performance impact of caffeine occurs best with non-habitual consumers.
Caffeine is a mild diuretic but does not lead to excess fluid loss during exercise or rest. Caffeine does not dehydrate you if daily doses do not exceed 400 mg per day. Per day, 400 mg of caffeine is considered safe and should not have a negative effect on fluid balance or urine output.
How to dose: Take 45 to 60 minutes before activity. The best time to consume caffeine is before exercise. Caffeine effects peak in 15 to 120 minutes after consumption. If taking caffeine during activity, consume with carbohydrates for greater efficacy.
Consuming 3 to 6 mg caffeine per kg BW (1.36 to 2.73 mg per pound) can improve vigilance, alertness, mood and cognitive processes.
Example: 130-lb. person x 1.36 mg = 176.8 mg in one sitting.
- 8 ounces of coffee provides 95 mg of caffeine.
- 8 ounces of black tea provides 47 mg of caffeine.
- 12 ounces of soda provides 29 mg of caffeine.
- Most pre-workout drinks contain 150-200 mg of caffeine per serving.
- One tablet of vivarin contains 200 mg of caffeine.
Please take note that larger doses (more than 400 mg per day) do not lead to greater performance benefits. Instead, it increases your risk of side effects like anxiety, jitteriness, depressed immune function, and depletion of serotonin. Caffeine’s half-life is between 1.5 to 9.5 hours. This wide range can be affected by oral contraceptives, obesity, smoking, altitude, genetics, and intake of other stimulants.
Danielle Fryer RDN, CSCS is an advocate for healthy living. Fryer is a registered dietitian nutritionist, specializing in sports dietetics, certified strength and conditioning specialist and yoga teacher. She has served in fitness and nutrition leadership roles in Pennsylvania, New Jersey, Alabama, and Arizona. She now lives in Scottsdale and works as the new Director of Health & Fitness at The Country Club at DC Ranch.