December 18, 2020

The Truth about Caffeine

by Lauren Hoover, MS RD

The Truth about Caffeine + a Healthier Peppermint Mocha Recipe! 

Do you rely on caffeine to wake you up in the morning or to keep you going in the afternoonIf so, know that you are not alone! Coffee is one of the most consumed beverages and the caffeine it delivers is the most widely consumed stimulant in the world. Caffeine is a compound found naturally in plants, including coffee, tea, and cacao, and is often added to products, such as energy drinks, preworkout supplements, hydration tabletsCrystal Light® and soda. SHIFT Dietitians are here to provide more information about caffeine, including recommended intake limits and how it affects hydration, fitness performance, and sleep. 

How does caffeine affect my body?  

Our bodies make a compound called adenosine as a byproduct of various metabolic reactions, particularly through the breakdown of ATP (our body’s form of energy). As adenosine builds up in the bloodstream, it interacts with specific cell receptors to relax the nervous system and, subsequently, causes drowsiness. Caffeine, however, is an adenosine blockerAs a result, it prevents drowsiness and conversely creates feelings of wakefulness and alertness. Moreover, blocked receptors catalyze the release of other natural stimulants that further contribute to the effects of caffeine. 

Research shows that in some individuals moderate caffeine intake can yield some improvement in health outcomes, such as reduced risk of heart disease and type 2 diabetes. However, caffeine is not an isolated factor in these studies and additional factors must be considered (e.g., antioxidants found in caffeinated beverages, like coffee and tea, diet and exercise routine of the participants, genetic predisposition etc.). Overall, the results of the research on caffeine and its health benefits are mixed, mainly due to the high variability of caffeine’s impact on physiology from one individual to another. The way in which caffeine affects us likely has a genetic component. Individuals metabolize caffeine from their systems at different rates producing different effects from individual to individual. Slow” metabolizers do not process caffeine effectively. They feel the jitters easily and are wired for several hours after intake. “Fast” metabolizers usually experience milder boost in energy, but alertness wears off more quickly than “slow” metabolizersThis variability is one of the reasons we avoid making general, population-based recommendations on caffeine consumption.  

What is caffeine withdrawal and how much caffeine is too much?  

Regular, sustained caffeine consumption can lead to the production of more adenosine receptors to compensate for the receptors blocked by caffeine. As suchsome individuals build a tolerance that necessitates higher levels of caffeine consumption to yield the same resultReducing or removing caffeine can decrease tolerance. If you would like to reduce or remove caffeine from your routine, then it is important to consider possible effects of caffeine withdrawalCaffeine withdrawal occurs when caffeine is abruptly removed from the diet. An excess of free adenosine receptors leads to symptoms like headaches and shakiness, among others. These symptoms can be mitigated by slowly reducing caffeine intake rather than going cold turkey 

Current recommendations by the FDA and USDA state up to 400 mg of caffeine (~4 cups of brewed coffee) per day appears to be safe for most adults. Unpleasant symptomsmainly anxiety, restlessness, and headachesare often associated with caffeine intake above this level. Keep in mind that caffeine is found in many products and in varying amounts. Please see the table below for the caffeine content of common products.  

Each individual experiences the effects of caffeine differently. Listen to your own body and how you feel. While research does support some health benefitshigh caffeine consumption has also been associated with disrupted sleep, increased blood pressure, increased risk of heart attack and increased risk of miscarriageBased on the literature, caffeine has a ~5-hour half-life (half-life is the time it takes a substance to be reduced by half). While most individuals experience peak effects from caffeine 30-60 minutes after consumption, caffeine stays in the system for much longer. Because of this, the American Academy of Sleep Medicine recommends avoiding consumption of caffeine within at least 6 hours before bedtime. If you are experiencing restlessness, anxiety, poor sleep or are pregnant, then consider reducing your caffeine intake.  

Are caffeine beverages dehydrating? 

Most research states that daily intake up to 550 mg (~5 cups of coffee) of caffeine will not cause fluid-electrolyte imbalances. We recommend drinking plenty of water throughout the day, and not solely relying on caffeinated beverages for hydration. 

Should I consume caffeine before I exercise? 

Current research supports the conclusion that performance benefits can be seen with moderate amounts of caffeine (~3 mg per kg of body weight). Caffeine can be effective because it reduces the perception of fatigue and allows exercise to be sustained at higher intensities/outputs for longer. These same benefits have been observed in research investigating a wide range of sports, endurance events, and prolonged high-intensity workouts. The effects on performance during strength/power (e.g., power lifting) workouts remain unclear. Given that every individual responds to caffeine differently, possible effects must be considered prior to using it as a pre-workout supplement. 

Caffeine Content by Beverage Type 
Brewed coffee, 8 oz.  90-140 mg (varies) 
Espresso, 1 oz.  65 mg 
Black tea, 8 oz.  45 mg 
Green tea, 8 oz.  28 mg 
Cola, 12 oz. can  35 mg 
Diet Cola, 12 oz. can  45 mg 
Monster®, 16 oz. can  160 mg 
Red Bull®, 8 oz. can  80 mg 
5-Hour energy®, 2 oz.  215 mg 

Do you have more questions about caffeine and how it fits into your life? Contact your SHIFT Registered Dietitian for more information. 


Looking for a festive coffee beverage for this winter season? See below for a healthier take on a Peppermint Mocha from SHIFT’s Registered Dietitians. 

– Lauren & Tavierney 

SHIFT Registered Dietitians


 Café Peppermint Mocha Recipe 

Serves 1 


8 oz. coffee of your choice (recommended dark or espresso roast) 

4 oz. warmed Fairlife® chocolate milk (use a frother, if desired) 

¼ tsp. pure peppermint extract 

Sweetener, if desired (e.g., 1 tsp. honey or sugar-free sweetener of choice) 


  1. Warm milk in microwave, stovetop, or with frother 
  1. Add peppermint extract and sweetener (if desired) to freshly brewed hot coffee. 
  1. Pour warmed milk into coffee and enjoy! 


Nutrient Breakdown 

Nutrient  Amount per serving  (Full recipe) 
Energy   95 calories  
Total Fat   2.2 grams  
     (Saturated Fat)    1.5 grams  
Total Carbohydrates   11.5 grams  
     (Dietary Fiber)   0.5 grams  
     (Sugar)   11 grams  
Protein   6.5 grams  



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