Caffeine: Helpful or Harmful?

By: Stacy Kennedy, MPH, RD, CSO, LDN; Reboot Nutritionist

Coffee and caffeine are often seen as the antithesis to a healthy diet and especially a juice only program like a Reboot.  But is caffeine actually helpful or harmful?  Just like most things in the world of nutrition, it all depends on your individual context.  


  • Coffee, tea and chocolate, our most common forms of caffeine in the Western diet, all contain antioxidants because they are derived from plants.  
  • Studies show that women who consume coffee may have a lower risk of developing certain forms of breast cancer.  A recent study in Australia found that consumption of black tea, green tea and decaf coffee were not associated with increased risk of colorectal cancer and herbal tea actually a reduced risk while iced coffee was associated with an increased risk of developing a specific form of colon cancer, possibly linked to the dairy content. 
  • Migraine sufferers can benefit from caffeine which can interfere with the rush of blood to the brain that is thought to be at least partly responsible for symptoms like headache, dizziness, aura (seeing colors or spots) and pain.  Caffeine constricts blood vessels which in this case can be a good thing.  


  • What are you putting in your coffee?  Nothing at all is the healthiest choice.  If you’re adding cream, half and half, whole milk, sugar or artificial sweeteners, it’s these additives not the coffee itself that is unhealthy when consumed on a regular basis.  Natural stevia without any added ingredients can be a healthy choice and there are many “creamers” on the market that are dairy free like coconut or almond milk based options.  
  • Frequency.  One cup of black coffee a day really isn’t harmful but drinking 3, 4 or 6+ cups a day especially when this replaces meals or water that our bodies crave and need, caffeine could certainly be seen as harmful. 
  • Caffeine is a drug that needs to be metabolized by the liver.  In small amounts it’s not at all harmful according to the latest scientific research.  But as with many things, when consumed in excess it’s a whole different story.     
  • Why do we recommend abstaining from caffeine during a reboot?  Simply put, a Reboot is a time when you’re drastically boosting up your intake of healthy fruits and veggies, some like kale and broccoli, contain compounds that can help support natural detoxification processes in the liver.  Since caffeine requires work by your liver to metabolize this substance, you’re effectively adding in more work when your goal is to reduce this work load.  For more on caffeine during your reboot, check out these FAQs and this article.

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Stacy Kennedy, MPH, RD, CSO, LDN; Reboot Nutritionist

Stacy is a Board Certified Specialist in Oncology Nutrition and an Integrative Nutritionist. She consults for various companies, focusing on health, wellness and innovative strategies to help increase individual’s fruit and vegetable intake. Stacy is an American College of Sports Medicine Certified Health Fitness Specialist; she holds a BS degree in Dietetics from Indiana University, completed her dietetic internship at Massachusetts General Hospital, and earned a Masters in Public Health from the University of North Carolina at Chapel Hill. She is a Senior Clinical Nutritionist at the Dana Farber Cancer Institute/Brigham & Women’s Hospital, Harvard Medical School teaching affiliates, in Boston, MA, with more than 20 years of experience. Stacy created and now serves as project manager and lead writer for nutrition services content on the Dana Farber website and the affiliated, nationally recognized nutrition app. Stacy is regularly featured on TV, radio, print and social media on behalf of Dana Farber and other organizations. Together with her husband, Dr. Russell Kennedy PsyD, they have a private practice, Wellness Guides, LLC. Stacy is an adjunct professor in Wellness and Health Coaching at William James College, currently teaching a graduate course in Health Coaching. Stacy is featured in the award winning documentary films, “Fat, Sick & Nearly Dead” and “Fat, Sick & Nearly Dead 2,” and serves on the Reboot with Joe Medical Advisory Board. Stacy lives in Wellesley with her husband, two sons and three dogs. She enjoys cooking, yoga, hiking and spending time with friends and family. Stacy is also one of the nutritionists who runs our Guided Reboot programs.

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