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Time for tea? How caffeine affects immune function?

Nutrition · Sep 1, 2020

While excess caffeine can raise cortisol levels and heighten our stress response1, a cup or two of tea or coffee can actually benefit our immune system.2

Some of the ways caffeine can aid our immune system:

  • Drinking filtered coffee is associated with lower levels of circulating inflammatory markers.3

  • Polyphenol antioxidants in coffee and tea can help prevent some cancers,4 heart disease,5 diabetes6 and neurological diseases.7

  • Ethylamine is a metabolic byproduct of L-theanine, a substance in black tea. Ethylamine primes the response of specific T cells, which aid the body’s defense against infection.8

These effects occur when caffeine is consumed in moderation. Up to 400 milligrams of caffeine per day (roughly 3 – 4 cups (250ml) of brewed coffee) is recognized as a safe or moderate amount for most healthy adults, while no more than 300 milligrams is recommended for pregnant or breastfeeding women.9

Caffeine affects everyone differently

It is important to note that caffeine can have varied effects depending on the person consuming it. Some factors that impact an individual’s response to caffeine include frequency of consumption, body mass, age, medication use and mental health. If you are sensitive to the effects of caffeine, any amount of caffeine may have unpleasant effects.

Too much caffeine can be bad

Drinking large amounts of caffeine can release higher levels of the stress hormone cortisol in response to physical and mental stress. Health concerns associated with this stress response can include elevated cholesterol and triglycerides, high blood sugar and suppression of your immune system. Consuming high doses of caffeine can also induce or worsen panic attacks, anxiety, restlessness, nervousness, insomnia, stomach upset, tachycardia, irritability and addiction.

If you think you exceed the ideal amount of caffeine to experience the above benefits, consider the following steps to energize naturally:

  1. Drink a tall glass of water upon rising and between meals.

  2. Stretch, walk, or climb the stairs.

  3. Avoid drinking caffeinated beverages in the afternoon and evening.

  4. Shorten the brew time or try herbal tea.

  5. Rest when possible.

For personalized support with optimizing your immune system, contact our nutrition team.


1 Lovallo, W. et al. 2006. “Cortisol responses to mental stress, exercise, and meals following caffeine intake in men and women.” Pharmacology Biochemistry and Behavior, Volume 83, Issue 3.

2 Horrigan, L. et al. 2006. “Immunomodulatory effects of caffeine: Friend or foe?” Pharmacology & Therapeutics. Volume 111, Issue 3.

3 Frost-Meyer, J. et al. 2012. “Impact of coffee components on inflammatory markers: A review.” Journal of Functional Foods. Volume 4, Issue 4.

4 Hashibe, M., Galeone, C., Buys, S. et al. 2015. “Coffee, tea, caffeine intake, and the risk of cancer in the PLCO cohort.” Br J Cancer.

5 Tung, W. et al. 2020. “Polyphenols bind to low density lipoprotein at biologically relevant concentrations that are protective for heart disease.” Archives of Biochemistry and Biophysics.

6 Bahadoran, Z. et al. 2013. “Dietary polyphenols as potential nutraceuticals in management of diabetes: a review.” J Diabetes Metab Disord.

7 Albarracin, S. et al. 2012. “Effects of natural antioxidants in neurodegenerative disease.” Nutritional Neuroscience.

8 Kamath, A. et al. 2003. “Antigens in tea-beverage prime human Vγ2Vδ2 T cells in vitro and in vivo for memory and nonmemory antibacterial cytokine responses.” Proceedings of the National Academy of Sciences.

9 Government of Canada. 2012. “Caffeine in food.”

Authored by:
Care Centres Team
TELUS Health Care Centres

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