Is Coffee Poison? | Cliff Harvey on Patreon

Cliff Harvey PhD
6 min readMar 3, 2019


TL: DR — NO!

Having said that…I don’t want to know if it is!

BUT — lately, I’ve seen popping up (again), articles with titles like “Coffee is Poison!” and rather than just saying “Um. No. It’s not.”

(Well, technically it can be…but y’know dose, frequency, exposure etc.)

I figured I’d look at what the actual science says about it.

Coffee might be protective against diabetes.

Systematic reviews suggest a dose-dependent correlation between coffee intake and reduced rates of diabetes with the greatest effects seen in those consuming the highest amounts of coffee (greater than six cups per day). (1–3) For every additional cup consumed, there is an approximately 7% reduction in diabetes risk and benefits are also seen from tea and decaffeinated coffee. (4)

Be more cautious if you have a familial history of heart disease or other risk factors.

Coffee does increase blood pressure (BP) acutely (although these studies use high amounts in the range of 200–300 mg, approximately 2–3 cups of coffee) and this has led clinicians to urge caution with coffee intake due to a perceived risk of cardiovascular disease (CVD). But there appears to be no correlation between long-term, habitual use of coffee with cardiovascular disease or chronic high blood pressure. (5, 6) Low intakes may even be more likely to increase blood pressure with 1–3 cups demonstrating an effect on BP and 3–5 cups showing no long-term effect. (7) Likewise, low intakes have been demonstrated to increase CVD risk slightly (less than three cups per day) with 3–5 cups per day associated with reduced CVD.(8)

Coffee is likely to be beneficial for liver disease

In chronic liver disease, patients who consume coffee have a decreased risk of progression to cirrhosis, a lowered mortality rate, and in chronic hepatitis C patient coffee was associated with improved responses to antiviral therapy. Moreover, coffee consumption is inversely related to the severity of steatohepatitis (fatty liver) in those with pre-existing non-alcoholic fatty liver disease (NAFLD). It is therefore recommended that those with liver disease should be encouraged to drink coffee daily. (9) Gallstone risk is also reduced with higher coffee intakes, with the highest consumption (around six cups or more) associated with the lowest risk. (10)

Women may have an increased risk of bone fracture with higher coffee intakes.

Fracture risk rises in a dose-dependent manner in women but not with men. There is little difference in fracture risk around two coffees per day. (11)

Coffee is no longer listed as a carcinogen by the World Health Organisation. BUT if you drink it too hot, it can increase risk of mouth and throat cancers

There does not appear to be any other strong link between coffee consumption and gastric cancer, (12) breast cancer, (13) or colorectal cancer, although there may be a small positive effect seen in women coffee drinkers. (14) There may also be a minor increase in urinary tract cancer associated with coffee drinking, (15) and cancer of the larynx also rises in a dose-dependent manner. (16)

Coffee — a healthy mood-enhancer.

Coffee may also offer some mild protective effect against cognitive decline and dementia, (17) and depression. (18)

What does it all mean?!

A systematic review of seventeen studies including over one million participants and 131,212 death events was conducted by Yimin Zhao and colleagues in May 2015. The review and meta-analysis determined a ‘U-shaped dose-response relationship’ between coffee intake and all-cause mortality. Mortality was reduced at all levels of coffee intake with the greatest effects seen at 3–5 cups. (19)

Based on the evidence, coffee is safe (for most people) and offers significant benefits to health.

The reason for the benefits is likely to be multifactorial and include the effects of caffeine itself and the range of antioxidant chemicals found in coffee.

The optimal health intake appears to be around 3–5 cups of coffee per day.


If you’re overly stressed out, not sleeping well, or you experience negative effects from caffeine; either reduce your dose, switch to decaf or tea (which still offer most of the benefits) or get rid of the coffee altogether.

Remember that what works for most, does not always work for you.


1. van Dam RM, Hu FB. Coffee consumption and risk of type 2 diabetes: A systematic review. JAMA. 2005;294(1):97–104.

2. Muley A, Muley P, Shah M. Coffee to Reduce Risk of Type 2 Diabetes? : A Systematic Review. Current Diabetes Reviews. 2012;8(3):162–8.

3. Ding M, Bhupathiraju SN, Chen M, van Dam RM, Hu FB. Caffeinated and Decaffeinated Coffee Consumption and Risk of Type 2 Diabetes: A Systematic Review and a Dose-Response Meta-analysis. Diabetes Care. 2014;37(2):569–86.

4. Huxley R, Lee C, Barzi F, et al. Coffee, decaffeinated coffee, and tea consumption in relation to incident type 2 diabetes mellitus: A systematic review with meta-analysis. Archives of Internal Medicine. 2009;169(22):2053–63.

5. Mesas AE, Leon-Muñoz LM, Rodriguez-Artalejo F, Lopez-Garcia E. The effect of coffee on blood pressure and cardiovascular disease in hypertensive individuals: a systematic review and meta-analysis. The American Journal of Clinical Nutrition. 2011.

6. Steffen M, Kuhle C, Hensrud D, Erwin PJ, Murad MH. The effect of coffee consumption on blood pressure and the development of hypertension: a systematic review and meta-analysis. Journal of Hypertension. 2012;30(12):2245–54.

7. Zhang Z, Hu G, Caballero B, Appel L, Chen L. Habitual coffee consumption and risk of hypertension: a systematic review and meta-analysis of prospective observational studies. The American Journal of Clinical Nutrition. 2011;93(6):1212–9.

8. Ding M, Bhupathiraju SN, Satija A, van Dam RM, Hu FB. Long-Term Coffee Consumption and Risk of Cardiovascular Disease: A Systematic Review and a Dose-Response Meta-Analysis of Prospective Cohort Studies. Circulation. 2013.

9. Saab S, Mallam D, Cox GA, Tong MJ. Impact of coffee on liver diseases: a systematic review. Liver International. 2014;34(4):495–504.

10. Zhang YP, Li WQ, Sun YL, Zhu RT, Wang WJ. Systematic review with meta-analysis: coffee consumption and the risk of gallstone disease. Alimentary Pharmacology & Therapeutics. 2015;42(6):637–48.

11. Lee DR, Lee J, Rota M, Lee J, Ahn HS, Park SM, et al. Coffee consumption and risk of fractures: A systematic review and dose–response meta-analysis. Bone. 2014;63:20–8.

12. Botelho F, Lunet N, Barros H. Coffee and gastric cancer: systematic review and meta-analysis. Cadernos de Saúde Pública. 2006;22:889–900.

13. Pillay L. A Systematic Review: Examining the Relationship Between Coffee Consumption and Breast Cancer: Georgia State; 2013.

14. Je Y, Liu W, Giovannucci E. Coffee consumption and risk of colorectal cancer: A systematic review and meta-analysis of prospective cohort studies. International Journal of Cancer. 2009;124(7):1662–8.

15. Zeegers MP, Tan FE, Goldbohm RA, van den Brandt PA. Are coffee and tea consumption associated with urinary tract cancer risk? A systematic review and meta-analysis. International Journal of Epidemiology. 2001;30(2):353–62.

16. Chen J, Long S. Tea and Coffee Consumption and Risk of Laryngeal Cancer: A Systematic Review Meta-Analysis. PLoS ONE. 2014;9(12):e112006.

17. Panza F, Solfrizzi V, Barulli MR, Bonfiglio C, Guerra V, Osella A, et al. Coffee, tea, and caffeine consumption and prevention of late-life cognitive decline and dementia: A systematic review. J Nutr Health Aging. 2015;19(3):313–28.

18. Grosso G, Micek A, Pajak A, Castellano S, Galvano F. Coffee, tea, caffeine and risk of depression: a systematic review and dose-response meta-analysis of observational studies. Molecular Nutrition & Food Research. 2015:n/a-n/a.

19. Zhao Y, Wu K, Zheng J, Zuo R, Li D. Association of coffee drinking with all-cause mortality: a systematic review and meta-analysis. Public Health Nutrition. 2015;18(07):1282–91.

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Cliff Harvey PhD

Author | Clinical Nutritionist | Researcher | Educator at