Is it harmful to drink four cups of coffee every day?

Hi. Glad to meet another coffee lover. I am personally addicted to coffee myself, and I am glad to share with you the current research findings about drinking coffee.

Firstly, drinking excessive amounts of coffee can lead to plenty of gastric problems, such as gastritis or gastro-oesophageal reflux disease. So if you have been diagnosed with a condition and your doctor specifically asked you to cut down or quit drinking coffee, please listen to him. He knows you and your condition personally and his advice will take precedence over what I write here.

Now that we get that out of the way, let's look at the research.

1. All causes of mortality - Two pieces of research published in 10 Jul 2017 in Annals of Internal Medicine reported coffee intake is linked to significantly lower risk for death from all causes. The more you drink, the lower the chances of you dying from any reason.[1]
2. Cardiovascular disease - Caffeine has been shown to reduce the risk of coronary disease (aka heart attack), heart failure, and atrial fibrillation.[1]
3. Stroke - A huge study (meta-analysis) found that drinking 1 to 6 cups of coffee a day cuts the risk of stroke by 17%, while other studies show it can reduce the risk by 20 - 25%.[2] Yeah for coffee!
4. Diabetes - believe it or not, many studies have shown regular coffee drinking with reduced risk of diabetes.[3] That is if you drink your coffee without sugar of course.
5. Cancer - Drinking coffee has been shown to reduce the risk for the following cancers - endometrial, prostate, head and neck cancers, breast, basal cell carcinoma, melanoma, and colorectal cancer.[4]
6. Neurodegeneration - Apart from giving you your daily mental boost, coffee appears to slow down progression in mild cognitive impairment, prevention of Lewy Body formation, and also to be neuroprotective in Parkinson's disease as well.[5]
7. Depression - Moderate coffee consumption has been found to reduce the risk of depression by 15-20%.[6]
8. Liver Disease - Coffee consumption has been shown to protect the liver, slowing the progression of alcoholic cirrhosis, Hepatitis C, and reducing the risk of hepatocellular carcinoma. Other research have found it to lower the risk of Non-Alcoholic Fatty Liver Disease (NAFLD), and liver fibrosis in patients who already have NAFLD.[7]

Sounds wonderful, right? Along with all medicine/drugs, there is always a downside. Here are the risks of coffee consumption:

1. Raising the blood pressure
2. Worsens anxiety
3. Insomnia
4. Increases the risk of glaucoma

So, to answer the question, there are plenty of health benefits that drinking 1-5 cups of coffee have been shown to provide. But the sugar and milk content in the coffee are actually harmful when taken in large amounts. So, keep your coffee to Kopi-O-Kosong (that is coffee without sugar and milk), and bottom's up!

Just stop when you have side effects.

Cheers!

Dr Seah Heap Yong

References:

1. Junya Sado, Tetsuhisa Kitamura, Yuri Kitamura, Rong Liu, Emiko Ando, Tomotaka Sobue, Yumi Sugawara, Keitaro Matsuo, Tomio Nakayama, Ichiro Tsuji, Hidemi Ito, Takaichiro Suzuki, Kota Katanoda, Suketami Tominaga, Coffee Consumption and All-Cause and Cardiovascular Mortality　― Three-Prefecture Cohort in Japan ―, Circulation Journal, 2019, Volume 83, Issue 4, Pages 757-766, Released March 25, 2019
2. Susanna C. Larsson, Nicola Orsini, Coffee Consumption and Risk of Stroke: A Dose-Response Meta-Analysis of Prospective Studies, American Journal of Epidemiology, Volume 174, Issue 9, 1 November 2011, Pages 993–1001
3. Rob M van Dam, Edith JM Feskens, Coffee consumption and risk of type 2 diabetes mellitus, The Lancet, Volume 360, Issue 9344, 2002, Pages 1477-1478, ISSN 0140-6736
4. André Nkondjock, Coffee consumption and the risk of cancer: An overview, Cancer Letters, Volume 277, Issue 2, 2009, Pages 121-125, ISSN 0304-3835
5. Mohammad Taghi Joghataie, Mehrdad Roghani, Fereidoun Negahdar, Leila Hashemi, Protective effect of caffeine against neurodegeneration in a model of Parkinson's disease in rat: behavioral and histochemical evidence, Parkinsonism & Related Disorders, Volume 10, Issue 8, 2004, Pages 465-468, ISSN 1353-8020
6. Wang, L., Shen, X., Wu, Y., & Zhang, D. (2016). Coffee and caffeine consumption and depression: A meta-analysis of observational studies. Australian & New Zealand Journal of Psychiatry, 50(3), 228–242.
7. Cadden, I. S., Partovi, N. and Yoshida, E. M. (2007), Possible beneficial effects of coffee on liver disease and function. Alimentary Pharmacology & Therapeutics, 26: 1-8.