Coffee has many purported health benefits related to plant polyphenols. Studies continue to find an association between coffee consumption and good health. In recent years, large studies have used complex computer analysis to look for trends in many patients over set periods of time. The UK Biobank provides data and is a good source for these types of studies.
Terminology:
Remember that an “association” is not the same as “causation” or clear proof. To prove causation, an overwhelming amount of evidence or proof by double-blinded placebo-controlled studies is required. An example of the overwhelming amount of evidence is "cigarettes cause lung cancer." In this case, the RR or relative risk (also called Odds Ratio or OR) is 7-9, or a person's risk is 7-9 times more than that of a nonsmoker. When RR is very high, we can be sure of the risk. An RR of 1.0 is the baseline, meaning a finding occurs at the same frequency in both the study group and the control group. An RR below 1.0 means that the frequency of the outcome occurs less in the study group than in the control group.
Any survey that evaluates something in the diet does run the risk of the data provided by patient questionnaires or recalls being weak due to over and underestimation. Both positive and negative bias may occur.
Let's review some of the possible benefits of coffee consumption.
Health Benefits of Coffee: Cardiometabolic Health & Longevity
Several studies show that the more coffee one drinks, the longer he or she lives. Much of the benefit is believed to come from the antioxidant plant polyphenols in coffee. Caffeine in the coffee also provides benefits.
Much of the effect on longevity is due to the associated lowering of all-cause cardiovascular events, including coronary heart disease, heart failure, stroke, and atrial and ventricular arrhythmias.1 Repeatedly, coffee has been shown to lower your risk of getting T2DM and obesity. Remember that adding sugar, artificial sweeteners, and plant-based milk replacement products may cancel the metabolic benefits of coffee, especially related to insulin resistance and obesity.
In my search concerning hypertension, I have found studies that are both neutral and beneficial concerning coffee’s effects. Although caffeine does cause blood pressure to increase temporarily, you should not expect coffee to cause hypertension.
Health Benefits of Coffee: the Liver
One of my favorite benefits that coffee delivers is to the health of the liver. As fatty liver disease has become the most common form of liver disease in women over 50 and the most common type of liver disease requiring liver transplant in Medicare beneficiaries, any little help the liver can get is appreciated.
For over a decade, multiple studies have found that coffee consumption is helpful to the liver. Antioxidants in coffee are beneficial, but some of the benefits may be directly from caffeine, which acts as an inhibitor of adenosine receptors, which tend to be over-expressed in the liver when it is unhealthy. All forms of liver disease can progress to cirrhosis, which is irreversible scarring of the liver. This progression increases the risk of liver cancer. If chronic coffee consumption occurs, those with all forms of liver disease have less progression to cirrhosis and liver cancer.
In some studies, coffee has not been found to lower the development of fatty liver, but once present, it has been shown to slow the progression to fibrosis (cirrhosis). One study found that drinking coffee had a decreased risk of developing steatotic liver disease (fatty liver) with an RR of 0.67 (remember, less likely) and, for people with liver disease, a reduced risk of developing liver scarring by 32%. 2
Health Benefits of Coffee: the Mind
It appears that both coffee and tea, either consumed on their own or both, decrease the incidence of stroke and dementia even when adjusting for confounding factors (ex, smoking status, high blood pressure, etc.) in chronic users. A prospective cohort study included 365,682 participants (50 to 74 years old) from the UK Biobank and followed them for 11-15 years ending in 2020. Coffee drinkers at 2-3 cups per day and tea drinkers at 3-5 cups had significantly lower risk of stroke and dementia. The combo drinkers at 4-6 cups had the lowest risk.3 One problem with the data is it is not clear for how many years one must be a coffee (or tea) drinker to reap the benefits.
Health Benefits of Coffee: Cancer risk?
A European study (using UK Biobank data) in which 59,647 medical records cases were examined found only a small increased risk of esophageal cancer when adjusting for BMI, smoking, and alcohol use. The small increase was found to be an OR (odds ratio or relative risk) of 2.79 or 2.79 times more likely than the risk of the control group.4 Consuming hot beverages is a known risk for esophageal cancer with OR's of OR=1.90, 2.29, and 2.39 reported when confounding variables were removed.5 One wonders if the temperature of the coffee may be driving force behind the OR of 2.79. This same study also found a reduced risk of ovarian cancer risk with an OR of 0.63. 4
A similar study looking specifically at breast cancer did not establish any increased risk of breast cancer.
A small study of 1,171 patients with previously untreated locally advanced or metastatic colon cancer who were in a study for biological cancer therapies. Irrespective of the therapy used, they found that those consuming 2-3 cups a day had less disease progression and overall survival. Those who consumed 4 or more cups had a further slight increase in benefits in the measured outcomes. Benefits were seen irrespective of caffeinated or decaffeinated coffee. 6
O'Keefe JH, DiNicolantonio JJ, Lavie CJ. Coffee for Cardioprotection and Longevity. Prog Cardiovasc Dis. 2018 May-Jun;61(1):38-42. doi: 10.1016/j.pcad.2018.02.002. Epub 2018 Feb 21. PMID: 29474816.
Kositamongkol C, Kanchanasurakit S, Auttamalang C, Inchai N, Kabkaew T, Kitpark S, Chaiyakunapruk N, Duangjai A, Saokaew S, Phisalprapa P. Coffee Consumption and Non-alcoholic Fatty Liver Disease: An Umbrella Review and a Systematic Review and Meta-analysis. Front Pharmacol. 2021 Dec 13;12:786596. doi: 10.3389/fphar.2021.786596. PMID: 34966282; PMCID: PMC8710778.
Zhang Y, Yang H, Li S, Li WD, Wang Y. Consumption of coffee and tea and risk of developing stroke, dementia, and poststroke dementia: A cohort study in the UK Biobank. PLoS Med. 2021 Nov 16;18(11):e1003830. doi: 10.1371/journal.pmed.1003830. PMID: 34784347; PMCID: PMC8594796.
Carter P, Yuan S, Kar S, Vithayathil M, Mason AM, Burgess S, Larsson SC. Coffee consumption and cancer risk: a Mendelian randomisation study. Clin Nutr. 2022 Oct;41(10):2113-2123. doi: 10.1016/j.clnu.2022.08.019. Epub 2022 Aug 25. PMID: 36067583; PMCID: PMC7613623.
Andrici J, Eslick GD. Hot Food and Beverage Consumption and the Risk of Esophageal Cancer: A Meta-Analysis. Am J Prev Med. 2015 Dec;49(6):952-60. doi: 10.1016/j.amepre.2015.07.023. PMID: 26590941.
Mackintosh C, Yuan C, Ou FS, Zhang S, Niedzwiecki D, Chang IW, O'Neil BH, Mullen BC, Lenz HJ, Blanke CD, Venook AP, Mayer RJ, Fuchs CS, Innocenti F, Nixon AB, Goldberg RM, O'Reilly EM, Meyerhardt JA, Ng K. Association of Coffee Intake With Survival in Patients With Advanced or Metastatic Colorectal Cancer. JAMA Oncol. 2020 Nov 1;6(11):1713-1721. doi: 10.1001/jamaoncol.2020.3938. PMID: 32940631; PMCID: PMC7499248.
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