Uncover the intricate relationship between coffee and health in our in-depth exploration of the brew’s impact on well-being.
What is coffee?
Depending on the person, coffee can be a necessity, a ritual, a social lubricant, or a crutch. Coffee can be a source of income for some and a budget drain for others. But what does the dictionary say?
coffee (noun)
1a: a beverage made by percolation, infusion, or decoction from the roasted and ground seeds of a coffee plant
b: any of several Old World tropical plants (genus Coffea and especially C. arabica and C. canephora) of the madder family that are widely cultivated in warm regions for their seeds from which coffee is prepared
c: coffee seeds especially roasted and often ground
d: a dehydrated product made from brewed coffee
also: a beverage made from this
2: a cup of coffee (1)
What is in coffee?
If you consider your morning beverage a complex beverage, you are right. Coffee contains more than 1000 bioactive compounds, the most well-known of which is caffeine. Other components include polyphenols (e.g. chlorogenic acids) and diterpenes (e.g. cafestol and kahweol) (2, 3). The actual composition of each cup of coffee will depend on the type of beans (Arabica or Robusta), the roasting process, the grind size and brewing process (2, 3, 4).
On the receiving end, your individual genetic makeup (2, 4) and gut microbiome influence how the coffee you ingest is metabolised and used (2).
Below is a brief description of the most notable components in coffee.
Caffeine
Caffeine is an alkaloid which antagonises adenosine, thus stimulating physical and cognitive alertness (3, 5). Caffeine may inhibit inflammation and oxidative stress in the body (5). The amount of caffeine in a cup of coffee depends on many factors including the type of bean and preparation method. The average ranges from 65 to 120mg (3).
The half-time of caffeine (i.e. how much time it takes for half of the ingested amount to leave the body) is approximately 3-4 hours. However, the actual half-life depends on many biological factors, including age, liver function, pregnancy status, and medications, potentially increasing this time to 11 hours or more (3).
Cafestol and kahweol
These diterpenes have been studied for their antioxidant (3, 5), anti-inflammatory and antiangiogenic properties (4, 5). They may be implicated in stopping tumour growth (5)
Polyphenols
Polyphenols have antioxidant and anti-inflammatory properties and are present in both caffeinated and decaffeinated coffee (4). The most prominent polyphenols present in coffee are chlorogenic acids. These acids may help prevent cancer via several mechanisms (5).
Melanoidins
These are compounds formed during the roasting process. They can exhibit antioxidant, antimicrobial, anti-inflammatory properties, among other potentially beneficial qualities. They act as prebiotics (i.e. food for gut bacteria), contributing to gut health (4).
Coffee and health
Coffee consumption has been associated with multiple benefits and several negative effects on health. As with many other aspects of health, there are no black-and-white causal relationships that can be made.
Benefits
All-cause mortality
- Coffee intake may lower the risk of all-cause mortality (i.e. dying from any cause) (2)
- Optimal dose: 3 cups per day (either caffeinated or decaffeinated) (2, 4)
Cardiovascular disease
- Coffee intake may lower mortality from cardiovascular disease, coronary heart disease, and stroke (2)
- Benefits have been reported for moderate doses of 3-5 cups per day (3, 6) with optimal dose = 3 cups per day (2)
- Higher benefit for women at higher levels of consumption for mortality from cardiovascular disease and coronary heart disease only (2)
Cancer
- Coffee consumption may lower the risk of mortality from cancer in non-smokers (2)
- High vs low coffee consumption may lower the risk of prostate cancer, endometrial cancer, melanoma, oral cancer, leukaemia, non-melanoma skin cancer (2), liver cancer (2, 5), and breast cancer (5)
- Coffee consumption may lower the risk of lung cancer in people who have never smoked (2)
- Decaffeinated coffee consumption may lower the risk of lung cancer (2)
- Optimal dose for lowest relative risk of cancer mortality = 2 cups per day (5)
Liver health
- Coffee consumption may lower the risk non-alcoholic fatty liver disease, liver fibrosis and cirrhosis, as well as mortality from cirrhosis (2)
- 2 or more cups of coffee per day in patients with pre-existing liver disease may lower the risk of fibrosis, cirrhosis, liver cancer and mortality (3)
- 2 or more cups of coffee per day may lower the risk of elevated ALT (alanine transaminase, a liver enzyme) and chronic liver disease (3)
- Coffee consumption may protect against infection with hepatitis B and C (3)
Metabolic health
- High vs low (e.g. 6 cups per day vs none) coffee consumption (caffeinated or decaffeinated) may lower the risk of type 2 diabetes (2, 3, 4)
- The risk reduction for type 2 diabetes is stronger for women than men (3)
- Coffee intake may increase insulin sensitivity and regulate glucose levels postprandially (3)
- High vs low coffee consumption may lower the risk of metabolic syndrome (2, 4)
Bone health
- High vs low coffee consumption may increase the risk of fractures in women (2)
Neurological health
- Coffee consumption may lower the risk of Parkinson’s disease (2, 4), depression (2) and Alzheimer’s disease (2, 4)
Other health outcomes
- Coffee consumption may lower the risk of gallstone disease (2), kidney stones (2, 4) and gout (2)
Negative effects
Cardiovascular disease
- Unfiltered caffeinated coffee consumption may increase total cholesterol, LDL-cholesterol and triglycerides (2, 4)
Cancer
- Coffee consumption above 4 cups per day may increase mortality from cancer in smokers (2)
- High vs low coffee consumption may increase the risk of lung cancer in smokers (2)
- Coffee consumption may increase the risk of urinary tract cancer (2)
- High coffee consumption (6.5 or more cups per day) may increase the risk of rectal cancer and stomach cancer (US population only) (5)
Gut health
- Coffee intake may temporarily damage the gut mucosa and increase gut permeability to certain compounds such as sucrose (4). On the one hand, this may explain why individuals suffering from gastrointestinal disorders are sensitive to coffee.
Bone health
- High vs low coffee consumption may increase the risk of fractures in women (2)
Prenatal exposure to coffee
- Mum’s high vs low coffee consumption may increase the risk of low birth weight, pregnancy loss and preterm birth (in the first and second trimester only) (2)
Sleep
- Coffee intake may have a detrimental effect on sleep depending on quantity, time of intake and individual metabolic function.
TBD
Gut health
- Coffee intake (either caffeinated and, to a lesser extent, decaffeinated) may increase gut motility, which can be a good thing for individuals with constipation and a bad thing for individuals with diarrhoea or incontinence (4)
- 3 cups of coffee per day may decrease the amount of certain bacterial species (e.g. Escherichia coli, Enterococcus spp., Clostridium spp., and Bacteroides spp.) and increase the amount of other species (e.g. Lactobacillus spp. and Bifidobacterium spp.). The health implications of these changes is yet to be determined (4)
References
- “Coffee.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/coffee. Accessed 11 Nov. 2023.
- Poole R, Kennedy OJ, Roderick P, Fallowfield JA, Hayes PC, Parkes J. Coffee consumption and health: umbrella review of meta-analyses of multiple health outcomes. BMJ. 2017 Nov;359:j5024.
- Nieber K. The Impact of Coffee on Health. Planta Med. 2017 Nov;83(16):1256–63.
- Iriondo-DeHond A, Uranga JA, Del Castillo MD, Abalo R. Effects of Coffee and Its Components on the Gastrointestinal Tract and the Brain-Gut Axis. Nutrients. 2020 Dec;13(1).
- Pauwels EKJ, Volterrani D. Coffee Consumption and Cancer Risk: An Assessment of the Health Implications Based on Recent Knowledge. Med Princ Pract Int J Kuwait Univ Heal Sci Cent. 2021;30(5):401–11.
- 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. 2014 Feb;129(6):643–59.
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