Key points
- Coffee drinking is associated with reduced incidence of many cancers, diabetes, cardiovascular disease, neurodegenerative disease, and liver disease
- Coffee can raise blood pressure acutely, but habitual intakes might not have this effect
- Hot drinks, including coffee can be related to cancers of the mouth and larynx due to scalding
while some people tout the health benefits of coffee, it is also frequently singled out as a ‘thou shalt not’ by many complementary health practitioners. So, what’s the evidence for the health benefits and risks of coffee? Is it a health panacea, or could it be putting you at risk?
Overall, for most people, the evidence is clear that coffee in moderation is associated with positive health effects.
For example, an umbrella review of meta-analyses up to 2016 found that coffee was associated with a probable decreased risk of breast, colorectal, colon, endometrial, and prostate cancers; cardiovascular disease and overall mortality; Parkinson’s disease; and type-2 diabetes, and caffeine was also associated with a probable decreased risk of Parkinson’s disease and type-2 diabetes (but increased risk of pregnancy loss).1
Overall, for most people, the evidence is clear that coffee in moderation is associated with positive health effects.
Coffee and diabetes
Other reviews have demonstrated that there is likely to be a dose-dependent correlation between coffee intake and reduced rates of diabetes. The greatest effects on diabetes reduction were seen in those consuming the highest amounts of coffee (greater than six cups per day).2-4 For every additional cup consumed, there is an approximately 7% reduction in diabetes risk and benefits are also seen from tea and decaffeinated coffee.5 The reasons for this aren’t entirely clear but could result from the provision of antioxidants from coffee, or increased metabolic rate and fat utilisation.
Coffee and cardiovascular disease
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. However, there isn’t a correlation between long-term, habitual use of coffee with cardiovascular disease or chronic high blood pressure.6, 7 Low intakes may even be more likely to increase blood pressure with 1-3 cups demonstrating an effect on BP while 3-5 cups aren’t related to long-term effects.8 Similarly, while coffee is commonly avoided because of a perceived risk of cardiac arrhythmia, amounts commonly consumed do not have any association with atrial fibrillation or arrhythmia.9-11 Likewise, low intakes have been demonstrated to increase CVD risk slightly (less than three cups per day) while 3-5 cups per day were associated with reduced CVD.12
Coffee and the liver
In chronic liver disease, patients who consume coffee have a decreased risk of progression to cirrhosis (a serious and terminal disease of the liver) and lowered mortality rate. In chronic hepatitis C patients, coffee is associated with improved responses to antiviral therapy. Moreover, coffee consumption is also correlated with reduced 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 drink coffee daily.13 Gallstone risk is also reduced with higher coffee intakes, with the highest consumption (around six cups or more) associated with the lowest risk.14
Coffee and bone health
Fracture risk rises in a dose-dependent manner in women (but not men) with high intakes of coffee but there is little difference in fracture risk around two coffees per day.15
Coffee and cancer
There does not appear to be any link between coffee consumption and gastric cancer,16 breast cancer17 or colorectal cancer.18 There may though be a minor increase in urinary tract cancer associated with coffee drinking19 and cancer of the larynx also rises in a dose-dependent manner,20 but this is likely due to trauma to the larynx from hot liquids, not from coffee per se. Decaffeinated coffee drinkers also appear to have a lower risk of ovarian cancer, but this effect isn’t seen with either standard coffee or caffeine.21 Coffee appears to also exert a modest protective effect in basal cell cancer.22 Overall, there is little evidence to suggest that coffee increases cancer risk.
Coffee and brain health
Coffee may also offer some mild protective effect against cognitive decline, dementia23 and depression,24 and it has been suggested that caffeine should be reinvestigated as a potential treatment for ADHD in place of common stimulant medications like Ritalin.25 Caffeine itself has a strong association with a reduced risk of Parkinson’s disease.26
Some of these positive effects could be due to increased ketone production (as caffeine increases ketone concentrations in the blood), provision of antioxidants, or subtle effects on fuelling from reduced glucose disposal in peripheral tissue, leading to increased glucose availability for the brain and central nervous system. Coffee is an adenosine antagonist (i.e. ‘blocker’ of the actions of the relaxing neurotransmitter adenosine) and antagonists of the A1 and A2a adenosine receptor subtypes such as caffeine, have been shown to reduce the physical, cellular and molecular damages caused by a spinal cord injury, stroke, and neurodegenerative diseases such as Parkinson’s and Alzheimer’s diseases. Interestingly, adenosine agonists have also shown neuroprotective effects,27 and this area requires further research to determine methods of action, dosage, and the myriad treatment possibilities.
Conclusions
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.28
So, based on the totality of the evidence, we must conclude, that for most people, coffee is safe and offers significant benefits to health. The reason for the benefits is likely to be multifactorial and include the effects of caffeine itself and also the range of antioxidant chemicals found in coffee. The optimal intake for health appears to be around 3-5 cups of coffee per day. However, this is highly individual dependent as caffeine metabolism rates (gene-dependent) vary widely and some people have adverse effects to chemicals within coffee and not necessarily to isolated caffeine.
For most people, coffee is safe and offers significant benefits to health
As with alcohol, if you do not drink coffee there is probably no good reason to start, but likewise, if you do drink coffee without any negative side effects there is absolutely no reason to stop (according to the evidence), and your daily cups/s of Joe could even be improving your health!
If you experience disrupted sleep, anxiety, or post-coffee ‘jitters’ you may want to perform a ‘self-experiment’ and reduce your intake. It is always prudent to reduce or eliminate caffeine-containing drinks later in the day, and a good rule-of-thumb is to have no more than 3-5 cups of coffee, with the last no later than 12-2 pm. The ‘take-home’ rule here is to listen to your body. If coffee disturbs your sleep, reduces your concentration ability, causes you to feel excessively fatigued during exercise; if you ‘crash’ after caffeine or it upsets your digestive system, then reduce or eliminate it and see how you feel.
In short—look at the evidence but be sensible!
The ‘take-home’ rule here is to listen to your body
References
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