How many cups of coffee a day is okay?

Evelyn Lewin

14/05/2019 3:08:00 PM

It seems each year brings with it more research in favour of coffee consumption. Dr Evelyn Lewin examines the seemingly ever-expanding data.

Empty coffee cups
New research shows having six cups of coffee negatively impacts cardiovascular risk.

If you are anything like me, you cannot imagine starting the day without a cup of coffee.
That cup is closely followed by my second, and it’s at that stage I start to really feel my morning fog lift.
The amount of coffee I consume throughout the rest of the day varies. But I often wonder how much caffeine consumption is ‘safe’ – and what the optimal intake of caffeine should be.
So when I came across new research today exploring this topic, I was intrigued.
Published in The American Journal of Clinical Nutrition, the research found that drinking six or more coffees a day can increase your risk of heart disease by up to 22%. The research looked at a UK Biobank data of 347,077 participants aged 37–73 to come to these conclusions.
‘In order to maintain a healthy heart and a healthy blood pressure, people must limit their coffees to fewer than six cups a day. Based on our data, six was the tipping point where caffeine started to negatively affect cardiovascular risk,’ researcher Professor Elina Hyppönen of the Australian Centre for Precision Health said.
By capping the upper limit of caffeine intake at six coffees a day, those of us who like a few brews may breathe a sigh of relief (even though six cups does sound like an awful lot of coffee).
But not all research into caffeine intake comes to such reassuring conclusions. 
Take 2015 research by the European Society of Cardiology. It found that coffee drinking was associated with an increased risk of cardiovascular events, mainly heart attacks, in young adults (aged 18–45) with mild hypertension.
The 12-year study of 1200 patients found that heavy coffee drinkers (defined as drinking four or more cups a day) had a four-fold increased risk of cardiovascular events, while moderate drinkers (1­–3 cups) tripled their risk.
(It must be reiterated, mind you, that these participants had mild hypertension to begin with.)
So, what do Australian guidelines recommend regarding safe levels of caffeine consumption?
According to Food Standards Australia New Zealand (FSANZ), there is no recognised health-based guidance value, such as an acceptable daily intake, for caffeine.
However, a FSANZ expert working group analysed the available literature in 2000 and concluded there was evidence of increased anxiety levels in children at doses of about 3 mg caffeine per kilogram of bodyweight per day. This equates to a caffeine dose of about 210 mg per day for adults, which is approximately three cups of instant coffee.
Apart from anxiety, and effects on sleep, I did not come across much research that paints a worrying picture when it comes to caffeine consumption.
On the contrary, it seems each year brings with it more and more research in favour of caffeine consumption.
That said, an umbrella review published in The BMJ in 2017 identified 201 meta-analyses of observational research and found high caffeine intake versus low/no intake was associated with poorer pregnancy outcomes (such as low birth weight, preterm birth and pregnancy loss), and fracture risk.
While there was no overall significant association with risk of fracture, the meta-analyses found a 14% increased risk for high versus low caffeine consumption, and 0.6% increased risk for one extra cup a day in women.
(Interestingly, coffee consumption was beneficially associated with lower risk of fracture in men).
Despite these findings, the review still concluded that coffee consumption was more often associated with benefit than harm for a range of health outcomes across exposures. It indicated largest relative risk reduction at intakes of 3–4 cups a day versus none, including all-cause mortality, cardiovascular mortality and cardiovascular disease.
High versus low consumption was also associated with an 18% lower risk of incident cancer.
While this research pointed to benefits of drinking 3–4 cups a day, it did not cap a level above which coffee consumption was considered ‘too much’.
A response to that review, by a Professor of Medicine, offered more clarity, saying that the ‘safety of coffee should thus be restricted to moderate intake, generally considered as <400 mg of caffeine a day (about 4–5 coffee drinks)’.
That is the same conclusion drawn by health direct.
While health direct says the research on safe caffeine consumption is not clear, it is likely that healthy adults can generally consume around 400 mg of caffeine a day.
Of course, we all need to be sensible about our coffee intake. We should not drink it if it makes us jittery, anxious, tachycardic or feel unwell in any other way.
I also set a personal limit on when I consume my brew, because any coffee after around 2.00 pm usually means I cannot sleep that night.
But to answer the original question – how many cups of coffee a day is okay? – after wading through the research and recommendations, I feel it’s probably okay for an average healthy adult to drink 3–4 cups of coffee a day, without exceeding more than five cups.

caffeine cardiovascular disease coffee

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DK   15/05/2019 9:14:20 AM

I do question why we see it as "normal" to want (or even need) to consume stimulants in our everyday lives. If you genuinely don't function well without caffeine, doesn't that tell you that you have a problem? If one of your patients said that they couldn't get there day started without consuming alcohol, nicotine, marijuana, or some other psychoactive agent, you would be talking to them about their addiction.

Why is caffeine any different?

Damien Zilm   19/05/2019 1:50:09 PM

A polymorphism of the gene coding for CYP1A2, the enzyme responsible for 95% of caffeine metabolism, may potentially divide the population into ‘slow’ and ‘fast’ caffeine metabolisers- is those who have a coffee before bed and those that won’t touch it after 1 pm. This must have an impact on the health implications.
I suspect there is a huge amount of research still to be done