There is conventional wisdom: too many cups of coffee can be bad for you. There are also, a surprising number of of extremely rigorous reports confirming a certain number of cups of coffee per day may be a good thing.
What is most often missing is the definition of ‘a cup’. How big is ‘a cup’ and what type of coffee? Given that long ago I learnt that the amount of caffeine in a ‘cup of coffee’ can vary by over a factor of 10x. When assessing advice on how many cups are good or bad, it becomes importance to be able to compare the type of cup of coffee you drink with the advice.
- The case for drink coffee and live longer.
- The Data. Is it Scientific?
- Objections? Any health case against coffee?
- How many cups is ok?
- Just what is in ‘a cup’ of coffee?
- How much caffeine per cup?
- Decaf Anyone?
- So, How Many Cups?
- Side Bar: Experiences with coffee at home.
- Is there enough coffee for everyone? As Coffee drinking goes global, will it remain affordable?
- Conclusion: How many cups per day?
Years ago I was looking to move from a capsules style coffee machine to an expresso machine which would make changing between regular and decaffeinated coffee more difficult. This triggered a research project: is decaffeinated coffee worth bothering with anyway? Apart from the pros and cons of decaf, the big thing I learnt is that the caffeine in a ‘cup of coffee’ can range from 40mg to over 400mg, which is from the same amount as a cup of tea, to the same amount as 10 cups of tea. Note that a ‘grande’ is 470ml (16 fl oz) and a shot of expresso is around 30 ml, so technically per ml there is more caffeine in the expresso, at least until frothed milk of a latte or cappuccino, or additional hot water of a long coffee is added. Surprisingly, ‘per cup’, expresso has the lowest level of caffeine of the common ways of having coffee.
On this page I will collect information on what is in a ‘cup of coffee’, as well as the research into positive and negative claims in the the impact on health. Plus, I encountered some questions as to how long coffee drinking will remain affordable. Early days, but information will grow.
The case for ‘drink coffee and live longer’.
This large prospective cohort study of a half million people found inverse associations for coffee drinking with mortality [that is coffee drinkers had less deaths], including among participants drinking 1 up to 8 or more cups per day. No differences were observed in analyses that were stratified by genetic polymorphisms affecting caffeine metabolism.JAMA- Journal of the American Medical Association report.
They followed a group of 1,567 people, aged 20 years and older, over an 18-year period.
The initial data came from the Valencia Nutritional Study, which was conducted in 1994. It assessed a range of food groups, including drinks, such as coffee.
Their findings suggest that drinking between one and six-and-a-half cups of coffee per day can lower your risk of cancer and what scientists call “all-cause” mortality (meaning, any kind of death).DW (Deustche Welle) – Spanish study shows coffee still good for your health
There is a body of evidence that some of the side effects of coffee may actually be good for you, and they appear to have nothing to do with caffeine. But Dr Karl Kruszelnicki’s grind is the observational studies that make up the ‘statistics’ behind the health benefits.Dr Karl Kruszelnicki: July 2016 (other comments quoted here)
Is this scientific?
The Spanish study reported in the above quote, is one I specifically was looking for a reference on, as it is have been widely peer reviewed, has a large sample size, and studied over an 18 year period. However, even that study does not match best scientific principles, because there is a limit to the ability to experiment on humans. To follow ‘best practice’, it is necessary to take the sample group at random, without regard to their existing coffee habits, and randomly divide into two subgroups. One subgroup would consume a placebo that is indistinguishable from coffee for the period of the trial, and the other group would consume coffee, and no one would know which group they are in. There are many reasons this type of trial would be neither practical, nor ethical.
Without the ‘double blind’ type rigour, there are limits to what can be inferred from the data. Since the participants are people who choose to drink coffee, they may already be different in other ways than non-coffee drinkers. Are they at the same wealth level? Are they more social? Still, all things considered, the weight of data is very compelling, and especially compelling with to reduction in diabetes levels. However, the adage still applies: correlations is not causation.
Objections? Any health case against coffee?
I am still to research this fully.
- Coffee: Good for you or bad for you?
How Many Cups Per Day is Ok?
Just what is in ‘a cup’ of Coffee.
Well, it is not literally a cup full of coffee. There is a recipe for what we call a ‘cup of coffee’, and it is mostly water.
Start with beans from a coffee plant. The beans go through steps of being pulped, fermented, dried, and milled, before finally being roasted. It is a lot of steps. Some time after roasting, grind the coffee. As soon as possible after grinding, run hot water through the ground coffee to extract the ‘essence’ of the coffee, which includes caffeine, and at least 20 other chemicals, many of which may be as significant as caffeine in terms of flavour, health and even staying awake.
So a ‘coffee drink’ is mostly water, infused by extracts from coffee. Then, there is most often added cream or milk, plus possibly sweetener.
Why Expresso is different.
Coffee made as expresso results in a different mix extracted from the beans. Expresso coffee uses water several degrees below boiling temperature, while almost all other methods of making coffee ‘pour’ boiling, or even slightly above boiling temperature, water over the ground coffee. Unless the water is as hot as possible, there will be insufficient extraction from the coffee grinds. However while a lower temperature gives very low yield, it also results in a more pleasing balance of extracts from the coffee, and avoid ‘burning the coffee’
To achieve the goal getting the flavour obtained at a lower temperature, the expresso process uses lower temperature water, and compensates by first compressing the coffee and forcing the less than boiling water through the packed ground coffee grinds under pressure. Using lower temperature water means that just adding cold milk or water would result in a tepid drink, so milk is heated by ‘frothing’ before being added to expresso. However by using heated frothed milk, far milk can be added without resulting a tepid drink. The result is that expresso coffees such as a latte or cappuccino may have a greater percentage of milk that is common with other coffee drinks.
How Much Caffeine per cup?
I will add some comparison data between filter, French press etc, but the main focus will be on determining caffeine per cup of expresso, as there are many variables. Techniques can be divided into ‘brewed’ coffee, using boiling water at atmospheric pressure, an expresso which uses lower temperature water at elevated pressure.
Expresso is lower in caffeine and the oils that contain the caffeine, due to the reduced extraction temperature and the use of pressure, which changed the mix of what is extracted from the beans. Expresso can be extracted at a range of temperatures, usually 90C to 95C, and collect and add data a I find it. But I will start with what I recall from previous research.
The following all affect the amount of caffeine:
- Tamping pressure.
- Extraction Temperature.
Arabica beans are lower in caffeine than Robusta beans, although these days almost all beans are Arabica.
Even when using the same method of preparation, caffeine levels vary between locations, as per this study by business insider, where brewed coffees varied between 145mg and 333mg of caffeine per cup. This data from Cicybell measures various sources at up to 517mg per cup.
From my original research years ago, I recall a study found that at one Starbucks coffee outlet, a ‘Grande’ of regular filter coffee had 400mg of caffeine, while an expresso from the same location had only 41mg of caffeine.
I have found that keeping brew temperature to 91oC/195oF with the coffee I am using, results in approximately 40mg per shot.
Is there any benefit to opting for decaf? I decided there are three main reasons for not bothering with decaf:
- Opting for expresso coffee means the number of coffee per day before exceeding coffee associated with positive health outcomes was beyond what I need.
- Decaf may be worth considering for those wanting brewed coffee, instant coffee or energy drinks, but not really for expresso drinkers.
- It is not necessarily the caffeine that should be removed from coffee.
- Removing the caffeine requires additional processing, and some methods can introduce substances to the coffee that may be worse than caffeine.
Expresso vs Decaf
If I was drinking brewed coffee, or instant coffee, then decaf could make sense. However given that any time brewed, filter, or instant coffee is all that is available, there is usually also little information how the decaf was decaffeinated, I find it better to simply limit the consumption of these products. The highest concentration of caffeine that may be problematic occurs in energy drinks of soda drinks, and while decaf may or may not make sense for these products, it is outside the scope for coffee itself.
Is Caffeine the problem?
So How Many Cups per day?
Based on caffeine alone, the following would be equivalent:
- Single shot expresso: 5 cups per day
- Black tea: 5 cups per day.
- Double shot expresso: 2.5 cups per day
- Large brewed coffee: 1 cup per day
- Small brewed coffee: 2 cups per day
- Instant coffee: 2 cups per day
It seems that 5 cups of single shot expresso per day consistently correlates with positive health outcomes, and to the extent this correlates with caffeine, the above table could be a useful guide.
The danger is people read ‘5 cups per day’ and forget this does not mean that 5 ‘grande’ cups of filter coffee, or even 5 cups of instant coffee is also associated with good health outcome. The data on positive health outcomes, does not also measure caffeine intake, and is most often associated with locations where caffeine per cup is closer to the 41mg of single shot, low temperature (92oC/197oF) extracted expresso, than a large 400mg boiling temperature extracted brewed coffee that has been concentrated by being constantly kept warm in the pot.
Sidebar: Experiences with coffee at home.
I have had a long history with making coffee at home. From freeze dried instant coffee, through to a coffee percolator, ‘Nespresso’ coffee pods in the mid 1990s, to a Jura Z5 coffee machine in 2004, and then the Breville ‘Oracle’ BES980 in 2016.
Each step was a step to better coffee. The Nespresso system allowed selecting a different variety of coffee for each individual cup of coffee.
It was when moving from capsules to a machine that freshly ground the coffee that I first researched the impact of caffeine. With the Nespresso a decaf coffee could be made at any time. How important is it to be able to choose a decaf?
The Jura Z5: 2004-2016.
After determining that decaf was not really necessary to avoid over indulging in caffeine, I progressed the the Jura Z5. This machine gave faithful service for around 12 years. It seems that Jura machines, at least at that time, were extremely well built, even if the grinding, tamping, and control over temperature did not produce the ultimate coffee. The Z5 allowed preparing two coffee at one, or one milk coffee from the single press of a button. However that ‘single press’ of a button milk coffee still in practice required connecting a supply of milk and then cleaning things afterwards. Despite the included milk thermos that could allow the milk to remain connected for 1 or 2 hours, in practice I most often used a cup of milk as a source for for the frothed milk, with the hose to the milk frother dangling in the cup. Of course as it was impossible to exactly judge the amount of milk there would still be some wastage, but less than when using the thermos, and as every surface in contact with milk requires cleaning, there was still the frother, hose, and cup used to hold the milk to clean. The machine required very little maintenance, but after 12 years it did develop a fault. Send the machine for repair, or replace?
The Breville BES980 ‘Oracle’: 2016-
After flirting with the idea of a fully manual coffee machine, I heeded the advice of a barista who suggested taking on a fully manual machine meant taking on an additional, and time consuming, hobby, I eventually chose the Breville ‘Oracle’.
There are many rave reviews of the Breville ‘Oracle’. It is regarded as making the best coffee possible without the user needing to learn the skills of grinding and tamping the coffee grounds.
However there are questions as to the reliability. Many have encountered problems. The first I have had is that the lid of the top water intake has corroded. It still works, but this lid appears to be aluminium and it is questionable as to whether trace aluminium finding its way in the water supply is acceptable.
Secondly, it seems now there are internal seals that leak. The result is that each time I need to use the machine I will need to add more water, as water remaining previously will leak into the water tray between uses, even when only 1 hour apart. The newest problem is that now on two occasions using the machine has tripped a power overload circuit breaker, which is a bigger concern. Not a fantastic record for a machine only 5 years old.
Tricks to Using the Oracle:
- How much coffee:
- The grinder keeps grinding until the filter basket is full. I found a video online on adjusting the level which will fine tune the amount of coffee from each grind.
- To change from 1 cup, to two cups, requires changing the basket fitted to the portafilter. The BES980XL originally came with only a 2 cup basket, but I later purchased a 1 cup basket from Breville. Further changes to dosing would require more basket variations, which are not available to my knowledge.
- Low Maintenance Milk Coffee:
- One trick is to froth the milk in the coffee cup itself first, then add the coffee. You can’t do artistic patterns on the coffee this way, and the purists may be horrified, but it cuts down on preparation and cleaning times.
Is there enough coffee for all? Coffee drinking is spreading globally, will it remain affordable?
The US is around 25th in a table of coffee drinking nations, and on average people in the US drink between 1/2 to 1/3 as much coffee per year as those in Scandinavia. The Finns, who drink 3x as much coffee as Americans, do also have a longer life expectancy, but not as long as Japanese, who have almost caught the US coffee consumption per capita, but are not there yet. So longer life cannot not be attributed to coffee alone, or the Japanese would not live longer than Americans, but the coffee is certainly not killing the Finns either, who also live longer than Americans.
In fact, most countries where people live longer than in the US, also drink more coffee than people do in the US. So what if the world all consumed coffee at the same rate, not as the Finns, but as the more moderate Americans, who themselves, might live a little longer if they drank more coffee?
The US consumption is listed on that table as 9.26 lbs (4.200kgs) per capita per year, and I have this data on total worldwide coffee production as 172.46 million 60 kg bags in 2019. Using the 9.26lbs per capita:
4.200 * 328 million / 60 = 23 million 60 kg bags.
Yet direct data from statistica shows actual US consumption at 26.5 bags. Close, but suggesting either not all coffee bags purchased are consumed, with 13% of the coffee not being consumed. In reality this, may also be discrepancy between sources of data.
Now consider if the entire globe of people in 2019 had equal access to those 172.46 million 60kg coffee bags produced globally, then multiplying the number of bags by the ratio of people in the US(0.323 billion) compared to the rest of the world (7.5 billion): would allocate only 7.7 million 60 kg bags to the US.
177.46 * (328,231,337 / 7,543,334,085) = 7.72
As 7.72 million bags is less than 1/3 of the coffee the US currently consumes, the poorer nations gaining wealth to the point where the level of coffee consumed in the US, which is 1/3 of that in Finland and possibly below the ideal consumption, became the global ‘typical’ level, then coffee production must increase threefold, or people in richer countries reduce their coffee consumption. The average US coffee drinker would drop from 2.9 cups per day, to less than 1 cup per day, or more realistically, the price of coffee rises until only 1/3 of current coffee drinkers can still aford coffee.
Factor in the expected population growth in the next few decades and their seems a very real risk that coffee will become a more scarce commodity as some countries more people will be able to afford and want to drink coffee in line with current trends, but finding land to grow three or even four times as much coffee is not really practical, given all the competing demands for more land..
This figures is less than means, even to reach Just to be conservative, using the using the lower figure of 23.18 show This matches closely with the statistic direct data
Those advocating population is not a problem will typically promote how there is no danger of the world starving, as we can easily produce sufficient wheat to feed an even bigger population. But what is our ability to provide ‘optional’ products for the world such as chocolate, or coffee? The reality is, we can provide more than enough wheat, which means those who are is less developed countries, and all addition people added through population growth, remain on a very basic diet and do not consume commodities such as coffee or chocolate, standards of living in the west can remain at current levels. However, people in China, India and elsewhere in Asia and Africa and developing nations continue, well developing, commodities and such as coffee and chocolate are going to move in the direction of housing, and become only accessible by the rich. The more people the world adds, the greater the challenge.
Choose your coffee, and covert any recommendations to apply them to your chosen coffee type. 5 single shot expressos per day seems to be ok, but I suggest reduce this number of cups for brewed, filter or instant coffee.
Be aware that coffee may become a precious commodity, so it still may become an expensive habit.
So if you are over 40, then consider multiple cups of coffee per day may even lengthen your life. But if younger, then also consider that coffee become expensive.