Coffee

An in-depth look at Coffee for Health and Performance

In the top 5 on almost every list of most consumed beverages, the world’s relationship to coffee is a complex and fascinating one. Equal parts addiction, routine, habit, enjoyment and flat out need depending on where you look, even Asia, a traditionally tea drinking culture, is starting to drink more coffee.

This article is, at least in part, to the responses I received to the caffeine portion of my article on placebo in performance and I couldn’t be more excited to write it, it is right in the niche of my passions; science, health, performance and coffee.

Coffee is More than a Caffeine Delivery Method

In the above linked placebo in performance article, I touched on the fact that coffee was difficult to use in research on caffeine for a number of reasons. The primary reason is that coffee’s caffeine content is quite variable (which is discussed further below), similarly it is worth acknowledging that coffee is so much more than just caffeine.

Polyphenols

Depending on roasting method (more below) coffee can have a high polyphenol content. Polyphenols are plant compounds with antioxidant properties which are great for human health. This is likely part of the reason that coffee is consistently found to be associated with longevity (for the record so is tea). Crucially, this is regardless of type including decaffeinated coffee. Without over-interpreting large observational data which is based on recall, it is interesting to see some of the data (as visualised below) suggesting that directionally, instant coffee has a weaker association with longevity. This again would fit polyphenols’ role because these deteriorate in the roasting, grinding a brewing process - but this is a very weak piece of data.

From Chieng 2022 et al

Roasting

Roasting is step one of a few which will significantly impact polyphenol content of coffee and its relative health benefits. Unsurprisingly for those who understand the science of polyphenols and cooking, longer roasting (to create darker roasts) means less polyphenols are present. Interestingly, it also means LESS caffeine.

As I touched on previously, many folks associated the bitter taste of coffee with ‘strength’ (an almost meaningless term of the world of coffee), and caffeine itself has a bitter taste, but the easiest way to make a coffee taste bitter is to over-roast or over extract it. None of which has to do with caffeine (in fact it may actually mean there is less caffeine in the coffee).

Brewing

Coffee brewing is middle school science, applied to something real world. It fundamentally boils down to dissolving ground coffee beans into water. As a result there a a number of variables that can be manipulated to change how this process happens, and done in concert, this creates an ‘optimal’ cup of coffee (or not).

The variables that are manipulated in coffee brewing are:

1. Temperature of the water - warmer dissolves better and quicker (you may remember saturating a solution and then heating it to supersaturate it in science class).

2. Duration - the longer the duration of extraction, the higher the caffeine content per dose of coffee (we will come back to dose).

3. Surface areas - this is why there are different grind sizes, a finer grind dissolves quicker via increased surface area.

4. Pressure - the driving force of the water through the coffee (or lack thereof) is part of extraction.

Some examples of this are espresso, with a fine-ish grind, high pressure, high temperature and short duration in comparison to cold brew, with a coarse grind, low pressure, low temperature and long duration extraction. Of course, these variables work together, in concert, so the above is less a recipe as much as an illustration of perhaps the two opposite ends of the spectrum.

Variables that impact coffee brewing/extracting, which are less discussed outside of baristas include:

1. Climatic conditions - temperature and humidity specifically. These are primarily an issue for espresso extraction but this is why cafe’s (good ones) will time their extraction and repeatedly adjust things like grind throughout the day as these variables change.

2. Water - solute content of water impacts extraction significantly (again, the basic science of this is pretty straight forward, we just most don’t think about it much - I certainly hadn’t until I moved somewhere with ‘hard’ water). This is the genesis of filters on espresso machines, but also why many cafe’s will use lower solute (distilled) water instead of tap water.

Caffeine Content

As discussed already, roasting and brewing significantly impact caffeine content in brewed coffee. Interestingly, so do different bean varietals (these are the coffee equivalent to different types of apples; green, red etc) and a few other factors involved with the plant but these are well beyond the control of anyone not growing the coffee, so I will leave it at that.

The challenge with caffeine content (and quantifying it), is that for the consumer, it is significantly impacted by both dose and brewing method but the two are linked. Generally we talk about coffee as a drink, that is; a latte or americano and these are slightly disconnected from the brewing (all of which are espresso in this case). That said, the number of espresso shots between these may differ and the amount of fluid they go into may differ. This is not to mention that even two espresso shots pulled consecutively will vary slightly in caffeine content.
When it comes to dose, this varies per brewing method, but also will vary slightly for different preferences by barista or cafe. That is, how much coffee (in grams) is used per gram (or millilitre) of water. This then yields the TDS (total diluted solids) which is a quantification of extraction, which in part dictates caffeine content.

So we have many moving pieces, meaning we can’t quite quantify either total caffeine (in mg) or relative caffeine (mg/ml) particularly accurately. Despite all of this, given the principles above the bottom is a good idea of relative caffeine contents of different brewing methods.

From Angeloni et al 2019

Coffee and Health

As mentioned, coffee is consistently associated with increased longevity this is despite the higher smoking rates of coffee drinkers as a population. Coffee consumption has also been linked to numerous specific health benefits (as opposed to generally longer life) including reduced risk of neurological conditions like stroke, dementia and Parkinson’s disease. I won’t list all health benefits, as much as to say, they’re numerous.

From Iriondo-DeHond et al 2021

How Much is Too Much Coffee?

As I have mentioned in other articles I have written, when it comes to any substance the toxicological statement “the dose makes the poison” applies. When it comes to coffee, all requisite caveats exist around different brewing methods, challenges with dose etc. These aside, the research on number of cups a day and health (which isn’t particularly strong given it’s recall, observational data) suggests somewhere around 2-3 cups of coffee a day is the sweet spot. A quick word to the wise: 3 espressos are not the same as 3 extravagant milkshake-esque ‘coffees’ from your local Starbucks. I vividly remember a client at a gym I worked at many years ago losing a significant amount of weight (which he was otherwise unable to lose despite efforts of himself and us at the gym) after we realised he had a coffee machine on his desk and was having many a day, including milk. Cutting the milk out from these was enough for him to start losing the weight. *This is not to demonise milk as much as to illustrate the ‘hidden’ caloric load coffee can present.

The Dark Side of Coffee

Despite the resoundingly positive nature of this article with respect to coffee (and my personal love and bias in favour of coffee) there are some potential negative aspects of coffee consumption for some people in some circumstances.

Caffeine can play a role in cardiac arrhythmias and most advice on arrhythmias suggests caffeine abstinence (at least as a trial to see if it is a factor), similarly it includes alcohol avoidance.

For anyone who’s prone to excessive caffeine intake (welcome my fellow caffiends), the association with caffeine and anxiety is very well known. Interestingly, L-Theanine an amino acid often found in green tea, tends to help manage/limit this. This again speaks to the difference between caffeine and coffee (or in this case green tea) - they contain more than just caffeine.

On a somewhat related note, caffeine (and thus coffee) can impact negatively sleep. Some would say that it always does, others suggest that it is dependant on time and dose of consumption. The half life for caffeine varies based on genetics of caffeine metabolism but remembering that it takes 4-5 half lives for a substance to be considered ‘gone’, most folks probably don’t completely eliminate all caffeine from their system within any 24 hour window.
The flipside of this, however is the fact coffee can be used to help shift your body clock when travelling and managing jetlag.

Coffee and the Urge

A common experience is the need to avoid consuming your first coffee until within the safe proximity to a toilet. The question of why this is the case is of particular interest (hint, like much of this article - it’s not the caffeine).

In one study coffee stimulated colonic motility in 29% of subjects. On first thought, this looks to explain things (don’t worry we will go deeper than this surface level) but on second thought, who are these 71% of folks who seem to be the opposite of every coffee related joke around?

Back to what’s causing the colonic motility, which increases within 4 mins of ingesting coffee (again, this was somewhat surprising to see in the literature but lines up well with most folks’ experience). One of the drivers of this is the gastrocolic reflex, which is a reflex linking eating (or in this case drinking) to your bowels working (think something like cleaning out the refrigerator before doing the groceries to clear room). In effect hormones released from the gut as a result of ingesting coffee act on the colon causing increasing waves of movement. This does happen with decaf and even warm water too though, so caffeine is clearly not at the centre of this phenomenon. However, there is some individual variability when it comes to sensitivity to this effect.

Whilst we are discussing matters of the colon, there’s some really interesting early research on coffee’s impact on the gut microbiome. Results are pretty inconsistent and not worth drawing too many conclusions from, particularly in light of ‘coffee’ being a heterogenous term for a number of beverages (+/- milk or alternative milk, +/- sugar or sweetener etc etc you get the point). That said, this should stand to reason, because everything we consume will impact the gut microbiome (and probably propagate flora that will make us crave more of that). *If you’re interested in the microbiome, don’t forget to subscribe to ensure you don’t miss my upcoming article on the microbiome.

Healthiest Way to Consume Coffee

Coffee is one of, if not the, healthiest beverage you could consume that isn’t called water. That said, like all things, there is a spectrum. It should be timed optimally or at least so as to minimally impact your sleep, and ideally should be black (have your milk if you’d like) or at least not some monstrosity with any number of syrups and sugars.

You can probably have up to 3 or so cups a day without significant consequence (unless you’re feeling effects of the total dose being too high for example sleep issues, anxiety etc). That said, not all cups or brew methods are created equal.

A quick note on brew method and health. There’s a body of literature pertaining to blood lipids (cholesterol) and coffee, suggesting that brew methods which use filter paper (think V60, Chemex, coffee machine, etc) are better/healthier than those that don’t (think french press, Turkish coffee, etc). Likewise, using a paper rather than metal filter looks to be better for the same reasons - a change I recently made. On a similar note, there are enough microplastics (and macro plastics) around, I’d be skipping the pods as much as possible.

Coffee and Performance

Success leaves clues, and the fact that some countries brought baristas to the Olympic Games should speak to the role it plays in the athlete lifestyle. Some of this is no doubt about the role coffee plays in our society from a social point of view. Beyond this though it has clear physiological benefits as a caffeine delivery vehicle. Specifically, when it comes to performance, caffeine improves almost all endeavours, including mental and physical performance (though there’s certainly some placebo effect as mentioned in the above linked article). Both caffeine and coffee have also been shown to increase glycogen resynthesis rate when co-ingested with carbohydrates (which may be part of its popularity post exercise).

Hopefully, you’ve enjoyed this perhaps even over a cup of coffee (and haven’t had to rush to the toilet as a result). The article was born out of interactions based on a previous one, which is both appreciated and helpful - so thank you to those who took the time and please do comment on substack or reply via email if you have thoughts or questions.

It is very rare that something society enjoys so widely is both considered as healthy and is as helpful as coffee is.

References

1. David Chieng, Rodrigo Canovas, Louise Segan, Hariharan Sugumar, Aleksandr Voskoboinik, Sandeep Prabhu, Liang-Han Ling, Geoffrey Lee, Joseph B Morton, David M Kaye, Jonathan M Kalman, Peter M Kistler, The impact of coffee subtypes on incident cardiovascular disease, arrhythmias, and mortality: long-term outcomes from the UK Biobank, European Journal of Preventive Cardiology, Volume 29, Issue 17, November 2022, Pages 2240–2249, https://doi.org/10.1093/eurjpc/zwac189

2. Loftfield E, Cornelis MC, Caporaso N, Yu K, Sinha R, Freedman N. Association of Coffee Drinking With Mortality by Genetic Variation in Caffeine Metabolism: Findings From the UK Biobank. JAMA Intern Med. 2018;178(8):1086–1097. doi:10.1001/jamainternmed.2018.2425

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