Coffee or not? A discussion of the science

This post won the 2019 ScienceSeeker award in Health, Medicine and Brain Science!Knowledge is Power ... so is Coffee

At 1.6 billion cups per day (equivalent to a 1/5 of the world population), coffee is seconded only by water in global popularity.

With such staggering statistics, it’s no surprise at the number of studies trying to ascertain the impact of coffee on human health and the environment. Will it raise your blood pressure, or reduce your risk of cancer? Is it unnecessarily increasing pesticide usage and polluting rivers or do coffee trees provide a natural habitat for many species?

In case you don’t feel like reading to the end, there’s probably no need for you to stop drinking coffee, so long as you’re under 400mg of caffeine per day (about 4 average cups of coffee). If you’re still with me, read on!


Firstly, a little Chemistry

Coffee contains over 1000 different compounds that contribute to the overall flavour; however, they’re also a major reason why researchers haven’t been able to pin down any mechanisms for the overall effects of coffee. But there are a few main groups of chemical compounds which we’ll explore.

  • Caffeine: The most widely known, this chemical is classified as a psychoactive drug! But before you get alarmed (I did say coffee was safe), all that means is that caffeine changes your brain function.

What? You’re still concerned?

Ok, the changes on your brain function are just the reason why coffee keeps you awake and may improve mental performance. It can do this because it blocks the action of adenosine, a neurotransmitter that’s linked with the onset of drowsiness, by binding to the same receptors as adenosine normally would in your brain, thereby altering normal brain function (and often ability to sleep) as well as increasing both heart rate and blood pressure until the caffeine is removed from your body. That’ll take about 6 hours to remove half and then another 6 to get down to a quarter and 6 more to get to an eight and so on and so on …

  • Trigonelline: This compound contributes to bringing out coffee’s flavour during roasting; however, it also degrades fairly rapidly at temperatures above 160 degrees Celsius and becomes niacin (vitamin B3). The concentration of niacin depends on how long the coffee was roasted, but it is classed as one of the essential nutrients for humans. So drink up, you’re being healthy!
  • Chlorogenic acids: These are a type of phenolic compound and coffee contains over 45 different types, contributing to its bitter taste. These compounds have also been shown to have both positive health benefits (read more below).
  • Kahweol and cafestol: These compounds contribute to the bitterness of coffee, but, on the plus side, they’ve been shown to have anti-carcinogenic properties … in other words, a cup a day might help prevent cancer.
  • Carbohydrates: Yes, your coffee contains carbs. In fact, green coffee is nearly 50% carbs by dry weight and mainly sucrose (normal sugar); however, that’s not the whole story. When roasted, most of these carbs actually react to form carbon dioxide and water, so generally less than a gram ends up in your cup.
  • Proteins: Proteins normally make up about 10% of your coffee and react with the carbs during roasting to form that lovely dark brown colour, which might also be very healthy for you, as we’ll see in the next section!


The Health Story

This is where we explore whether or not coffee is actually good for you and much of the exciting research about the compounds listed above.

The Good

Studies on long-term coffee drinkers show a correlation between regular coffee consumption and decreased risk of contracting type 2 diabetes, Parkinson’s disease, various cancers or heart disease. However, keep in mind that correlation does not equal causation so that unless a mechanism to explain how a compound acts on the body is identified, we cannot say for sure that it’s the coffee and not just that coffee drinkers tend to have certain predispositions.

Now, onward! Type 2 diabetes is a serious metabolic condition characterised by abnormally high blood glucose levels because of underproduction or resistance to the hormone insulin which stimulates cells to take up glucose after you eat. Regular coffee drinkers (including decaf coffee) have been shown to have better glucose tolerance and corresponding decreased risk of type 2 diabetes; however, as mentioned above, the mechanism of action is unknown. Studies performed on rats linked the anti-oxidant chlorogenic acids and trigonelline with the better glucose tolerance, but as the study reports, “the long-term effects of caffeine intake on glucose metabolism are unknown”.

With Parkinson’s disease, researchers are pretty sure that coffee doesn’t help relieve symptoms of patients, but caffeine some of the antioxidants present in coffee have been shown to have some neuroprotective effects, thereby reducing the risk of contracting Parkinson’s.

Coffee has also been correlated with a decreased risk of some cancers, including liver, colon, oral and oesophageal. It’s thought that the diterpene compounds, kahweol and cafestol are anti-carcinogenic and act by making some common carcinogens (cancer-causing molecules) less able to mutate the genetic code to lead to cancer.

Studies have also been performed to compare the likelihood of developing heart disease as a coffee drinker as compared to non-coffee drinkers. Results are conflicting, to say the least. Many long-term studies have found that regular coffee (and caffeine) consumption has reduced the rates of heart disease, but there is no known mechanism for this and it could be because of the type of people who consume coffee or the behaviour associated with drinking coffee (what else you eat, or how you start the day) that actually explains the results. So we don’t know, and as for the not-so-good, read on!

The Bad

Caffeine does cause an increase in blood pressure and a release of adrenaline, also causing the heart to beat faster. For people with pre-existing heart conditions this can be a problem; however, it may have little effect on healthy individuals.

And remember back to those anti-carcinogens? Well, on the other side of the scale, your coffee also contains some carcinogens such as 4-methylimidazole and 2-propenamide which are both a byproduct of the same reactions during roasting that reduced the carbs and produced the brown colour. But on the flip side again, much of what we eat, including red or barbecued meat and alcohol are also known carcinogens (classified by a link to increased rates of cancer) along with a multitude of other normal foods, so there’s not a lot you can do to avoid them anyway.

Also, many people who drink coffee add milk, cream or sugar without realising the amount which has been implicated as contributing to obesity. But if you’re drinking in moderation with little milk or sugar then you’ll be fine.


The Environmental Side

Coffee used to be great for the environment where it grew. That was when it was grown in its natural environment under the shade of larger trees and providing a home for many birds and other fauna. It was a win-win: the shade kept insects away from coffee berries while the large trees protected the topsoil and the coffee leftovers were an ideal fertiliser.

Welcome in the ‘coffee revolution’.

Suddenly faced with far greater demand on the coffee trade, farmer began to grow large crops of coffee in the sun without any other plants. This destroyed the healthy interrelationship, requiring pesticides for insects no longer kept away by shade and fertilisers because the coffee pulp wasn’t used to naturally enrich the soil and the extra sun also reduced soil quality. The dependant fauna had to find a new home.

That’s all not to mention the deforestation required to make room for the coffee trees, or the water pollution from coffee processing and all those herbicides, pesticides and fertilisers.

So that’s obviously a down side to your day-to-day coffee. Shade grown coffee can still be purchased, but it’s definitely more expensive and depends how much your conscience is triggering you (think of all those poor birds without coffee trees).


To Conclude

Coffee overall probably has more health benefits than unwanted side effects because who doesn’t want a bit of cancer and disease protection with their morning cup. However, as with all things, moderation is the key and exceeding 400-500 mg of caffeine (about 4 normal cups of coffee) is not recommended and that’s about the point where the health benefits shown in most studies take a u-turn and increase your risks.

We can see most coffee isn’t great for the environment, just like most of our modern-day food and products so if you’re really concerned, buy shade-grown! Otherwise you can compost leftover coffee grounds onto your garden, or if you use coffee capsules try finding your brand on TerraCycle’s free recycling programs to avoid filling up the landfill with 3 million capsules a day, just in Australia!

Anyway, I hope you’ve learnt something about coffee and some of the science about it’s effects on health and environment. And now I’m leaving to finish my beautiful caramel coffee while curled up reading!

12 thoughts on “Coffee or not? A discussion of the science

  1. Hello! Nice blog you got here.

    I enjoyed reading about the chemistry of coffee as I did not know about the other chemicals besides caffeine. There are a lot of contradicting studies about coffee and you have done a good job summarising the pros and cons.

    I really liked the formatting of the post and the clear and concise writing style. Looking forward to reading your next post. 🙂


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