Is coffee bad for you?

People have an undying love for coffee. Around the world, it’s estimated that 2 billion cups are drank every single day. Lots of people can’t start the morning without one, and there’s now a coffee shop on every corner in every city. 

COFFEEConsidering this popularity, it is perhaps unsurprising that the health benefits/health damaging effects of coffee are never far from the news. This year alone has seen 25 different articles on the Daily Mail Online, detailing why the drink is going to make you live longer or shorter, depending on the article. Of those 25, 14 were extolling the benefits of coffee, while 11 were describing the opposite.

On one particularly impressive week the site published six separate articles on the topic, claiming among other things that coffee is nature’s Viagra, that it protects against liver cancer, and that it can cause miscarriage and birth defects. If you were to ask somebody whether coffee was good or bad for them, I sincerely doubt that they would know. So what does the evidence say?

Quite a lot actually. There have been many studies on the role that coffee may play in different diseases, which I will get in to below. As is almost always the case however, the first thing to say is that there’s probably no need to change your habits. Whether coffee is good for you or bad for you, the effect seems to be minor. If you love your coffee, there’s no need to cut back. If you’re not a drinker, there’s no need to start.

Before I get into the health implications of coffee, it is worth mentioning that aside from the drink itself, people should really think about the way they drink their coffee. It is thought that at least 58 billion paper cups are thrown away each year, made from 32 million trees, and requiring a staggering 100 billion litres of water for their production. It is an extraordinarily wasteful industry, and something as simple as buying a reusable cup can make a significant difference, particularly if it is not made from plastic.

Latte Food Background Wood Espresso CoffeeBelow I have described what the current literature has to say regarding coffee consumption and various diseases. Ultimately, it is safe to say that for a healthy person with no underlying conditions, normal coffee consumption is probably good for you. The benefit is small in all cases, so it is not something to worry about. As always, there are caveats involved (whether you take sugar in your coffee, whether you drink decaffeinated, how hot it is when you drink it…), but I have tried to answer the major questions below. It is worth pointing out that although an individual coffee drinker is unlikely to see any benefit from their habit, due to the large number of drinkers around the world coffee drinking could potentially have a large impact on the overall health of the population.

Ultimately, it is safe to say that for a healthy person with no underlying conditions, normal coffee consumption is probably good for you.

Q: How much coffee is too much?

In general, various safety authorities suggest that 2 – 3 cups of coffee in one sitting is perfectly fine, provided that people don’t drink much more than 6 in a day. For most people, 8 – 10 cups will begin to produce negative side effects, including migraine, anxiety, nervousness, trembling, insomnia and an increased heart rate. These side effects are all caffeine related, and this seems to be the main culprit in the coffee-related problems. Obviously the amount of caffeine differs in different coffee brands and brews, and the numbers above relate to roughly one shot of espresso per cup. There has not been any study confirming or refuting long-term detrimental side effects of regularly drinking more than 6 cups per day (apart from extreme cases when people far exceed this), so we can’t really say either.

A: 6 cups seems to be the recommended daily limit for a healthy person, but this is largely precautionary.


Q: Does coffee change your risk of dying?

The simplest thing we can look at is whether coffee makes you live longer. There have been numerous studies into this, and their results have been mixed. It is pretty clear that coffee doesn’t in general shorten life. Several studies have found no correlation between coffee consumption and longer life, however some have found the opposite. The most recent work I could find suggests that those drinking more than 4 cups a day were at a lower risk of dying, however this was only true in people over 45 years of age. This work was presented at a conference and has yet to be published, so I haven’t been able to have a look at their analysis. However, confusingly, other studies have found that those who drink small amounts of coffee (1 cup a day) get a benefit, but that benefit disappears if you drink more than 4 cups. Some studies claim that women benefit more than men, and others that the benefits depends on what ethnic group is being studied. All in all, the literature is mixed, which is a clear sign that if there is an effect, it is a tiny one. It is interesting to note though, that the scientists who carried out the most recent study found that even people who drank decaffeinated coffee got some of this benefit, meaning that the effect may only partially be as a result of caffeine intake.

A: Coffee may extend life in certain circumstances, but if it does, the effect is tiny.


Q: Are coffee and cancer associated?

As coffee drinking and smoking often went hand in hand in the past, it is difficult to separate the two in studies. What is clear is that the results are mixed. A Japanese study suggested that high coffee consumption (over 5 cups a day) had a protective effect. Another recent analysis suggested that coffee is not associated with the large majority of cancers, with a few exceptions. Coffee seems to have a protective effect against liver cancer, but the size of this effect is debatable. However as most liver cancers are related to either smoking or obesity, there are far bigger interventions that can be made to protect against this cancer. There have been studies showing a slightly reduced incidence of endometrial, skin, gallbladder, oral, and kidney cancer in coffee drinkers, but these studies have yet to be confirmed. Finally, there was a suggestion that coffee drinkers were more prone to prostate cancer, but recent studies have cast doubt on this.

A: Coffee seems to have a protective effect against liver cancer, and potentially against several others.


Q: Does coffee affect heart health?

It was thought for a long time that coffee was associated with cardiovascular diseases, hypertension, and heart failure. This makes intuitive sense; when people have too much coffee, they often feel like their heart is racing. Several studies seemed to show this was the case, however none of the studies were thorough enough to tell for sure. More recent studies have shown that this is not the case, and that coffee has either a neutral or a beneficial effect on heart health. For example, some studies show that coffee is protective against coronary heart disease in women, and reduces the risk of death in patients who have had a heart attack. Other studies show no change or an increase in coronary heart disease risk, so any effect is likely to be small.

A: Coffee has a neutral or slightly beneficial effect on heart health.


Q: How about the effect of coffee on mental health?

The number of studies looking at this is smaller than in the previous paragraphs. However, those that have been done do show that coffee has a slight protective effect on depression risk, although some of those studies were of poor quality. Due to the sleep disturbing effects of excess caffeine, there is reason to think that this may also have a detrimental effect on mental health, but the evidence has not backed this up.

A: Coffee seems to have a slight beneficial effect on mental health


Q: Does coffee play a role in neurodegenerative diseases like Alzheimer’s and Parkinson’s?

Lifelong coffee consumption seems to have a protective effect on the development of Alzheimer’s and Parkinson’s. In both cases the effect was more pronounced in the early stages of the disease, and in the case of Parkinson’s, it the effect was bigger in men than in women.

A: Long-term coffee drinking has a slight protective effect in age-related dementia


Q: Does coffee protect your liver?

It is in liver disease that we see the biggest protective effect of coffee. Liver enzymes tend to be lower in coffee drinkers (which is a good thing). Interestingly, this tends to be more pronounced in patients at the highest risk of liver disease, such as alcoholics. It is also beneficial in non-alcoholic liver disease and other metabolic syndromes. Coffee inhibits the Hepatitis C virus, and drinkers show lower levels of damage in their livers, and as mentioned above, coffee seems to have a protective effect against liver cancer.

A: Coffee has a slight but significant protective effect against almost all kinds of liver disease and damage


Q: Does coffee affect fertility?

There is very little evidence that coffee consumption has a measurable effect on fertility. Several studies have shown a slight decrease in semen quality with high caffeine intake, and others show a very slight increase in the time to pregnancy for caffeine drinkers. This study included energy drink consumption have far higher levels of caffeine than coffee, so the results were probably skewed by that population. Several larger studies have found no correlation between coffee consumption and an increased time to pregnancy.

A: Coffee drinking does not decrease fertility.


Q: Is coffee safe in pregnancy?

Many women avoid caffeine during pregnancy, preferring to err on the side of caution in this case. The WHO recommends limiting caffeine intake during pregnancy to 3 cups or fewer per day, and the evidence supports this conclusion. Studies have shown that high caffeine intake is associated with a slightly higher risk of pregnancy loss and developmental defects. If drinking fewer than 3 cups per day however, there is no evidence of an increase in foetal malformation, neurodevelopmental defects, or miscarriage.

A: High coffee consumption may cause issues in pregnancy, but no problems have been seen for those drinking 1 – 2 cups per day.

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