Coffee is said to increase blood pressure and deprive some people of sleep. On the other hand, it is supposed to reduce the risk of diabetes and increase the elasticity of our blood vessels. So, what is true? Is coffee good or bad for us? Here’s our lowdown.

In the morning, it gets us going; at lunchtime, it banishes the post-meal coma; in the afternoon, it’s the perfect excuse for a break: Coffee. Once known as a traditional tea-drinking nation, the United Kingdom is now one of the largest coffee consuming countries in Europe, according to the Foreign Office’s Centre for the Promotion of Imports from developing countries (CBI). In 2018, the UK was the fifth-largest coffee market in Europe, after Germany, Italy, France and Spain.

So, why do we love it so much? The roasted bean contains more than 800 aromatic substances but only about two calories per 100 millilitres. On top of tasting good, it keeps us perky. But is it a vice? After all, coffee has the reputation of being unhealthy because it makes us jittery, disrupts our sleep, causes the heart to pound and is even said to shorten our lives. However, the idea that coffee drinkers die earlier is now considered outdated. Coffee is among the best researched commodities, and evidence that coffee has health benefits is stacking up.

Why have studies shown coffee to be unhealthy?

A possible reason might be that early studies did not account for unhealthy lifestyle choices. For example, coffee drinkers are often also smokers. If this factor is not excluded in a study, coffee may get blamed for harm caused by nicotine. By the same token, abstainers may have lots of healthy habits, such as following a real food diet, exercising regularly, and getting enough sleep. What if it was the sum of those habits that was keeping them healthy rather than their caffeine avoidance? For these reasons getting accurate data on the impact of coffee drinking can be very tricky.

During our research for this blog, it seemed that there are probably as many studies that attest to the drink’s adverse effects as those that show positive results. Some points are still disputed among scientists, but others are now considered well-proven or disproven.

It is undisputed that caffeine, one of the numerous ingredients in coffee, perks you up and may keep you awake. Caffeine attaches to certain molecules on cells called adenosine receptors. Adenosine is a messenger substance, which builds up over the day and, once enough has accumulated and latched on to the receptors, triggers tiredness. As caffeine blocks the receptors, adenosine cannot exert its function. Hence the stimulating effect.

You may also have heard that caffeine accelerates heart activity. Yet, several recent studies, including a literature review looking into the effect caffeine has on people with heart arrhythmia, found no evidence of this. A study published earlier this year found that coffee consumption was associated with longevity! The researchers noted that the more coffee people drank, the lower their risk for heart failure. Interestingly, that benefit didn’t extend to people who drank decaf.

Some people react to caffeine by breaking out into a sweat, trembling and feeling jittery – especially if they have consumed large amounts of it. Indeed, coffee has been found to increase cortisol, which does explain those symptoms. If you are stressed, we recommend cutting back on caffeine (from any source) as it will only increase your cortisol levels further.

Caffeine works differently for everyone

The stimulating effect of caffeine usually kicks in after 15 to 30 minutes and can last for several hours. How quickly the substance is broken down in the liver varies greatly from person to person and is influenced by genes, among other things. While some people metabolise half of the caffeine after four hours, others still have 50 per cent of the ingested caffeine in their bodies after as long as eight hours.

Children, young people, and pregnant women react differently to it than (non-pregnant) adults – a good reason children and adolescents should steer clear of energy drinks, which contain more caffeine than tea or coffee. The concentration of caffeine in the body tends to decrease faster in smokers than in non-smokers, and medication also influences how and for how long caffeine works. A study conducted at the University of Barcelona showed that its stimulating effect is stronger in men than women. Those who drink coffee regularly get used to it and react less strongly to the caffeine than someone who rarely has any.

This also explains why some people react to coffee with sleep disturbances and others do not. Those who experience sleep disturbances should either avoid coffee altogether or drink their last cup before lunch. With all this variation, the best thing to do to find out how it affects you is to quit caffeine for a few weeks and check whether you feel better for it. If you are a 3-a-day or more coffee drinker then we suggest you cut down gradually – from 3 to 2 until you stop craving the third, and from two to one until you stop craving the second, until finally you cut it out completely.

Does coffee increase blood pressure?

People with high blood pressure are often warned to avoid coffee. After all, caffeine is thought to drive up the pressure in the blood vessels – and it does, but not if it is consumed as coffee. A review of randomised controlled trials revealed that the effect was only significant in studies that used pure caffeine, not those that used coffee. Doctors, therefore, no longer ban coffee for their hypertensive patients as a matter of course, although we still recommend that you go easy on it if your blood pressure is very high.

Is coffee a diuretic?

The myth that coffee does not count towards our liquid intake has been disproved. Coffee does have a diuretic effect, but it is only slight. Coffee drinkers probably feel the need to go to the toilet more because of the large amount of water they drink per cup.

In more news in coffee’s favour, it has been scientifically shown to reduce the risk of diabetes – a result of extensive observational studies. Caffeine does not seem to be the decisive ingredient for this effect, as it also occurs with decaffeinated coffee. Presumably, other components of coffee have a favourable influence on the blood sugar level.

Many people have noticed that coffee also affects their stomach and intestines. Some people’s guts are sensitive to it, while others find that it improves their digestion and alleviates constipation. This, again, shows how varied the effects of the bean can be. The bitter substances in coffee attack the stomach lining, which may be why sensitive people can get stomach aches. Depending on the type of coffee, roasting and preparation, coffee is more or less digestible in individual cases. Espresso, for example, is often quite well tolerated. This is because the longer roasting time of the espresso beans breaks down more acids, which makes espresso easier on the stomach. Boiled and unfiltered coffee, on the other hand contains the chemicals cafestol and kahweol, which have been seen to raise total and LDL cholesterol – but hardly anyone drinks coffee prepared like that anymore.

In summary, research on coffee is still not conclusive. The problem is that the findings are often based on epidemiological and observational studies, where actual coffee consumption is measured on the basis of recall questionnaires (“How many cups of coffee did you drink over the past year?”) or interviews, both of which are notoriously unreliable. Also: How large is a cup of coffee? And how strong was the coffee? How was it prepared? Add to that the wide variety of reactions to coffee in different people, and it becomes obvious that researching coffee is not an easy task.

On the plus side, however, more and more papers are coming out that suggest that coffee has been misjudged in the past and could be better for us than its reputation suggests. In healthy individuals, moderate amounts of coffee are unlikely to cause any harm.

We hope you can use the information in this blog to determine your own personal coffee tolerance. Our talk How to Have Great Energy All Day explains how over-consumption of stimulants affects blood sugar and energy levels. Please call 07966 478974 for more information.

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