This is something I have been thinking of researching for some time.

I absolutely love coffee and lately have been trying to adjust to the fact that I can only have a few cups in the morning if I want to ensure my eight-hour beauty sleep. I have read a lot about the negative side of coffee but recently have been coming across some the pros as well. So let’s look at what my deep dive found.

Coffee is the most consumed psychostimulant beverage used globally, which is not surprising. The main factor is the amount of caffeine it contains, which can vary according to the type of beans used, how much they are roasted and how the coffee is made. An average 200ml cup of coffee would contain about 90mgs of caffeine. It was interesting to see how one study showed that the amount of caffeine can vary from 58 to 259mgs depending on the chosen coffee brew. (1) The same study also mentions that coffee sold as decaffeinated can contain minimum of 18mg per dose …so is decaf actually decaf?

How much is enough?

Various health organisations around the world advise 300-400mgs of caffeine to be safe per day. The NHS recommends that women who are pregnant or breastfeeding should not consume more than 200mgs per day. (2) The caffeine in coffee can cross the placenta and hence limiting intake during pregnancy is best.

Depending on age, gender, body size and liver health caffeine can be metabolised in different ways by individuals. (3) I have seen this in my own family where some members get palpitation with even a small cup of coffee and hence prefer to stick with tea for their caffeine hit.

One needs to be aware that caffeine is present in other drinks like tea, green tea (my patients are surprised when I tell them about this!), cacao, energy drinks, various chocolates as well as cola drinks.

What are the effects?

Caffeine in coffee mainly antagonises the adenosine receptors of the brain, which is responsible for the alertness and wakefulness it causes. As it is both water and fat soluble, it can easily cross the blood brain barrier. (4) However it is interesting to know that these adenosine receptors are not just present in the brain, in fact they are spread out throughout the body, which is why the stimulating effect of coffee is not just limited to the brain. Coffee can cause the blood vessels to constrict as well as dilate due to the effect of caffeine. This can lead to 5-10 mmhg rise of systolic blood pressure in people who do not drink coffee regularly. However, this has not been seen in habitual coffee drinkers. (5) The diuretic effects of coffee are well known. The caffeine can increase the kidney filtration rate and also prevent the sodium reabsorption mechanism in the kidneys. (6) The effects of caffeine on the gut are also significant. The gastrointestinal motility can be increased and the efficiency of calcium absorption within the gut can be slightly reduced.

Good side of coffee

  • Up to 3-4 cups of coffee per day can reduce the risk of number of chronic diseases like heart disease, stroke, type 2 diabetes, non-alcoholic liver disease and liver cancer. Moderate coffee intake has been associated with lower risk of overall death. (7)
  • Helps with constipation by increasing gut motility. This can be a problem in some people with IBS (Irritable bowel syndrome), when it can lead to diarrhoea. I would not advocate adding coffee to your routine solely for this purpose though!
  • In moderate amounts can be a source of B2, magnesium as well as polyphenols which are powerful antioxidants.
  • Can reduce the risk of oestrogen dependent cancers like endometrial cancer. (8) This has been linked to the anti-inflammatory benefits of caffeine as well as its ability to reduce the spread and multiplication of cancer cells.
  • Coffee causes mental alertness and increases concentration with moderate consumption. The polyphenols and antioxidants present in coffee have been associated with neurological benefits and can have an anti-depressant like effect. (9)
  • May reduce the risk of gallstones. There have been some studies done in both men and women, which have shown that people who consistently consumed coffee where significantly less likely to develop gallstones. Commonest gallstones are made of cholesterol. Studies show that components of coffee prevent the cholesterol from forming crystals in the gallbladder. (10), (11)
  • There is consistent evidence that Caffeine can protect the dopamine levels of the brain, and reduce the risk of Parkinson’s Disease. (12)

‘Not so good’ side of coffee

  • Disrupts sleep-this is one of the biggest downsides of drinking coffee. Research shows that the caffeine in the expresso 16hours before bedtime can affect the quality of sleep. (13) In fact research shows that 

Caffeine taken up to six hours before bedtime can disrupt the quality and quantity of sleep (even with the recommended 400mgs).

  • Increases Anxiety-There is plenty of evidence that higher intake of coffee is linked with anxiety as well as panic attacks. (14)
  • Acid reflux symptoms may be worse- A small study (15) showed that caffeine in coffee and tea have an adverse effect on function of the lower oesophageal sphincter. This can aggravate the symptoms of acidity which often presents as burning in centre of chest, sore throat or irritation at the back of the throat.
  • Coffee acts as a diuretic and hence it is advised by NICE (National Institute of Clinical Excellence) and the NHS, that people who have urinary incontinence should avoid coffee. This can also be a problem for night time urination and hence best to avoid coffee after midday.
  • Reduces bone strength and increases risk of Fracture-There is some evidence that when there is a high intake of coffee (more than 800mgs per day) this can lead to high levels of excretion of calcium in urine which can then lead for osteoporosis. However, this needs more robust randomised controlled trials to confirm if this is actually just an association due to lower intake of calcium in coffee drinkers. (16)
  • Reduces absorption of iron– The tannin in the coffee can inhibit the absorption of iron and hence it is best to avoid coffee one hour either side of meals. This is an important change I do advise my patients to make, if they are deficient in iron.
  • Can be addictive– The body can develop tolerance to coffee with regular use. This means that people can have withdrawal symptoms like fatigue and headaches when they do not have their regular caffeine intake. The American Psychiatric Association has labelled it as ‘caffeine use disorder’.
  • Palpitation– As mentioned previously coffee can actually reduce the risk of cardiac health diseases however it is important to understand that some people are more sensitive to caffeine than others. Hence this can cause palpitation or rise in the pulse rate in some. This is something I often see in my own patients. It is important to get all other investigations done to rule out any other conditions as a cause for the palpitation but it may be worth just reducing the coffee to one or two cups in the morning.
  • Hidden calories when the tall order is loaded with caramel, whipped cream and various flavoured syrups the calories can add up without even knowing. Though honestly speaking this is more of a side effect of the ‘coffee-on-the-go’ culture rather than due to coffee itself.

So looking at this information my take is that coffee in moderation, enjoyed during the first half of the day, in healthy adults can be beneficial. I have enjoyed a good cuppa as I write this blog. Hope you find this information useful.

Have a good week.


References for those who are interested.