I’m a coffee drinker, and believe this beverage has done little to deserve its quite unhealthy reputation. Much of the negativity concerning coffee comes from the fact that it’s generally rich in caffeine. One effect of caffeine is to raise blood pressure – and raised blood pressure has links with heart disease and stroke. Perhaps, not surprisingly, those seeking to reduce their risk of ‘cardiovascular events’ such as heart attacks and strokes are advised to limit their consumption of coffee. Such advice is generally offered even more strenuously to people who have a history of high blood pressure (hypertension), for obvious reasons.
This week, the American Journal of Clinical Nutrition published a paper on-line which assessed relevant evidence regarding the effect of coffee drinking on blood pressure and cardiovascular disease in individuals with a history of high blood pressure . The review looked at three lines of evidence. Here’s a summary of each type of evidence and the findings of the review.
1. Studies where individuals consumed the equivalent of 200-300 mg of caffeine (1.5 – 2 cups of filter coffee) in the short term
Putting several studies together revealed that this does increase blood pressure for up to 3 hours. Rise in blood pressure was about 8 and 6 mmHg in the systolic (higher) and diastolic (lower) blood pressure values, respectively.
2. Studies where individuals consumed coffee over a 2 week period
These studies showed that, overall, coffee did not increase blood pressure. Some of the explanation here is that individuals can become ‘habituated’ to caffeine, with its effects on the body lessening in time.
3. Studies looking at the link between coffee consumption and cardiovascular disease over time
These studies showed that, overall, higher intakes of coffee were not associated with increased risk of cardiovascular disease.
In short, coffee seems like a generally safe option for people with a history of raised blood pressure.
One of the points the authors of this paper make is that while caffeine can have adverse effects on markers for disease (such as blood pressure), other elements in coffee can have beneficial effects. For example the compounds chlorogenic acid and trigonelline and the mineral magnesium improve glucose metabolism, reduce inflammation and enhance the healthy functioning of the inside of the blood vessels.
While I’m a fan of coffee, I do recommend some caution. Too much caffeine, in addition to effects on the cardiovascular system, can do other things too such as disrupt sleep, which can have implications for health and wellbeing. Some people metabolise caffeine (in the liver) very quickly and throw back a double espresso after dinner and still sleep like babies. Others, though, are not so fortunate, and can be tripped up by caffeine consumed hours before. If you think you’re caffeine-sensitive, then I’d advise keeping coffee intake generally low and confining it to the morning only.
I’ve found in my experience that most individuals who over-drink coffee tend to drink it indiscriminately. In other words, they will drink instant coffee, machine coffee, coffee served in meetings etc. whether they want it or like it or not. For most of these people, coffee-quaffing is just habit. I suggest a more discerning approach:
If you really like coffee, have something you really like.
Brewing some decent coffee for yourself in the morning might be an approach here. Another is only to take coffee from places where you can be sure of the quality. Here in London we have a ton of coffee shops including several chains. The three chains with the most presence are Starbucks, Costa and Nero’s. I think Nero’s serve the best coffee, so I have a ‘Nero’s or nothing’ policy. This makes it very difficult for me to drink much coffee in any given day. I don’t drink much coffee, but the ones I have I really savour.
1. Mesas AE, et al.The effect of coffee on blood pressure and cardiovascular disease in hypertensive individuals: a systematic review and meta-analysis. Am J Clin Nutr epub 31 August 2011