Coffee can boost your blood pressure

You can adapt to almost anything. If you watch enough reality television you will come to accept that human beings can be self-absorbed, vindictive, small-minded, and trivial. Yet if you tune in to this programming only rarely, or never, if you do catch a few moments of “I’m an Apiarist: Find me a Courtesan” you will probably be shocked at the depths to which people will sink. That’s why it does matter what you expose your mind to on a regular basis because it will normalise it. Your body is the same, it adapts to things that it is constantly exposed to, such as caffeine. We know that caffeine is a stimulant and it increases blood pressure in the short term but we also know that people who drink a lot of coffee develop a tolerance to it. What researchers in a new study wanted to discover was would coffee (or caffeine) consumption affect your blood pressure in the short term if you had not had coffee for a while.

For the study the researchers had people with an average age of 52 with normal blood pressure have tests carried out over a few weeks. The subjects had their blood pressure taken three times, one week apart, and on each occasion they consumed no coffee, caffeinated drinks, alcohol, grapefruit, marmalade, or medications for 48 hours before the test. The intent of this was to allow enough time for caffeine to get out of the subjects’ systems. The half-life of caffeine (the time taken for the body to eliminate one-half of the caffeine present) varies widely between people, depending on factors such as age, bodyweight, pregnancy status, medication intake and liver health. However, in healthy adults, the half-life is approximately 5 to 6 hours. So in most cases 48 hours should see all caffeine out of the system.

On one occasion just before the test they had two 300ml cups of black coffee. On another occasion they had the maximum recommended dose of a drug called felodipine (a drug that is a calcium channel blocker which works by widening the blood vessels). On the last occasion they had two cups of black coffee plus the dose of felodopine.

The results showed that after abstaining from coffee for just two days the tolerance of the subjects to coffee did reduce and there was an immediate increase in blood pressure after drinking coffee. Additionally, combining coffee with felodipine resulted in higher blood pressure than taking only felodipine. According to the researchers it might be that caffeine counteracts the calcium-channel blocking effects of felodipine. To overcome the effect of the coffee the researchers found that you needed to double the amount of felodipine taken.

The statistics tell us that 15-20 per cent of people only drink coffee occasionally. If those people have a coffee before they go for a blood pressure test then they could potentially be prescribed anti-hypertensive drugs when there is no need.

Source: American Journal of Hypertension