Sammanfattning
Ingestion of caffeine creates a blood plasma concentration of the substance that influences adenosine receptors located in cell membranes. There caffeine induces an antagonistic effect on the biological processes regulated by the adenosine receptors. The immediate effect of caffeine ingestion is an increase in blood pressure, although the response is very individual. Ingestion of an amount of caffeine corresponding to that in a cup of coffee induces a blood pressure increase of 2-10 mm Hg. The increase is more pronounced in hypertensive, pregnant, middle-aged and old subjects. In studies of caffeine's »chronic« effect on blood pressure, varying results have been seen. It is unlikely that regular caffeine ingestion, corresponding to the amount consumed by the average person in Denmark, exerts a prolonged unhealthy effect on blood pressure. Receptor adaptations to prolonged caffeine ingestion that reduce the antagonistic influences are a possible explanation for the neutral effect on blood pressure observed in people who consume caffeine regularly.