Have Another Cup; Coffee Does Not Raise Blood Pressure in Most
Following a healthy diet is one healthy lifestyle habit that can help control blood pressure. One common impression is that patients must abstain from coffee or switch to decaffeinated, but a meta-analysis of several studies conducted by researchers at Michigan State University finds that habitual coffee drinkers may not have to give up that cup of joe after all.
Coffee Drinkers Have Only Slightly Greater Tendency Toward High Blood Pressure
Zhenzhen Zhang, from the Department of Epidemiology, and colleagues found six prospective cohort trials enrolling 172,567 participants all together. All studies reviewed the association between coffee drinking and incident hypertension. Because two previous meta-analyses of trials came to the conclusion that coffee consumption was linked to slightly higher blood pressure over a short term (85 days or less), the researchers focused on trials that reviewed longer-term consequences. The chosen studies had a mean follow-up range of 6.4 to 33 years.
Of the coffee drinkers, just one in five participants eventually developed high blood pressure.
Compared with the lowest category of coffee consumption (under one cup a day), the relative risk for hypertension for participants who drank 1 to 3 cups a day was 1.09, meaning that coffee drinkers had less that a 1% greater risk of having high blood pressure. For those drinking 3 to 5 cups a day, the relative risk was 1.07.
The researchers concluded that the results suggest that habitual coffee consumption of more than three cups per day is not linked to increased risk of high blood pressure compared to drinking less than one cup per day.
The researchers did not compare the effect of caffeinated versus decaffeinated coffee consumption because not all the studies they examined looked at this consistently. Caffeine is known to cause a short, dramatic increase in blood pressure possibly due to blocking a hormone that keeps arteries widened or by causing the adrenal gland to release more adrenaline.
Dr. Sheldon Sheps MD of the Mayo Clinic says that some people who regular drink caffeine have a higher average blood pressure than those who drink none, but others do not – possibly reflecting a genetic difference in tolerance. He suggests that patients who have hypertension measure their blood pressure within 30 minutes of drinking a caffeinated beverage and if the numbers increase by five to 10 points, they should consider limiting caffeine intake.
"Habitual coffee consumption and risk of hypertension: a systematic review and meta-analysis of prospective observational studies", Zhenzhen Zhang, Gang Hu, Benjamin Caballero, Lawrence Appel, and Liwei Chen, American Journal of Clinical Nutrition, first published online 30 March 2011.