Those daily extra cups of joe not linked to hypertension

An extra shot of espresso can surely help wake you up in the morning, but what does it mean for your blood pressure? It is well known that coffee’s caffeine content can raise blood pressure temporarily, especially in people who have hypertension. Could habitually drinking high amounts have long-term effects on blood pressure too?

Java lovers will rejoice in a large study’s findings that more cups daily isn’t associated with increased risk of hypertension. The study, published in American Journal of Clinical Nutrition on March 30, was a systematic review and meta-analysis that examined six prospective cohort studies.

Two previous meta-analyses of randomized controlled trials found an association with slightly raised risk of hypertension. But these trials all lasted only 85 days or fewer days. In the new study, a total 172,567 participants and 37,135 incident cases of hypertension were followed over the course of six years.

Four of the six studies evaluated reported a nonlinear association between coffee consumption and hypertension, whereas two reported no statistically significant association. The pooled results revealed a relative risk of 1.09 (1.01; 1.18) from drinking 1 to 3 cups daily (a slightly elevated risk), 1.07 (0.96, 1.20) from drinking 3 to 5 cups daily, and 1.09 (0.96, 1.21) from drinking five or more cups daily.

The researchers suggested that the results of the study may be explained by coffee drinkers developing a tolerance to caffeine’s acute effect on blood pressure, which is thought to be result of caffeine’s binding to receptors that trigger a sympathetic nervous system response.

Additionally, another explanation may be that other ingredients in coffee like magnesium, potassium, or flavonoids could have a counterbalancing effect on blood pressure, which the researchers suggest may explain an inverse “J-shape” relationship between habitual coffee drinking and hypertension risk.

Since the way people metabolize caffeine in the liver can depend on genetics, the authors suggest more research is needed to determine coffee’s effects on non-white populations.

Reference

Zhang Z, Hu G, Caballero B, Appel L, and Chen L. 2011. Habitual coffee consumption and risk of hypertension: a systematic review and meta-analysis of prospective observational studies1–3. Amer J Clin Nutr. doi: 10.3945/ajcn.110.004044.

Published by David Despain, MS, CFS

David is a science and health writer living on Long Island, New York. He's written for a variety of publications including Scientific American, Outside Online, the American Society for Nutrition's (ASN) Nutrition Notes Daily, and Institute of Food Technologists' (IFT) Food Technology magazine and Live! blog. He's also covered new findings reported at scientific meetings including Experimental Biology, AAAS, AOCS, CASW, Sigma Xi, IFT, and others on his personal blog "Evolving Health." David is also an active member of organizations including the National Association of Science Writers (NASW), the American Association for the Advancement of Science (AAAS), the American Society for Nutrition, the Institute of Food Technologists, and the National Audubon Society. David has a master's degree in human nutrition from the University of Bridgeport, and a bachelor's degree in English from University of Illinois at Springfield. He also earned his Certified Food Scientist credential from the Institute of Food Technologists.

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