Scientists from Duke-NUS Medical School have found that drinking tea and coffee in specific ways may influence a person’s risk of developing high blood pressure.
The research, conducted by Choy-Lye Chei and colleagues, was published in The European Journal of Nutrition.
Caffeine is a naturally occurring chemical with stimulant effects. It is found in coffee, tea, cola, cocoa, guarana, yerba mate, and more than 60 other products. It works by stimulating the central nervous system, heart, muscles, and the brain centers that regulate blood pressure.
As a stimulant, caffeine increases activity in the brain and nervous system and boosts the circulation of hormones such as cortisol and adrenaline. In small amounts, caffeine can help people feel more alert and focused.
However, the relationship between coffee and tea consumption and the risk of high blood pressure remains controversial.
In this study, researchers analyzed data from 63,257 Chinese adults aged 45 to 74 who were living in Singapore between 1993 and 1998.
Participants provided information on their coffee and tea consumption, along with other lifestyle factors. High blood pressure was assessed during two follow-up interviews conducted between 1999 and 2004, and again between 2006 and 2010.
Over an average follow-up period of 9.5 years, the researchers identified 13,658 new cases of high blood pressure.
Compared with people who drank one cup of coffee per day, those who consumed three or more cups daily had a lower risk of developing high blood pressure. In contrast, compared with people who drank tea less than once a week, daily drinkers of black or green tea showed a slight increase in risk.
The team also observed a dose–response relationship between total caffeine intake and high blood pressure risk. Compared with people who consumed less than 50 milligrams of caffeine per day, those with the highest intake (300 milligrams or more per day) had a 16% higher risk.
Overall, the researchers concluded that drinking coffee less than once per week or three or more cups per day was associated with a lower risk of high blood pressure than drinking one cup per day. Caffeine may partly explain the increased risk observed among daily tea drinkers and those who consumed one cup of coffee daily.
The authors suggest that the inverse U-shaped relationship between coffee intake and blood pressure risk indicates that, at higher levels of consumption, other compounds in coffee may counteract the effects of caffeine and provide protective benefits. Future studies are needed to test this hypothesis.
