Researchers from Zurich, Switzerland found that something other than caffeine may also affect the cardiovascular systems of coffee drinkers. And for habitual drinkers, another ingredient may eventually suppress some of caffeine's effects. Just what coffee does to the heart remains unclear.
Previous research has found that drinking coffee can cause a slight increase in blood pressure in some, while some studies have shown the beverage has no effect on blood pressure or can actually reduce it.
The current study investigated the effects of regular and decaffeinated coffee on six regular coffee drinkers and nine others who said they opted for coffee only on occasion. The investigators found that the blood pressures of occasional coffee drinkers rose after they drank coffee, while regular consumers experienced no blood pressure increase after drinking coffee.
Occasional drinkers also showed a blood pressure increase after drinking decaffeinated coffee--a finding that suggests the beverage contains an ingredient besides caffeine that could affect cardiovascular health. Along with an increase in blood pressure, these participants also experienced a jump in the activity of their sympathetic nervous systems (which increases heart rate) that lasted for 60 to 90 minutes.
To explain why the blood pressure of regular coffee drinkers didn't jump after a cup of java, the researchers suggested something may suppress the effect of caffeine on blood pressure--either an ingredient in the coffee or a change that occurs in the bodies of regular drinkers. Additional experiments revealed that while regular coffee drinkers may develop some type of tolerance to the beverage, it is not to the caffeine.
The findings don't suggest people who drink coffee should stop in order to protect their cardiovascular health, although the study did not examine the effects of heavy coffee drinking on blood pressure and nervous system activity. For those who drink one cup a day or so, the beverage is reasonably safe, the researcher said.
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