Medicineworld.org: Coffee and Blood Pressure
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Coffee And Blood Pressure
There is some evidence from prior studies to suggest that caffeine consumption increases cortisol stimulation. Caffeine also increases adrenaline levels. These effects are believed to be associated with the stimulatory effects of coffee and may also contribute to the development of high blood pressure Ref 2, 3.
Results of the study, reported in the March 25 issue of the Archives of Internal Medicine, also showed that those who drank five or more cups of coffee a day were up to 1.6 times more likely to develop high blood pressure than non-coffee drinkers, eventhough these associations were less significant after the scientists took into account alcohol intake, smoking and other characteristics associated with coffee drinking.
"Overall, coffee drinkers had higher blood pressures than people who did not drink coffee, but there was no set 'dose-response' relationship," says Michael J. Klag, M.D., M.P.H., lead author of the study and director of the Division of General Internal Medicine at Hopkins. Still, Klag says people who already have hypertension should reduce their coffee intake because other studies have clearly shown that avoiding caffeine-containing drinks can lower blood pressure.
The research team analyzed data from the Johns Hopkins Precursors Study, a long-term study of male medical students who enrolled at Hopkins between 1948 and 1964 and who continue to be followed. In medical school and through the follow-up period, information on family history and health behaviors has been collected.
For this report, coffee intake, blood pressure and presence of high blood pressure were assessed in 1,017 white males during school and up to 11 additional times over an average follow-up of 33 years. At the study's start, the men were young (average age 26), were at a healthy weight, and had desirable blood pressure and cholesterol levels. Coffee intake was assessed during medical school, every five years after graduation until 1984, and in 1978, 1986, 1989 and 1993. After 1986, participants were asked about caffeinated coffee. Blood pressure and incidence of high blood pressure were determined annually through mailed surveys.
Overall, 82 percent of the participants reported they drank an average of two cups of coffee daily. Coffee drinkers were more likely to drink alcohol and to smoke cigarettes. During the follow-up period, 281 men developed high blood pressure around age 53. By age 60, the incidence of high blood pressure (28 percent) was greater among men who drank coffee in medical school than in those who did not (19 percent). Risk of high blood pressure was slightly greater in those drinking three or four cups a day compared with those who abstained.
The majority of coffee drank most likely waccording tocolated and unfiltered, Klag says.
"The coffee we drink today is probably a little healthier than what this population consumed, since coffee filters didn't come into widespread use until after 1975," he says. "Passing boiled coffee through a paper filter removes terpenes - chemical particles that raise cholesterol".
The effect of caffeine on blood cortisol levels were examined in a separate study by measuring blood pressure during rest and in response to a challenging psychomotor task in men with a low versus high risk of essential hypertension. Testing consisted of quiet rest (20 minutes); oral placebo (grapefruit juice) or caffeine administration. The combination of task plus caffeine produced the highest blood pressures in men at risk for hypertension. Cortisol levels were found to be sustained during rest in members of the high risk group after they had consumed caffeine. The high-risk subjects also showed a significant rise in cortisol during (+3.7 micrograms/dl) and after (+4.0 micrograms/dl) work on the reaction time task after caffeine consumption.
Ref 1: Klag, M.J. et. al., "Coffee Intake and Risk of Hypertension," Archives of Internal Medicine, March 25, vol. 162, pp. 657-662.
Ref 2: Hypertension. 1989 Aug;14(2):170-6.
Ref 3: J Physiol 569.1 pp 347-355.
Did you know?
In a long-term study of more than 1,000 men, drinking a daily cup of regular coffee raised systolic pressure (the upper number) by 0.19 mmHg and diastolic blood pressure (the lower number) by 0.27 mmHg. Coffee drinkers also had a greater incidence of high blood pressure (28 percent) than their non-coffee drinking counterparts (19 percent) Ref 1.
Medicineworld.org: Coffee and Blood Pressure
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