Caffeine ups blood pressure in hard-core users too

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Caffeine ups blood pressure in hard-core users too

Last Updated: 2004-03-31 10:58:14 -0400 (Reuters Health)

By Amy Norton

NEW YORK (Reuters Health) - Even people who would never start the day

without their coffee fix may not become tolerant to the blood

pressure-raising effects of caffeine, new research suggests.

Although it's still unclear how important caffeine is in contributing to

high blood pressure, the new findings suggest that people at risk of

hypertension may want to reconsider that second cup of java, researchers

say.

The study of 97 adults who regularly consumed caffeine found that half

showed small spikes in blood pressure shortly after taking caffeine

capsules, even after spending the previous five days downing the

equivalent of six cups of coffee per day.

The findings counter the idea that regular caffeine users develop

complete tolerance to the stimulant's blood pressure effects, according

to researchers.

Dr. R. Lovallo, with the VA Medical Center and the University of

Oklahoma Health Sciences Center in Oklahoma City, and his colleagues

report the findings in the journal Hypertension.

Many laboratory studies have shown that caffeine causes a short-term

rise in blood pressure, but population studies have failed to

definitively link caffeine intake to a higher risk of hypertension. One

of the proposed explanations is that in real life, caffeine fiends

develop a tolerance to its blood pressure effects.

To test that idea, Lovallo and his colleagues had healthy adult

volunteers go through a four-week trial that measured their blood

pressure responses to a caffeine " challenge " -- two separate doses of

caffeine, given four hours apart, that were each equivalent to two to

three cups of coffee.

During one of the study weeks, participants were given placebo pills,

which did not contain caffeine, for five days before the challenge

tests. On another week, they took pills containing 300 milligrams of

caffeine -- about three coffee cups' worth -- each day before challenge

testing; and on a third week, they took daily doses of 600 milligrams of

caffeine.

The idea was that, if regular users become tolerant to caffeine,

participants would show much smaller blood pressure responses to the

challenge tests during the caffeine weeks than during the placebo week.

The researchers found, however, that while half of participants were

" completely tolerant " to caffeine after taking caffeine capsules for

five days, the other half continued to show a blood pressure response.

All were regular consumers of caffeine before the study, taking in the

equivalent of four to five cups of coffee a day.

The blood pressure responses were small, a matter of a few points on a

blood pressure reading. And for most people, according to Lovallo, the

minor blood pressure change that may come with a morning coffee is

likely harmless.

" For most people, it's probably fine to consume moderate amounts of

caffeine, " he told Reuters Health.

Where things get more complicated is with people who have a family

history of hypertension or have borderline " pre-hypertensive " blood

pressure. There's evidence caffeine has a greater blood pressure effect

in these individuals, Lovallo said, and they might want to limit their

intake.

Dr. G. Myers of the University of Toronto in Ontario, Canada,

agreed that moderation is in order when it comes to caffeine.

There is " little evidence, " he writes in an accompanying editorial, that

drinking two to four cups of coffee a day causes a blood pressure

increase of " any clinical importance. " He advises that people with or at

risk of high blood pressure not consume any more caffeine than that.

" At the moment, " Myers writes, " it would seem premature to add moderate

caffeine consumption to our list of 'perils of daily living'. "

SOURCE: Hypertension, April 1, 2004.

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Mayo Clinic in Rochester

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s Hopkins Medicine

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