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Yes, caffeine causes a temporary spike in blood pressure lasting up to a few hours, but the long-term picture is hazier.
Coffee may seem like a simple, well-understood drink to those of us who enjoy its effects, but it’s actually a central nervous system stimulant containing hundreds of bioactive compounds that exert subtle and not-so-subtle effects throughout the body.
The majority of researchers refute the claim that drinking coffee can increase the risk of hypertension (sustained high blood pressure) or heart disease, while a smaller group offers what seems to be contradictory evidence.
Even within each of these camps, there are disagreements as to how caffeine causes (or why it doesn’t cause) these issues.
Further confounding the answer is the subjectivity factor—does caffeine raise blood pressure to the same extent for those with or without hypertension, old people versus young people, postmenopausal women, and so forth?
We’ll play arbiter today between the pro- and anti-caffeine-raises-blood-pressure crowds, but don’t expect an outright solution; this one’s a bit of a mess still.
The argument for a long-term rise in blood pressure resulting from caffeine consumption is thin, but short-term spikes are a thing.
Does caffeine raise blood pressure?
Acutely, yes—the vast majority of researchers agree that caffeine causes a spike in blood pressure lasting up to three hours or so.
The most commonly agreed upon mechanism by which this process takes place is referred to as the pressor effect.
Compounds that exert a “pressor” or “vasopressor” effect are essentially vasoconstrictors; they cause the narrowing of blood vessels.
Narrower blood vessels means increased blood pressure, regardless of the heart’s output.
Though researchers largely agree on the fact that this is a thing in the case of caffeine, the “how” is very much in question.
Some argue that caffeine inhibits the hormonal signals required to keep our blood vessels wider, while others point to the opposite issue (causing a similar result), i.e., that it overclocks hormones that cause constriction.
In the case of non-hypertensive populations, this effect is mostly harmless, but certainly not desirable for those already dealing with hardened and plaque-filled arteries.
Still, the majority of the research community agree that caffeine is unlikely to cause sustained increases in blood pressure beyond this acute effect.
In an academic review of five trials testing the blood pressure-raising effect of caffeine on people with hypertension, the Autonomous University of Madrid, Spain found that “the administration of 200-300mg caffeine produced a mean increase of 8.1 mm Hg … in systolic BP and of 5.7 mm Hg … in diastolic BP.”
Importantly, the authors noted that this blood-pressure-raising effect of caffeine consistently lasted less than or equal to three hours.
Perhaps just as significant was the observation that a sustained rise in blood pressure was not observed as part of the long-term effects (two weeks) of caffeine consumption in studies that included this perspective.
Similarly, the researchers found that there was no evidence among seven cohort studies that regular coffee intake increased the risk of coronary vascular disease (CVD).
While these findings seem to bode well for coffee enthusiasts with hypertension, it doesn’t mean there are zero risks, as acute surges in blood pressure can still invite cardiac events.
This study from the University of Oklahoma Health Sciences Center found that people with high blood pressure experienced a more dramatic rise in blood pressure following caffeine consumption.
The 182 male participants recruited for the study were divided into five groups based on their level of hypertension (or lack thereof), including “optimal,” “normal,” “high-normal,” “stage 1 hypertension,” and “diagnosed hypertension.”
All participants were given 3.3mg/kg of caffeine or a fixed dose of 250mg of caffeine, and were then tested at the 20, 45, and 60-minute mark.
Specifically, “diagnosed hypertensive men had a pre-to-postdrug change in BP that was >1.5 times greater than the optimal group.”
This effect also pushed several participants in the “high-normal” group into the stage 1 group, but it was strongest among those with diagnosed hypertension.
Another finding from the University of Oklahoma Health Sciences Center sought to expose any differences in the effect of caffeine consumption (80mg x 3/day) on 165 men and women.
These participants were divided into groups by age and “hormonal status,” referring to any hormone therapies that postmenopausal women were undergoing (none, estrogen alone, or estrogen and progesterone.)
Though there were little to no differences in the blood pressure response to caffeine observed across these demographics, researchers did find that the pressor effect was not diminished with ongoing caffeine intake.
This is important for the argument of developing a tolerance, as even if people become less subjectively aware of feeling “buzzed,” the pressor effect apparently doesn’t follow suit.
This brings us to a logistical point: even if caffeine doesn’t cause permanent or semi-permanent increases in blood pressure, drinking two cups of coffee a day can still keep your blood pressure elevated for up to six hours.
Even temporary increases in blood pressure can be harmful for some, and everyone reacts to caffeine differently. When in doubt, ask your doctor.
As always, following your physician’s orders is priority number one when it comes to establishing safe levels of caffeine consumption, whether you have hypertension or any other issue that could potentially affect blood pressure.
For those in more of a prevention mindset, know that even though caffeine doesn’t likely produce permanent or semi-permanent increases in blood pressure, two cups a day can still keep you elevated for up to six hours.
As such, moderation is key for those looking to keep their blood pressure at healthy levels without fully sacrificing their favorite morning beverage.
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