What Caffeine Does To Your Blood Pressure

by Mark Miller August 17, 2017

Caffeine and blood pressure

As you might guess, three cups of espresso raised the blood pressure of people who were not used to coffee. (Creative Commons/Photo by DocteurCosmos)

Caffeine appears to raise blood pressure, in some people in the short term and in others in the long term. This is an important question because 80 percent of Americans drink coffee every day and about 90 percent of people worldwide consume caffeine in one product or another. It's also an important question because high blood pressure can cause strokes or heart attacks.

A Mayo Clinic says if you have high blood pressure, ask your doctor if you should stop drinking coffee or taking caffeine in other beverages or products.

Of those with short-term blood-pressure increases, an article Mayo's website states:

Caffeine can cause a short, but dramatic increase in your blood pressure, even if you don't have high blood pressure. It's unclear what causes this spike in blood pressure. Some researchers believe that caffeine could block a hormone that helps keep your arteries widened. Others think that caffeine causes your adrenal glands to release more adrenaline, which causes your blood pressure to increase.

Of those with long-term blood-pressure increases, the article states:

Some people who regularly drink caffeinated beverages have a higher average blood pressure than do those who drink none. Others who regularly drink caffeinated beverages develop a tolerance to caffeine. As a result, caffeine doesn't have a long-term effect on their blood pressure. It seems that caffeine has a stronger blood pressure increasing effect in men who are older than 70 or who are overweight.

Testing caffeine and blood pressure

To test whether caffeine has an effect in raising your blood pressure, check it between 30 and 120 minutes of ingesting caffeine. An increase of five to 10 points indicates you are sensitive to caffeine, and you should cut back on it, Mayo Clinic says. To avoid withdrawal symptoms such as headaches, irritability and fatigue, cut back over several days.

A doctor can tell you whether to stop taking caffeine or limit your intake of it if you do have high blood pressure. He may advise you to cut back and have no more than 200 milligrams of caffeine per day. That equates to about two 12-ounce (355 ml) cups of coffee or five Viter Energy Mints. While the amount of caffeine varies a lot in coffee, Viter Energy Mints contain 40 milligrams.

If you lift weights or do physical labor and have high blood pressure, avoid caffeine before engaging in those activities, Mayo Clinic says.

Research on caffeine and blood pressure

Scientists, of course, have researched whether caffeine raises blood pressure. Some have found that it does, and one 1987 Italian study actually found that caffeine lowers blood pressure, Harvard Medical School reports.

It has become so accepted that caffeine raises blood pressure, that doctors advise avoiding caffeine before having your blood pressure checked because it may raise it enough to falsify test results.

But what is the evidence for caffeine raising blood pressure? Harvard Medical School reports that researchers from the United States and Switzerland studied 15 volunteers who didn't have high blood pressure and were nonsmokers. Only six habitually drank coffee. Harvard says:

The researchers monitored each volunteer's blood pressure, heart rate, and sympathetic nervous system under four conditions: before and after drinking a triple espresso, before and after drinking a decaffeinated triple espresso, before and after receiving 250 mg of caffeine by intravenous injection, and before and after an intravenous placebo (salt solution).

A triple espresso

A triple espresso did raise blood pressure readings except in the habitual coffee drinkers. In those who didn't drink coffee, it raises systolic readings 13 mm Hg on average and diastolic by 7 mm Hg.

Harvard Medical School says:

Espresso is strong stuff, but an intravenous slug of caffeine should be even more potent. Indeed, blood caffeine levels rose to the same degree after the caffeine injections and the espresso. But the straight-up caffeine had a much smaller effect on blood pressure than the espresso, boosting systolic blood pressure by an average of just 6 mm Hg. Moreover, the coffee drinkers and the nondrinkers responded similarly to intravenous caffeine.

But there was an anomaly. Harvard says there are hundreds of substances in coffee, and caffeine is usually the one named as raising blood pressure. "But the disparity between espresso and pure caffeine suggests there is more to the story. The decaffeinated espresso proved the point. It did not raise blood caffeine levels, but it boosted the average systolic blood pressure of the nondrinkers by 12 mm Hg, virtually as much as the high-test brew."

Their conclusions: Coffee raises blood pressure in people who don't drink it regularly. Younger people also are more sensitive to coffee's blood-pressure effects.

Does coffee cause heart disease? No

This leads us to the question: Does coffee cause heart disease? Harvard Medical School's article cited a two-year study of 45,589 men age 40 to 75. That study, done by Harvard, did not find a link between coronary artery disease or stroke and coffee consumption even if the subjects were heavy drinkers of coffee.

It's interesting to note that "while regular coffee proved harmless, decaf was associated with a slightly increased risk of heart disease, though the link was weak. The Scottish Heart Health Study was even more reassuring, reporting a reduced risk of heart disease in coffee drinkers, with heavy drinkers getting the most benefit. And although some coffee drinkers are annoyed by a feeling of rapid pulse, coffee does not seem to cause serious disorders of the heart's rhythm, even in recent heart attack patients."

Other risks of coffee and caffeine

So while it appears there is little risk for high blood pressure among regular coffee drinkers, the question occurs: Are there other risk factors for health in consuming coffee and/or caffeine?

Coffee can cause:

  • Difficulty falling asleep or outright insomnia
  • Anxiety and nervousness
  • Tremors or jitters
  • An increased heart rate

And for those who consume a lot of caffeine, it may cause dizziness or headaches and excessive urination and dehydration.

So many benefits

But the benefits of coffee and possibly caffeine alone, ranging from mental to physical, are so many that experts advise people not to stop taking it but rather to take it in moderation, no more than 400 mg per day.

The European Food Safety Authority did a study of how much caffeine is OK. It found what Mayo and the National Sleep Foundation reported "that about 400 mg per day does not raise safety concerns." Also, about 200 mg in one dose right before exercise is OK.

As many philosophers and doctors have said down through the centuries, all things in moderation. Don't overdo it, and you should be OK.

Mark Miller
Mark Miller

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