Caffeine is known to increase blood pressure (BP) but many trials have found coffee to be beneficial for high BP (hypertension) patients.
The underlying science is still unclear but in this article, I plan to shed some light on current understanding as well as various caveats.
Benefits of Coffee
Coffee has hundreds of plant compounds but most of its benefits seem to accrue from its caffeine. Black tea and green tea may show similar properties, but they have one-fourth the caffeine in coffee.
Coffee is found to be protective in:
- Type 2 diabetes;
- Parkinson’s Disease;
- Heart disease; and
- Liver disease.
In some aspects such as blood pressure, caffeine increases BP but coffee seems to not raise it in many individuals. This is thought to be due to healthy antioxidant compounds in coffee, such as phenols. But why is the benefit seen only in some people? And could you be one of them?
Let us look at what science knows so far.
Does Coffee Increase Blood Pressure?
When people are given 200 to 300 mg of caffeine (equal to 2–3 American or 4–6 Indian coffee cups), their blood pressure increases quickly and significantly. I will come to this ‘cup’ thing a bit later.
Within thirty minutes of consuming caffeine, systolic and diastolic blood pressures increase by 3–15 mmHg and 4–13 mmHg, respectively. They peak in one to two hours and stay high for four hours. The body takes up to ten hours to clear caffeine from the system.
This BP rise is attributed to caffeine blocking an enzyme needed for blood vessels to stay relaxed. In technical terms, caffeine acts like a ‘vasoconstrictor’—contracting vessels and raising BP.
Caffeine also stimulates your body into producing adrenaline—a stress hormone—which can raise your BP.
Note: If you are going to your doctor for a BP checkup, abstain from any caffeine drink for at least four hours before the visit.
A study of 34 different studies (called a meta-study!) found that the average systolic and diastolic BP rise with 300 mg of caffeine is about 8 mmHg and 6 mmHg, respectively.
The study also showed that regular consumption of this much caffeine a day had neutral to beneficial effects on blood pressure, heart disease, heart failure, and heart arrhythmias.
Thus, it starts getting confusing. Caffeine increases blood pressure, but coffee seems to be benefitting the heart health.
Another combined study of seven large studies showed that drinking lots of coffee (seven American cups or more—that is nearly two litres of coffee a day—crazy!) reduced the risk of developing hypertension. And the more coffee consumed, the higher the risk reduction.
Coffee seems to be better in larger amounts but wait!
Another study found that people with serious hypertension (systolic BP above 160 mmHg or diastolic BP above 100 mmHg) had double the risk of dying from cardiovascular disease if they had two or more American cups of coffee a day. But if they drink less than that, or consume any amount of green tea, their risk does not seem to increase.
So a lot of coffee consumption is bad only if one has a very high BP and is beneficial otherwise.
Is Caffeine The Main Culprit?
Way back in 2002, some Swiss scientists asked a simple question: what if caffeine is not the culprit for high blood pressure? They devised a simple experiment. They took some regular coffee drinkers and non-coffee drinkers. They gave them a strong triple-espresso (250 mg caffeine), a decaffeinated triple-espresso (no caffeine), a caffeine injection of a similar amount (250 mg caffeine), or a salt injection (placebo). They did not tell the participants if they were getting caffeine or not.
They found something intriguing.
- When they gave caffeine injections, everyone’s BP rose by 6 mmHg;
- When they gave triple espresso, the regular coffee drinkers had no change in their BP but non-coffee drinkers had systolic BP rising by 13 mmHg.
- When they gave decaffeinated triple espresso, we would expect no effect but it had exactly the same effect as triple espresso—no change in BP of regular coffee drinkers and 12 mmHg rise in systolic BP of non-coffee drinkers.
It appeared that caffeine was not the real culprit. There was ‘something else’, which was there in regular as well as decaf espresso coffee, that was causing the rise in non-coffee-drinkers. Regular coffee drinkers were somehow habituated to it, leading to no BP rise.
This Swiss experiment tells us that contrary to expert advice, decaffeinated coffee may not be safe enough in high BP patients. I would suggest erring on the side of caution.
How Much Caffeine Is In A Cup?
- A standard American cup is 8 oz. or about 240 mL. It has 80 to 100 mg of caffeine, as per the U.S. Food and Drug Administration (US FDA). The exact amount varies based on the method of preparing coffee, with an average of about 95 mg of caffeine.
- In India, a typical coffee cup is 150 mL and has a good amount of milk. So You can consider 50 mg of caffeine in a cup in India.
- Decaffeinated coffee has 97 per cent of its caffeine removed. Expect 2-3 mg of caffeine in a cup.
- An American cup of black tea or green tea has 30 to 50 mg of caffeine. So an Indian cup should have 20 mg.
- Note that most soft drinks have 20 to 30 mg of caffeine in 250 mL. And most cans of such drinks have 350 mL. So you are going to consume 30 to 40 mg of caffeine per can.
- Some energy drinks have much higher caffeine contents—a wide range of 40 to 250 mg per 250 mL. A 350 mL can gives 55 to 350 mg of caffeine in one go. Be careful!
As you can read, the data is not clear-cut. So do not expect any absolute verdicts. However, here is what experts advise about coffee consumption and high blood pressure:
- If you are hypertensive, it is best to check with your doctor about how much coffee you can drink a day.
- As per the US FDA, normal people should not consume more than 400 mg of caffeine a day. That is less than four American or eight Indian cups of coffee.
- People with hypertension should take less than 200 mg of caffeine a day. That is two American or four Indian cups of coffee.
- If you have very high blood pressure (160/100 mmHg or above), do not exceed 100 mg of caffeine—one American or two Indian cups of coffee—a day.
- Treat decaffeinated coffee the same as regular coffee for determining the amounts, though many guidelines suggest that decaf coffee is totally safe.
- If you have a high BP problem, do not drink coffee for four hours before performing any exercise or strenuous activity.
Now, some guidelines about other caffeinated drinks and high blood pressure:
- The limits for green tea, black tea, and caffeinated soft drinks will be about two and a half times the respective coffee amounts.
- Energy drinks can be a major problem; check their labels for contents.
- Total caffeine intake adds up from various sources. So if you have some coffee, tea, and energy drink on the same day, total their caffeine content before taking a decision.
- Even your chocolate and some medications contain caffeine. Always read the labels.
To Read More
- GoodRx Health: Does Caffeine Raise or Lower Blood Pressure? Here’s the Latest Research
- Mayo Clinic: Caffeine: How does it affect blood pressure?
- Healthline: How Does Coffee Affect Your Blood Pressure?
- MedicalNewsToday: Does coffee raise blood pressure?
- American Heart Association News: People with very high blood pressure may want to go easy on the coffee
- Research Paper (2022): Coffee and blood pressure: exciting news!
- Research Paper (2021): Coffee and Arterial Hypertension
- Research Paper (2018): Coffee Consumption and Cardiovascular Disease
- Research Paper (2011): Habitual coffee consumption and risk of hypertension
- On this Website: How Much Tea Or Coffee Is OK In A Day?
First Published on: 28th June 2023
Image Credit: Image by Freepik