Caffeine is present in your morning cup of coffee, your afternoon tea, or the energy drink that helps you stay awake at work. But behind that familiar feeling of alertness, caffeine is actually making significant changes inside the body, especially to blood pressure.
How does caffeine affect blood pressure?
1. Blood pressure changes when consuming caffeine
Caffeine is a stimulant that acts on the central nervous system. It works by blocking receptors in the brain that stimulate the release of adenosine, a neurotransmitter (chemical messenger) that promotes sleepiness and relaxation.
By blocking adenosine, caffeine can promote alertness and enhance physical performance as well as cognitive function. It can also cause a temporary increase in blood pressure by triggering the following chain of events:
- Increased nerve cell activity: Inhibiting adenosine increases the excitability of other neurotransmitters, leading to increased nerve cell activity in the brain.
- Activation of the endocrine system: The pituitary gland interprets the increased activity as a “distress signal” and instructs the adrenal glands to release a hormone called epinephrine (adrenaline).
- Epinephrine’s effects: Epinephrine, the hormone responsible for the body’s “fight or flight” response, causes rapid physiological changes to better cope with the perceived threat, including increased heart rate and increased blood pressure.
2. How long do the effects last?
The effects of caffeine on blood pressure do not stop after an hour. On average, blood pressure begins to rise after about 30 minutes. The effects usually peak about 1 to 2 hours later. However, the body cannot “process” caffeine too quickly. Depending on the individual, the time caffeine remains in the blood (called the half-life) can last from more than an hour and a half to nearly 10 hours.
If you drink coffee in the late afternoon or evening, it can cause your blood pressure to remain high until you go to bed, even affecting your sleep, which is also a factor that causes blood pressure to lose control. People who drink coffee every day will gradually get used to this effect, and their body will gradually reduce its reaction to caffeine. However, if you are someone who does not drink coffee regularly, just one cup can make you feel your heart beat faster, restless or slightly dizzy.
3. How serious is the effect?
Research shows that drinking about 300 mg of caffeine (equivalent to 2 shots of espresso or 3-4 small cups of coffee) can increase blood pressure by 5-7 mmHg at the systolic level and about 3 mmHg at the diastolic level. For healthy people, this is a temporary change and is not a cause for concern.
However, for people with cardiovascular disease, fatigue, insomnia or stress, the increase in blood pressure after drinking caffeine can last longer, causing discomfort or worsening the condition.
Should people with high blood pressure abstain from caffeine?
It is not necessary to give up coffee completely. For most adults, caffeine intake under 400 mg per day is still considered safe, even if you have mild hypertension.
However, if your blood pressure is often high (for example, 160/100 mmHg or higher), consuming high doses of caffeine every day can increase the risk of cardiovascular events. Some studies have shown that, for people with severe hypertension, drinking two cups of caffeinated coffee per day can double the risk of death from stroke or heart attack. When reduced to one cup per day, this risk is also significantly reduced.
Tips for Loving Coffee and Worrying About Blood Pressure
There’s nothing wrong with loving the alertness that coffee brings. But if you’re trying to control your blood pressure, use caffeine wisely. You can:
- Watch your body: How do you feel after each cup of coffee? If your heart is racing, you feel lightheaded, or you have trouble sleeping, adjust your dosage.
- Time your coffee right: Avoid coffee on an empty stomach or too late in the day.
- Sweeter your options: Low-caffeine coffee, green tea, or herbal tea can also be substitutes that will still help you stay alert.
- Ask your doctor: especially if you’re taking medication for high blood pressure or have heart complications.
