Does caffeine affect heart rate variability?

Coffee wakes you up in the morning and improves mood. In a short time, caffeine spreads throughout the body through the bloodstream. It increases heart rate and affects the functioning of other organs. HRV is also influenced by caffeine, not only in the short term. Studies show that caffeine can affect heart rate variability in the long term.

While writing this article, I read numerous scientific studies on the impact of caffeine on HRV, which is fascinating. Surprisingly, researchers arrived at different conclusions. Some observed a deterioration in HRV, others wrote about improvement, and some didn’t observe any influence at all.

And although the research results are inconclusive, a clear pattern can be identified:

Individual studies indicate that caffeine can be particularly beneficial for individuals with poor HRV.

How caffeine affects the body

It seems that caffeine actually stimulates the parasympathetic rather than the sympathetic nervous system, contrary to what might initially appear.

Regardless of which nervous system it stimulates, the effect of caffeine is well-known: increased heart rate, elevated blood pressure, bronchial and blood vessel dilation. Under the influence of caffeine, the body becomes more active.

The invigorating effect of coffee occurs due to the blocking of the neuromodulator adenosine in the brain. By inhibiting adenosine, the activation of neurotransmitters such as dopamine takes place, improving the conductivity of impulses in synapses.

The consumption of caffeine not only brings physical benefits but also helps us mentally: it improves concentration and increases productivity. Mood is also enhanced, especially when consuming caffeine in a social setting.

Caffeine helps diabetics

At diabetics, HRV is often reduced, indicating an increased risk of cardiovascular diseases. Richardson and colleagues studied the impact of caffeine on HRV in individuals with type 1 diabetes and healthy participants. Both groups took 250 milligrams of caffeine in tablets twice a day for two weeks, equivalent to approximately three to four cups of filtered coffee per day.

HRV was measured after two weeks. HRV improved positively in both groups. For diabetics, sNN50 (which, like pNN50, reflects parasympathetic nervous system activity) increased by 103 percent, and in healthy participants, it increased by 38 percent. Frequency analysis parameters showed similarly positive results. The HR parameter increased, and the LF parameter decreased compared to pre-regular caffeine intake.

How long does the effect of caffeine last after consumption

To assess the impact of caffeine on HRV, it’s important to understand how long it lasts and when it reaches its maximum effect.

Caffeine is absorbed through the gastrointestinal tract within 45 minutes. The peak concentrations in the blood plasma are reached within 15–120 minutes. Caffeine easily crosses the blood-brain barrier.

The half-life of caffeine helps estimate how long its effects last. The duration of its presence in the blood largely depends on age.

The half-life in adolescents and adults ranges from 2.5 to 5 hours, while in infants and small children, it can be up to 100 hours.

For smokers, it is reduced by 30–50 percent.

The half-life may double in women taking oral contraceptives. Caffeine also breaks down more slowly in pregnant women.

As for the impact on HRV, various studies show results ranging from 30 to 150 minutes.

Do not drink coffee before measuring HRV

The impact on the autonomic nervous system explains why caffeine should not be consumed before measuring HRV. But don’t forget that caffeine is not only found in coffee (50–100 mg per 150 ml) but also in black or green tea (20–60 mg per 150 ml), cola (32–60 mg of caffeine in 330 ml), energy drinks (approximately 80 mg per 250 ml), and semi-sweet chocolate (approximately 75 mg per 100 g).

If you measure HRV through Wellhero and, after the measurement, choose the mark indicating coffee consumption, Wellhero will automatically exclude this measurement from the sample for determining the algorithm’s baseline parameters of your body. However, you will be able to assess the impact of caffeine on your HRV.

Despite decaffeinated coffee containing almost no caffeine, there is a study that shows it briefly increases parasympathetic activity.

How much caffeine is beneficial for HRV?

According to the European Food Safety Authority (EFSA), up to 200 milligrams of caffeine in a single dose is considered safe for healthy adults. Depending on the roast and preparation, this is equivalent to two to three cups of coffee per day.

Coffee enthusiasts are advised not to exceed 400 milligrams per day.

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