Coffee has been a great power in my life;
History has observed its effects on a monumental scale. Some claim coffee inspires them, while some claim it only makes boring people even more boring. Some have conjectured that coffee sets the blood in motion and stimulates the muscles; Some claim it accelerates the digestive processes, chases away any sleep, while giving us the chance to involve ourselves a little longer in the exercise of our intellects. I say the moment caffeine enters your stomach, and flares are shot up to the brain; from that moment on, everything becomes agitated. The ‘logic’ artillery rushes up with clattering wagons and ammunition; the ‘metaphor’ cavalry is deployed with a spectacular gallop; the sharpshooters sight and fire at the ‘imaginations’ command.

Enough with the fables and the legends.

What is Caffeine?

Chemically, caffeine is a member of the Methylxanthine Alkaloid family and is known as 1,3,7-trimethyl xanthine. Alkaloids are interesting natural chemicals that include at least one nitrogen molecule. Caffeine looks like a white powder when separated, but don’t let that deceive you—it tastes quite bitter.

Caffeine Consumption: A Global Perspective

One of the few fitness-related subjects where the general public shares, if not surpasses, the enthusiasm of fitness fanatics is caffeine. Since everyone might use a morning energy boost and caffeinated beverages like tea and coffee play a significant role in many cultures, interest from non-lifters is natural. According to some estimates, the consumption of caffeine in India is estimated at 91,000 tonnes in 2023. The average daily caffeine intake of Indian adults is around 98 mg to 232.9 mg, and about 44% of them drink a caffeinated beverage regularly¹. Although that may seem excessive, the average daily consumption of caffeine in Finland and Sweden is more than 400 mg².

I wouldn’t dare interfere with the morning caffeine fix, but we shouldn’t ignore caffeine’s possible negative qualities simply because we like its best qualities, especially after the two recent lawsuits that linked the intake of a specific caffeinated product at an American restaurant chain to fatal cardiac arrhythmias.

How Caffeine Works: The Double-Agent Effect

In our body, caffeine acts like a double agent inside our blood vessels. The lining of your blood vessels (called the vascular endothelium) relies on clear chemical signals to decide whether to open up (relax) or tighten up (constrict). Caffeine sends mixed messages to this system at the exact same time. Very cool and weird right?

So, to keep blood flowing smoothly, endothelial cells release a chemical called nitric oxide (NO), which tells the blood vessels to relax and widen. Caffeine is the gas pedal and the brake pedal for Nitric Oxide. What?

The Gas Pedal (Vasodilation) effect:

Firstly, caffeine causes calcium to be released from storage inside endothelial cells (via ryanodine receptors). This increase in intracellular calcium activates an enzyme called endothelial Nitric Oxide Synthase (eNOS). As a result, eNOS speeds up the production of nitric oxide, signaling the blood vessel walls to relax and widen.³

The Brake Pedal (Vasoconstriction) effect:

Simultaneously, caffeine acts as an adenosine receptor antagonist, meaning it blocks adenosine from binding to its natural receptors (called A2a receptors) on the vessel lining. Normally, adenosine binding to these receptors triggers a cascade that keeps eNOS active and produces NO. But by blocking these receptors, caffeine shuts down this signal, suppressing baseline NO production and thus causes our blood vessels to constrict.³

Therefore, by caffeine hitting both the “gas pedal” (stimulation) and the “brake” (inhibition) on nitric oxide, your blood vessels can react differently depending on how much caffeine you consume or your baseline blood pressure.

cGMP:

Another cool phenomenon that happens is nitric oxide uses a helper chemical inside the cell called cGMP which signals the blood vessels to relax.³

Think of cGMP as a team of little vigilante police inside the cell. These cGMP police tell the muscle cell to lock up the calcium that keeps the muscle tight. Without calcium to stay squeezed, the muscle relaxes. The blood vessel opens up wider, blood flows smoothly, and your blood pressure goes down. (Medicines like Viagra or nitroglycerin use this exact pathway.)

Normally, the body quickly breaks cGMP down so blood vessels do not stay expanded forever. But, caffeine blocks the enzymes that clean up cGMP. By preventing cGMP from breaking down, caffeine forces this “relax” signal to stick around longer than it usually would.

Because caffeine is triggering all these opposing reactions at once, your body experiences a tug-of-war:

• The Narrowing Effect: Caffeine triggers the sympathetic nervous system (fight-or-flight) and can directly shrink the inside space (lumen) of blood vessels, which makes arteries stiffer and raises blood pressure temporarily.³
• The Widening Effect: Simultaneously, the boost in nitric oxide production and the preserved cGMP levels work to keep the vessels relaxed and open.³

Caffeine creates conflicting signals. Some pathways try to relax your blood vessels while others try to constrict them. Which mechanism “wins” often depends on caffeine dosage, individual sensitivity, and whether blood pressure is elevated at the time.

Clinical Research: Gray et al Study

Next, we take a look at Gray et al⁴, which looked at the Cardiovascular effects of caffeinated energy drinks in familial Long QT Syndrome, so let’s jump in and see what they found.

Purpose

The study aimed to determine the acute cardiovascular effects of consuming caffeinated energy drinks in patients diagnosed with familial Long QT Syndrome (LQTS), specifically evaluating potential risks in dangerous heart rhythms (QTc prolongation) and blood pressure changes.

Subjects & Methods

The researchers studied 24 patients with confirmed LQTS (aged 16–50 years; 54% female; mean age 29±9 years). Most participants (83%) were taking beta-blockers, and 58% were symptomatic prior to diagnosis. This was a randomized, double-blind, crossover trial where patients acted as their own controls, separated by at least a 1-week washout period. Participants fasted from caffeine for 48 hours and alcohol for 24 hours prior to testing.

Intervention:

• Two cans of sugar-free Red Bull which has 160 mg caffeine and 2000mg taurine in 500mL.
• A placebo cordial-based drink without caffeine or taurine (500ml).

These beverages were administered in two equal portions at 0 minutes and 30 minutes. Over a total observation window of 90 minutes, researchers recorded serial 12-lead electrocardiograms (ECGs) and blood pressure every 10 minutes, alongside signal-averaged ECGs (SAECG) and blood draws for serum caffeine and taurine assays every 30 minutes.

Participant characteristics are presented in Table 1.