Caffeine and headaches – what’s new?

Caffeine and its many effects

Caffeine is one of the most popular ingredients in our diet. People all over the world love it. Around 80% of people in the world consume caffeine-containing foods and drinks regularly, many on a daily basis. In addition to its stimulating and invigorating effects, caffeine is also said to have other health-promoting properties, including beneficial effects on the heart, against diabetes or even in Parkinson’s disease. However, caffeine can also cause sleep problems, especially when consumed in the evening.

Our bodies absorb caffeine quickly and nearly completely. Almost 100% of the caffeine we drink in coffee or tea enters the bloodstream and can take effect inside our bodies. Caffeine levels vary by drink. Filter coffee has about 100 mg per cup, black tea has significantly less (45 mg) and green tea has around 30 mg. The effects last a long time. It takes about four to eight hours to get half of the caffeine you’ve consumed out of your body.

A key player: adenosine

Readers may be familiar with the term “adenosine” from our May 2024 article, “Migraine: energy shortage in the brain?”, which mentions adenosine triphosphate (ATP), the main energy carrier in our cells. ATP is the source of adenosine in the human body. When ATP is broken down during energy production, adenosine remains as the “end product”.

It’s thought that adenosine produced in this way accumulates in the body throughout the day and into the evening. When adenosine concentrations reach a certain level, we start to feel sleepy or just plain tired. This makes adenosine important in our sleep-wake cycle. Adenosine links energy levels with nerve activity. Adenosine mediates effects in our nervous system. Substances that do this are also known as neurotransmitters or neuromodulators. These substances control a wide range of nerve cell functions. They do this by binding to specific sites on the target cells, known as receptors. Receptors act like switches that activate various processes.

Adenosine and caffeine compete with each other

This is where caffeine comes in. It has a very similar chemical structure to adenosine, allowing it to compete for the same receptors without having the same sleep-inducing effect. When caffeine occupies a certain proportion of these receptors, adenosine (the actual messenger substance) cannot attach in amounts large enough to trigger sleepiness. This helps explain why caffeine reduces adenosine’s sleep-inducing effects. It blocks the neurotransmitter’s receptors. We experience this property of caffeine as a “pick-me-up”. Taking caffeine makes us (feel) more alert and focused than we would be without it.

Caffeine and headaches

Many studies have examined caffeine’s effects on headaches, but with mixed results. The seeming confusion is because the processes involved are so complex. However, the differences are understandable when you look at the details.

Our bodies have at least three different types of adenosine receptors. The exact effect of the substance depends crucially on the type of signaling pathway where binding occurs, how extensively binding happens, and how interactions between the many receptors play out. This gives an idea of the vast number of interactions that can occur when conditions change.

It was previously thought that caffeine causes blood vessels to constrict, thereby reducing blood flow in the brain. This was believed to be the basis for the pain-relieving effect reported by many migraine patients. However, it is now known that the constriction of blood vessels is not directly linked to this perceived benefit. The processes that regulate blood flow in the brain are much more complicated than previously thought. Current theories suggest that caffeine may work differently based on whether it is consumed regularly or occasionally. Research had to circle back a bit and start again from the beginning. Old beliefs had to be questioned. It is possible that the contradictory results are because different signaling pathways exist: some that relate to the competition with adenosine for receptors, and others that have a direct effect on blood vessels.

Adenosine and migraine aura

Some migraine sufferers with aura experience fatigue and extreme tiredness in the run-up to an attack. Adenosine may also be involved in these symptoms that may happen hours before the pain sets in. Research has also shown that administering adenosine can trigger migraine headaches. The fact that caffeine can help prevent or lessen pain attacks suggests it can counteract adenosine’s effects.

What are the recommendations based on research so far?

Research into caffeine’s impact on headaches has made significant strides in recent years. Mainly, scientists have a better understanding of how caffeine works. However, anyone expecting spectacular recommendations for everyday caffeine intake is likely to be disappointed. Basically, people who find that taking caffeine helps reduce their headache pain can continue to do so. Moderate caffeine consumption seems to be fine. Some studies even report that it has mostly positive health effects. However, those who are pregnant or breastfeeding should follow recommended caffeine limits to avoid excessive intake.

And as far as sweetened caffeinated drinks and energy drinks are concerned, experts do advise caution. The recommendation is to avoid them if possible. These drinks are often high in sugar and may cause more harm than the short caffeine boost is worth. These products are associated with a serious risk of weight gain, type 2 diabetes and heart problems, especially among young people who are the main consumers. Avoiding these drinks can save money and is the best way to reduce the associated health risks.

While the exact mechanisms by which caffeine influences headaches are not fully understood, clinical experience suggests that irregular caffeine consumption can trigger migraine attacks in migraine sufferers. Many report an increase in attacks if they deviate from their usual caffeine habit. One common trigger seems to be abrupt discontinuation of workday coffee consumption on weekends, for instance when the first cup on a Sunday is drunk much later than usual and is not followed by several more cups throughout the day. Medical research so far seems unable to provide a coherent explanation for why fluctuations in caffeine intake may promote migraine attacks. However, if this is a factor for you, try to maintain a similar caffeine consumption pattern every day of the week – including weekends and holidays.