Caffeine is the most widely used psychoactive substance in the world, and it is currently the subject of three quite different strands of life sciences research. This summer, the government confirmed a ban on selling high-caffeine energy drinks to children, built on a systematic review covering more than a million young people. Geneticists have spent the past decade mapping why the same cup of coffee can leave one person wired and another person barely affected. And a widely discussed analysis of when people drink coffee, rather than how much, has produced one of the more surprising findings in recent cardiovascular research. None of this makes caffeine a new subject for science. What has changed is how precisely researchers can now say who it affects, how and when.

A Ban Built on 1.2 Million Children

On 16 July 2026 the government confirmed that England will ban the sale of high-caffeine energy drinks, defined as drinks other than tea or coffee containing more than 150mg of caffeine per litre, to anyone under 16. The ban covers shops, vending machines and online sales, though not business-to-business transactions, and takes effect in April 2027, with retailers who break the rules facing fines of up to £2,500. The government estimates that around 100,000 children in England currently drink high-caffeine energy drinks every day.

The evidence base behind the decision came largely from Fuse, a public health research collaboration between Newcastle and Teesside universities, whose systematic review pulled together 57 studies covering more than 1.2 million children and young people across more than 21 countries. The review linked energy drink consumption in children to anxiety, stress, depression, sleep disruption and poorer concentration and academic performance, as well as physical effects including raised blood pressure and tooth decay, with consumption running higher among boys than girls. Public Health Minister Sharon Hodgson said “the evidence is clear that this can cause anxiety, affect their sleep and concentration and can have a detrimental impact on their education,” while Education Minister Olivia Bailey framed the ban as complementing the government’s separate overhaul of school food. A public consultation held between September and November 2025 received 1,095 responses before the policy was finalised.

Why the Same Cup Hits People Differently

The reason caffeine affects a teenager’s concentration and an adult’s blood pressure so unevenly from person to person comes down largely to genetics. A genome-wide association study using data from six population cohorts, including the UK Biobank, identified four genomic regions that reliably predict how quickly someone metabolises caffeine, close to the genes CD83, AHR, CYP1A2 and CYP2A6. Of these, CYP1A2 does most of the practical work, since it encodes the liver enzyme responsible for breaking down the large majority of caffeine the body absorbs.

People with certain variants of this gene are “fast metabolisers,” clearing caffeine from their system quickly and generally tolerating higher doses with less disruption to sleep or heart rate. Others are “slow metabolisers,” for whom the same cup of coffee stays active in the bloodstream for much longer, with correspondingly greater effects on anxiety, sleep and blood pressure. The same study found that people with genetic variants linked to slower caffeine metabolism tended, on average, to drink less coffee in the first place, which researchers interpreted as evidence that people unconsciously self-regulate their intake based on how strongly they feel its effects. It is a useful reminder that “I can’t handle caffeine like my friend can” is not simply a matter of habit or willpower, but is, for a meaningful share of the population, a measurable difference in liver enzyme activity.

It Is Not Just What You Drink, It Is When

A study published in the European Heart Journal in 2025 added a further layer that most previous coffee research had not properly separated out, timing. Researchers analysed data from 40,725 adults in the US National Health and Nutrition Examination Survey, collected between 1999 and 2008, alongside a separate cohort of 1,463 adults, tracking self-reported coffee timing against death records over roughly a decade of follow-up.

People who drank coffee exclusively in the morning, defined broadly as before noon, had a 16 per cent lower risk of death from any cause and a 31 per cent lower risk of death from cardiovascular disease specifically, compared with people who did not drink coffee at all. People who drank coffee throughout the day, by contrast, showed no reduction in mortality risk compared with non-drinkers, despite often drinking similar total amounts. Around 36 per cent of participants were classed as morning-only drinkers, 16 per cent drank throughout the day and the remaining 48 per cent did not drink coffee. The researchers’ working explanation is that caffeine consumed later in the day interferes more with melatonin production and sleep quality, and that disrupted sleep and circadian rhythm are themselves established risk factors for cardiovascular disease, meaning the coffee itself may not be the direct cause so much as a marker of when someone is disrupting their own sleep pattern.

One Molecule, Three Different Research Questions

Put alongside each other, these three strands are really answering different questions about the same substance. The energy drinks ban is a population-level policy response built on evidence that children, whose bodies and brains are still developing, are particularly vulnerable to caffeine at the doses found in some drinks. The genetics research explains why adults given an identical dose can have wildly different experiences of it, rooted in enzymes most people will never think about. The timing research suggests that even for people who tolerate caffeine well, when they drink it may matter as much as how much. None of this settles the question of whether coffee is, on balance, good or bad for any individual person, and researchers in each of these fields would likely say that is the wrong question to ask about a substance this widely used and this differently metabolised. What has changed is that the answer is no longer a shrug. It is genetics, timing and dose, each measured separately, and each pointing in a slightly different direction depending on who is asking.

Sources: GOV.UK; Fuse (Newcastle University and Teesside University); Human Molecular Genetics (Cornelis et al., UK Biobank); European Heart Journal.