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One afternoon in the summer of 2019, I began to feel an annoying flicker in the corner of my eye, which intermittently stopped and started. It took me a few minutes to realise that one of my eyelashes was twitching.

I’d recently turned 30 and thoughts swiftly flooded through my head – was this a sign of excessive screen time? The early symptoms of some hideous disease? And then I realised that over the past week, I’d been regularly drinking three cups of particularly strong coffee. Following a subsequent week-long “caffeine holiday”, things went back to normal.

It would take me another five years to fully understand why. For my new book, The Age Code, I have been investigating hidden vulnerabilities within our DNA which can influence how we respond to certain nutrients or diets which can alter the rate at which we age. It turns out that one of the best examples of this is caffeine.

I decided to have my DNA sequenced, by a Canadian company called Nutrigenomix, with the aim of finding out, among other things, the exact variant I carried of a gene called CYP1A2. This controls the behaviour of an enzyme which acts as one of the body’s primary detoxifiers, helping us break down compounds including caffeine.

In recent years, geneticists have discovered that when it comes to this gene, the population is split into two camps – half of us metabolise caffeine slowly, the other half can process it up to four times faster. If you’re in the former group, your body eliminates caffeine slowly and is more impacted by its stimulating effects.

My DNA test confirmed I’m a slow metaboliser – as suggested by the eyelash twitching. For me and my fellow slow metabolisers, a single cup of coffee is equivalent to drinking around three.

This is particularly important because in recent years research has highlighted that coffee consumption may play a significant role in health and ageing. For example, trigonelline, a plant chemical found in coffee, has been linked with helping to preserve muscle mass as we get older, while numerous other studies are increasingly showing that a daily dose of caffeine seems to help with slowing brain ageing.

“Caffeine definitely plays a role in inhibiting oxidative stress, something which damages cells in the brain and is one of the biggest features of Alzheimer’s disease and Parkinson’s,” says Ralph Martins, a professor of neurobiology at Macquarie University in Australia.

But the amount of caffeine you should be consuming, and whether it helps or hurts you, varies depending on whether you’re a fast or slow metaboliser. According to Sara Mahdavi, a clinician scientist and research fellow at the Harvard TH Chan School of Public Health, fast metabolisers can definitely benefit from three or four cups per day. But for slow metabolisers, it’s now thought to be better for your long-term health to stick to a single cup before switching to decaffeinated options, otherwise the overload of caffeine in your bloodstream can place excessive strain on your heart.

“Fast metabolisers can handle the caffeine and also really benefit from the other antioxidants within coffee,” says Mahdavi. “But slow metabolisers are much more vulnerable to the toxic effects of caffeine. It’s a vasoconstrictor, which means it causes the muscles around blood vessels to tighten, and when they have three cups of coffee, they’re vasoconstricting by multiple folds.”

Now, you probably don’t need to get a nutrigenetics test to figure out whether you’re a fast or slow caffeine metaboliser – you just need to listen to your body. While my eyelash twitching was a giveaway, other people can find themselves feeling particularly jittery, suffering from heart palpitations or struggling to concentrate after two cups of coffee. These are signs that they might be slow metabolisers. Since my own discovery, I now try to limit myself to a single cup per day before switching to decaffeinated or lower caffeine options such as tea.

But the role of nutrigenetics extends far beyond caffeine. DNA tests are set to play an important role in public health, by offering new information on how people metabolise nutrients. According to James Brown, founder of the nutrigenetics company Muhdo Health, people with certain variants of the genes FUT2 and TCN1 are more likely to struggle to absorb vitamin B12 through their guts.

Brown says this is particularly important information for anyone considering going on a plant-based diet as these people will be markedly more vulnerable to developing deficiencies, something which can affect cognitive health. “If you’ve got poor B12 metabolism from a genetic point of view, coupled with the fact now that you’re not having meat, you’re not having dairy or any of the sources that are really going to give you enough B12, then you’re going to go downhill quite quickly,” he says.

Likewise, around a fifth of the population are thought to have two copies of a particularly problematic variant of a gene called MTHFR, which influences our ability to clear an amino acid called homocysteine from the blood. Homocysteine is produced when we metabolise protein from food, and it’s a key building block which our body uses to construct and repair new tissues. But if you’re part of the unlucky 20 per cent and your body doesn’t clear it well, homocysteine can cause irreparable damage to your blood vessels.

Because many people are not aware that they carry this genetic variant, they’re unknowingly at a much greater risk of developing blood clots and premature cardiovascular disease. They could counter the effect by getting more vitamin B12 and folate in your diet, through consuming organ meats, cooked lentils and leafy green vegetables, or taking supplements.

“If you have the MTHFR mutation, and you’re not eating the right foods or taking a vitamin B12 supplement, your blood vessels will be ruined when you’re 50 years old,” says the geneticist Wei-Wu He, executive chairman of the Human Longevity organisation, and one of the founding scientists of the Human Genome Project.

Nutrigenetics can also reveal more about ourselves. As well as being a slow caffeine metaboliser, I discovered that I carry a variant of the FUT2 gene which means I need to make sure I keep consuming vitamin B12-rich foods or perhaps taking a supplement in years to come. But I also discovered that I’m a “supertaster” for fats – explaining why I’m particularly partial to deep-fried or greasy foods like fish and chips, and more prone to overeating if I allow myself too many of them.

In the future, geneticists believe that nutrigenetics can start to play a role in clinical decision-making, allowing doctors to make more accurate recommendations when it comes to certain nutrients that will particularly benefit an individual patient.

When I interviewed Professor Baukje de Roos at the University of Aberdeen, she explained that we know that consuming omega-3s in the form of fish oil is an effective way, on average, of lowering the levels of blood fats called triglycerides, a key risk factor for heart disease.

But the extent to which omega-3s are effective also depends on a variety of factors, ranging from a person’s gender to the amount of low-grade inflammation in their body, the profile of various fats in their blood, and their genetics. In future, de Roos hopes that it will become possible to screen people and develop an algorithm which would pinpoint the individuals who are most likely to see a significant boost to their cardiovascular health from taking omega-3s.

“That’s the ultimate goal,” she says. “Can we prescribe dietary interventions for people who we know will benefit from them?”

Having such granular data could even make it more feasible to persuade health insurers to cover the costs of dietary changes. “We know that healthy diets are more expensive, but can we get the insurance companies to consider the idea of, ‘Why do we always automatically pay for a drug when we know that in some groups, we could do a dietary intervention which is equally effective and doesn’t have the side effects that drugs do?’” she says. “So that could be the future, but we still need a lot more evidence to get there.”

The Age Code : The New Science of Food and How It Can Save Us by David Cox is published by Fourth Estate

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KYIV – In the waiting area of the Superhumans Center in the Ukrainian city of Lviv, two patients, one in a wheelchair with an arm and two legs amputated, are playing table tennis as others watch on. A massive screen is showing relaxing scenes of nature, with an accompanying soothing soundtrack playing in the background.

Danylo Turkevych, the head of the surgery department – who started his medical practice right as the full-scale Russian invasion began – said the challenge during the war of achieving fast and effective medical care for those on the front lines has been immense.

“Evacuation of patients would take two to three weeks, sometimes even months, to get them from Dnipro, Donetsk and Kharkiv to Lviv,” he says of the early days of the conflict, when he worked at a state hospital.

However, in many ways the challenges have only grown since then.

Wartime conditions in Ukraine have created an ideal environment for serious antibiotic-resistant infections to develop. These so-called “superbugs”, which are resistant to many, if not all, commonly used antibiotics, can be deadly and spread far.

The most concerning is Klebsiella pneumoniae, a bacteria estimated to be responsible for over 100,000 deaths a year.

When it comes to Ukraine, a combination of overcrowded hospital wards, weak infection control and micro-dosing of antibiotics to prolong supplies are resulting in the spread of superbugs.

Turkevych says the situation with AMR is going from bad to worse. “I may be a fatalist but I think we are already in the post-antibiotic era, because it’s not only a Ukrainian problem, it’s a problem in the whole world,” he said.

Rising death toll

According to a report in The Lancet, 1.14 million deaths globally in 2021 were directly attributed to antimicrobial resistance (AMR). From 2025 to 2050, researchers forecast that more than 39 million deaths will be linked to AMR.

Meanwhile, as Ukrainian patients with war-related wounds have been evacuated to hospitals across Europe, difficult-to-treat infections have been reported in Germany, Denmark and the Netherlands.

A study by the University of Helsinki and HUS Helsinki University Hospital found that of the eight per cent of Ukrainian refugees who had been hospitalised for war-related injuries, close to 80 per cent carried multi-drug resistant (MDR) bacteria.

“We strongly recommend targeted MDR screening and strict contact precautions for patients hospitalised in conflict zones,” it said.

Richard Sullivan, the co-director of the Centre for Conflict & Health Research at Kings College London, said that European programmes tend to be focused on high-threat infectious diseases such as dengue fever and rabies, leaving gaps in how antimicrobial resistance is tracked.

He told The i Paper that while some hospitals have been good at swabbing and looking for resistant infections, others have not been so good. “The problem is there’s so many other things going on that until we have a massive crisis, it’s very hard to do something about this.”

“We are living in a world where there is no money. The idea that we’re going to coordinate and do better surveillance is lovely on paper. In reality, unless there is government‑mandated reporting and analysis, it doesn’t get done,” Sullivan said.

A worrying technique

When antibiotic resistance expert Olena Moshynets, a microbiologist at The Institute of Molecular Biology and Genetics in Kyiv, started her research on AMR resistance a decade ago, there were already multiple-drug resistant bacteria in the country.

“Ukraine was more isolated, a lot of people travelled abroad, but they were healthy,” she said. Now, with Ukrainian wounded being sent for treatment abroad, that is often not the case.

Meanwhile, a technique called negative pressure wound therapy, which is a technique using a suction pump, tubing, and a dressing, creates further problems.

“It was a really good way to close soft tissue,” said Turkevych. “But people tend to overuse it and you then have a high risk of growing bacteria deep in the soft tissue of the bone. Due to that, we had a huge number of delayed amputations.”

In February, Turkevych operated on a patient with an infection of the tibia bone. “In this scar tissue, there was dense fabric from his trousers and metal particles from the explosion, we had to cut all that off, clean the wound and then do an operation to close the defect,” he said.

The patient was able to keep his limb, but others are not so fortunate, and amputation often becomes the only way to stop the spread of infection, Turkevych said.

“If you get multi-drug-resistant bacteria and we are able to treat it, sometimes amputation is the only possible way to salvage the person,” he added. “If it’s not amputated it will spread.”

In some patients, even amputation is not enough to stop the antibiotic-resistant infections proliferating.

“It won’t kill you but there are studies that show the patient will produce that bacteria in two or three years after the initial surgery,” Turkevych said. “You’re basically becoming a biological weapon.”

A country on the edge

Prevention is better than a cure, but a severe lack of funds and essential medication is making it almost impossible in Ukraine to address the root causes.

The first step is to bring back nurses, says Moshynets. “We may have one nurse for each 30 beds. It’s impossible to keep on top of infection prevention and control, it doesn’t matter how great the nurse is.”

She added that while the official position of Ukraine’s health ministry is that they have funds to cover all needed medication, the reality on the ground is very different.

“My colleagues, just normal doctors, tell me their salaries have been reduced and they don’t have normal antibiotics, even in Kyiv. That’s a big problem when it comes to AMR,” she said.

The State Institution Center of Public Health of the Ministry of Health of Ukraine, which is responsible for infection prevention and control as well as antimicrobial resistance and related data, did not reply to a request for comment.

This acute shortage makes healthcare outcomes far worse for patients. Moshynets recalls a recent case where a patient had a liver abscess as a result of a case of Klebsiella. After their first unsuccessful treatment, the clinician reached out to Moshynets for advice.

“The strain was already resistant to the first antibiotic that was used,” she says. But when Moshynets when back to ask why this was given to the patient, she was shocked by the doctor’s reply: “He said that was the only antibiotic we had.”

For Sullivan, his fear is that infections originating from the battlefields of Ukraine could soon spread across the rest of Europe.

“Modern battlefields like Ukraine create the perfect storm for AMR,” he said. “Massive environmental toxicity, ordnance and destroyed infrastructure, contaminated wounds, long evacuation pathways as well as mobility from hospital to hospital create the ideal conditions for AMR, which is no respecter of borders.”

Ultimately, Sullivan said, monitoring closely and having a better understanding of where and how to mitigate the threats is “crucial for stopping the wider spread of AMR”.