At some point in 2020, I found myself confronting an uncomfortable thought: even after training as a doctor and spending two decades working in health, I suddenly felt as if I knew almost nothing.
The feeling crept in through the booming world of health and wellness podcasts. Their hosts were, more often than not, male, American, impressively credentialed and strikingly certain about both their theories and their takeaways.
Before long, complex health concepts were turning up in ordinary conversations. Friends and colleagues would pull out microbiome reports, share genetic test results or talk me through the readings from the continuous blood-glucose monitors they had started wearing.
They would describe carefully curated supplement routines featuring compounds such as NMN, glutathione, CoQ-10 and alpha-GPC, then show me streams of fitness data gathered from their devices.
Around the same period, I was appearing on BBC television and radio, and the questions from viewers and listeners increasingly reflected this wave of new health and wellness claims.
As I looked more closely at the advice people were asking about — should I take NAD? Could a CGM help me lose weight? Does red-light therapy ease joint pain? What about turmeric? Should I be tested for microplastics? Is a blood test for “biological age” worth doing? — I discovered that clear, definitive answers were often difficult to find.
This book grew out of my effort to make sense of the wellness industry, both as a health broadcaster and as someone trying to take care of my own body.
Xand van Tulleken is a doctor, broadcaster and presenter who spent a decade practising acute medicine in the NHS. He trained at Oxford, Harvard and the Liverpool School of Tropical Medicine, and is now an Honorary Associate Professor at University College London
I began by asking ‘What works?’ and spent months poring over scientific evidence, with a huge amount of help from colleagues and experts. And the answer turns out to be: very little. By the end, I hope you’ll have a rule of thumb about what works and what doesn’t. I want you to be able to look at a product on a shelf or an Instagram post or an article in the paper and say: ‘Oh, I know why they’re selling that! I know what they’re up to!’
You’ll be able to see who has made you even consider buying the product in the first place, and be aware of all the ways the product might harm you.
Vitamin myth exposed
Let’s start with vitamins.
There are only 13 human vitamins, but together they form the foundation of all modern nutrition science, and, most importantly, they’re crucial to how we understand the chemistry of life. Vitamin A (found in carrots) is essential for vision in low light; the B vitamins are important for energy production, the nerves and the blood; you don’t need to know any biochemistry to associate vitamin C with good skin and hair, and not catching a cold.
It’s completely reasonable to believe that our vitamin intake isn’t optimal today. OK, we don’t see much scurvy any more, but we don’t eat nearly as much fruit and veg as we should: diet-related ill-health is a leading cause of death in the UK and the US.
So, a daily vitamin supplement might well prevent a kind of mild scurvy or mild rickets, supercharging our bones, skin, hair and immune systems.
This is a logical train of thought, helped along by the supplement industry’s suggestions to us.
But there’s a problem. Millions have been spent on large research trials in all vitamins and they have almost all come to the same conclusion: multivitamin supplementation – including vitamin C supplementation, which doesn’t actually stop us getting colds − does not prevent chronic diseases such as cancer and cardiovascular disease in the general population. Nor does it decrease your risk of premature death.
And it may even increase your risk of dying sooner.
Antioxidant threats
In 2007, a team of scientists including Christian Gluud, a professor at Copenhagen University Hospital, published a paper, in a prestigious medical journal, analysing how supplements – including vitamins A, C and E, beta-carotene and trace mineral selenium – affected mortality.
The team gathered up data from 68 randomised trials of supplements (collectively including almost 250,000 participants) and combined the data, effectively giving them a huge trial population of their own.
Continuous blood-glucose monitors analyse a person’s glucose levels – but the results they give have a significant margin of error
At the time, there was such enthusiasm in the medical community for antioxidants that to many it seemed certain that Christian and his colleagues would find a benefit.
But the results told a different story. When I called Christian in 2025, he summarised the findings like this: ‘We looked into antioxidant vitamins and found out that they killed people.’
His team’s study concluded that antioxidant supplements, including vitamin C, do not reduce mortality. Even more surprisingly they found that taking vitamin A, beta-carotene, and vitamin E could increase mortality. The study had a huge impact in the scientific world: today it has been cited over 1,500 times.
Very few papers achieve this level of recognition. But despite its scale, it wasn’t considered the final answer. The team went back to their analysis as more data from other trials came in.
Christian described persuading his team that they needed to go through every single trial: ‘Three years, very hard work, another 70 trials or so, and when we added everything up, exactly the same thing: 4 per cent increased mortality, highly significant,’ he recalled.
… then death threats
Next, the team removed anything that could distort the data – and the mortality increased. In their last meta-analysis, mortality increased by up to 16 per cent.
‘We were shocked! We were surprised!’ he says. ‘I remember when we did the first analysis, I said to my colleagues: “Maybe it kills!” And then when we added more trials… then, actually, it did look like it killed.’ The death threats he and his team subsequently received suggested the body count may get even higher, though to this day the team has no idea where they came from.
Whoever was behind the threats, the supplement industry had no need to worry: in the wider world, Christian and his colleagues’ results barely made a splash.
Waste of money
Nearly 20 years later we take more and more of these supplements. The scientific evidence and people’s behaviour are completely at odds.
Perhaps this is because many of us might be willing to accept a small increase in our risk of dying sooner if the supplements improved our health in other ways. But other large randomised controlled trials have provided yet more evidence that we should stop spending money on multivitamin supplements.
Two huge, long-duration trials – the Women’s Health Study, which looked into the effects of vitamin E and betacarotene on cancer and cardiovascular disease, and the Heart Protection Study, which ran from 1994 to 2001 and assessed the effects of antioxidant vitamins on heart health – found no reduction in cancer or cardiovascular disease.
Then there was the Physicians’ Health Study II, another landmark trial, which evaluated the long-term effects of a daily multivitamin on cancer and cardiovascular disease prevention. This study did find a modest reduction in total cancer incidence but no significant effect on major cardiovascular events.
One vital lesson
These negative results provide an important lesson for anyone looking at the supplement literature today: just because a drug works in cells, or mice, or dogs, or even certain kinds of people, doesn’t mean it’ll work for everyone.
And just because a drug seems like it should work, doesn’t mean that it will. In 2022, the COSMOS trial was published, showing that a daily multivitamin did not significantly reduce the incidence of invasive cancer or cardiovascular disease, or affect all-cause mortality.
The authors’ conclusions were that their findings ‘do not support’ use of multivitamins for cancer or cardiovascular disease prevention among generally healthy older men and women.
This information, which would have been quite useful for the millions of people taking multivitamins around the world, received minimal press coverage. COSMOS was a large, expensive trial. It followed up 21,442 older people for over three years, and randomised them to a multivitamin, a cocoa extract, both, or neither.
It’s likely to have cost well over $100million. Because such a huge amount of information can be gathered from a study like this, researchers can analyse the data to look for other effects beyond the main questions they were trying to answer, and so several other studies have come out of COSMOS, which have looked at cognition (brain function) and biological ageing.
‘Daily multivitamin could help slow ageing process’ was the headline of a 2026 article in The Times announcing the results of one of these studies.
Anyone taking a daily pill would have been reassured: the study was done by good scientists from a good university, and published in a good journal.
And unless they had an academic library card, it would have cost them £29.95 to download the actual study, so they’d have had little choice but to go with the reporting on it, which was fairly uncritical.
The study used five blood test ‘clocks’ to measure biological age. These tests are convenient for researchers, and they make money for the companies selling them, so it would be great if they did work. But there’s no evidence that an improved score on the tests will translate into a longer healthier life.
If we take the tests at face value, and assume they do tell us something meaningful about our health, the most advanced test the researchers used, the DunedinPACE ‘third-generation clock’ generally considered the most sensitive to interventions, showed no significant improvement effect.
Only two of the five clocks showed significant (but minor) improvements. The inventor of the DunedinPACE test, Daniel Belsky, highlighting the limitations of our knowledge about these tests, said: ‘People should not read this study and think, Oh, I should take a multivitamin.’
So the data is not persuasive, and bear in mind that the original study’s authors did not advocate taking multivitamins.
But the interpretation of the study, in headlines from Good Housekeeping to the Harvard Gazette, was very enthusiastic.
Slowing dementia
Three other analyses from the same trial, published in 2022, 2023 and 2024, looked specifically at cognitive decline.
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This is an area in which we’re all extremely vulnerable. Dementia and decreasing brain function as we age are a cause of anxiety for many of us. So headlines like: ‘Daily multi-vitamins may improve brain function in older people’ and ‘Want to slow memory loss after 60? A multivitamin may be the answer’ are very exciting.
Almost no one has the time or the expertise to dig into the details. But the benefits these
trials found were small: it would be very hard to imagine any individual noticing the improvements in real life.
Furthermore, cognition was not the main thing the trial was measuring.
These studies are a long way from persuading me to spend money on supplements.
Around 90 per cent of the participants in the COSMOS study were white, the only multivitamin tested was a single brand (Centrum Silver) and the pills were donated by the company. The trial was funded in part by Mars Edge, the nutrition arm of the Mars company. It seems impossibly difficult for a non-expert just reading the newspaper and trying to take care of themselves to understand the gap between claims and reality.
None of these studies will be the last word on vitamins and minerals. There are further studies ongoing, and a recent study from Harvard suggested that a daily multivitamin might help prevent age-related cognitive decline.
And, of course, vitamin and mineral supplements are useful for some people in some situations.
If you’re prescribed iron because you’re anaemic, or vitamin B12 because you’re vegan, or magnesium if you have a heart condition, then it might be more helpful to think of what you’re taking as a drug rather than a supplement: something given to solve a specific medical problem.
Why don’t they work?
It seems a shame that none of the vitamins and minerals do much to improve the health of people who are healthy.
But it’s also very strange: why don’t supplements work, when consuming their ingredients in food seems to work so well?
After all, eating lots of plants is one of the best ways of improving our health. One of the problems with substituting vitamin pills for food, though, seems to be ‘competitive absorption’ – nutrients interfere with each other.
For example, calcium can prevent iron absorption. Zinc can interfere with copper absorption. Iron and zinc can also compete under certain dosing conditions.
Understanding this discrepancy is essential for a deep understanding of human biology: supplements don’t work because humans are complex. To understand the complexity of a human body, it helps me to imagine that I am the CEO of a vast manufacturing company.
If, as CEO, I want to do something as simple as keeping my blood salt levels constant, I’ll have to involve my kidneys, bladder, heart, blood vessels and the thirst centre in my brain just for starters, and I’ll have to minutely manage eating, drinking, urinating and sweating.
Meanwhile I have rogue cells causing cancer, or dying, or dysfunctioning, which I need to deal with. And although I’m the CEO, I’m not on the shopfloor; I don’t really even know what the company does or what the shareholders want.
One of the reasons it has proven so hard to unpick what exactly vitamins do, beyond preventing diseases of deficiency, is that many vitamins do several jobs.
Vitamin A, for instance, is a signalling molecule that tells embryos how to develop, a light-sensing component of visual pigments in the eye, and a regulating molecule for the maintenance of skin turnover and immune function.
Our bodies put vitamins to a lot of different uses. Perhaps more than any other collection of biological molecules, they illustrate the fundamental complexity of the human body.
Think of it like motorways
The best description of the difficulty of intervening with complex systems was given to me by a tired pharmaceutical executive who was trying to explain to me why drugs often don’t do what we think they should do.
‘The M4 and the M40 lead into London, don’t they?’ he said impatiently. I agreed that they do; I have driven both roads many times.
‘Right, so these motorways bring thousands of cars into London every day. And here’s the problem: there’s too much traffic in London. Now you want to prescribe something to fix the London traffic, and you know that around 30 per cent of the cars that clog the roads enter the city by the M4. So you just close the M4 and that’s 30 per cent traffic reduction right there.
‘But does the amount of traffic in the city go down by 30 per cent? No! It might not go down at all. People will take the M3 or the M1 or the M40, they’ll get up earlier, leave later and so on. It’s the same in the body: there are many routes to the same destination. So, just adding more of something to a pathway doesn’t work any more than closing the M4 will fix the traffic. It’s a complex system.
‘Not just that,’ he continued, ‘but who’s to say that the traffic is the problem? The traffic is essential to the economy: it brings in goods and workers. It’s a problem from your point of view, but in a complex system your view of the problem might be someone else’s view of the system working well. Healthy cities with bustling economies have traffic.’
I thought about this later on as I sat in a taxi in traffic. Many of the things we’re promised in adverts or on social media, are simple fixes: put this thing in your body and it will boost or improve it.
But if we want to think about our wellness, we have to think about complexity. I’m not the mayor of London, so I don’t need to wrangle with the car lobby and the cycling lobby and the taxi drivers and everyone else who wants me to sort the traffic.
But I am mayor of me! And my body looks after almost all the complexity for me. It’s a good way to think about wellness: if you’re being sold a simple solution for a complex problem, it probably won’t work.
There are loads of other things you can do to live longer and improve your life instead.
Are supplements more effective than an improved diet or doing the crossword? It strikes me as unlikely, but I’m happy to wait for the results to be replicated.
We take supplements because we have a cultural, and perhaps an innate, predisposition towards adding things to our diet, and because the marketing is powerful. But the evidence that these products don’t work really is very clear.
Ignore the hype around vitamin D
By the 1990s and 2000s, large observational studies were linking low vitamin D levels to almost every health problem imaginable: cancer, diabetes, multiple sclerosis, tuberculosis, upper respiratory tract infections, asthma, heart disease and dementia.
The studies (which can show if two things occur together, but don’t prove that one is responsible for the other) seemed to show that the higher a person’s vitamin D levels, the lower their risk of developing a condition.
Gwyneth Paltrow’s lifestyle and wellness brand Goop has recommended vitamin D supplements to improve health
When I qualified as a doctor in 2002, it felt like the vitamin could explain everything. And because vitamin D supplementation was so safe, the hype quickly moved beyond academia.
Television doctors urged everyone to take vitamin D. When I started broadcasting, I did too. From Gwyneth Paltrow’s company, Goop, to Oprah Winfrey, everyone seemed to be recommending it.
Medical journals declared a ‘pandemic’ of deficiency in vitamin D, after the US Endocrine Society defined ‘deficiency’ as less than 20 ng/mL.
The excitement around the laboratory and observational data that had been building was enough to raise money to fund randomised controlled trials.
The largest – the VITAL trial that began in 2011 – included more than 25,000 participants. More trials followed, and by 2023 about a dozen large-scale randomised controlled trials of vitamin D supplements had been published. The total bill was probably close to $500million.
And this is the big reveal: in all these large trials, vitamin D didn’t show any of the non-classic benefits people had been so excited about.
I look at the research papers myself. One commentary reads: ‘Vitamin D did not prevent cancer or cardiovascular disease in trial participants. Nor did it prevent falls, improve cognitive functioning, reduce atrial fibrillation, change body composition, reduce migraine frequency, improve stroke outcomes, protect against macular degeneration or reduce knee pain.’
A large Australian study found no effect on life expectancy.
Most astonishingly, even for fracture prevention, the area where many assumed vitamin D would surely help, in a trial population including thousands of people with osteoporosis, the supplements did not reduce fractures.
None of this means that you shouldn’t take vitamin D.
The NHS advice is good: ‘People at high risk of not getting enough vitamin D, all children aged one to four, and all babies (unless they’re having more than 500ml of infant formula a day) should take a daily supplement throughout the year.’ The rest of us should all consider taking a small dose in the winter.
But all this will do is prevent vitamin D deficiency diseases: rickets and osteomalacia.
It won’t do all the other stuff the wellness industry claims.
Adapted from Make Me Well by Xand Van Tulleken (Cornerstone, £22), to be published September 10. © Xand Van Tulleken 2026. To order a copy for £19.80 (offer valid to 20/09/26; UK P&P free on orders over £25) go to www.mailshop.co.uk/books or call 020 3176 2937.
