What your vitamins and supplements are really doing to you: So many swear by them, but

Which area of a casino makes the most money? You might think it’s the big money tickets, the blackjack – or perhaps the roulette table?

It’s actually the slot machines – because they don’t cost much, are even cheaper to maintain and are so addictive people just keep playing, even when they’ve lost a small fortune.

When Dr Nick Tiller was investigating the marketing tricks and claims behind the booming health and wellness industry for his new book, he kept thinking of those casino slot machines.

Because the more he uncovered, he says the more apparent it became that the slot machines of the wellness industry are vitamins and dietary supplements.

Cheap to make, these supplements also have huge profit margins and are growing ever more popular by the year.

They are the definition of easy money – indeed, Dr Tiller came across supplements selling at a vast 60-fold mark-up on the production cost.

Little wonder then, that by 2028, it’s predicted the global supplements market will be worth more than £232billion.

Already, more than six in ten Britons take daily vitamin and mineral supplements.

And gone are the days when people just took a single multivitamin – today, the trend is for vitamin ‘stacks’, to cover all health ‘bases’. Perhaps you might have a multivitamin for your age group, then a magnesium supplement to help you sleep and a vitamin C booster for your immune system.

With such huge sales, and for all of the purported powers attributed to supplements, we should be the healthiest generation in history. Yet chronic conditions such as type 2 diabetes and cardiovascular problems are soaring.

This, says Dr Tiller – a doctor of exercise physiology who has worked with British Olympic athletes as well as NHS patients – shows that supplements in the main are nothing more than ‘a con’.

From their marketing (at best, dishonest; at worst, potentially dangerous, he says) to what’s actually in them (spoiler alert: often less than advertised) – not to mention what he says are patchy regulations that control their production and sale – many appear to be far from the health essential we might imagine (although the supplements industry may dispute some of this).

Perhaps most significantly, Dr Tiller argues in his controversial new book which Good Health is reporting on exclusively, there is scant clinical evidence they actually increase our lifespan.

In 2024, ‘researchers at the NIH Division of Cancer Epidemiology and Genetics in Maryland… tracked more than 390,000 adults over two decades and found no difference in mortality between supplement users and non-users. If anything, mortality rates were slightly higher among the supplement group,’ he writes. The higher mortality rates are likely, he says, because people take supplements to ‘compensate for poor lifestyles’.

Dr Tiller goes on: ‘These results weren’t a fluke. A team at Johns Hopkins University came to the same conclusion after reviewing a series of solid trials – one analysis of 450,000 people found that multivitamins did not reduce risk for heart disease or cancer.

‘Another study tracked cognitive function, including memory loss, in 5,947 men for 12 years, revealing no benefit of multivitamins.

‘A third study of 1,708 heart attack survivors who took a high-dose multivitamin or placebo for up to 55 months showed similar rates of later heart attacks, heart surgeries and deaths.’

All in all, there was ‘no benefit from multivitamins on the risk of heart disease, heart attack, cancer, cognitive decline or all-cause mortality, even in people who’d already had heart attacks’.

As he puts it: ‘There’s simply no benefit to the broad and indiscriminate use of multivitamins in adults, [whether] as pills, powders, or globby green smoothies.’

Yet supplement companies make all sorts of claims – from physical to mental health improvements.

In a particularly resonant comparison, Dr Tiller argues the dog food industry is better regulated.

‘Manufacturing those enormous bags of dog food, the contents of which look like pebbles and smell worse than your dog, is rigidly controlled by over 50 pieces of legislation,’ he says.

This is because dog food often uses the same raw materials as human food, and so benefits from many of the same legal protections.

Even claims about a dog food’s benefits, he says, such as ‘helps support healthy gums’, ‘must be truthful, substantiated and not misleading. It’s a robust and tightly regulated system’.

Making and selling human dietary supplements, though, says Dr Tiller, is considerably – some might say worryingly – easier.

Supplements come under the food regulator, the UK Food Standards Agency, and when it comes to vendors it merely stipulates they register with their local authority as a food business operator, a system originally designed for cafes, bakeries and corner shops.

To see what this entails, Dr Tiller registers himself with his local authority. He says: ‘My application to become the sole trader of a fictional health food store, NBT Power Pills – operating from a domestic address in Greater London, and selling dietary supplements nationally and internationally – takes me just three minutes and 40 seconds.’ He adds that with just some ‘discretionary advice on suppliers, hygiene and labelling. I’m allowed to trade after a 28-day waiting period’.

While there are some laws guiding what he sells – products must be safe to consume – he claims that ‘enforcement is usually reactive… lower-level breaches can persist for a long time unless a customer complains or falls seriously ill and the issue can be directly traced to my product’.

And, ‘I’m not allowed to mislead consumers or make unauthorised medical claims, such as alleging to cure a disease.

‘But vagueness is my ally. As long as I stick to ambiguous claims like “promotes recovery”, “supports immunity” or “promotes wellbeing”, I can imply health benefits without saying anything testable.’

‘Oversight of supplements falls to the Advertising Standards Authority (ASA),’ says Tiller, but he claims ‘it only investigates complaints’ and is stretched so thin across tens of thousands of ads that small businesses selling supplements ‘aren’t a priority’.

In short, it means, says Dr Tiller, ‘that if I were to actually launch my own range of “NBT Power Pills”, I could do so confidently, with little oversight or risk of consequences. Until I made someone sick.’

Legally, supplements don’t even have to contain what’s on the label, with regulations generally allowing deviations of up to 20 per cent from declared values, depending on the nutrient.

‘For example, major discrepancies have been reported between the contents and labels of protein powders, bars and drinks – in some cases measuring less than half of what’s stated, according to research published in the journal Scientific Reports in 2023.

‘Other investigations – like one from the journal JAMA Internal Medicine in 2023 – have found the listed contents of vitamin D supplements, selenium and fish oils to also be unpredictable. 

‘Indeed, one study published in Nature Scientific Reports from 2015 on fish oils found that fewer than 10 per cent of brands met or exceeded amounts claimed on the labels; most provided less than 67 per cent of what was expected.’

Not containing as much nutritional value as is claimed is one thing. Being contaminated with something not on the label is quite another.

Dr Tiller cites a case from 2005 when the German drug surveillance authority seized batches of vitamin C, multivitamins and magnesium, which had been contaminated with anabolic steroids.

‘The problem is now so widespread that the American Food and Drug Administration maintains a database of more than 700 supplements adulterated with “hazardous” hidden ingredients.

‘The rules have changed in places since 2005, but not in the way that matters most: supplements aren’t as regulated as medicines, and still reach the market without medicine-style pre-approval.’

As well as surprise nasties, there’s also the issue that too much of certain vitamins can be hazardous.

An excess of vitamin C can cause cell damage and diarrhoea. And more than the recommended dose of vitamin B6 has been linked to nerve damage. But you’ll rarely see warnings of such excess in the wellness world.

Any claimed evidence of a health benefit can also be murkier than it initially appears, says Dr Tiller, because ‘much of the research into supplements is funded by the very companies that manufacture the product. It means even seemingly positive findings can’t be taken at face value’.

He points out that one of the most common claims made about modern supplements is that they ‘cure’ inflammation, or have an ‘anti-inflammatory’ effect. 

Chronic inflammation is linked to a wide range of diseases, from heart disease to cancer, yet eliminating inflammation altogether would be a biological disaster – in some cases it’s essential, protecting against infection, coordinating recovery from injury and repairing damaged tissue. It also underpins the immune response to vaccination.

Still, the word ‘inflammation’ has now been ‘rebranded as the root of all evil’, says Dr Tiller, and blamed for everything from brain fog and burnout to skin problems. And so we are told to take omega-3 and ginger supplements, among others, to ‘fix’ inflammation.

However, there are some supplements available, says Dr Tiller, which are worth ‘serious consideration’. 

‘Nearly half the global population is deficient in vitamin D,’ he adds, ‘which can undermine bone health, immune function and more. Because few natural foods contain meaningful amounts (fatty fish, like salmon and mackerel, are best), some people may need fortified foods or supplements.’

He began taking vitamin D himself, after a blood test revealed he had a deficiency. A keen gym-goer, he also takes protein powder to support his muscles, and creatine – a compound that helps muscles produce energy during short bursts of high-intensity activity.

He advises anyone who wants to take a supplement to first consult their doctor, or seek impartial advice from places such as the NHS website or online platforms like the Cochrane Library, both of which provide objective summaries of the best available evidence, much of it free.

But generally speaking, his message is clear: you’d be better off saving your money, rather than indulging in the latest ‘must-have’ pill or potion.

Adapted from The Health And Wellness Lie, by Dr Nick Tiller, (Green Tree, £22) published July 16. © Dr Nick Tiller, 2026. To order a copy for £19.80 (offer valid to 14/07/26; UK p&p free on orders over £25) go to mailshop.co.uk/books or call 020 3176 2937.