COSMOS study: can multivitamins slightly slow ageing?

A widely cited US study suggests that taking a daily multivitamin may slightly slow certain ageing processes in people aged over 70. Yet the headlines conceal a more complicated picture: the effects are small, their clinical relevance is unresolved, and industry played a substantial part in funding the research.

What the COSMOS project investigated

The new paper forms part of the large COSMOS project, short for “Cocoa Supplement and Multivitamin Outcomes Study”. Researchers at Brigham and Women’s Hospital in Boston, a Harvard-affiliated hospital, set out to establish whether supplementation with multivitamins or cocoa extracts could produce measurable effects on ageing.

For the section of the study now under discussion, they enrolled almost 1,000 women and men, all aged at least 70. Participants were randomly assigned to one of four groups and, for two years, took daily:

• a commercially available multivitamin plus 500 mg of cocoa extract;
• cocoa extract only, together with a placebo;
• the multivitamin only, together with a placebo; or
• two placebos.

The trial was double-blind: neither the participants nor the researchers knew who was receiving which treatment. This type of design is considered the gold standard in medical research because it largely removes expectation effects.

Epigenetic clocks: how ageing was assessed

Rather than simply counting chronological years, the scientists used so-called epigenetic clocks. The underlying principle is that biological ageing can be inferred from the genome – more precisely, from chemical DNA markings known as methylation.

Specifically, the team examined five different “epigenetic signatures”. These are based on methyl-group patterns at particular DNA sites and are regarded as statistical markers of:

• biological age;
• the pace of ageing;
• the risk of premature death.

Blood samples were taken at the start of the study, after 12 months and after 24 months. This allowed the researchers to track whether the epigenetic clocks progressed at different rates across the four groups.

The key message: multivitamins appear to marginally slow some epigenetic ageing markers – especially in older adults who were already “biologically older”.

What the researchers actually found

The analysis found that, in the group receiving the multivitamin (with or without cocoa), epigenetic ageing slowed slightly across all five measured signatures. The effect was particularly apparent in two clocks closely associated with mortality.

Across the two-year period, the result equated mathematically to a “gain” of around four months of biological age compared with the placebo group. In other words, according to these markers, those taking multivitamins appeared biologically a little younger than participants who received only inactive pills.

Notably, the effect was stronger among people who already showed accelerated epigenetic ageing at the beginning of the trial. Those whose markers appeared “older than their actual age” therefore benefited marginally more.

The study found no convincing benefit from cocoa extract itself. Whether combined with the multivitamin or taken alone, it produced no clear positive changes in the epigenetic clocks.

Why the findings should not raise unrealistic hopes

The study authors themselves only partly share the media excitement surrounding the claim that “multivitamins slow ageing”. In Nature Medicine, they explicitly describe “statistically significant, but limited effects” and stress that considerably larger and longer-term studies are needed.

The study does not demonstrate a miracle cure for wrinkles or frailty, but a small statistical effect in laboratory markers.

Above all, it remains uncertain whether the observed changes in epigenetic clocks lead to tangible health consequences. Does minimally slower epigenetic ageing actually reduce the risk of heart attack, dementia or cancer? Or is it mainly an interesting laboratory value with little practical impact?

Epigenetic clocks are not yet a routine clinical tool

Although many of these epigenetic markers are regarded as reasonably good tools for predicting longevity in large population studies, doctors do not yet use them in routine care. The tests are complex, expensive and not yet fully validated scientifically.

In addition, the mechanisms behind epigenetic changes often remain unclear. It is only partly understood exactly how diet, lack of exercise, stress, medicines or food supplements affect these clocks.

Industry influence: who funded the COSMOS project

Another issue attracting criticism is that the study was not funded solely by public research bodies. Alongside US health authorities, several companies and trade organisations from the food and supplement sectors were among its funders.

Supporters included, among others:

• food company Mars, through its Mars Edge nutrition division;
• Pfizer Consumer Healthcare, now known as Haleon;
• Foxo Technologies, a provider of epigenetic tests;
• American Pistachio Growers, an association representing the pistachio industry;
• the Council for Responsible Nutrition, a lobbying organisation for supplement manufacturers.

The researchers state that they worked independently and experienced no influence over the content from funders. Nevertheless, an uncomfortable question remains: would the same findings be received much more calmly without financial involvement from the supplements industry?

Tablet or plate: what does more for ageing?

Study leader Howard Sesso himself points out that multivitamins are only one small piece of a far larger puzzle. Overall dietary habits and lifestyle are what matter. There has so far been no direct comparison between taking a daily pill and consistently following a healthy diet.

A realistic order of everyday priorities could look like this:

• stopping smoking and drinking as little alcohol as possible;
• daily activity and strength training within one’s own capabilities;
• a high-fibre diet rich in vegetables, fruit, wholegrains and pulses;
• sufficient sleep and reducing stress;
• only then considering whether an additional multivitamin could be useful.

Many professional bodies still advise healthy people to obtain vitamins and minerals primarily from a balanced diet. Supplements can be useful for confirmed deficiencies or particular circumstances – for example, vitamin D deficiency, pregnancy or after certain operations. The COSMOS study does not support a blanket claim that multivitamins act as a fountain of youth.

What older people can take from the study

Anyone already taking multivitamins need neither celebrate the new findings enthusiastically nor throw the bottle away in outrage. The results instead call for a sober interpretation:

• There are indications of a slight slowing in certain ageing markers.
• The clinical relevance remains uncertain.
• Further research with independent funding is needed.
• A healthy everyday lifestyle is likely to have much greater effects on lifespan and quality of life than any pill.

Anyone considering starting a multivitamin should ideally discuss it with their GP, particularly at an older age when many medicines may be taken at the same time. Some vitamins can be harmful at high doses or interact with medicines.

What a realistic “anti-ageing check” with a doctor could involve

Rather than relying on costly epigenetic laboratory tests, it is worth first looking at established health factors. Many GP practices use straightforward but well-proven measures:

People who are doing well in these areas substantially reduce their personal disease risk – regardless of whether an epigenetic clock ticks a few months more slowly in a laboratory.

Where research on multivitamins and ageing still needs to go

Future studies will probably need to combine several levels of evidence: epigenetic markers, conventional clinical outcomes such as heart attacks or dementia, and real-world quality of life. Only if changes in epigenetic clocks are reliably linked to fewer illnesses and more healthy years of life will using such markers in everyday care be worthwhile.

The question of combination effects also remains intriguing: how do epigenetic clocks respond when somebody improves their diet, becomes more active, reduces stress and possibly takes a multivitamin at the same time? Individual studies of pills provide only a very small part of the answer.