If only living longer was as easy as popping a pill or two each day. While vitamin supplements might give some individuals the edge against select conditions, in general they're unlikely to help anybody see any extra birthdays.

New research finds that multivitamins won't help extend your life, although evidence from other studies suggests they may have some health benefits that help people live better in their older years.

Researchers at the US National Institute of Health (NIH) pooled data from three large studies surveying more than 390,000 adults about their diet and health to look at multivitamin use and health outcomes over nearly three decades.

"Many US adults report using multivitamins to maintain or improve health," NIH epidemiologist Erikka Loftfield and colleagues write in their published paper.

But whether promises of better health translate to a longer life is another question. The findings from this analysis confirm the largely negative results of prior studies, indicating a regime of daily multivitamins won't lengthen your life.

On the contrary, the risk of dying of any cause was a smidge higher (just 4 percent) among multivitamin users in the first few years of follow-up compared to non-users.

There might be a few reasons for this, which are difficult to untangle. People with niggling, age-related health issues may have been more likely to try multivitamins, for example.

However, folks who take multivitamins often eat healthier, exercise more, smoke less and earn enough money to afford supplements – all factors that could improve health.

The same was true in this study. Participants were generally quite healthy, with no history of cancer or other chronic diseases, but multivitamin users tended to eat better quality diets and had lower body mass index (BMI) scores – an oft-criticized and now discouraged health screening tool.

These confounding factors – which were well accounted for in the study – have clouded previous analyses; the wide variety of multivitamins has also made it downright difficult to compare them from one observational study or clinical trial to the next.

Even before the results of the investigation, experts were lukewarm at best on the benefits of taking multivitamins, maintaining that it depends on who is taking them, why, and how.

Taking specific vitamins can help those with medically diagnosed deficiencies, such as iron or vitamin B deficiencies, or supplement the extra demands of pregnancy.

A few recent trials also suggest daily multivitamins could help improve memory and slow cognitive decline, but only in older adults and for a short period of time. Vitamins with antioxidant properties, such as vitamin C and zinc, also appear to stave off macular degeneration, a condition of progressive vision loss in older age.

However, supplements can be harmful or risky if taken in excessive doses or with other vitamins, or if they interact with prescription medications.

Beta carotene supplements increase the risk of lung cancer in smokers, while vitamin K may reduce the efficacy of blood thinning medications, and calcium and zinc limit the absorption of antibiotics used to fight bacterial infections.

Multivitamins also aren't regulated in the same way prescription drugs or over-the-counter medications are, leaving the door wide open to overblown marketing claims of their effectiveness, which don't have to be backed up with evidence.

Getting our daily requirement of vitamins from our diet as opposed to topping up with supplements is for most people a safer way to go. For example, a 2023 study found switching to healthier foods can add up to 10 years to your life.

"The bigger the changes made towards healthier dietary patterns, the larger the expected gains in life expectancy are," the team behind that study explained at the time.

But again, eating healthily comes down to who can afford it, and what access they have to nutritious, fresh food options.

The new research has been published in JAMA Network Open.