Multivitamins have ignited a fierce scientific debate over whether nutritional supplements are beneficial to our health or a multi-billion-dollar racket.
A long-term randomized controlled trial in the United States has now produced some of the strongest evidence to date that nutritional supplements may slow aging.
"A lot of people take a multivitamin without necessarily knowing any benefits from taking it, so the more we can learn about its potential health benefits, the better," says senior author and epidemiologist Howard Sesso at Mass General Brigham.
When it comes to vitamins, the data on health and longevity is seriously conflicted. In the US, more than 100,000 vitamin and dietary supplements are available for purchase, and while previous research suggests that supplements generally won't help you live longer, multivitamins may have health benefits in older age.
This new study, led by researchers at Brigham and Women's Hospital and Harvard Medical School, has now rigorously analyzed two supplements to determine if they could directly slow the biological aging process.
These include a broad-based multivitamin–multimineral (MVM) and 500 milligrams of cocoa flavanols.
The study analyzed the data of nearly 1,000 participants in the COcoa Supplement and Multivitamin Outcomes Study (COSMOS), who had an average age of around 70. Compared to those who took a placebo, participants who took a daily multivitamin for two years showed slower aging, according to two biological aging clocks.
The cocoa extract, meanwhile, had no impact on any of the five 'age' clocks considered by researchers, despite being linked to health benefits in other studies.
Sesso and colleagues say their results on multivitamins are "encouraging". But they admit that larger sample sizes and longer trials are needed to determine whether these supplements ultimately translate into meaningful clinical benefits.
It's worth noting, however, that participants who took the multivitamins also showed benefits in inflammation and cognitive function.
"Within COSMOS, we are fortunate and excited to build upon a rich resource of biomarker data to test how two interventions may improve biological aging and reduce age-related clinical outcomes," says Sesso.
To date, only a few small-scale randomized controlled trials have investigated the effects of vitamins on epigenetic aging, and many have focused on a single vitamin rather than a broad-based approach.
Epigenetic aging clocks are inherently imperfect because they rely on associations and predictions, but they have recently emerged as powerful ways to estimate how fast or slow a person is aging biologically relative to their chronological age.
The clocks work by analyzing DNA patterns in the blood to predict how the aging process will unfold. Interfering with some of these biomarkers has the potential to slow down the aging process, and multivitamins may be a way to do just that.
"There is a lot of interest today in identifying ways to not just live longer, but to live better," says Sesso.
"It was exciting to see the benefits of a multivitamin linked with markers of biological aging. This study opens the door to learning more about accessible, safe interventions that contribute to healthier, higher-quality aging."
In the current trial, the two epigenetic clocks that were linked to multivitamin use were PCPhenoAge and PCGrimAge. These second-generation models have stood out in prior research and are associated with a range of healthy longevity metrics.
Ultimately, a daily multivitamin for two years was linked to a yearly decrease of 0.113 years on the PCGrimAge clock and 0.214 years on the PCPhenoAge clock. Based on associations shown in previous research, the observed clock changes could correspond to a lower cancer risk over 10 years, a reduction of roughly 3 to 7 percent.
Participants who showed accelerated aging on these clocks before the trial were particularly affected by the multivitamins. On the PCGrimAge clock, participants' rates of aging slowed nearly twice as much as those who showed normal aging at baseline. This suggests that multivitamins may be improving health outcomes by filling a nutritional deficit.
Related: 5 Things You Ought to Know Before Buying Supplements
"Considering that extending healthy lifespan by one year may save $38 trillion in the US population, our findings suggest that a daily MVM may represent a highly cost-efficient, accessible intervention to improve public health," the research team concludes.
Some of the study authors received grants from private companies with financial interests in nutritional supplements, but their research was conducted independently, peer-reviewed, and relied on a trial that was primarily funded by the US National Institutes of Health.
In a corresponding piece for Nature, two epigenetic researchers, Calen Ryan and Daniel Belsky, who were not involved in the current study, called the findings "a major advance for the supplement field."
"However," they add, "whether such interventions can increase healthspan remains an open question."
The study was published in Nature Medicine.