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A daily omega-3 supplement seems to slow biological ageing in older people, particularly if combined with vitamin D and exercise.

We already knew that omega-3s – “good” fats found in seeds, nuts and some fish – can boost our immunity, heart health and brain function.

They have also been linked to changes in , chemical tags on DNA that alter the activity of genes and, in turn, how cells behave. This suggests that omega-3s reduce the pace of , often defined as a measure of how quickly someone’s body is deteriorating compared with the general population’s.

To explore this further, at the University of Zurich and her colleagues split 777 people in Switzerland, aged 70 to 91, into eight groups. They also wanted to find out how omega-3 may work alongside vitamin D supplements and exercise.

“Omega-3 plays on multiple pathways of ageing, such as being anti-inflammatory. Similarly, vitamin D and exercise have multiple benefits,” says Bischoff-Ferrari. “We thought, if you play on each of these differential pathways, do you get an additive benefit?”

Some of the participants were already taking these supplements or doing strength training at the start of the study. It didn’t seem ethical to tell them to stop exercising or stop taking certain supplements, says Bischoff-Ferrari, so they were allowed to continue.

On top of their existing lifestyle habits, each group was told to take varying combinations of a daily 1-gram dose of omega-3, placebo pills and 2000 international units of vitamin D. In addition, some groups were instructed to do 30 minutes of strength training three times a week.

For instance, some people were told to take omega-3 pills, but not vitamin D supplements or to do any additional strength training, while others were told to add in strength training and take vitamin D, but not omega-3.

At the start of the study, the researchers estimated the participants’ biological ages using epigenetic clocks previously developed by the team and other researchers. These analysed DNA markers called methyl groups in their blood samples that generally decline with age, impairing cell function.

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By doing the same three years later, the scientists found that the participants who were told to take omega-3 only had aged by around 3 months less, on average, than those who were only given placebo pills. They accounted for factors that could affect the results, such as the participants’ actual age, sex, weight and height.

“This is the biggest trial we have today that hints that a simple supplement contributes to slowing biological ageing,” says Bischoff-Ferrari.

What’s more, those who took omega-3 along with vitamin D and did strength training aged even less, compared with people who didn’t introduce any of these habits as part of the trial. “The effect was somewhat more pronounced, almost four months of rejuvenation,” says Bischoff-Ferrari.

These effects may seem small but could be important for some, says at King’s College London. “For an older person, in about three months, there could be a lot of age-related decline going on, so this becomes more significant,” he says.

But epigenetic clocks are not a perfect measure of biological ageing. “Just because biomarkers on your DNA indicate that you resemble someone who is younger, it doesn’t necessarily mean that you are healthier in some way,” says Siow.

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Further research should assess what the changes mean for measures such as cognition, ability to exercise and heart health, he says. Bischoff-Ferrari’s team is now analysing the participants’ data on such outcomes.

Another limitation of the study is that the participants were relatively healthy and active, and mostly not deficient in vitamin D. Further studies that involve people without these characteristics, and who are younger and live in other countries, are needed, says Bischoff-Ferrari.