Scientists from the University of California San Diego and the University of Freiburg found that participants who followed a vegan diet for four weeks developed changes in DNA methylation, a process that helps control how genes are switched on and off, that were associated with healthier immune function and slower biological ageing.
The findings of the study add to growing evidence that dietary choices can influence health surprisingly quickly.
How a vegan diet changed the body in just four weeks
The randomised clinical trial involved 48 healthy adults. After eating the same plant-based diet for a week, participants were randomly assigned to either a vegan diet or a meat-rich diet for four weeks.
Both groups consumed similar numbers of calories, allowing researchers to focus on the effects of the foods themselves rather than weight loss.
After analysing more than 800,000 DNA methylation sites across the genome, researchers found those following the vegan diet showed changes linked to reduced inflammation and healthier immune function.
Specifically, the vegan group was predicted to have fewer neutrophils (immune cells that can drive inflammation when present in high numbers), alongside higher levels of CD4 T cells, which help regulate immune responses.
The researchers also found changes affecting pathways involved in lipid metabolism, insulin signalling, DNA repair and cellular stress responses.
Perhaps the most striking finding came when the team measured participants’ biological age using so-called epigenetic clocks – tools that estimate biological ageing from DNA methylation patterns rather than chronological age.
Two of the clocks suggested biological ageing slowed during the four-week vegan intervention, although a third clock measuring chronological ageing showed no significant change.
‘Our genes are not our destiny’
Co-senior author Dr Jerome Mertens, associate professor of neurosciences at UC San Diego School of Medicine, said in a statement that: “Our genes are not our destiny. The remarkable finding isn’t simply that one diet outperformed another.
“It’s that the epigenome responded measurably in just four weeks, showing that our biology is far more dynamic – and responsive to everyday choices – than we often assume.”
The researchers stress that the study was relatively small and only lasted one month, meaning larger, longer-term trials will be needed to determine whether these molecular changes translate into a lower risk of diseases such as cancer or heart disease.
Co-senior author Dr Max Storz, from the University of Freiburg Medical Center, said the findings nevertheless provide “an important foundation” for understanding how diet influences long-term health.
The power of a plant-based diet
While the latest research doesn’t prove a vegan diet can prevent disease or reverse ageing, it adds to a growing body of evidence linking plant-based eating with better long-term health.
Earlier this year, researchers reported that plant-based diets can help reduce markers of inflammation, while previous research from Stanford University found that eight weeks on a vegan diet reduced biological age estimates in identical twins.
Large observational studies have also consistently linked diets rich in fruit, vegetables, wholegrains, legumes and nuts (and lower in red and processed meat) with healthier ageing and a lower risk of chronic diseases, including cardiovascular disease, type 2 diabetes and some cancers.
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