These changes were not seen in the twins whose diet included meat, eggs and dairy products.
Some experts suggested that, long-term, a vegan diet may result in nutritional deficiencies and may not suit all ages, while others said the differences observed in the study could have been down to weight loss.
By the end of the study, the researchers observed decreases in biological age estimations based on levels of DNA methylation – a type of chemical modification of DNA that is used to estimate biological age.
Biological ageing refers to the decline in functioning of tissues and cells in the body, as opposed to chronological age (the number of years a person has lived).
Previous research has reported that increased DNA methylation levels are associated with ageing.
However, Varun Dwaraka, of epigenetic testing company TruDiagnostic, and Christopher Gardner of Stanford University in California, said it was unclear to what extent the differences between the pairs could be attributed to the differences in diet.
Tom Sanders, professor emeritus of nutrition and dietetics at King’s College London, in the UK, who was not involved in the study, said the research found some difference in terms of ageing for vegans.
He noted that it did not consider the fact that vitamin and mineral deficiencies often take years to appear, and that some research suggests a vegan diet may not be good for older people’s health.
Dr Duane Mellor, dietitian and spokesman for the British Dietetic Association, said that although the study compared a vegan diet to an omnivorous diet, these diets were not entirely matched in terms of calories.
He explained: “It is possible that a reduction in energy intake could potentially have altered how the participants’ DNA was changed.”
The findings are published in the journal BMC Medicine.
