Researchers assembled 21 pairs of adult identical twins and fed one of each pair an omnivorous diet for eight weeks, while their sibling was put on a vegan diet for the same time.
The omnivore diet included 170 to 225 grams of meat, one egg, and one and a half servings of dairy per day.
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The authors investigated the impacts of the diet on the participant’s DNA and gene activation by analysing blood samples collected at the start, week four, and week eight of the study.
By the end of the study, the authors observed decreases in estimates of biological age — known as epigenetic ageing clocks — in participants who ate a vegan diet but not among those that ate an omnivorous diet.
They also observed decreases in the ages of the heart, hormone, liver, and inflammatory and metabolic systems of the vegan participants.
However, they acknowledged the extent to which those changes could be attributed to diet alone were unclear.
The vegan dieters also lost two kilograms more – on average – than the omnivores, which could have contributed to the bodily changes.
Further research is needed to investigate the relationship between dietary composition, weight, and ageing, in addition to the long-term effects of vegan diets, the authors said.