A new study has looked into the influence of switching to a vegan diet in twins, finding that even a short-term change in meal choices appeared to alter biological markers of aging. The observational study raises interesting questions about the influence of diet on biological age, including what the long and short-term effects of a switch to a vegan diet are, and whether excluding meat or lowering calories is a more significant contributing factor.
The small study enrolled 21 twins to observe what changes occurred when one followed a vegan diet while the other ate an omnivorous diet – that included meat – for two months. Specifically, the authors were looking at changes in the levels of DNA methylation, which refers to the way epigenetics alters how our genes are expressed. As a general rule, increased DNA methylation is considered a marker of aging.
DNA methylation can be analyzed by taking blood samples, and so these were collected from the study participants at baseline and the eight-week mark. These were then compared to see if and how participants on the vegan versus omnivorous diet changed over the two months.
The twins that were allocated a vegan diet showed a reduction in biological age, as well as a reduction in the aging markers for heart, hormone, liver, and inflammatory and metabolic systems. This reduction was not seen in the twins who ate an omnivorous diet, so why was that?
As an observational study, the experiment can’t assume cause and effect, meaning the authors can’t say for certain that the change in biological age can be attributed to a vegan diet. Another possible explanation comes down to weight loss, as those who went on a vegan diet lost, on average, two kilograms of weight from the start of the study to the end.
While it’s interesting to observe a reduction in biological age after only a short period of time, the length of the study also means that the long-term effects of dietary shifts weren’t included.
“Unless a vegan diet is supplemented with vitamin B12 they develop vitamin B12 deficiency that causes chronic and often insidious damage to the nervous system,” said Tom Sanders, Professor Emeritus of Nutrition and Dietetics, King’s College London (KCL), in a Science Media Centre release. “Long-term observational studies of vegans also find adverse effects on bone density that is probably caused by very low calcium and marginally adequate protein intakes.”
“Although, observational studies indicate that vegan diets may have favourable effects on health in middle-age (such as a lower risk of cardiovascular disease and type 2 diabetes), this is not the case in older vegans who seem more likely to suffer from muscle loss, low bone density and neurological disorders which have a significant impact on the quality of life. Indeed, life-expectancy does not differ in vegans compared with those who select mixed diets.”
Furthermore, there is no guarantee that altering DNA methylation will lead to a longer life. When it comes to observational studies and longevity, you could do worse than to take a look into the lifestyle of people living in the Blue Zones.
The study is published in BMC Medicine.
