Populations that have eaten a vegetarian diet over several generations have an increased risk of heart disease and cancer, according to a report published in the journal Molecular Biology and Evolution.
The report argues that communities who haven’t consumed meat for generations are more likely to carry genetic mutations that raise the likelihood of inflammatory disease and cancer.
The authors, from Cornell University in the US, believe that the mutation is the result of an adaptation which made it easier for vegetarians to absorb fatty acids from plants. They believe that the mutation, found in the FADS2 gene, causes these fatty acids to be converted into arachidonic acid.
The researchers studied the genomes of a vegetarian settlement in Pune, India. They compared them with those of a community in Kansas with a Western diet, and found a ‘significant genetic difference’ between the populations.
Tom Brenna, the study’s lead author, said: ‘Those whose ancestry derives from vegetarians are more likely to carry genetics that more rapidly metabolise plant fatty acids.
‘In such individuals, vegetable oils will be converted to the more pro-inflammatory arachidonic acid, increasing the risk for chronic inflammation that is implicated in the development of heart disease, and exacerbates cancer.
‘The mutation appeared in the human genome long ago, and has been passed down through the human family. To make the problem worse, the mutation also hinders the production of beneficial omega-3 fatty acid which is protective against heart disease. Although it may not have mattered when the mutation first developed, since the industrial revolution there has been a major shift in diets away from omega-3 — found in fish and nuts — to less healthy omega-6 fats, found in vegetable oils,’ Brenna said.
What the study has actually found is that populations who have had a vegetarian diet for many generations in a row — in other words, over multiple decades — may have a tendency towards DNA mutations that can potentially increase the likelihood of cancer and inflammatory disease occurring. What should not be taken from this is the idea that vegetarianism is suddenly harmful to one’s health — the evidence that such a diet lowers the risk of diabetes, stroke and obesity remains convincing.
However, this may explain a paradox that has baffled doctors for many years, which is why vegetarian populations appear 40 per cent more likely to suffer bowel cancer than meat eaters — puzzling, since eating red meat is known to raise this risk.
Vegetarians should continue to ensure they are getting enough protein, iron, vitamins and calcium from their diet — by using supplements if necessary — but should also now consider switching to vegetable oils low in omega-6 linoleic acid such as olive oil. This may help to mitigate against any potentially harmful genetic impact on the metabolism of certain vegetable oils in the body.
Research score: 4/5