You are what your ancestors ate

Evidence of a genetic variation — an allele — has been discovered in populations that have historically favoured vegetarian or seafood diets.

The vegetarian allele has evolved in populations in India, Africa and parts of East Asia that have eaten a plant-based diet over hundreds of generations. The adaptation allows these people to efficiently process omega-3 and omega-6 fatty acids and convert them into compounds essential for early brain development. If they stray from a balanced omega-6 to omega-3 diet, it may make people more susceptible to inflammation and, by association, increased risk of heart disease and colon cancer.

In Inuit populations of Greenland, who mainly consume seafood, researchers from Cornell University uncovered that a previously identified adaptation is opposite to the one found in longstanding vegetarian populations. While the vegetarian allele has an insertion of 22 bases (a base is a building block of DNA) within the gene, this insertion was found to be deleted in the seafood allele.

“The opposite allele is likely driving adaptation in Inuit,” said Kaixiong Ye, co-lead author of the paper published in the journal Molecular Biology and Evolution. “Our study is the first to connect an insertion allele with vegetarian diets, and the deletion allele with a marine diet.”

FADS1 and FADS2 are enzymes that are essential for converting omega-3 and omega-6 fatty acids into downstream products needed for brain development and controlling inflammation. Meat and seafood eaters have less need for increased FADS1 and FADS2 enzymes to get proper nutrition because their omega-3 and omega-6 fatty acid conversion process is simpler and requires fewer steps.

The researchers analysed frequencies of the vegetarian allele in 234 primarily vegetarian Indians and 311 US individuals and found the vegetarian allele in 68% of the Indians and in just 18% of Americans. Analysis using data from the 1,000 Genomes Project similarly found the vegetarian allele in 70% of South Asians, 53% of Africans, 29% of East Asians and 17% of Europeans.

“Northern Europeans have a long history of drinking milk and they absorbed enough end products from milk for long-chain fatty acid metabolism so they don’t have to increase capacity to synthesise those fatty acids from precursors,” said Ye.

“One implication from our study is that we can use this genomic information to try to tailor our diet so it is matched to our genome, which is called personalised nutrition,” he added.