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March 30, 2016

You are what you eat; scientists link dietary differences to specific genetic mutations

You may have heard the old adage “you are what you eat.”

Cornell University scientists found evidence that a vegetarian diet over multiple generations can bring about a specific genetic mutation in humans, according to a new report in the journal Molecular Biology and Evolution.

Short-term genetic evolution

The mutation identified in the study is linked to a greater risk of inflammation-related diseases like heart disease and colon cancer for those who have it switch from a balanced omega-6 to omega-3 diet.

The study team said their work is the first to trace a greater frequency of a specified mutation to a mainly vegetarian population from Pune, India (around 70 percent), compared to a meat-eating American population (less than 20 percent).

The researchers came to their conclusion by analyzing data from the 1000 Genomes Project. The team found evolutionary evidence the vegetarian diet, over many generations, may have driven the greater frequency of a mutation in the Indian population. The mutation, known as rs66698963 and discovered in the FADS2 gene, is an insertion or deletion of a DNA sequence that handles the expression of two genes, FADS1 and FADS2. These genes are crucial to creating long chain polyunsaturated fats. Of these, arachidonic acid is a primary target of the pharmaceutical industry because it is a main offender for those at risk for inflammation-related conditions.

Treating individuals based on if their genetic copies of the insertion and their impact on fatty acid metabolites can be an essential thing to consider for precision medicine and nutrition, the study team said.

The insertion mutation may be popular in populations subsisting mainly on vegetarian diets and perhaps populations having minimal access to diets rich in polyunsaturated fats, particularly fatty fish. The deletion of the same sequence could have been adaptive in populations which are derived from marine diet, such as the Greenlandic Inuit, the researchers said. They added that a follow-up the study with added international populations would offer more insight on the mutations and these genes as a genetic marker for disease probability.

"With little animal food in the diet, the long chain polyunsaturated fatty acids must be made metabolically from plant PUFA precursors. The physiological demand for arachidonic acid, as well as omega-3 EPA and DHA, in vegetarians is likely to have favored genetics that support efficient synthesis of these key metabolites,” the study team said in a press release. "Changes in the dietary omega-6 to omega-3 balance may contribute to the increase in chronic disease seen in some developing countries."

"This is the most unique scenario of local adaptation that I had the pleasure of helping uncover,” said study author Alon Keinan, a population geneticist at Cornell. "Several previous studies pointed to recent adaptation in this region of the genome. Our analysis points to both previous studies and our results being driven by the same insertion of an additional small piece of DNA, an insertion which has a known function. We showed this insertion to be adaptive, hence of high frequency, in Indian and some African populations, which are vegetarian. However, when it reached the Greenlandic Inuit, with their marine diet, it became maladaptive."

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