Human genome shaped by vegetarian diet increases risk of cancer and heart disease
Researchers have found evidence that a vegetarian diet has led to a genetic mutation that may increase people’s risk of heart disease and colon cancer.
In a new study 1 published in the journal Molecular Biology and Evolution 2, researchers compared a primarily vegetarian population from Pune, India to a traditional meat-eating American population, mostly from Kansas. The researchers found a higher frequency of the mutation called "rs66698963" in the Indian population.
This mutation helps people convert plant fatty acids into important nutrients, including omega-6 arachidonic acid. Arachidonic acid is important for muscle growth and healthy neurological function in humans and is usually contained in meat, eggs and dairy.
However, arachidonic acid is also known for its pro-inflammatory and pro-blood clotting properties. Today, this genetic mutation can be a problem because omega-6 fats are readily available in an increasing number of foods and oils. Consequently, people with this mutation are retaining higher levels of arachidonic acid in their blood and tissues.
In the present study, we show that rs66698963 controls the basal levels of omega-6 arachidonic acid in humans. Moreover, and forming the bulk of the results reported in the current study, lead co-author Alon Keinan and post-doctoral fellow Kaixiong Ye revealed that the genotypes of rs66698963 are selected by evolution in a manner predictable based on the traditional diets in several populations around the world. Vegetarians for instance would favor the genotype that produces higher arachidonic acid, whereas fish and meat eaters favor the one that produces less.
What is the mutation’s relationship to heart disease and colon cancer?
Both heart disease and cancer are increasingly recognized as diseases enhanced by chronic low level inflammation. Omega-6 arachidonic acid mediates and enhances inflammation and thus may well be a contributing factor to the decades long development of heart disease, as well as accelerating the development of cancer cells and tumors.
What implications does your study have for vegetarians in developing and developed countries?
Persons with one of the genotypes that we call the I/I genotype, have on average higher omega-6 arachidonic acid levels, probably because of increased synthesis from plant fatty acids. The I/I genotype is favored in traditional vegetarian populations.
The plant omega-6 linoleic acid – from which the arachidonic acid is derived – is normally at low levels in traditional whole food diets as well as in fruit oils such as olive oil and avocado oil, or in dairy fat. However, it is a factor of 10 or more higher in industrially produced oilseeds such as traditional sunflower, safflower, corn, soy and peanut oils. The increasing availability of high omega-6 seed oils in the developing world will be most pro-inflammatory and pro-clotting for those persons with the genetics of traditional vegetarians because their genotype will maintain higher omega-6 arachidonic acid in their blood and tissues.
Omega-6 arachidonic acid also suppresses omega-3 docosahexaenoic acid needed for brain development starting in pregnancy and through 20 years of age. These are major issues as the fat content of the diet for well-nourished persons is from 15 percent to 45 percent of calories and much of this is cooking and salad oil.
2. Molecular Biology and Evolution
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