Why is it that some people can only stay healthy by sticking to a strict vegetarian diet? Why is it that others can eat a steak a day, remain slim, avoid heart disease and feel like a million dollars? The answers may lie with your heritage.

Cornell University researchers have found a fascinating genetic variation that they said appears to have evolved in populations that favored vegetarian diets over hundreds of generations. The geography of the vegetarian allele is vast and includes people from India, Africa and parts of East Asia who are known to have green diets even today.

Researcher Kaixiong Ye said that the vegetarian adaptation allows people to “efficiently process omega-3 and omega-6 fatty acids and convert them into compounds essential for early brain development.”

Omega-3 is found in fish, whole grains, olive oil, fruits and vegetables, while omega-6 is found in beef, pork products, and many packaged snack foods, such as cookies, candies, cakes and chips, as well as in nuts and vegetable oils.

Nutritionists believe that getting a good balance of these two types of fatty acids in the diet is essential to staying healthy. Our body can’t produce these substances naturally so it must get them from food.