Nutrition vs. Nutritionism Nutrition is the most important and malleable factor influencing people’s life span (how long we live) and health span (how well we live). Studies on fraternal vs. identical twins show that genetics account for 25 to 30 percent of a person’s longevity. The other 70 to 75 percent proves that while favorable genetics clearly play a role, the environment, including a bad diet, can easily overcome those gifts, hence why the US has seen reduced life expectancy four years in a row.
