Dr. Michael Greger is the founder of nutritionfacts.org, which is "a free, non profit, science based public service providing daily updates on latest in nutrition research".
In this video he states that fact that nutrition and diet is the #1 leading cause of death and disability in the United States of America.
He states, "Premature death and disability is preventable with a healthy diet" but that doctors aren't taught enough about nutrition in medical school, that's why it matters what you eat!