Harvard University researchers have analyzed massive amounts of data to determine the impact of 12 dietary, lifestyle and metabolic risk factors such as tobacco smoking and high blood pressure, and used a mathematical model to determine how many fatalities could have been prevented if better practices had been observed.
While we are all aware how damaging, for example, tobacco smoking is to general health, it was amazing that omega-3 deficiency proved to be a major factor, responsible for as many as 96'000 death cases in the US per year: http://www.nutraingredients-usa.com/Research/Omega-3-deficiency-causes-96-000-US-deaths-per-year-say-researchers