Our purvAcharyas reccomended a pristine diet for us. Swami Desikan composed the Aahara Niyamam so that the food we eat is pure and does not have a counter effect. It is this spartan life style that enabled our acharyas to live for 100 to 125 years in strong health.
This article is from the BBC. It is quite important to all of us who feel that the "western" lifestyle is much more healthier.