How Much Food Will Be Needed In 2050?

There have been many articles that compare the population of 2050 and the food requirements needed by that population. Examples include "Making Safe, Abundant Food Supply a Global Reality" and "Food Needs and Population" (additional resources). Dr. Terry Etherton highlights some of the approaches to population estimates and then seeks to translate into the quantity of food that would be needed to feed that 2050 population.
The question emerges, then, of whether there is more accurate approach for estimating projected food needs in 2050?