I think taking into account the nutritional bang for the buck matters 
also, and what quantities need to be consumed in order to be 
well-nourished and to prevent hunger. Anecdotally, I need a lot less 
beef than I do veg. Grains, man I could eat those all day and never feel 
satisfied!

Day, Wally wrote:
>> Comparing by volume can be tricky.  An acre of wheat can yield 3000 lbs,
>> while an acre of tomatoes can yield 40 tons -- obviously a gigantic
>> difference by volume.  However, in terms of available energy (calories),
>> the wheat has only about 1/3 less calories per acre than the tomatoes.
>> Still less, but not nearly as much as the volume difference would lead you
>> to believe.
>>     
>
> Another factor to consider - grains can be stored immediately and indefinitley quite easily. Fruits and veggies, however, require a wide range of storage methods (drying, canned, frozen, etc.). What should be added into the above equation - how much of that energy is "lost" because of improper storage methods and/or waste during storage prep? Obvioulsy, it would be best if everyone worldwide ate fresh, off-the-vine, food everyday. But how practical is that? (I can't believe I'm defending grains, but for the sake of discussion I will :)
>