I have a question. Some activists frequently make the point that certain diets are not only more calorie rich than others, but take more food calories to produce (meat-heavy diets, for instance, often demand many times the calories in grain as a feed for livestock as the number of calories they produce in meat, we hear). We might, taking a cue from virtual water, think of these as virtual calories.
Does anyone know how this is measured? Better yet, does anyone know a simple, yet evidence-based resource for exploring the virtual calories embedded in different foods? (And is there an existing term for what I'm calling virtual calories?)
In 2006 the Food and Agriculture Organization put out a nice report on the costs. Some of the energy costs are given, but this report probably underestimates the field to table path. Summing everything up is non-trivial, but this is a good starting place
Food, Energy, and Society, Third Edition
This book seems to have a lot of good information on the topic of the energy costs used to produce food.
The following paper is Sweden-specific, but does a decent job in quantifying "life cycle energy inputs" for various foods.
It also references a number of other studies up to that point (2003).
There doesn't seem to be some sort of interactive, global database for such a thing, however, which appears to be what you're seeking.
Well, if you want to find embodied production energy (as opposed to nutritional calories), many LCA programs / databases have data on foods. SimaPro, for instance, has a bunch of bread, meat, veggies, cheese, and seafood in its default database. Using this, you could compare several things--embodied energy, embodied pollution, everything measured in the EcoIndicator methodology. (Unfortunately doesn't include embodied water.)
If you're looking to compare food value, you might consider measuring by grams of protein instead of calories. Just a thought. Both are meaningful, but for different reasons.
Lots of resources at http://www.fcrn.org.uk
Thought you might enjoy this fun quiz.