Why is it that if you drink too much caffeinated coffee, drinking a decaff doesn't cancel some of the caffeine out?
Similarly, I have found that a pound of pasta and a pound of anti-pasto don't mutually annihilate in a burst of energy, as the amateur physicist in me expected.
In the supermarket I noticed sugar-free decaffeinated coke. What does that leave? A can of fizzy caramel-flavored water?
On a related topic, four kinds of food I have learned to avoid are:
-- Anything with the word "food" in its name, like "cheese food product". If they have to tell you its food, there's something seriously worrying there. (Originally I thought that the rule should be "don't eat anything with the word 'product' in its name, but eventually I realized that the Food part is much scarier than the Product part.)
-- Anything with a Best Before date measured in years (unless its alcohol)
-- Anything whose label has to tell you what it isn't, like "not a dairy product"
-- Specialities of the region. When I was younger and more naive, I thought that when these words appeared on a menu in some remote little restaurant it meant you were getting some authentic local speciality that was so good, it was a carefully guarded secret hidden from the wider world. Wrong. It turns out its code for "parts of the animal nobody else would be crazy enough to eat". If you're really lucky it won't actually be recognizable as the animal part in question, unlike the time I thought that pig's trotters sounded "authentic".
Haggis is probably the ultimate example of a regional speciality. To make haggis, you basically take a sheep, shear it (optional), stick your hand down its throat, take a firm grip on its stomach, then pull firmly until it turns inside out. Stuff the result with cereal and anything else that happens to be handy, then boil. Serve to passing Englishmen or anybody else foolish to be willing to force down a "traditional" dish.