It's a myth that we don't tax food. We plainly do. The Excise Tax Act spells out what's called the definition of basic groceries. Some foods, such as Froot Loops, are exempt from tax. Bacon is exempt from tax. Club soda, which is generally a healthful food, is taxable. The tax rules are basically based on these 1950s notions of what is a sensible diet, and they have to be updated. Nutrition science has changed dramatically since then.
On February 2nd, 2012. See this statement in context.