Vanilla and vanillin

In an article about artificial vs. natural flavors, Edible Geography discusses the history of vanilla -

While cinnamon in the United States is a government-sanctioned imposter, plain old vanilla is, surprisingly enough, a relatively recent addition to the American flavourscape. In addition to Chase’s fake fruit syrups, the mid-nineteenth century saw vanilla replace rosewater in creams, jellies, puddings, cakes, pies, cookies, sodas, and more, in just a few decades. This wholesale taste takeover came about as the result of the accidental discovery, in 1842, of a method for artificially pollinating the vanilla orchid — which in turn led to natural vanilla extract becoming cheap enough to be ubiquitous.

That price has continued to drop as vanilla — America’s favourite ice-cream flavour by a significant margin — can now be made in any number of ways, some of which have stretched the boundaries of U.S. FDA definitions of “natural,” and “artificial” flavouring

It seems straightforward, initially: Natural vanilla flavour must be extracted from chopped up vanilla beans... Artificial vanilla flavour consists of nature-identical vanillin (the chemical that gives vanilla its characteristic flavour) that is made from something other than vanilla beans — typically wood pulp, as a by-product of the paper industry, although it can sometimes be derived from coal tar.

However, just to add a further twist, vanillin can also be made by using a particular bacteria to ferment the ferulic acid found in corn and wheat bran, and, because the FDA has determined that a flavour is “natural” if it is derived from edible sources and made using physical, microbiological, or enzymatic means analogous to a normal cooking process, this ferulic vanillin (which is chemically identical to the wood pulp and coal tar vanillin) is considered a natural flavouring — although (the FDA has ruled, after extensive consultation) it is not a natural vanilla flavour, because it doesn’t come from vanilla beans.

 - and notes in passing that vanillin has been synthesized from cow dung (by FDA ruling an artificial, not natural flavour).

Pure, true vanilla is "the second most expensive spice after saffron" (because extracting it from the seed pods is so labor intensive).  So what we're eating is vanillin, not true vanilla.