I've already talked about lead acetate and the fact that it was almost certainly the first artificial sweetener before, and I've been reading about it again lately. Here's something I didn't know - it may have helped cause the fall of Rome.
Here's how it worked. Roman households loved a condiment called defrutum - a reduction of grape juice or crushed grapes, sort of a demi-glace. The syrup, like molasses or honey, was used as a source of intense sweetness that wasn't prone to spoiling like fruit.
Grape juice, like any other acidic liquid, will dissolve a small amount of many metals - copper pots were thought to impart an off-taste to the reduction, and lead was said to give the best flavor (ostensibly because of the sweet lead acetate - the vessel provided the lead cations, and the partial fermentation of the juice provided some acetic acid).
I am not a Roman historian and there seems to be some disagreement as to exactly how much of a role lead in general, and, specifically, defrutum played in the decline of Rome.
What's certain, however, is that lead acetate is the only molecule that's been noted for its efficacy as a sweetener and as a hair dye.
Rome : Lead Acetate :: America : High Fructose Corn Syrup
But how did it cause the fall of Rome?
Chronic ingestion of lead causes stupidity, debility, sterility, and insanity. Dose the mob; spare the ruling, merchant, and military classes. It was applied the the other way around, of course. Hereditary upper classes are most often exactly wrong.
Probably a bigger problem was adulteration of cheap red wines with lead salts - it sweetens the wine while removing the unpleasant tannin-derived aftertaste. Beethovens deafness is said to be result of drinking the stuff every day.
I don't know how much lead in wine contributed to downfall of the empire (from what I heard there was plenty of other reasons - and Romans lasted longer than many other, lead-free empires)
So... historians haven't done AA on Roman skeletons / hair samples to quantify lead levels?