It could also be something much more benign like potassium and sodium ions. They are allegedly what make some mineral water sweet.
That's what I was thinking. The Romans would use lead bowls to make their water taste better.
They used lead vessels to make wine taste sweeter as well. Saying that makes me curious as to what it would actually taste like. Stevia extract and aspartame are sweet but don't taste the same and both different from suger, what is lead like? The second thing that makes me wonder is, do I already know since I live in a city with some lead contamination in the tap water.
Didn't the Romans actually end up making red wine vinegar in the lead pots (letting the wine go bad), and the acetic acid reacted with the lead to form lead acetate (a.k.a. "sugar of lead")?