The September 2005 Decanter magazine features a letter from Dr Chris Exley of Keele University who points out that it is not known whether Stelvin screwcap enclosures can release aluminum into wine.
aluminum is a known neurotoxin, and our bodies have no need for it. So while screwcaps may be perfectly safe, we don’t know what the risks are yet.
I checked out Dr Exley’s credentials (in case his PhD was in some unrelated field like Medieval History) and he is a chemist who has done considerable work on aluminum toxicity. That said few of his publications that I was able to read online featured much in the way of findings, most are calls for research. And this is what he is doing with this letter to Decanter.
I think there is no doubt now that screwcaps are superior to cork for preserving wine quality, but this aluminum issue needs to be investigated.
PS Yes soft drink cans are made from aluminum.