The op talks about sulforaphane but then links to an article about vitamin a and e(I don't know why) They're totally different chemicals that work through completely different pathways.

And a study on vitamin a and e etc doesn't tell you much about other supplements. Just like how a study on does whether or not statins are associated with reduced mortality tells you little about whether or not ACE inhibitors are associated with reduced mortality.

Also I don't think op meant primary source as in primary vs secondary sources but meant in the sense of "this doctor primarily uses Cochrane as his source for information"