Adding to this discussion, the TGA is the Australian equivalent of the FDA.

This quote may be relevant (the emphases are mine):

"(2) Vitamins

An advertisement for vitamins shall not imply that vitamin supplements:

(a) are a substitute for good nutrition or a balanced diet; or

(b) are in any way superior to or more beneficial than dietary nutrients or that normal health may be affected by not taking vitamin supplements."

Source: https://www.comlaw.gov.au/Details/F2007L00576 .

What I have emphasised sums up my opinion of vitamin supplements. They are unlikely to be of much benefit to somebody who eats in a healthy way unless (of course) there is medical evidence which suggests otherwise.