I too viewed Giles Yeo on Horizon last evening (available on iPlayer).
A thought that struck me early on was this, supplements are classed as food and foodstuffs are not tested nearly as rigorously as pharmaceuticals so it follows that very little research has gone into RDAs. Where and by whom were these RDAs set? If, as I suspect, they were set by a committee in a similar way to those set for cholesterol, BMI, Dietary Guidelines etc then I personally would think twice about them as well as being sceptical about the risks/benefits of supplements as stated by the manufacturers.
I have a nasty, suspicious mind that cannot fathom a GRAS label so show me the evidence.