I am sceptical about the need for supplementation, specifically as it relates to training but equally as it relates to general health. Mark Sissons and Michael Eades do make some good arguments in favour of it, but I remain unconvinced that for me it's the right way to go. I prefer to focus on getting a high quality diet and let my body extract from that what it needs. Otherwise you get sucked into a kind of vortex of 'what ifs' that lead to an ever-increasing number of tablets sitting on front of you on the breakfast table each morning.
Rusty Moore has just published an interesting (and free!) paper in which he interviews a a couple of people who work, or have worked in the industry. Worth a read. You can download it by clicking on the picture to go to Rusty's post.