Yes, but it's actually easier than people think. You don't have to make a science of it or measure doses, just ditch flavor enhancers and avoid preservatives, read the labels on stuff you buy (yes, time-consuming at first, but you'll have to do it less and less as you gain experience), favor fresh produce over junk food and get lots of sunshine.

Exactly.

Plus you simply don't know if e.g. the oats in that tin of oatmeal you're working through were grown in soil that had adequate (for you) amounts of selenium.

Taking a "One A Day" vitamin just to make sure you hit all the bases is a minimal reasonable precaution.

A balanced diet is not difficult!

Its a no-brainer to me that if you are worried enough about your health to simply change your diet to add a bit more fruit and veg rather than spend money on magic pills without any medical or scientific basis.

this comment also echos my thoughts: http://news.ycombinator.com/item?id=1367101