I like the idea of the human body as a machine that requires certain fuels and chemicals and minerals etc to run optimally. I have also noticed the benefits of eating well and the benefits of, for example, getting enough vitamin C when ill.

So this page on netdoctor.co.uk is very handy and interesting to read. It lists all the vitamins and minerals we need and what they do. The biology student in me finds that very neat — I just dug up my biology textbook from secondary school. The article linked above also notes which foods provide these vitamins and minerals, how much you should have per day, etc..