Interesting articles from the Guardian on the "Encode Project" which released its results this week.

Breakthrough study overturns theory of 'junk DNA' in genome | Science | The Guardian
Soon science could enable us all to run as fast as Usain Bolt | Johnjoe McFadden | Comment is free | The Guardian

Basically it seems (I am pretty clueless when it comes to this stuff) to say that much of what was previously thought of as "junk" DNA in fact contains many crucial switches for turning genes on and off.
"Up to 18% of our DNA sequence is involved in regulating the less than 2% of the DNA that codes for proteins"
""Regulatory elements are the things that turn genes on and off," says Professor Mike Snyder of Stanford University, who was a principal investigator in the Encode consortium. "Much of the difference between people is due to the differences in the efficiency of these regulatory elements. There are more variants, we think, in the regulatory elements than in the genes themselves."
Genes cannot function without these regulatory elements. If regulation goes wrong, malfunctioning genes can cause diseases including cancer, atherosclerosis, type 2 diabetes, psoriasis and Crohn's disease. Errors in the regulation of a gene known as Sonic Hedgehog, for example, are thought to underlie some cases of human polydactyly in which individuals have extra toes or fingers."

So if it turns out the crucial thing is not the genes themselves but the switches that control them, the most logical thing seems to be to program your switches the right way - by eating the right way.