...Because myelin is composed of lipids and cholesterol, Benton 
(1996) hypothesized that g levels may be related to dietary variables. 
Using a random sample of 7076 British citizens, Benton found that 
individuals consuming a high-fat diet had reaction times that were 
significantly faster than individuals who consumed a low-fat diet. The 
effect was so pronounced, at the .00001 p-level, that the RTs of white 
collar workers consuming low-fat diets were slower than blue collar 
eating high-fat diets. For most researchers in the psychology, 
Spearman’s g derives its importance from its behaviorally manifested 
relationship with educational, economic, and social outcomes. However, 
these studies and others (e.g., Vernon & Mori, 1990) indicate that g is 
equally grounded in a varied number of physiological and biological 
processes...

http://theoccidentalquarterly.com/vol3no1/hk-factor.html

You can't trust a lot of what you read on the internet, but this 
article on intelligence seemed interesting.

     ...Especially invoked was the claim of social anthropologist Franz 
Boas that skull measurements differed considerably between earlier and 
later European migrants to the U.S., suggesting that better nutrition 
and prenatal care could lead to big improvements in IQ and brain size...

I actually have a very small head myself, if that means anything, I 
suppose my brains are small too. ;--) I hope this web site isn't a 
front for some racist group.