You make a good point about diet and IQ. The Bell Curve does consider nutrition's role in IQ. Though, there have been findings that contradict each other on whether diet is only circumstantial evidence. Two of the most critical studies are Stein et al 1972 and Benton and Roberts 1988. To quote another article about this here is the following explanation of those two studies: There has been only one major study of the effects of prenatal malnutrition (i.e. malnutrition of the mother during pregnancy) on long-term intellectual development. Stein et al (1975) analyzed the test scores of Dutch 19-year-old males in relation to a wartime famine that had occurred in the winter of 1944-45, just before their birth. In this very large sample (made possible by a universal military induction requirement), exposure to the famine had no effect on adult intelligence. Note, however, that the famine itself lasted only a few months; the subjects were exposed to it prenatally but not after birth.

In contrast, prolonged malnutrition during childhood does have long-term intellectual effects. These have not been easy to establish, in part because many other unfavorable socioeconomic conditions are often associated with chronic malnutrition (Ricciuti, 1993; but cf. Sigman, 1995). In one intervention study, however, pre-schoolers in two Guatemalan villages (where undernourishment is common) were given ad lib access to a protein dietary supplement for several years. A decade later, many of these children (namely, those from the poorest socio-economic levels) scored significantly higher on school related achievement tests than comparable controls (Pollitt et al, 1993). It is worth noting that the effects of poor nutrition on intelligence may well be indirect. Malnourished children are typically less responsive to adults, less motivated to learn, and less active in exploration than their more adequately nourished counterparts.

Although the degree of malnutrition prevalent in these villages rarely occurs in the United States, there may still be nutritional influences on intelligence. In studies of so-called "micro-nutrients," experimental groups of children have been given vitamin/mineral supplements while controls got placebos. in many of these studies (e.g., Schoenthaler et al, 1991), the experimental children showed test-score gains that significantly exceeded the controls. In a somewhat different design, Rush, Stein, Susser, & Brody (1980) gave dietary supplements of liquid protein to pregnant women who were thought to be at risk for delivering low birth-weight babies. At one year of age, the babies born to these mothers showed faster habituation to visual patterns than did control infants. (Other research has shown that infant habituation rates are positively correlated with later psychometric test scores: Colombo, 1993.) Although these results are encouraging, there has been no long-term follow-up of such gains. (End Quote)

What role nutrition has on intelligence, however, is strictly considered as enviromental. The inherited portion of intelligence is not affected by the nutrition debate.

I appreciate your argument about the real significance of IQ in success. IQ shows one's ability to manipulate information. It doesn't show adaptability. You should check out a book about everyone's potential genius. It is called "Dumbing Us Down" by John Taylor Gatto. He believes that testing intelligence has very little merit.

Great comment.