Nutrition and fertility: some iconoclastic results.

In this paper, the evidence available is used to conclude that, as levels of nutrition increase from insufficient to excessive, fertility first increases and then decreases. This suggests that the relationship between fertility and nutrition has the shape of an inverted U. Next, the hypothesis is explicitly tested using countries as units of observation. In the statistical analysis, the possibility of spurious relationships is carefully controlled. The results strongly support the hypothesis that, for existing levels, additional intake of nutrients decreases the levels of fertility.