Programmed for sex: Nutrition-reproduction relationships from an inter-generational perspective

Reproduction is our biological reason for being. Our physiology has been shaped via countless millennia of evolution with this one purpose in mind, so that at birth we are 'programmed for sex', although this will not kick-start functionally until puberty. Our development from an early embryo is focused on making us fit to reproduce and is intimately connected to nutrition and energy stores. Fluctuations in food supply has probably been a key evolutionary shaper of the reproductive process, and this review hypothesizes that we have developed rapid, non-genomic adaptive mechanisms to such fluctuations to better fit offspring to their perceived (nutritional) environment, thus giving them a reproductive advantage. There is abundant evidence for this notion from 'fetal programming' studies and from experimental 'inter-generational' studies involving manipulation of parental (especially paternal) diet and then examining metabolic changes in resulting offspring. It is argued that the epigenetic reprogramming of germ cells that occurs during fetal life, after fertilisation and during gametogenesis provides opportunities for sensing of the (nutritional) environment so as to affect adaptive epigenetic changes to alter offspring metabolic function. In this regard, there may be adverse effects of a modern Western diet, perhaps because it is deficient in plant-derived factors that are proven to be capable of altering the epigenome, folate being a prime example; we have evolved in tune with such factors. Therefore, parental and even grandparental diets may have consequences for health of future generations, but how important this might be and the precise epigenetic mechanisms involved are unknown.