Our bodies are, for the most part, a direct reflection of what we eat and how our genetic makeup sets up physiological processes to utilize what we eat. Therefore, it is not surprising that the construction of the body of the fetus is strongly influenced by what food the mother ingests. The fetus can utilize food stuffs carried by the mother in the form of fat, and can obtain some minerals, such as calcium, from other stored resources that the mother has retained in her body. However, how much and what the mother eats plays a critical role in the development of her baby.
Poor nutrition is known to have a significant impact on the development of the CNS of the fetus. Nutritional inadequacies that are of physiological significance can affect brain development in the prenatal period through effects on neuroanatomy, neurochemistry, or both. The structural effects are primarily due to the influence of nutrients on cell division and growth (Rao and Georgieff 2000). These effects could result in fewer neurons being developed. It could also result in adverse effects on non-neuronal supporting structures in the brain, such as oligodendrocytes that play a critical role in the myelination of neurons. Without appropriate myelination, nerve conductance is slowed and cognitive performance is hampered. The effects of nutritional inadequacies on the neurochemistry of the brain are most easily seen in effects on neurotransmitters. This effect can be through the alteration of levels of neurotransmitters, on the release and uptake of the neurotransmitters or on the sensitivity of the receptors.
Nutritional changes, like many other perturbations of fetal development, vary in their effect based on the timing of change. In research with rats it is known that iron deficiency around the time of birth results in smaller brain size (Rao, et al. 1999), and permanent negative effects on learning and behavior (Felt and Lozoff 1996). However, iron deficiency occurring after the rat pup has been weaned has minimal effects (Chen, Conner and Beard 1995).
An additional factor that is observed throughout the nutritional literature is that a nutrient can negatively affect brain development by being in short supply or by being overabundant. Stated another way, many nutrients are regulated within narrow therapeutic ranges (Rao and Georgieff 2000). For example, Vitamin A is a nutritional component that is necessary in normal brain development. However, if this component is ingested or absorbed through the skin by pregnant women in high levels, it is associated with microcephaly and mental retardation (Willhite, Hill and Irving 1986).
Inadequate nutrition can be general, or it can be specific to one or more nutrient compounds. Our review of the effects of nutrition during pregnancy on child outcomes will begin with a discussion of general nutritional deficiencies and then consider a number of specific nutrients that have been linked to poor child outcomes.