 Omega-6 and Omega-3 polyunsaturated fatty acids are essential nutrients that must be acquired through the diet. Though it is genuinely recommended that people consume more Omega-6 than Omega-3, modern diets tend to include too much Omega-6 and not enough Omega-3. More balanced consumption of these fatty acids is important for brain development, but how the modern high Omega-6, low Omega-3 diet influences brain development has been unclear. In a recent study, mice that consumed a high Omega-6, low Omega-3 diet during pregnancy and early lactation had offspring with abnormal brain development. The researchers determined that the mother's dietary fatty acid imbalance changed the levels of these fatty acids and their metabolic products in the brains of the offspring, altering the production of brain cells. The brain is composed of neurons and supporting cells called glia. Both of these cells are produced by neural stem cells or NSCs. The production of the correct number of neurons and glia by NSCs is critical for brain function and because this process occurs before birth, it can be influenced by the nutrients and environment provided by the mother. To study the effects of maternal fatty acid intake on offspring neurodevelopment, the researchers fed pregnant mice a diet that was high in Omega-6 fatty acids and low in Omega-3s, similar to a modern diet, especially a Western diet. The pups of these mothers exhibited abnormally thin neuronal layers in some regions of the brain's neocortex, the part of the brain responsible for motor control and sensory perception. NSCs from these pups also produced greater numbers of astrocytes, a type of glial cell, suggesting that the impaired neocortical development resulted from an increased production of glia by NSCs. The processing of Omega-6 and Omega-3 fatty acids produces several types of metabolites, small molecules that have important biological functions, including regulating the development of NSCs. Therefore, the researchers next investigated whether the levels of these metabolites were altered in the brains of the pups of the high Omega-6, low Omega-3 mothers. They found changes in a particular class of metabolites called epoxy metabolites, some increased in concentration, others decreased. Two epoxy metabolites in particular showed large changes in concentration. Treating NSCs from the mouse pups with high or low concentrations of those two epoxy metabolites could also increase or decrease the number of neurons and glia produced. Taken together, these findings indicate that an imbalanced maternal fatty acid intake impairs neurodevelopment by changing the levels of epoxy metabolites. As adults, these pups also displayed increased anxiety-like behavior, demonstrating that the developmental effects that were produced in the offspring resulted in long-term behavioral consequences. This study suggests that consumption of the modern diet, especially during pregnancy and early lactation, could have negative consequences for brain development and anxiety-related behavior. Future studies will need to investigate other dietary factors and critical time periods that could influence this process.