Research over the last 5 years has firmly established that learning and memory abilities, as well as mood, can be influenced by diet, although the mechanisms by which diet modulates mental health are not well understood. One of the brain structures associated with learning and memory, as well as mood, is the hippocampus. Interestingly, the hippocampus is one of the two structures in the adult brain where the formation of newborn neurons, or neurogenesis, persists. The level of neurogenesis in the adult hippocampus has been linked directly to cognition and mood. Therefore, modulation of adult hippocampal neurogenesis (AHN) by diet emerges as a possible mechanism by which nutrition impacts on mental health. In this study, we give an overview of the mechanisms and functional implications of AHN and summarize recent findings regarding the modulation of AHN by diet.