Diet plays an important role in neuron formation in the adult brain, and adjusting how much and how often one eats affects both this process—called neurogenesis—and learning and memory abilities.
Meal frequency is more important than calorie intake in regulating adult neurogenesis in the hippocampus in mice, Sandrine Thuret of King’s College in London has found. Although adult mice fed a calorie-restricted diet (10 percent fewer calories than that fed to control-group mice) on a normal eating schedule exhibited more newborn cells than those in the control group, few of these new cells were neurons. But mice that were fed regularly only every other day—receiving the same average calorie intake as the dieting mice—showed “[dramatically] increased neurogenesis,” and also showed an increase in learning and memory abilities, Thuret said.
Restricted-calorie diets have been shown to increase life span, reduce neuronal damage and enhance learning abilities in animal studies. This study is the first to suggest that less-frequent meals, rather than simple calorie reduction, contributes to neurogenesis. The mice that fasted every other day showed a 30 percent to 40 percent increase in cell growth, with no significant cell loss later on.
Cutting back on food appears to have an impact at the genetic level as well, Thuret said. “Remarkably, we also showed that diet has an influence on the level of expression of genes in the brain,” she said, adding that the genes affected by restrictive diets are critical for cognition.
A study in the December 2006 European Journal of Neurology suggested that a high-fat diet decreases neurogenesis, said Elizabeth Gould, a professor of psychology at the Neuroscience Institute of Princeton University. “Eating every other day is not the opposite of a high fat diet, but you can see that these are related,” said Gould, who was not involved with Thuret’s study.
Other factors have been shown to influence neurogenesis as well, she said: “We know that physical activity increases neurogenesis, and there is a study showing that sexual experience increases neurogenesis.” In addition, she said that “learning can increase new neurons and also decrease the survival of cells born at a different time point.”
Recent studies have also examined whether fluoxetine (Prozac) and other drugs for treating depression affect neurogenesis.