You are what you eat

New research raised the striking possibility that even small amounts of junk foods may produce significant changes in gene expression that could negatively impact physiology and health.Even the most health-conscious eaters find themselves indulging in junk foods from time to time.A pair of papers published in Cell journal by A.J. Marian Walhout, professor of molecular medicine at the University of Massachusetts Medical School (UMMS), describes how metabolism and physiology are connected to diet.Using C. elegans, a transparent roundworm often used as a model organism in genetic studies, Dr. Walhout and colleagues observed how different diets produce differences in gene expression in the worm that can then be linked to crucial physiological changes."In short, we found that when C. elegans are fed diets of different types of bacteria, they respond by dramatically changing their gene expression program, leading to important changes in physiology," Walhout said."Worms fed a natural diet of Comamonas bacteria have fewer offspring, live shorter and develop faster compared to worms fed the standard laboratory diet of E. coli bacteria," she added.Walhout and colleagues identified at least 87 changes in C. elegans gene expression between the two diets.Surprisingly, these changes were independent of the TOR and insulin signaling pathways, gene expression programs typically active in nutritional control. Instead, the changes occur, at least in part, in a regulator that controls molting, a gene program that determines development and growth in the worm.This connection provided one of the critical links between diet, gene expression and physiology detailed in "Diet-induced Development Acceleration Independent of TOR and Insulin in C. elegans.""Importantly, these same regulators that are influenced by diet in the worms control circadian rhythm in humans," said Lesley MacNeil, PhD, a postdoctoral student in the Walhout Lab and first author on the paper."We already know that circadian rhythms are affected by diet and this points to the real possibility that we can now use C. elegans to study the complex connections between diet, gene expression and physiology and their relation to human disease," she added.Strikingly, Walhout and colleagues observed that even when fed a small amount of the Comamonas bacteria in a diet otherwise composed of E. coli bacteria, C. elegans exhibited dramatic changes in gene expression and physiology.These results provide the tantalizing possibility that different diets are not "healthy" or "unhealthy" but that specific quantities of certain foods may be optimal under different conditions and for promoting different physiological outcomes."It's just as true that a small amount of a 'healthy' food in an otherwise unhealthy diet could elicit a beneficial change in gene expression that could have profound physiological effects," Walhout said.