Usually, we think of food as fuel—a source of calories and nutrients that have obvious effects on our health if we overindulge or are malnourished. Now, researchers at the University of Massachusetts Medical School have found in a laboratory study that the precise composition of a diet can have profound health effects, suggesting that exactly what’s in each mouthful may matter more than anyone anticipated.
The findings, reported in two studies in Cell on Thursday, point to the existence of a still-unidentified substance, such as a hormone, that alters the health of microscopic roundworms dramatically. Worms given a diet spiked with even a little bit of a particular soil-dwelling bacteria matured more quickly, had fewer offspring, and died earlier than worms on a standard laboratory diet.
“If it’s really true you can have these massive effects on your well-being or disease by having even small amounts of a certain diet, that’s crazy, really,” said A.J. Marian Walhout, co-director of the systems biology program at UMass Medical School who led the work. “Of course, we don’t know if in a largely healthy diet a little bit of chocolate cake is going to kill you, or if a little bit of broccoli means you’ll be fine.”
Walhout and her colleagues stumbled on the research question by chance, after noticing a strange disparity in roundworms whose guts had been genetically tweaked to glow when a region of DNA was activated by their diet. To the scientists’ surprise, worms served different foods responded differently. The standard laboratory diet, a strain of the bacteria E. coli, caused the worms’ guts to glow green. A diet of a soil-dwelling bacteria left them dim. At first, Walhout thought that might mean that the soil-dwelling bacteria were just a food that the worms processed less efficiently.
“Maybe it’s lettuce; it has few calories. If you mix a little bit of lettuce with hamburger you should override this,” Walhout said.
So she and her team tried adding a tiny amount of the soil-dwelling Comamonas bacteria to the lab diet. After all, if you mixed lettuce and hamburger, the hamburger should compensate for the low-calorie lettuce. But it was as if the Comamonas bacteria, even in minuscule amounts, contained a chemical compound that flipped a switch—altering something deep about the roundworms’ digestion. Their guts did not glow green.
What’s more, the researchers found the two different bacteria had large effects on the worms’ health. The worms fed the laboratory diet laid well over 200 eggs, whereas the ones on the Comamonas bacteria had only 150 offspring. They not only had fewer young, they died much sooner.
Although they are far from humans, the roundworms, called C. elegans, are frequently used in biology research to explore ancient biological processes that are shared by more complex organisms. Walhout hopes to identify the constituent of the diet that can so radically change the worms’ health. Then, researchers can begin to see whether the compound has effects on mammalian cells, too.
They also hope that the worm can be a good test subject for screening the effects of diet on a range of genes that are involved in health, perhaps using them to study rare metabolic diseases in people.