Study: Digestion linked to time of day

Recent research from Penn's School of Medicine indicates that there is a genetic basis for the belief that the time of day when we eat food could be as important as the type of food we eat.

According to scientists, the body operates a master "molecular clock" located in the brain. The recent study has linked the clock to most tissues in and functions of the body, including those related to metabolism.

A team of researchers led by Garret FitzGerald, chairman of Penn's Department of Pharmacology, discovered the molecular clock in the heart and blood vessels, and studied how the brain controls this clock through a hormone.

"The molecular clock may directly or indirectly act to regulate genes involved in these peripheral functions," said lead author Dan Rudic, a research associate in Pharmacology.

Many metabolic genes, which regulate digestion functions, were found among the approximately 10 percent of genes with activity levels that vary over a 24-hour period.

Nutritionists have speculated that the amount of calories ingested at once may impact human metabolism, but now they are revising theories to include the timing of food intake, as well.

"The molecular clock has a profound effect in the regulation of metabolism, both fat and sugar breakdown," Rudic wrote in an e-mail interview. "Mice that have a disrupted molecular clock are impaired in their ability to control metabolism."

"Our data suggests that the timing of metabolism is tightly regulated," Rudic said. "Thus, if the time we eat is not properly coordinated with the timing of metabolism, this may impact our levels of circulating fat and sugar in our bloodstream, which could impact the development of metabolic disorders such as diabetes."

The exact effect of this gene is still unclear, but the researchers believe that the clock operates to mediate the impact of a high-fat diet.

"This suggests that altering when fat calories are eaten might be exploited to reduce the likelihood of inducing diabetes," FitzGerald said in a recent press release.

"Remember, it may not be just what you eat and how much you eat, but also when you eat it," he added in the e-mail.

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