Resetting the circadian clock: Shift workers might want to skip high-iron foods

http://www.eurekalert.org/pub_releases/2014-10/uouh-rtc102114.php

PUBLIC RELEASE DATE:
21-Oct-2014

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Contact: Phil Sahm
phil.sahm@hsc.utah.edu
801-581-2517
University of Utah Health Sciences
@UofUHealthCare
Resetting the circadian clock: Shift workers might want to skip high-iron foods
Researchers identify role of iron in liver's regulation of blood glucose levels

(SALT LAKE CITY)—Workers punching in for the graveyard shift may be better off not eating high-iron foods at night so they don't disrupt the circadian clock in their livers.

Disrupted circadian clocks, researchers believe, are the reason that shift workers experience higher incidences of type 2 diabetes, obesity and cancer. The body's primary circadian clock, which regulates sleep and eating, is in the brain. But other body tissues also have circadian clocks, including the liver, which regulates blood glucose levels.

In a new study in Diabetes online, University of Utah researchers show that dietary iron plays an important role in the circadian clock of the liver. Judith A. Simcox, Ph.D., a University of Utah postdoctoral fellow in biochemistry, is the study's lead author.

"Iron is like the dial that sets the timing of the clock," Simcox says. "Discovering a factor, such as iron, that sets the circadian rhythm of the liver may have broad implications for people who do shift work."

Each of the body's circadian clocks operates on its own schedule to perform its necessary functions. The circadian clock in the brain, for example, is set by light, telling people to wake up in the morning and sleep when it's dark. Ideally all the body's clocks would work on their correct schedules. But, as anyone who has ever been on a graveyard or swing shift knows, working off-hours can cause one's circadian clocks to get out of synch and disrupt sleeping and eating patterns.

Numerous studies have found that shift workers experience higher incidences of obesity, diabetes and other metabolic disorders. The risk for cardiovascular disease, stroke and cancer also is higher among those workers. In 2007, a World Health Organization subcommittee declared that shift work is probably carcinogenic.

The liver's circadian clock is set by food intake. As people sleep this clock helps maintain a constant blood glucose level, but then causes it to spike just before they wake up. When the clock in the liver gets out of synch with the one in the brain, it may contribute to metabolic diseases, according to Donald A. McClain, M.D., Ph.D., University of Utah professor of medicine (endocrinology) and biochemistry and senior author on the study.