Those on night shifts have higher rates of type 2 diabetes, obesity and cancer because of the disruptions to their body’s circadian clock.
The circadian clock in the brain, regulates sleep and eating but other body tissues also have circadian clocks.
The one in the liver regulated blood glucose levels.
Researchers at the University of Utah have found that iron in the diet plays and important role in the circadian clock of the liver.
“Iron is like the dial that sets the timing of the clock” says Judith Simcox of the university, the study’s lead author.
“Discovering a factor, such as iron, that sets the circadian rhythm of the liver may have broad implications for people who do shift work,” she adds.
Each of the body’s circadian clocks operates its own functions.
The one in the brain is set by light, telling people to wake in the morning and sleep when it’s dark.
Working shift hours can disturb these rhythms and disrupt sleeping and eating patterns.
Numerous studies have found that shift workers have higher rates of obesity, diabetes and other metabolic disorders.
Their risk of heart disease, stroke and cancer is also higher.
In 2007 a World Health Organisation subcommittee declared that shift work was probably carcinogenic.
In the case of the liver its circadian clock is set by food intake.
When people sleep the liver clock helps maintain a constant blood glucose level and then causes it to spike just before they wake up.
When this clock is out of synch with the one in the brain, scientists believe this disturbed pattern may contribute to metabolic disease.
The Utah study found that iron rich foods promote a healthy liver rhythm when linked to the natural clock cycle.
But a graveyard shift could result in abnormal blood glucose levels.
“When a shift worker eats foods high in iron at night it could exacerbate the lack of synchronization between the clock in the liver and the main one in the brain,” says Donald McClain, the University’s professor of medicine.
“By tending to flatten the circadian variation of metabolism, high iron in tissues may also interfere with the normal day to night fluctuations associated with a healthy metabolic system.”
More research is needed to see how the results of their study could affect dietary recommendations for everyone, and shift workers in particular.
The investigators are quick to point out that too little iron is also unhealthy. Ultimately, they hope their studies define an optimal range of iron that is much narrower than the current “normal” range.
The study is published in Diabetes online.