Your trusted source

Workers punching in for the graveyard shift should avoid steak and spinach, as new research shows eating foods high in iron disrupts the body clock, the Daily Mail reports.

The body's circadian clocks regulate sleeping, waking and digesting food over a 24 hour period.

These cycles activate processes in all the cells in the human body, affecting the release of hormones controlling metabolism and other functions.

The brain is the body's 'master' circadian clock, ensuring all the other body clocks are in sync.

It is set by light, telling us to wake up in the morning and sleep when it's dark.

Night shifts disrupt this natural cycle, and it is known that people who work these have a higher risk of type 2 diabetes, obesity and cancer.

Researchers have now discovered that eating iron-rich foods disrupts the circadian clock in the liver, which helps maintain constant blood sugar levels to give body cells enough energy.

Normally the liver's circadian clock maintains a constant blood sugar level when a person is asleep. The level then spikes just before they wake up.

Iron acts like a cog in the liver's circadian clock, prompting the liver to go into overdrive, strictly controlling blood sugar levels, preventing the spike.

This would be healthy when it occurs in the liver's natural clock cycle.

But if it happens at a time that is out of sync, such as during a night shift, it could result in abnormal blood sugar levels.

For night shift workers, the circadian clock of the liver is already out of sync with the brain's circadian clock, and eating iron could exacerbate that lack of synchronisation.

This could lead to diseases like obesity, diabetes, and stroke, the researchers said.

As part of the study researchers fed iron to mice as part of their natural eating cycle.

They found that iron in the diet increases the concentration of heme, an oxygen-carrying compound found in haemoglobin, in cells.

When heme binds to a circadian protein, the protein's activity increases.

This causes the liver to increase its activity of controlling blood sugar levels.

Therefore, eating iron-rich foods caused the liver to increase its activity in regulating blood sugar.

This interferes with the normal fluctuations associated with a healthy metabolic system and leads to diseases like obesity, cancer, diabetes and stroke.

The study's lead author Judith Simcox, a postdoctoral fellow at the University of Utah said: 'Iron is like the dial that sets the timing of the clock.

'Discovering a factor, such as iron, that sets the circadian rhythm of the liver may have broad implications for people who do shift work.'

Another of the study's authors Professor Donald McClain, also of the University of Utah, added: 'When a shift worker eats foods high in iron at night it could exacerbate the lack of synchronsation between the clock in the liver and the main one in the brain.

'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.'