Drinking milk may lower the risk of suffering cardiac arrest, according to researchers.
They found people with the lowest blood calcium levels are twice as likely to have their heart suddenly stop working.
Raising such levels by drinking more milk or snacking on cheese offers protection, scientists at Cedars-Sinai Heart Institute in Los Angeles believe.
Cardiac arrests, which are often confused by the public with heart attacks, are fatal in more than 90 per cent of cases.
It occurs when the heart suddenly stops pumping blood around the body – if it is not restarted with defibrillator the patient will die within minutes.
It is far more serious, for example, than a heart attack, in which a blood clot cuts the oxygen supply to the heart but patients often survive.
Figures suggest that 100,000 lives are lost in Britain each year from cardiac arrests. The number is almost four times higher in the US.
How was the study carried out?
The new study, which was based on blood calcium measurements from 712 patients, was published in the journal Mayo Clinic Proceedings.
Those with blood calcium levels in the lowest quartile had twice the odds of sudden cardiac arrest compared to those in the highest quartile.
The findings kept true even after accounting for risk factors of heart disease, often a cause of cardiac arrest, and medication usage.
What did the researchers say?
Lead author Dr Sumeet Chugh said: ‘Our study found that serum calcium levels were lower in individuals who had a sudden cardiac arrest than in a control group.’
Dr Hirad Yarmohammadi, who was involved in the study, said the findings are a ‘step towards’ discovering less-established risk factors.
Patients in the lowest quartile had calcium levels of less than 8.95 milligrams per decilitre, which is just within the normal range of 8.5-10.2mg.
Researchers said that more investigations are needed to determine why lower blood calcium levels are linked to cardiac arrest.
Cardiac arrest guidelines
Their findings come after experts warned in June that airplanes need to carry more medical equipment in case someone on board has a cardiac arrest mid-flight.
Defibrillators and ECGs should be made available on all journeys in case of such an emergency, draft guidelines by the German Society for Aerospace Medicine stated.
And data last month suggested that triathlon competitors may be more likely to die suddenly and suffer a fatal trauma or cardiac arrest than previously thought.
A study of more than nine million participants found cardiac arrests struck 1.74 out of every 100,000 competitors – almost double that of marathon runners.