The research – of almost 100,000 Danish people over 40 years – showed that people in Northern Europe were only receiving a fraction of their Vitamin D from the winter sun.
Researchers at Copenhagen University Hospital said, although additional Vitamin D is proven to be beneficial from cold months October to March, it is not yet known which way is best to produce or administer it.
Prof Børge Nordestgaard, Chief Physician at Copenhagen University Hospital, said: “Our study shows that low vitamin D levels do result in higher mortality rates, but the best way of increasing vitamin D levels in the population remains unclear.
“We still need to establish the amount of vitamin D to be added, as well as how and when it is most effective: Should we get vitamin D from the sun, through our diet or as vitamin supplements?
“And should it be added in the foetal stage via the mother, during childhood or when we have reached adulthood?”
Those low in the vitamin are advised to eat Vitamin D-packed foods such as omega-3 rich fish, milk and eggs and potentially take supplements that are available from chemists or with a doctor's prescription for higher doses.