A large-scale study has found the so-called "sunshine vitamin" Vitamin D may help arm the immune system against colds and flu.
US researchers found that people with the lowest vitamin D levels reported having significantly more recent colds or cases of the flu.
The finding casts new light on the tendency of people in northern climates to develop colds and flu during the winter – as vitamin D generation in the body depends on sun-light.
The risks were even higher for those with chronic respiratory disorders, such as asthma or emphysema.
The study analysed data from the Third National Health and Nutrition Examination Survey (NHANES III), conducted by the National Center for Health Statistics.
Researchers studied Vitamin D blood levels from almost 19,000 adult and adolescent participants for the research, reported in the Archives of Internal Medicine.
They found that those with the lowest levels were about 40 per cent more likely to report a cold.
Researcher Dr Adit Ginde from the University of Colorado Denver said the findings showed the important role for Vitamin D in the prevention of common respiratory infections.
"Individuals with common lung diseases, such as asthma or emphysema, may be particularly susceptible to respiratory infections from vitamin D deficiency."
The researchers add: "Circumstantial evidence has implicated the wintertime deficiency of vitamin D, which the body produces in response to sunlight, in the seasonal increase in colds and flu."
But the authors stressed that the study results needed to be confirmed in clinical trials before the vitamin could be recommended to prevent colds and flus.
Arch Intern Med. 2009; 169(4):384-390
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