Vitamin D could lower the risk of asthma in children by up to 40 per cent, according to a new report.
Researchers say that lack of vitamin D could be involved in the increase in asthma and allergies. They believe the increase in the two conditions has come at the same time as a decline in exposure to the sun, the main source of vitamin D.
The theory is that as people have become more prosperous over the past 50 years, more time is spent indoors - travelling in cars rather than walking, for example - which has resulted in less exposure to sunlight.
"Coupled with inadequate intake from foods and supplements, this then leads to vitamin D deficiency, particularly in pregnant women, resulting in more asthma and allergy in their offspring," say the researchers from Harvard University.
"Our studies show that higher vitamin D intake by pregnant mothers reduces asthma risk by as much as 40 per cent in children aged three to five."
They suggest that low levels of vitamin D may affect the development of foetal lungs and immune system, leading to a higher risk of asthma and allergies.
The researchers say the theory explains the geographic pattern for cases of asthma and allergies, with a higher prevalence in Westernised nations, and in areas further away from the equator.
They add: "We believe these patterns can be explained by a decrease in exposure to the sun and the limited sources of vitamin D in the diet to compensate for this decrease in sun exposure, leading to vitamin D deficiency.
"Providing adequate vitamin D supplementation in pregnancy may lead to significant decreases in asthma incidence in young children."
Source - Daily Mail