More evidence of Vitamin D's cancer-inhibiting properties has surfaced, this time with respect to lung cancer.

A new study by U.S. researchers finds that the closer people live to the equator, the less their chance of developing lung cancer. Those living in colder climes have slightly higher risks of developing lung cancer, the study found.

Previous studies have linked increased levels of Vitamin D with a reduction in the development of malignant tumours, particularly breast cancer. Ultraviolet radiation from the sun causes the body to produce vitamin D.

The findings are available online and are to be published in the January 2008 issue of the Journal of Epidemiology and Community Health.

Researchers at the University of California in San Diego investigated the incidence rates of lung cancer in 111 countries and correlated these findings with the countries' latitudes. Factors taken into consideration included the level of cloud cover and aerosol emissions, and the populations' smoking rates.

Smoking accounted for 85 per cent of all cases of lung cancer, the study found. High cloud density and elevated levels of aerosol emissions — factors that reduce how much UVB light can get through — were associated with higher rates of the disease in both men and women.

The results of the study, though suggesting more sunlight is beneficial to people who want to prevent lung cancer, should be interpreted with caution, according to the Canadian Cancer Society. It suggests people obtain a few minutes a day of sunlight to get the maximum benefit but avoid excessive sunning due to the increased risk of skin cancer.

The society suggests Canadians take 1,000 international units of Vitamin D each day in winter.