They found that 37.5% of the women were deficient in vitamin D and 38.5% had levels considered insufficient.
Ten years after their diagnosis, 83% of those who had adequate vitamin D levels were still alive, compared with 79% of those with insufficient levels and 69% of those who were deficient.
None of the patients were given vitamin D supplements.
Worldwide, approximately 1,150,000 women develop breast cancer each year and 410,000 die from it.
Epidemiologist Frank C. Garland, of the Moores Cancer Center at UC San Diego, and his colleagues used data that recently became available from an international database of cancer incidence, called Globocan, developed by the World Health Organization's International Agency for Research on Cancer.
They plotted countrywide incidence of breast cancer for each country against that country's latitude.
Controlling for known variables such as meat, vegetable and alcohol intake, cigarette consumption, weight and fertility, they found that breast cancer incidence rose with increasing distance from the equator -- and thus with decreasing exposure to sunlight.
Incidence rates were about 30 cases per 100,000 at the equator and reached 90 to 100 per 100,000 at latitudes that encompassed New Zealand, Uruguay, France, Iceland and the United States.
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thomas.maugh@latimes.com
