Leukemia rates are two times higher in people living at higher latitudes who are exposed to lower levels of sunlight and are more likely to be vitamin D deficient, according to the results of a recent study published in PLOS One.
Researchers analyzed age-adjusted incidence rates of leukemia in 172 countries and cloud cover data and found the highest leukemia rates in countries closer to the North and South Pole, such as Australia, New Zealand, Chile, Ireland, Canada, and the United States. The lowest rates were in countries closer to the equator, such as Bolivia, Samoa, Madagascar, and Nigeria.
According to the study authors, the body uses vitamin D to tightly bind cells together, causing increased contact inhibition of cancer, and control mitosis, which may help to prevent the uncontrolled proliferation of white blood cells that is characteristic of leukemia. Levels of the hormone can be increased by consuming foods high in vitamin D (e.g., fish, fortified dairy, eggs, mushrooms), supplements, or increased ultraviolet B exposure.
The study validates the researchers’ other findings of an association of lower vitamin D levels and increased incidence of breast, colon, pancreas, and bladder cancers and multiple myeloma. It also correlates with findings from the Harvard Health Professionals Follow-Up Study, where a 25 nmol/L increase in modeled 25-hydroxyvitamin D, the primary metabolite of vitamin D, was associated with a 66% decrease in risk of leukemia. However, the authors cautioned that additional studies are needed to provide final evidence.