Researchers have found that the risk of Type 1 diabetes in children may be strongly associated with Vitamin D and exposure to sunshine.

Low incidence of type 1 diabetes was noted in people living in equatorial regions, while higher incidence was noted in populations at higher latitudes where sunlight was scarcer.

Photosynthesis of vitamin D3 is set in motion by ultraviolet exposure, while this form of vitamin D is also available through diet and supplements. "This is the first study, to our knowledge, to show that higher serum levels of vitamin D are associated with reduced incidence rates of type 1 diabetes worldwide," said Cedric F. Garland, Dr. P.H., professor of Family and Preventive Medicine in the UCSD School of Medicine, and a member of the Moores UCSD Cancer Center.

About 1.5 million Americans cope with type 12 diabetes every day, and type 1 diabetes ranks second only to asthma as the most chronic disease among children. Type 1 diabetes is diagnosed in some 15,000 Americans each year, and causes blindness and kidney failure in youth and middle age.

"This research suggests that childhood type 1 diabetes may be preventable with a modest intake of vitamin D3 (1000 IU/day) for children, ideally with 5 to 10 minutes of sunlight around noontime, when good weather allows," said Garland. "Infants less than a year old should not be given more than 400 IU per day without consulting a doctor. Hats and dark glasses are a good idea to wear when in the sun at any age, and can be used if the child will tolerate them."

Even after allowing for the fact that equatorial regions will have lower per capita healthcare expenditures than more developed countries, the association of UVB irradiance to incidence of type 1 diabetes remained strong. The researchers created a graph with a vertical axis for diabetes incidence rates, and a horizontal axis for latitude. The latitudes range from -60 for the southern hemisphere, to zero for the equator, to +70 for the northern hemisphere. They then plotted incidence rates for 51 regions according to latitude. The resulting chart was a parabolic curve that looks like a smile.

In the paper the researchers call for public health action to address widespread vitamin D inadequacy in U.S. children.

"This study presents strong epidemiological evidence to suggest that we may be able to prevent new cases of type 1 diabetes," said Garland. "By preventing this disease, we would prevent its many devastating consequences."

The study was published June 5, 2008 in the online version of the scientific journal Diabetologia.