Medically reviewed by Cynthia Haines, MD
Scientists are learning more about the connection between diabetes and vitamin D. Find out why vitamin D deficiency may be a risk factor for type 1 diabetes.
Numerous studies have found an association between low levels of vitamin D and increased risk for type 1 diabetes, but researchers are still exploring whether low vitamin D is actually a cause of the disease.
A recent study published in the American Journal of Epidemiologyfound that young adults who have sufficient levels of vitamin D may lower their risk for developing type 1 diabetes later in life by as much as 50 percent. Though the results are still preliminary, the study offers the strongest evidence to date that vitamin D might protect against type 1 diabetes.
The study compared vitamin D levels in 310 active members of the U.S. military who had been diagnosed with type 1 diabetes to levels in a second group of healthy controls from the same population. The researchers determined the individuals’ vitamin D status by testing frozen blood samples on file with the Department of Defense, which were taken before any of the participants were diagnosed with diabetes. "Among non-Hispanic white individuals, we found that having levels of vitamin D that were 75 nanomoles per liter (nmol/L) or greater was associated with a 50 percent reduced risk of developing type 1 diabetes," says lead author Kassandra Munger, ScD, a study research associate at Harvard School of Public Health in Boston.Researchers have also looked at whether vitamin D supplements early in life offer protection against diabetes at an older age. A review of five studies published in the journal Archives of Disease in Childhood found that infants who received vitamin D supplements were less likely to develop type 1 diabetes.
Explaining the Diabetes and Vitamin D Connection
While it has not been proved that a vitamin D deficiency can cause diabetes, there seems to be a correlation. Type 1 diabetes is an autoimmune disease in which your body’s own immune cells attack the pancreas, the organ where insulin is made, says Michal L. Melamed, MD, MHS, associate professor of medicine and epidemiology and population health at the Albert Einstein College of Medicine in the Bronx, N.Y. Vitamin D has immune-modulating properties, and low vitamin D levels have been associated withother autoimmune disease and allergies. "The thought is that vitamin D is needed for the immune system to function properly," says Dr. Melamed. "If the body lacks vitamin D, the immune system starts attacking the person’s own body."
Why It’s So Hard to Get Vitamin D
The recommended daily allowance of vitamin D for adults ages 19 to 70 is 600 international units (IU). People over 70 years old should take 800 IU. Sun exposure, food, and supplements are ways to get vitamin D. But vitamin D deficiency is common because only a few foods contain vitamin D and many people avoid sun exposure or don't get enough of it.
Body weight can also impact vitamin D levels. Obese individuals have lower circulating vitamin D levels than people of normal weight because vitamin D is sequestered in fat, says Maria Skamagas, MD, assistant professor in the division of endocrinology, diabetes, and bone disease at the Mount Sinai School of Medicine in New York.
Fatty fish such as salmon and tuna and eggs are among the foods with the highest amounts of naturally-occurring vitamin D, says Melissa Li-Ng, MD, an endocrinologist at the Cleveland Clinic. Fortified milk and fortified cereals contain moderate amounts of vitamin D – read labels to find the best choices.
Sun exposure is an excellent source of vitamin D, but it carries health risks too. Although light-skinned people can get approximately 10,000 IU in five to 30 minutes of exposure, many people take precautions to protect themselves from skin cancer by using sunscreen and covering up with clothing, Munger says. In winter months, especially in northern regions, the sun is not strong enough to allow for vitamin D production.
"Most people, especially during the winter months when sun exposure is minimal, need a vitamin D supplement," Melamed says. Before popping pills, ask your doctor to check your vitamin D levels using a simple blood test. Your doctor can use the results to determine if you should take supplements and recommend an appropriate dose.
