New research shows that neither intake of vitamin D nor circulating levels of 25(OH)D are associated with increased risk of islet autoimmunity (IA) or the development of Type 1 diabetes in young children. The findings appear to be at odds with earlier research, which contradicted the conclusions of the study. The study was published in the journal Diabetologia.
The study involved 198 children who had developed islet autoimmunity among an original group of 2,644 children in the U.S. Researchers regularly measured both vitamin D intake and 25(OH)D levels in the children. 128 of the children had been diagnosed with plasma 25(OH)D levels in a check-up at nine months of age.
Neither vitamin D intake nor 25(OH)D levels were shown to be associated with an increased risk of islet autoimmunity, even after adjusting for confounding factors such as Type 1 diabetes, DQB1*0302 genotype, ethnicity, and HLA-DR3/4.
Researchers measured the antibodies present in the children at the ages of nine, 15, and 24 months. They measured vitamin D intake through parent questionnaires that inquired about the frequency of eating certain foods until the children were nine years old; at 10, the researchers obtained the information from the children directly.
The research team acknowledged that the findings of the study were “somewhat contradictory” to previous research on the subject, which suggested that supplementing the diet of infants with vitamin D could offer a protective effect against Type 1 diabetes.
“Our study, which uses a powerful combination of prospectively collected reports of vitamin D intake and a biomarker of vitamin D status, does not support an association between a child’s usual vitamin D intake or 25(OH)D levels… and the risk of IA (islet autoimmunity) or progression to type I diabetes,” said the research team.
They noted that they still needed to test the actual effects of vitamin D supplements during infancy — whether low intake of vitamin D was harmful or very high intake was beneficial.
Earlier this year, Anastassios Pittas, M.D., with Tufts Medical Center in Boston, presented research findings at the annual meeting of the American Diabetes Association suggesting that higher levels of vitamin D in the blood were associated with a reduced risk of developing Type 2 diabetes. However, the study does not prove a cause-effect relationship, simply a correlation. Though the findings are not enough to provide a direct causal relationship, Dr. Pittas stated that if the findings were confirmed, “…there are huge implications because vitamin D is easy and inexpensive.”
Similarly, a study presented in 2010 at the annual meeting of the Endocrine Society by Dr. Esther Krug, M.D., appeared to show that vitamin D deficiency could be a risk factor for glucose intolerance and that such deficiencies are commonly noted in people with poor diabetes control. Again, the study did not prove a cause and effect relationship between vitamin D levels and diabetes, but it suggested a correlation. As vitamin D deficiencies became more pronounced in the study participants, their diabetes control worsened.
Vitamin D is naturally present in very few foods. Some foods are fortified with vitamin D while many people take dietary supplements. It is also produced when sunlight hits the skin, which begins the vitamin D synthesis process. Vitamin D is important for calcium absorption; it is necessary for bone growth and bone remodeling, and without the vitamin, bones can become weak and brittle. Vitamin D thus helps older adults prevent osteoporosis in addition to its many roles throughout the body.
