The consensus view is that there is no substitute for a healthy diet and regular exercise, but a growing body of evidence suggests that vitamin D supplements may protect against a wide range of auto-immune diseases including type-1 diabetes.

A systematic review published in the March 13, 2008 issue of Archives of Disease in Childhood examined data from five observational studies—four case-control and one cohort. Data were available for 6455 infants—1429 infants with type-1 diabetes and 5026 controls. There were no randomized controlled trials in the literature, so the authors’ conclusions were based on the five observational studies.

Meta-analysis showed that the risk of type-1 diabetes was significantly reduced in infants who were supplemented with vitamin D compared to those who were not supplemented. There was some evidence of a dose-response effect, with those using higher amounts of vitamin D at lower risk of developing type-1 diabetes. Lastly, there was a suggestion that the timing of supplementation might also be significant for the development of type-1 diabetes.

What is the incidence of type-1 diabetes?
Type-1 diabetes occurs when the islet cells in the pancreas are unable to produce insulin. The disease is most common among people of European descent, suggesting a strong genetic component. According to study authors, Christo Zipitis and Anthony Akobeng, the incidence of type-1 diabetes is increasing at an annual rate of 3 percent. It is estimated that the number of new cases will rise 40 percent between 2000 and 2010.

They also noted that timing of the supplementation could also be a factor in the type-1 diabetes risk, with supplementation of vitamin D-rich cod liver oil between the ages of seven and 12 months at a 45 per cent lower risk, compared to infants supplemented between 0 and six months of age.

Despite the promising results, Zipitis and Akobeng cautioned that, “Adequately powered, randomized controlled trials with long periods of follow-up are needed to establish causality and the best formulation, dose, duration, and period of supplementation.”

The mechanism by which vitamin D supplementation may protect against the development of type-1 diabetes is unclear. Evidence suggests that vitamin D may play a role in the immune system. There is also evidence that vitamin D may protect beta-cells (pancreatic cells) and prevent damage caused by cytokines (a class of proteins).

Omega-3 fatty acids show similar results
Researchers from the University of Colorado at Denver reported that an increased intake of omega-3 fatty acids from marine sources may reduce a child’s risk of developing type-1 diabetes by as much as 55 percent.

Published in the September 26, 2007 issue of the Journal of the American Medical Association, Norris and colleagues looked at 1770 children at high risk for developing type-1 diabetes. The authors found that eating a diet rich in omega-3 fats was associated with a lower incidence of autoantibodies in the blood that signal the immune system to attack insulin-producing cells in the pancreas.

Omega-3 fatty acids are known to have anti-inflammatory properties, and inflammation is believed to play a major role in the development of type-1 diabetes through destruction of insulin-producing cells.

“The thinking is that omega-3 may increase the body’s ability to fight the inflammation that leads to type 1 diabetes,” said lead researcher Jill M. Norris.

Norris added, “While the findings are intriguing, they do not prove omega-3-rich foods protect against type-1 diabetes.”

Omega-3 and type-1 diabetes
A 2003 study from Norway was one of the first human trials to suggest a protective role for omega-3 fatty acids in type-1 diabetes. Researchers reported a lower incidence of omega-3-rich cod liver oil supplementation during infancy in children with diabetes, compared to children without the disease.

The Denver, Colorado study included 1,770 children newborn to 3 years of age. The children either had a parent or sibling with type-1 diabetes or had genetic tests that showed increased risk for developing the disease. The children were followed on average 6 years.

Intake of omega-3 fatty acids was determined through annual food-frequency questionnaires. Red blood cells from 244 children in the study were also tested for fatty acid composition to confirm the questionnaire findings.

Parents were asked how often their children ate canned tuna and oily fish such as salmon or mackerel. They were also asked about home cooking oil. Oily fish like salmon, sardines, and mackerel are among the best food sources of omega-3s, but dark green vegetables, canola oil, sunflower oil, and flaxseed oil are also good sources. Increasingly, eggs, breads, juices, and other foods are being fortified with omega-3s.

The research confirmed that children who reportedly had higher intakes of omega-3 fatty acids also had less evidence of the autoantibodies associated with progression to type-1 diabetes.

More omega-3 research is planned
An interventional trial funded by the National Institutes of Health should offer more clues about the association between diet and type-1 diabetes, including the role of omega-3 fatty acids.

The trial is designed to investigate whether babies with at high risk for developing type-1 diabetes show fewer signs of inflammation when given supplements of omega-3 fatty acid, docosahexaenoic acid (DHA), from infancy.

An expanded version of the trial will determine whether DHA protects infants and children from the development of the autoantibodies that lead to diabetes. If researchers find a direct link between DHA supplementation and a reduction in the inflammatory activity that leads to diabetes, omega-3 supplementation could become a major strategy for preventing the disease.

Michael Clare-Salzler, MD, professor of pathology, immunology, and laboratory medicine, University of Florida College of Medicine at Gainesville will lead the study. He told WebMD that many questions must be answered before this happens.

“If supplementation does work, the timing may be critical,” he says. “That is what this trial is all about. We want to test this hypothesis that if we get to babies early with anti-inflammatory therapy we can block the development of these autoantibodies.”