In the September 2001 issue of InFocus, there was a report of a study showing that megadoses of vitamin D may slow the progress of multiple sclerosis (MS). Now comes word of a study to assess the relationship between vitamin D intake in women and the risk of developing MS.

      In this newly reported study, researchers from Harvard School of Public Health selected more than 185,000 women from the Nurses Health Study and Nurses Health Study II based at Brigham and Women Hospital. All were free of MS. The participants completed dietary questionnaires every four years between 1980 and 1999 that assessed their vitamin D intake along with other dietary information.

      During the span of the Harvard study, 173 women developed MS. When compared to women who did not use vitamin supplements, those with the highest levels of vitamin D intake through supplements (400 IU per day or more) had a reduced risk of 40 percent of developing MS. There was no reduction in risk associated with vitamin D intake through food alone.

      Kassandra Munger, lead author of the study and a researcher in the Department of Nutrition at the Harvard School of Public Health, commented that it has been suspected that vitamin D may play a role in reducing the risk of developing MS. Since the main source of vitamin D intake among the women in this Harvard study was multivitamins, it may be difficult to isolate the effects of vitamin D use from other vitamins. "However," states Dr. Munger, "none of the other vitamins was itself significantly associated with risk of MS after adjusting for total vitamin D intake or vitamin D from supplements." She points out that more research is needed.

      Another article, entitled "Maternal Vitamin D Intake in Food Decreases Risk of Autoimmune Diabetes in Offspring," reported results of a study carried out in Denver. Dr. Jill M. Norris and colleagues from the University of Colorado Health Sciences Center examined whether an association exists between maternal dietary intake of vitamin D, omega-3 fatty acids, and omega-6 fatty acids during pregnancy and the appearance of islet autoimmunity in offspring. They asked 233 mothers of children newly recruited to the Diabetes Autoimmunity Study in the Young (DAISY) to recall their food and nutritional supplement intake during pregnancy using the Willett food frequency questionnaire.

      The researchers followed the children for a mean of four years for the appearance of insulin, gestational diabetes mellitus, and IA-2 autoantibodies. Sixteen subjects developed at least one autoantibody during follow-up. The group of mothers with affected children had an average daily vitamin D intake in food of 167.6 IU while the group with unaffected children had an average intake of 252.3 IU.

      Analysis showed that maternal intake of vitamin D through food was significantly associated with a decreased risk of the appearance of islet autoimmunity in offspring. The authors write, "Interestingly, we did not find an association between vitamin D intake via supplements and islet autoimmunity, which is similar to observations in another epidemiological study." They comment that the reasoning is not clear, but the results could be due to different bioavailability or the presence of an unidentified nutrient in vitamin D-containing foods.

--Excerpted from "High Intake of Vitamin D Linked to Reduced Risk of Multiple Sclerosis," InteliHealth, Jan. 12, 2004; and Diabetes Care, 2003 (from Medscape)