Southerners May Be Less Likely to Have Crohn's
Study Shows Women Who Live in South Are Less Likely to Have Crohn's Disease and Ulcerative Colitis
Impact of Moving From North to South
Fewer than 10% of nurses moved from one area of the country to another during the 20 years they were followed. Moving from the North to the South was associated with a 35% lower risk of ulcerative colitis and a 50% lower risk of Crohn's disease. There weren't enough women who moved from the South to the North to assess its impact on inflammatory bowel disease.
The study does not show cause and effect. Future research will be aimed at separating out the protective effects of vitamin D from those of ultraviolet light, Khalili says.
In the studies, women in the Nurses' Health Study I and II filled out questionnaires every two years that asked whether they had ulcerative colitis or Crohn's disease. If they said yes, the diagnosis was confirmed by a review of their medical records.
The women were asked where they lived when they were born, and at age 15 and age 30. U.S. regions below 37 degrees latitude were considered southern -- places like Southern California, Florida, and Arizona, according to Khalili. Areas above 42 degrees latitude were considered northern: Massachusetts and Rhode Island, for example.
At age 30, 61,923 of the nurses lived at northern latitudes, 84,286 lived at middle latitudes, and 29,703 lived at southern latitudes.
Sunanda Kane, MD, a gastroenterologist the Mayo Clinic in Rochester, Minn., says there's no reason to think the findings wouldn't apply to men, too. Kane reviewed the findings for WebMD.
Vitamin D Supplements and Crohn's Disease
Brian Bosworth, MD, of Weill Cornell Medical Center in New York City, reported results on the first 20 people in an ongoing study looking at the effects of vitamin D supplementation on Crohn's disease. All had vitamin D deficiency, defined as blood levels less than 30 nanograms per milliliter (ng/ml) of blood.
They took either 1,000 International Units (IU) or 10,000 IU of vitamin D3 daily.
After six months, average vitamin D blood levels were about 74 mg/ml in the high-dose group, compared with 32 ng/ml in lower-dose group. Levels above 30 are considered normal.