March 1, 2012 — Increased intake of vitamin D may significantly reduce the risk for Crohn’s disease (CD) in women, according to an article published online December 12 and in the March issue of Gastroenterology.
Investigators led by Ashwin Ananthakrishnan, MD, from the Division of Gastroenterology, Massachusetts General Hospital in Boston, found that vitamin D–sufficient women were 62% less likely to be diagnosed with CD during a 22-year period compared with those deemed deficient. The direct relationship between vitamin D ingestion and reduction in CD risk was not affected by smoking status or contraceptive use.
“Our results strengthen the rationale for considering vitamin D supplementation both for treatment of active CD or prevention of disease flares,” the authors write, suggesting that routine screening of vitamin D status may be indicated for people with a genetic predisposition for the disease.
“The recommendations seem reasonable,” Edward V. Loftus Jr, MD, professor of medicine at Mayo clinic in Rochester, Minnesota, told Medscape Medical News, noting that the findings on this “hot topic” are “very provocative.”
“Many patients are worried about medication safety, so any vitamin that might either reduce the risk of Crohn’s or might decrease relapse rates is going to be well received by patients,” Dr. Loftus added.
Higher Predicted Vitamin D Status Linked to Reduction in CD Risk
To examine the association between vitamin D status and CD, investigators examined data for 72,719 women (median age, 53 years; range, 40 – 73 years) enrolled in the prospective Nurses’ Health Study who had completed an assessment of diet and lifestyle in 1986.
Predicted 25(OH)D status was estimated using a multivariate model based on many factors such as dietary and supplemental vitamin D intake, body mass index, physical activity, race, sunlight exposure, and ultraviolet radiation exposure. The model was previously validated using direct plasma measurements from 542 men in the Health Professionals Follow-up Study.
During a follow-up period of 22 years (1,492,811 person-years), 122 women were diagnosed with CD at a median age of 64.0 years (range, 48 – 80 years) and a “median interval between assessment of predicted plasma 25(OH)D level and disease diagnosis” of 10 years.
An analysis of the data based on predefined plasma 25(OH)D levels showed that vitamin D–sufficient women (levels ≥ 30 ng/mL) were 62% less likely to be diagnosed with CD during the 22-year interval than those with deficient vitamin D levels (<20 ng/mL; hazard ratio [HR], 0.38; 95% confidence interval [CI], 0.15 - 0.97; P trend = .048).
After adjusting for risk factors such as smoking status and contraceptive/hormone use, investigators found that women in the highest 2 quartiles of predicted plasma 25(OH)D level had a significantly decreased risk for CD compared with those in the lowest quartile (multivariate HR, 0.50 [95% CI, 0.28 – 0.90] and 0.55 [95% CI, 0.30 – 1.00], respectively; P trend = .02).
Each 1 ng/mL increase in plasma 25(OH)D level was associated with a 6% relative reduction in CD risk (multivariate HR, 0.94; 95% CI, 0.89 – 0.99; P = .03) that was not affected by smoking status or contraceptive use.
Although higher intake of dietary vitamin D/supplements was linked to a decrease in CD risk, the trend did not achieve significance because of the small number of cases in this stratum (800 IU/day vs 150 IU/day; multivariate HR, 0.15; 95% CI, 0.02 – 1.12; P trend = .099).
Other study limitations include use of self-reported questionnaire data and the fact that 597 potential cases could not be evaluated either because the patients denied permission to review records or the records were unavailable.
However, the biggest drawback may be the use of estimated, rather than directly measured, plasma 25(OH)D levels, Dr. Loftus told Medscape Medical News.
“The biggest question for me is that we don’t have actual plasma 25(OH)D levels in these women. The level was predicted or imputed based on a multivariate model that was developed in men and validated in men,” Dr. Loftus emphasized, adding that to his knowledge, the model has not been validated in women.
The study was supported by a Research Scholars Award of the American Gastroenterological Association, the IBD Working Group, the Broad Medical Research Program of the Broad Foundation, and the National Institutes of Health. One author has been a consultant for Procter and Gamble, Shire Pharmaceuticals, and CytokinePharma, and receives research support from Procter and Gamble and Warner Chilcott. One author is a consultant for Policy Analysis Inc, and another author has served as a consultant for Bayer HealthCare and Millennium Pharmaceuticals. The remaining authors have disclosed no relevant financial relationships.
Gastroenterology. 2012;142:482-489. Abstract