Fiber Reduces Crohn's Disease Risk in Woman

Fiber Cuts Crohn's Risk in Women

By Nancy Walsh, Staff Writer, MedPage Today

Published: May 23, 2012

Reviewed by Dori F. Zaleznik, MD; Associate Clinical Professor of Medicine, Harvard Medical School, Boston.

Action Points

• This study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.
• Women prospectively followed in the Nurses' Health Study I and II were found to have a lower risk of Crohn's disease if they consumed a diet high in fiber from vegetables and fruit, but not from cereals or whole grains.
• Note that high soluble or insoluble fiber intake was not found to influence the risk of ulcerative colitis.

SAN DIEGO -- High fiber intake was associated with a 38% reduction in risk of Crohn's disease in women, a researcher reported here.

Data from the Nurses' Health Study I and II showed the hazard ratio for Crohn's disease among women whose fiber intake was highest was 0.62 (95% CI 0.40 to 0.95) compared with those consuming the lowest amount of fiber, said Ashwin N. Ananthakrishnan, MBBS, of Massachusetts General Hospital in Boston.

Crohn's disease is believed to result from a combination of genetic and environmental factors, and some evidence suggests that dietary fiber may play a role, possibly through effects on the gut microflora, epithelial barrier function, and the prevention of bacterial translocation.

However, previous studies have been retrospective in design, included small numbers, and were subject to recall bias.

To prospectively investigate the effects of fiber on inflammatory bowel disease, Ananthakrishnan and colleagues analyzed data from 164,248 women in the Nurses' Health Study.

During 3,010,426 person-years of observation, there were 248 cases of Crohn's disease, for an incidence rate of 8 per 100,000 person-years, and 308 cases of ulcerative colitis, with an incidence rate of 10 per 100,000. Self-reports of these diagnoses were confirmed with a review of patients' medical records.

The median age of the Crohn's patients was 54, and the ulcerative colitis patients were 2 years younger.

Intake of various types of food was assessed every 2 years on a validated food frequency questionnaire. Patients in the lowest quintile of fiber intake averaged 11 grams per day, while those in the highest quintile consumed 25 grams per day.

The risk of Crohn's disease in the highest quintile was primarily lowered with consumption of soluble fiber:

• Fruit, HR 0.55 (95% CI 0.36 to 0.83)
• Vegetables, HR 0.72 (95% CI 0.48 to 1.06)
• Cruciform vegetables, HR 0.73 (95% CI 0.50 to 1.08)

The trend toward significance for cruciform vegetables suggested a role for the aryl hydrocarbon receptor in risk reduction, the researcher said.

In contrast, consumption of insoluble fiber did not decrease risk:

• Cereals, HR 0.89 (95% CI 0.58 to 1.35)
• Whole grains, HR 1.04 (95% CI 0.67 to 1.61)

There was no observed dose response among women in the medium quintiles of fiber intake, with the risks for the second and fourth quintile being quite similar.

"There may be a threshold effect," Ananthakrishnan said.

Unlike for Crohn's disease, increased fiber intake had no effect on risk for ulcerative colitis, with a hazard ratio of 0.88 (95% CI 0.60 to 1.28) in women with the highest level of consumption. Intake from the various specific sources of fiber also was not associated with a reduction in risk for ulcerative colitis.

Limitations of the study included its inclusion of mostly white women and their older age.

Further research is warranted to explore the biological mechanisms by which fiber influences the risk for Crohn's disease, Ananthakrishnan concluded.