Sunday, January 6, 2013

Fiber and Low Residue Diets


IBD and Fiber


The intake of fiber is one of the cornerstones of most IBD diets.  The vast majority recommend that those suffering from IBD consume low-fiber foods.  At the extreme, the low residue diet recommends the removal of just about all fiber.  What is fiber and what does the evidence say about its effect on IBD?

Fiber is the part of plants that is indigestible, and is often broken up into two categories – soluble fiber and insoluble fiber.  Soluble fiber is broken down in the digestive system (through fermentation) and is believed to have cholesterol lowering effects and other health benefits.  Insoluble fiber, primarily cellulose, is not broken down and adds bulk to fecal output and absorbs water in the intestines.  Examples of foods with high fiber content in each category are as follows (1):*

Soluble
Insoluble
Apples
Apple and Tomato Skins
Barley
Asparagus
Carrots
Brussel Sprouts
Oranges
Cabbage
Ripe Bananas
Cauliflower
Sweet Potatoes
Chick Peas
Tomatoes
Green beans
White Potatoes
Kidney Beans

Potato Skins

Spinach

Whole grains

Fiber, specifically soluble fiber, has been shown to reduce cholesterol and assist in the absorption of vitamins and minerals.  Additionally, it has been shown to help regulate sugar intake in diabetics.  Insoluble fiber can assist in weight loss (because it is not digested, it gives a “full” feeling without the calories).

A high fiber diet was originally touted as reducing the risk of colon cancer.  Initially, several smaller studies showed a very small reduction in risk, between 10 and 20%, but the relative risk error bars crossed 1.0 in most of them.  Recent studies have found no link between overall fiber consumption and colon cancer development.

Negatively, a high fiber diet can cause bloating and associated abdominal discomfort, largely due to the fermentation that occurs when it is processed in the intestines.  This discomfort is cited as aggravating already inflamed intestinal tissue, exacerbating Crohn’s or UC symptoms.  When tested, though, does it really have that effect?

Specific to IBD, the low residue diet is a frequent recommendation, and can be carried over as a long term nutrition plan.  That said, the evidence for doing so is extremely weak.  A prospective study comparing a low fiber, low residue** diet with a normal diet concluded:

There was no difference in outcome between the two groups, including symptoms, need for hospitalisation, need for surgery, new complications, nutritional status, or postoperative recurrence.(4)

It should be noted that the comparison was between a low fiber diet and a normal fiber diet.  The study draws no conclusions about the impact of a high fiber diet.  Unfortunately, a high fiber diet has been shown to have no great impact on the course of the disease or symptoms either (5).

Despite the lack of clinical evidence, it is especially common to recommend a low fiber diet in those with active inflammation and structuring.  While there is no evidence to support this to promote healing, it is frequently recommended by physicians to avoid the potential life threatening formation of an obstruction.  

The most common reason for obstruction in adults is the formation of a bolus of fiber, or a phytobezoar (big ball of plant material).  These form from insoluble fiber that isn’t digested, usually in patients with deceased stomach acid production (a study of patients taking acid reducing drugs with their IBD may be warranted…).  Because of structuring and inflammation, the risk and impact of phytobezoar formation should theoretically be much higher in active IBD, though more study is required to confirm this.

Bottom Line


·         Fiber, especially soluble fiber, should not be avoided and normal amounts are acceptable if tolerated.
·         Neither high fiber diets nor low residue diets have been shown to have a positive impact on those already diagnosed with IBD.
·         Insoluble fiber should be limited for individuals with low stomach acid production, structuring, and extensive inflammation.

* Most foods contain both soluble and insoluble fiber – the foods listed represent high content sources in the listed category.
** While used synonymously, low residue and low fiber diets are not the same.  Low residue diets exclude fiber, but also other higher residue foods (such as milk products).

1.       JW Anderson and SR Bridges.  Dietary fiber content of selected foods.  American Journal of Clinical Nutrition.  1988.
2.       Fuchs CS, Giovannucci EL, Colditz GA, et al. Dietary fiber and the risk of colorectal cancer and adenoma in women. New England Journal of Medicine, 1999.
3.       Simons CCJM et al. Bowel Movement and Constipation Frequencies and the Risk of Colorectal Cancer Among Men in the Netherlands Cohort Study on Diet and Cancer. American Journal of Epidemiology, 2010.
4.       Levenstein, S., et al. Low residue or normal diet in Crohn's disease: a prospective controlled study in Italian patients. Gut, 1985.
5.       Russell, R. I. (1991), Review article: dietary and nutritional management of Crohn's disease. Alimentary Pharmacology & Therapeutics, 1991.
6.       Emerson, A. P. Foods high in fiber and phytobezoar formation. Journal of the American Dietetic Association, (1987): 1675.

2 comments:

  1. Thank you for this informative post. Although my doctor recommended a low fibre diet during this Crohn's flare, I had my suspicions that not all fibre is equal when it comes to how it impacts the intestines. I'm also intrigued to learn that there were no appreciable difference in the outcomes of the case studies comparing low-fibre and normal-fibre diets in IBD patients. This is welcome news, as I've grown weary of eating reams of "white" food!

    ReplyDelete
  2. Thank you, this has been very helpful. I will be visiting your blog again!

    Stay Healthy
    Lola
    http://instagram.com/agrapefruitwithlola
    http://agrapefruitwithlola.blogspot.co.uk/
    https://www.facebook.com/grapefruitwithlola

    ReplyDelete