Inflammatory Bowel Disease: Nutritional Considerations
Nutritional factors may be important in IBD. The factors currently
believed to help prevent or treat IBD are as follows:
- Breast–feeding: A large study found that the
risk for ulcerative colitis was 25 percent lower and the risk for
Crohn’s disease 35 percent lower in individuals who were
breast–fed. Breast–feeding may protect against IBD in several ways:
by protecting against gastrointestinal infection during infancy,
by stimulating the early development of the gastrointestinal tract,
and by delaying exposure to cow’s milk.
- A Western dietary pattern: Western diets that
are relatively high in meat, dairy products, and sugar, and low
in fiber and other plant constituents have been associated with
a higher risk of IBD. In contrast, traditional diets in other regions
of the world are more plant–based, including higher amounts of
vegetables, fruits, nuts, and seeds. It is difficult to identify
specific aspects of the diet that are responsible for this pattern.
Possible candidates that have been studied will be discussed below.
However, it may be that interventions to reduce risk need to address
the overall dietary pattern, rather than its components.
- Animal protein: Dietary data from Japan suggest
that the westernization of traditional Asian diets is associated
with increased risk for IBD. A study looked at the difference in
typical Japanese dietary intake from 1966 to 1985. When the incidence
of Crohn’s disease and the daily intake of various dietary
components were evaluated, animal protein intake emerged as the
strongest independent risk factor.
Animal protein contributes significantly to the amount of a toxin
called hydrogen sulfide in the colon, which may increase disease
activity in ulcerative colitis. Additionally, hydrogen sulfide
may also interfere with the actions of butyrate, an important anti–inflammatory
molecule in the colon.
Among patients with ulcerative colitis, meat intake significantly
increases the rate of relapse. Red meat and processed meat intake
increases the rate of relapse more than five–fold. Conversely,
a pilot study that restricted animal protein and other forms of
sulfur resulted in a complete absence of IBD relapse. However,
further studies are needed to confirm these effects.
In contrast, diets that primarily provide vegetable sources of
protein result in lower amounts of hydrogen sulfide in the colon
and have been associated with a decreased risk of Crohn’s
- Dairy products: Individuals with IBD are
often sensitive to cow’s milk. Further, those with IBD and
documented cow’s milk allergy have been shown to develop
ulcerative colitis at an earlier age than did people with this
disease who were free of milk allergy. Patients with IBD often
have antibodies to cow’s milk protein, and these correlate
with disease activity in Crohn’s disease. Studies also indicate
milk increases both intestinal permeability and production of proinflammatory
cytokines, both of which are involved in IBD.
Preliminary research findings indicate that
allergies to foods other than dairy products might be involved
in IBD, but further study is required before hypoallergenic diets
are established as an effective IBD treatment.
Some evidence suggests that a milk–borne infection may play a role
in the development of Crohn’s disease. Bacteria called Mycobacteriaum
avium, which are commonly found in milk products, are known
to survive pasteurization and cause a Crohn’s disease–like
illness (Johne’s disease) in dairy cows. Interestingly, these
bacteria have been found with far greater frequency in patients
with Crohn’s disease than in those with ulcerative colitis
or healthy people. However, the pathogen has not yet been proven
to be a causative agent in Crohn’s disease, and the benefit
of treating it with antibiotics has not been established.
- A high–fat diet: Diets that are
high in fat, particularly animal fat, and cholesterol have been
shown to be associated with significant increases in the risk for
IBD. This may be due to increases in inflammation caused by certain
fats, called omega–6 fats. These are primarily found in animal
products and some vegetable oils (e.g., corn, safflower, and sunflower
The intake of foods containing partially hydrogenated fats, including
fast foods, fried foods, margarine, baked goods, and packaged foods,
is also associated with IBD risk. In countries where margarine
consumption has increased, an increase in Crohn’s disease
followed. Persons eating fast foods at least twice per week had
three times the risk for Crohn's disease and four times the risk
for ulcerative colitis, compared with those who avoided these foods.
- A low–fiber diet: Compared with persons consuming
small amounts of fiber, those eating 15 grams or more per day had
only half the risk for developing Crohn’s disease. In particular,
fiber intake from fruit appears more strongly associated with reduced
risk of IBD. In addition, individuals eating high–fiber diets were
more likely to remain in remission, or had significantly fewer
and shorter hospitalizations and required less intestinal surgery,
than a control group of patients who did not have a change in their
Most high–fiber foods are also high in naturally occurring antioxidant
vitamins and minerals, as well as protective plant compounds, called
carotenoids and flavonoids. These substances help to limit oxidative
stress, a condition found in individuals with IBD as a result of
inflammation in the colon.
- High sugar intake: Studies have
consistently found an association between higher intakes of sugars
and the development of IBD. However, these associations may merely
reflect lifestyle patterns common in populations with IBD. A biological
mechanism has not been established for sugar’s effect in IBD, and larger
clinical trials have not documented significant benefits of a diet
low in refined carbohydrates. Further studies are required to determine
if such a diet helps prevent or treat IBD.
- Dietary supplements: Because IBD affects areas
of the intestine that are responsible for absorbing nutrients,
some patients with IBD may have nutrient deficiencies. Others may
have an increased need for certain antioxidants due to oxidative
stress. Serum concentrations of several nutrients (beta–carotene,
vitamin C, vitamin E, selenium, and zinc) were also significantly
lower or deficient in IBD patients. These deficiencies indicate
a need for intake of foods with high amounts of vitamins, minerals,
and other essential nutrients, and possibly a multiple vitamin–mineral
- B–vitamins: Supplements of B–vitamins may be
effective in IBD patients. B–vitamins (vitamin B6, vitamin B12,
and folic acid) decrease blood levels of homocysteine, which
is thought to play a role in the development of IBD and has been
shown to be in higher concentrations in the blood of individuals
with IBD. However, clinical trials to assess benefits of homocysteine–lowering
with B–vitamins in IBD have not yet been published.
- Vitamin K: People with Crohn’s disease
often have low levels of vitamin K in their bloodstreams. Although
specific studies have not yet evaluated the benefit of vitamin
K supplementation, a high intake of vitamin K–containing foods
(e.g., green leafy vegetables) is advised.
- Omega–3 fatty acids: Children with active disease
have been shown to have lower levels of the alpha–linolenic
acid, the primary omega–3 fatty acid. Long–chain omega–3 fatty
acids (found in fatty fish, such as salmon) may decrease disease
activity, and have been found in some studies to reduce medication
requirements and help patients achieve remission more quickly
than placebo. Whether plant sources of omega–3 fatty acids
(e.g., flax oil) are equivalent to fish oils for this condition
is not yet clear.
- Botanical therapy: Boswellic acids (the
biologically active ingredient of Boswellia serrata) are
an inhibitor of an enzyme that promotes inflammation. Bowellia
acids were found to be effective in treating both Crohn’s
disease and ulcerative colitis. In fact, one study showed that
Boswellia achieved a remission rate greater than treatment with
medical drugs. Clinical studies with larger numbers of patients
are needed to assess these benefits.
- Probiotic therapy: Lactobacilli, streptococci,
bifidobacteria, Saccharomyces boulardii, and certain E.
coli subspecies have been postulated to be useful by limiting
the growth of harmful bacteria in the gut. A number of clinical
trials have indicated reductions in disease activity and longer
remission in patients with IBD who were treated with single or
In addition to the nutritional interventions above, exercise can
benefit IBD patients. Although only limited evidence
suggests that exercise reduces risk for the onset of IBD, patients
get many other benefits from regular activity. These include improvement
of psychological symptoms; improvements in muscle strength and
bone health, which are often impaired with steroid therapy; and
a reduced risk for colon cancer.