Irritable Bowel Disease
Diet is thought to be one of the most important factors in
the cause of diseases of the large bowel, including colorectal
cancer and inflammatory bowel disease (IBD). Whilst the role
of individual fatty acids in human colorectal cancer risk
is not clear, the amount and type of fat appears to be important.
Epidemiological studies indicate that diets high in saturated
fats increase the risk of cancer, whereas diets high in polyunsaturated
fats rich in omega-3 fatty acids derived from oily fish or
fish oil are thought to decrease the risk of cancer. [i] Patients
with colon tumours have an abnormal cell turnover rate and
are at increased risk of developing further colorectal malignancies;
high doses of fish oil have been shown to reduce the rate
of cell growth in such individuals.[ii] Indeed current research
is investigating the potential efficacy of EPA supplementation
in reducing the risk of colorectal cancer.[iii]
Inflammatory bowel disease includes both Crohn’s disease
and ulcerative colitis. Both conditions are the result of
an exaggerated or insufficiently suppressed immune response,
leading to damage of the mucous membrane, allowing toxins
and bacteria to seep through the intestinal wall and into
the blood stream, further accelerating the inflammatory process.
[iv] Diverticulosis coli is another common condition involving
development of mucosal folds and inflammation of the colon.
Substances produced from the omega-6 fatty acid arachidonic
acid are considered primarily responsible for inflammatory
processes and the intestinal inflammation seen in inflammatory
bowel disease. Prostaglandin formation from omega-3 and omega-6
fatty acids uses different pathways that share common enzymes.
The ratio of omega-3 to omega-6 will therefore affect which
pathway is the most active. Unfortunately the ratio of inflammatory
omega-6 fatty acids in the diet is much higher than that of
anti-inflammatory omega-3 fatty acids. If there is a higher
intake of EPA, however, this causes competition with arachidonic
acid (AA) for the utilisation of specific enzymes, and inhibits
the production of inflammatory prostaglandins. [vi] The ability
of EPA to reduce the inflammatory response suggests great
potential for alleviating symptoms of inflammatory bowel disease.