The long chain Omega 3 fatty acids acids, EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) have been in the news again. This time a study (1) has linked these healthy fats to a reduced risk of colon cancer. Long chain omega 3 fats are found in oily fish such as trout, salmon, mackerel and sardines and have been linked to a reduced risk of a number of conditions.
Previously I wrote about diet and lifestyle changes that could possibly be linked to a reduced risk of colon cancer. This study (1) looked specifically at omega 3 fatty acids and colon cancer. There have been a few very small animal and human studies that suggest fish oil supplementation may fight inflammation in the colon but this study looked at the relationship between dietary fatty acid intake and bowel cancer risk in over 1,500 white individuals (including 716 colon cancer patients and 787 healthy control individuals) and 369 African Americans (213 had colon cancer and 156 were control individuals). The results of the study (1) showed that among the white participants those who had the highest omega 3 consumption had a significantly reduced risk of colon cancer compared to those who consumed the least. The researchers looked at EPA and DHA and found that risk of colon cancer fell with increasing intake. When looking at white and African American subjects together they found there was a reduced risk of colon cancer with increasing omega 3 intake but separate analysis of the African American subjects in isolation did not find a similar relationship – this is interesting but no conclusion can be drawn until further studies are undertaken.
The researchers (1) also found that people who had an imbalance between omega-6:omega-3 , with more omega 6 in relation to omega 3, were also more likely to have colon cancer – however, omega 6 intake itself did not affect the risk. I have written about the importance of the omega6:omega 3 ration previously here
The authors conclude (1)“Study results support the hypothesis that long-chain omega-3 PUFAs have beneficial effects in colorectal carcinogenesis. Whether or not the possible benefit of long-chain omega-3 PUFAs varies by race warrants further evaluation”.
In another recent study (2) an omega 3 fatty acid supplement has been shown to be useful to people at risk of developing an inherited form of bowel cancer. The study took part in the UK and involved individuals diagnosed with FAP (familial adenomatous polyposis) an inherited condition which may be responsible for around one in 100 bowel cancer cases. The, EPA, omega-3 fatty acid preparation seemed to significantly reduce the size and number of pre-cancerous growths (polyps) over the six month trial period.
FAP causes polyps to form in the lining of the large bowel. Patients usually undergo bowel surgery but remain at risk of developing polyps and cancer, regular endoscopic checks are required by the patients. The research team are now interested to see if the EPA supplement could help to prevent the non-hereditary form of bowel cancer which is the third most common cancer in the UK.
In a press release (3) the lead study researcher, Professor Hull, said that the EPA supplement could be useful to individuals with FAP: ”A safe and effective drug therapy may reduce the number of invasive check-up procedures, which can be unpleasant and always involve a small amount of risk”. “There is definitely a clinical need for an effective, preventative therapy that is both safe and well tolerated as the existing drug therapy for FAP can be associated with an increased risk of heart attack in older individuals,” The researchers note (2) that the effects of the EPA supplement were similar to those produced by the medication celecoxib (a selective cyclo-oxygenase-2 inhibitor), which is used to help curb the growth of new and existing polyps in patients with FAP. The use of celecoxib has been associated with harmful cardiovascular side effects in older patients (3)
The study (2) was small but well designed, it involved 55 patients with FAP and lasted 6 months. 28 of the individuals were given 2g of a highly purified EPA supplement daily. The patients given the supplement had a significant reduction in the number and size of polyps whereas the placebo group who were not given EPA showed and increase in polyp size and number over the same period. In the press release (3) professor Hull mentioned more about the EPA preparation used: “The particular preparation of EPA that we used delivers approximately four times as much beneficial polyunsaturated fatty acid per day as is derived from eating two to three portions of fish a week. The supplement is also designed to be released into the small intestine, minimising nausea and halitosis often associated with taking over-the-counter fish oil supplements”
There is now a need for larger studies to see if the high dose, purified preparation is safe and effective for all individuals. As mentioned in past posts omega 3 fats are very important to health and sadly many people in the UK do have low levels since their consumption of oily fish is often low. Including a minimum of 2 portions weekly is a good idea for health. Supplements containing EPA and DHA can also be considered for those who do not eat fish. Vegetarians and vegans can get some of the shorter chain omega 3 fatty acids (alpha linolenic acid) from flaxseeds/linseeds and walnuts but the body finds it very hard to bioconvert these into the longer chain EPA and DHA fats, which seem crucial for health. EPA and DHA supplements made from alage are now available for vegetarians and vegans and may be worth considering.
(1) Kim S et al. 2010. Intake of Polyunsaturated Fatty Acids and Distal Large Bowel Cancer Risk in Whites and African Americans. Am J Epidemiol. Apr 14. [Epub ahead of print]
(2) West NJ et al. 2010. Eicosapentaenoic acid reduces rectal polyp number and size in familial adenomatous polyposis. Gut. 2010 Mar 26. [Epub ahead of print]
(3)Press release. BMJ-British Medical Journal (2010, March 21). Omega 3 curbs precancerous growths in those prone to bowel cancer, study suggests. ScienceDaily. Retrieved April 27, 2010, from http://www.sciencedaily.com /releases/2010/03/100317212648.htm
Written by Ani Kowal
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- Fish oil supplements associated with a reduced risk of breast cancer
- Green tea may be linked to reduced stomach cancer risk in women
- Study links fish and omega 3 fats to reduced risk of age-related macular degeneration in women
- Folic acid linked with reduced risk of cancer
