Large study links oleic acid, olive oil's major fat—to reduced risk of ulcerative colitis; prior analysis of same study linked the disease to the omega-6 fats abundant in other vegetable oils
by Craig Weatherby
Ulcerative colitis is characterized by inflammation of the large intestine (colon) and rectum, and it afflicts about 300,000 Americans.
It can be a truly dreadful disease, causing abdominal pain, diarrhea, malnutrition, and weight loss.
The causes of ulcerative colitis (UC) remain unknown, and it can appear at any age, although most cases occur between the ages of 15 and 30 or from age 50 to 70… with women suffering from it more frequently than men.
Drugs may decrease the number of attacks, and some alternative treatments—Boswellia herb, probiotic bacteria, and benign intestinal worms—are showing promise in clinical trials.
So it comes as welcome news that diets high in olive oil have been linked to a 90 percent lower risk of UC.
Better yet, the researchers estimated that consuming just two to three tablespoons of olive oil per day could cut UC rates in half.
We'd add that you should choose extra virgin olive oil—and avoid oils with relatively high amounts of omega-6 fats—for reasons we'll explain below.
Olive oil's “mono” fat appears helpful
Rather than olive oil per se, the link that researchers actually found was between lower risk of UC and higher intake of oleic acid… the monounsaturated fat that's abundant in olive oil.
Other oils are equally high in oleic acid, and the most common ones are listed below in descending order of approximate oleic acid content, from highest to lowest:
- Macadamia nut oil
- Olive oil
- Sunflower oil (hi-oleic type)
- Safflower oil (hi-oleic type)
- Sunflower oil (mid-oleic type)
- Canola oil
- Peanut oil (and peanut butter)
Unlike regular or virgin grades, only EVOO contains an extremely potent group of antioxidants called tyrosols, which get stripped from the other two grades during chemical refinement.
In clinical trials, extra virgin grade olive oil beats the pants off other, lesser grades with regard to reducing inflammation in artery linings. And like artery linings, the linings of the intestines and rectum consist of epithelial cells, so they, too, might benefit from the tyrosols in EVOO.
Putting that distinction aside, the best choices for everyday use are oils high in oleic acid and low in omega-6 fatty acids… a criterion that makes canola oil, peanut oil, and mid-oleic sunflower oil the least attractive options on the above list.
This is because omega-6 fatty acids tend to promote existing inflammation (as in UC) or induce an inflammatory disease in people with a predisposition to it.
Prior study linked excessive omega-6 fat intake to higher UC risk
An analysis of data from the same large study that produced good news about oleic acid linked increased risk of UC to diets high in omega-6 fatty acids… which have become the unhealthful norm in America and many other countries.
As the authors wrote, “The data support a role for dietary [omega-6] linoleic acid in the etiology [origins] of ulcerative colitis. An estimated 30 percent of cases could be attributed to having dietary intakes higher than the lowest quartile of [omega-6] linoleic acid intake” (IBD in EPIC et al. 2009).
(Researchers often divide study participants into “quartiles” or fourths, based on their relative consumption of the dietary factor being studied.)
Omega-6s are grossly overabundant in the American diet because the cheapest, most commonly used oils are the ones highest in these fatty acids: corn, soy, cottonseed, and regular (i.e., not “hi-oleic”) safflower and sunflower oils.
Human beings evolved on diets that delivered about three omega-6 molecules for every one omega-3 molecule... but the average American now consumes 20 to 40 omega-6s for every omega-3.
It's no wonder we're being plagued by diseases that are either caused or exacerbated by excess inflammation—from dementia and cancer to diabetes, allergies, autoimmunity, and cardiovascular disease—and including colitis.
Large UK study links higher oleic acid intake to reduced UC risk
The study was led by Dr. Andrew Hart and his colleagues at Britain's University of East Anglia (Hart A et al. 2010).
They studied more than 25,000 people aged 40-65 living in Norfolk, UK, who volunteered for the EPIC study (European Prospective Investigation into Diet and Cancer) between 1993 and 1997.
The participants, none of whom had ulcerative colitis at the outset, completed detailed food diaries which were later analyzed by trained nutritionists.
By 2004, 22 participants in the study had developed UC and the researchers compared their diets with those who did not develop the disease.
The UK team found that those with the highest intake of oleic acid were 90 percent less likely to have developed the disease.
As Dr. Hart said, “Oleic acid seems to help prevent the development of ulcerative colitis by blocking chemicals in the bowel that aggravate the inflammation found in this illness” (UEA 2010).
And he estimated a huge preventive effect: “We estimate that around half of the cases of ulcerative colitis could be prevented if larger amounts of oleic acid were consumed. Two-to-three tablespoons of olive oil per day would have a protective effect” (UEA 2010).
We'd need more research to confirm these results before the link can be said to be definite.
Clinical trials using oleic acid capsules would be ideal, but if positive results are obtained from other large population studies, it will be reasonable to propose that oleic acid offers UC-prevention potential.
- Hart A et al. Dietary Oleic Acid May Protect Against the Development of Ulcerative Colitis – A UK Prospective Cohort Study (Abstract #100). Presented at DDW 2010, Ernest N. Morial Convention Center, New Orleans, LA, Sunday, May 2, 11:45 a.m. CT. Accessed at http://www.ddw.org/wmspage.cfm?parm1=914
- Hart AR, Luben R, Olsen A, Tjonneland A, Linseisen J, Nagel G, Berglund G, Lindgren S, Grip O, Key T, Appleby P, Bergmann MM, Boeing H, Hallmans G, Danielsson A, Palmqvist R, Sjodin H, Hagglund G, Overvad K, Palli D, Masala G, Riboli E, Kennedy H, Welch A, Khaw KT, Day N, Bingham S. Diet in the aetiology of ulcerative colitis: a European prospective cohort study. Digestion. 2008;77(1):57-64. Epub 2008 Mar 18.
- IBD in EPIC Study Investigators, Tjonneland A, Overvad K, Bergmann MM, Nagel G, Linseisen J, Hallmans G, Palmqvist R, Sjodin H, Hagglund G, Berglund G, Lindgren S, Grip O, Palli D, Day NE, Khaw KT, Bingham S, Riboli E, Kennedy H, Hart A. Linoleic acid, a dietary n-6 polyunsaturated fatty acid, and the aetiology of ulcerative colitis: a nested case-control study within a European prospective cohort study. Gut. 2009 Dec;58(12):1606-11. Epub 2009 Jul 23.
- University of East Anglia (UEA). Olive oil could guard against developing ulcerative colitis. May 1, 2010. Accessed at http://www.eurekalert.org/pub_releases/2010-05/uoea-ooc042210.php