Ulcerative colitis is a painful chronic condition, in which the lining of the bowel becomes severely inflamed and blistered. It has been linked to other complications, including an increased risk of bowel cancer.
Linoleic acid is found in many dietary sources, including red meat, various cooking oils, and some margarines.
The researchers base their findings on food diaries (food frequency questionnaires) from more than 200,000 people, between the ages of 30 and 74 in the UK, Germany, Italy, Sweden and Denmark.
All the participants, who were taking part in the European Prospective Investigation into Cancer (EPIC) study, were matched with four comparison groups of people without ulcerative colitis, and monitored for the development of the condition.
In all, 126 people developed ulcerative colitis after an average period of 4 years. Almost half the cases occurred in women (47%); the average age at diagnosis was 60.
After adjusting for other factors likely to influence the results, including smoking, age, total energy intake, and use of aspirin, those whose diets included the most linoleic acid were almost 2.5 times as likely to develop the condition as those whose diets contained the least.
If the association is causative, nearly a third of cases (30%) of ulcerative colitis could be attributable to high intakes of linoleic acid, suggest the authors.
Once in the body, linoleic acid is converted to arachidonic acid, which is a component of the cell membranes in the bowel.
Arachidonic acid can then be converted into various inflammatory chemicals, high levels of which have been found in the bowel tissue of patients with ulcerative colitis.
The research also found that the highest intake of omega 3 fatty acid (docosahexanoic acid), found in oily fish such as salmon and herring, reduced the likelihood of developing ulcerative colitis by 77%.