On the other hand, the highest intakes of omega-3 were associated with 77 per cent reduction in the risk of the disease, according to findings of the European Prospective Investigation into Cancer and Nutrition (EPIC) with 203,193 men and women published in Gut.
The study adds to a small but growing body of evidence supporting the importance of balance between omega-3 omega-6 fatty acids.
Talking to NutraIngredients.com, study author Dr Andrew Hart from the University of East Anglia said that the findings may ultimately be more relevant to people already suffering from ulcerative colitis, rather than for the entire population.
“I think it is a balance between the omega-3 and omega-6,” said Dr Hart “We’ve shown a positive correlation for omega-6 with a plausible biological mechanism, and a negative correlation for omega-3 with a plausible biological mechanism for that.”
Dr Hart stressed that other studies need to replicate these findings and that it was far too early to make any public recommendations.
Commenting on the mechanism, Dr Hart wrote that omega-6 fatty acids are present in the cell membrane of colon cells in the form of arachidonic acid. This can be metabolised to prostaglandin E2, leukotriene B4 and thromboxane A2, all of which have pro-inflammatory effects.
On the other hand, omega-3 fatty acids, and particularly the anti-inflammatory effects of docosahexaenoic acid (DHA), which may prevent colonic inflammation.
Dr Hart analysed data from 203,193 people from UK, Sweden, Denmark, Germany and Italy aged between 30 and 74. Food frequency questionnaires were used to assess dietary intakes. Linoleic acid is found in foods such cooking oils (especially corn and sunflower oils), red meat (particularly beef and pork), and polyunsaturated margarines.
During the course of four years, 126 cases of ulcerative colitis were documented. Dividing the participants into four groups depending on their linoleic acid intakes, Dr Hart calculated that highest average intake of linoleic acid was associated with 149 per cent increase in the risk of ulcerative colitis.
Conversely, the highest average dietary intakes of DHA were associated with a 77 per cent reduction in ulcerative colitis risk.
“The positive association [between omega-6 and ulcerative colitis] may reflect a causal association because of both a plausible biological mechanism and supportive evidence from other epidemiological studies,” wrote Dr Hart.
“The association needs to be further investigated in other aetiological work in different populations to assess consistency. If the positive association is causal, then there is substantial potential for reducing the incidence of ulcerative colitis through dietary modification,” he concluded.
Published online ahead of print, doi:10.1136/gut.2008.169078
“Linoleic Acid, a Dietary N-6 Polyunsaturated Fatty Acid, and the Aetiology of Ulcerative Colitis - A European Prospective Cohort Study”
Author: A.R. Hart