Do omega 3 fatty acids reduce Crohn's symptoms?

"What can high-omega-3 foods do for you? " on the world's healthiest foods
excellent sources: flaxseed, salmon, walnuts
very good sources: cloves, oregano, cauliflower, sardines, mustard seeds, cabbage, broccoli

"Omega 3 Blood Test: Monitor and Improve Your Omega 3 Levels" from Rebuild, the blog

The Vital Omega-3 and 6 HUFA Test™ from Vital Choice

"Omega-3 fatty acids and inflammatory bowel diseases – a systematic review" in British Journal of Nutrition (2012) 

"Despite their well known anti-inflammatory actions, the clinical usefulness of omega-3 PUFA in inflammatory bowel disease is controversial. We aimed to systematically review the available data on the performance of omega-3 PUFA as therapeutic agents in these patients. ... Overall, available data do not allow to support the use of omega-3 PUFA supplementation for the treatment of both active and inactive inflammatory bowel disease. Negative results are quite consistent in trials assessing the use of omega-3 PUFA to maintain disease remission, particularly ulcerative colitis, and to a lesser extent Crohn's disease. Trials on their use in active disease do not allow to draw firm conclusions mainly because the heterogeneity of design (ulcerative colitis) or their short number (Crohn's disease). In most trials, the appropriateness of the selected placebo is questionable. Conclusion: The present systematic review does not allow to make firm recommendations about the usefulness of omega-3 PUFA in inflammatory bowel disease."  [Emphasis mine.]

"The Effects of an Oral Supplement Enriched With Fish Oil, Prebiotics, and Antioxidants on Nutrition Status in Crohn’s Disease Patients" in Nutrition in Clinical Practice (2011)
"Background: Research in the treatment of Crohn’s disease (CD) supports anti-inflammatory benefits of n-3 fatty acids from fish oil, prebiotics, and antioxidants. A nutritionally balanced inflammatory bowel disease nutrition formula (IBDNF) enriched with these compounds has the potential to improve nutrition status and disease activity in CD. ...
Conclusions: IBDNF has the potential to deposit fat-free and fat mass, improve vitamin D status, and improve quality of life in CD patients."

"Omega-3s Fish Oil Craze: Is It an Environmental Disaster?" in The Insider, Health World Net (2011)

"Immunomodulatory Effects of (n-3) Fatty Acids: Putative Link to Inflammation and Colon Cancer" in J Nutr (2007)

"From a dietary perspective, fish oil containing (n-3) polyunsaturated fatty acids (PUFAs) has antiinflammatory properties, but for years the mechanism has remained obscure. Of relevance to the immune system in the intestine, we showed that (n-3) PUFA feeding alters the balance between CD4+ T-helper (Th1 and Th2) subsets by directly suppressing Th1 cell development (i.e., clonal expansion). This is noteworthy because Th1 cells mediate inflammatory diseases and resistance to intracellular pathogens or allergic hypersensitivity, and Th2 cells mediate resistance to extracellular pathogens. Therefore, any changes induced by (n-3) PUFAs in T-cell subset balance and function are important because the outcome is expected to suppress the development of autoimmune diseases and possibly the occurrence of colon cancer."

"Supplementation with omega-3 fatty acids may have a therapeutic effect in supporting Crohn's disease remission" in Inflamm Bowel Dis (2000)
"This study indicates that an immunomodulating formula containing n-3 fatty acids and/or AO may have the potential to play a role in the treatment of CD."

Do PUFA deficiencies cause CD?

Polyunsaturated Fatty Acids (PUFA) from Wikipedia

Omega 3 fatty acids from Wikipedia

Omega 6 fatty acids from Wikipedia

Omega 9 fatty acids from Wikipedia

Conjugated fatty acids from Wikipedia

"Genes involved in the metabolism of poly-unsaturated fatty-acids (PUFA) and risk for Crohn's disease in children & young adults" in PLoS ONE (2010)
"Epidemiological evidence for the role of polyunsaturated fatty-acids (PUFA) in Crohn's disease (CD) is unclear, although the key metabolite leucotriene B4 (LTB4) is closely linked to the inflammatory process. We hypothesized that inherited variation in key PUFA metabolic enzymes may modify susceptibility for CD.
...
Inherited variation in enzymes involved in the synthesis/metabolism of LTB4 may be associated with CD. These findings implicate PUFA metabolism as a important pathway in the CD pathogenesis."

"Epidemiologic analysis of Crohn disease in Japan: increased dietary intake of n-6 polyunsaturated fatty acids and animal protein relates to the increased incidence of Crohn disease in Japan" in Am J Clin Nutr (1996)
"The multivariate analysis showed that increased intake of animal protein was the strongest independent factor with a weaker second factor, an increased ration of n-6 to n-3 polyunsaturated fatty acids. The present study in association with reported clinical studies suggests that increased dietary intake of animal protein and n-6 polyunsaturated fatty acids with less n-3 polyunsaturated fatty acids may contribute to the development of Crohn disease."

"Peripheral blood mononuclear cell fatty acid composition and inflammatory mediator production in adult Crohn's disease" in Clinical Nutrition (2004)
"CD is associated with a greater availability, and not a deficiency, of n-3 PUFA in PBMC, but lower concentrations of AA, and lower rates of production of PGE2 and IFN-γ, compared to healthy controls."

"Genes involved in the metabolism of poly-unsaturated fatty-acids (PUFA) and risk for Crohn's disease in children & young adults" in PLoS One (2010)
"Inherited variation in enzymes involved in the synthesis/metabolism of LTB(4) may be associated with CD. These findings implicate PUFA metabolism as a important pathway in the CD pathogenesis."