Effects of fish oil supplementation on eicosanoid production in patients at higher risk for colorectal cancer

Eur J Cancer Prev. 2019 May;28(3):188-195. doi: 10.1097/CEJ.0000000000000455.


Fish oil supplementation may represent a potential chemopreventive agent for reducing colorectal cancer risk. The mechanism of action of fish oil is unknown but presumed to be related to eicosanoid modification. The purpose of this study was to evaluate the effects of fish oil supplementation on the levels of urinary and rectal eicosanoids. We conducted a randomized, double-blind, controlled trial of 2.5 g of fish oil per day compared with olive oil supplementation over a 6-month period. Study participants had a history of colorectal adenomas. Randomization was stratified based on the gene variant rs174535 in the fatty acid desaturase 1 enzyme (FADS1), which affects tissue levels of arachidonic acid. A total of 141 participants were randomized. Urinary prostaglandin E2 metabolite (PGE-M) was measured at baseline, 3, and 6 months and rectal prostaglandin E2 (PGE2) at baseline and 6 months. Repeated-measures linear regression was used to determine the effect of the intervention on each outcome measure. Overall, fish oil supplementation was found to reduce urinary PGE-M production compared with olive oil (P=0.03). Fish oil did not reduce rectal PGE2 overall; however, it did significantly reduce PGE2 in the subgroup of participants not using aspirin or NSAIDs (P=0.04). FADS1 genotype did not seem to modify effects of fish oil on PGE2 production. We conclude that fish oil supplementation has a modest but beneficial effect on eicosanoids associated with colorectal carcinogenesis, particularly in those not taking aspirin or NSAIDs.

Publication types

  • Randomized Controlled Trial
  • Research Support, N.I.H., Extramural

MeSH terms

  • Adenoma / diet therapy*
  • Adenoma / etiology
  • Adenoma / metabolism
  • Adenoma / pathology
  • Aged
  • Colorectal Neoplasms / diet therapy*
  • Colorectal Neoplasms / etiology
  • Colorectal Neoplasms / metabolism
  • Colorectal Neoplasms / pathology
  • Delta-5 Fatty Acid Desaturase
  • Dietary Supplements*
  • Double-Blind Method
  • Eicosanoids / metabolism*
  • Female
  • Fish Oils / administration & dosage*
  • Follow-Up Studies
  • Humans
  • Male
  • Middle Aged
  • Prognosis
  • Risk Factors


  • Delta-5 Fatty Acid Desaturase
  • Eicosanoids
  • Fish Oils
  • FADS1 protein, human