Omega-3 Fatty Acids

Also known by these names

  • O3FAs
  • ω-3 fatty acids
  • n-3 fatty acids
  • omega 3s
  • Individual O3FAs:
    • Docosahexaenoic acid (DHA)
    • Eicosapentaenoic acid (EPA)
    • Alpha-linolenic acid (ALA)

Key Points

  • Omega-3 fatty acids are found naturally in many fish and a few seeds and walnuts.
  • Omega-3s are widely available as supplements.
  • BCCT is interested in omega-3s because evidence shows benefits in several types of cancer treatment, and preliminary evidence shows omega-3s may reduce risks of breast and colon cancer.
  • While omega-3s are generally considered safe, a few cautions and interactions are noted.

Omega-3 fatty acids are a type of polyunsaturated fatty acid (PUFA) found naturally in these foods and supplements:

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Clinical Practice Guidelines

2013 evidence-based clinical practice guidelines from the American College of Chest Physicians recommended oral nutritional supplementation with omega-3 fatty acids to improve the nutritional status for lung cancer patients with sarcopenia (loss of muscle tissue).2

Treating the Cancer

Working against cancer growth or spread, improving survival, or working with other treatments or therapies to improve their anticancer action

Clinical Evidence

A group of men with prostate cancer combining omega 3 supplements with a  low-fat (15 percent of calories from fat) diet for four to six weeks before prostatectomy was compared to a control group consuming the standard American diet with 40 percent of calories from fat and no fish oil supplementation. At prostatectomy, the supplement group had smaller prostates (both benign and malignant components), lower proliferation index, and plasma that inhibited growth of prostate cancer cells in vitro more than the plasma from the control patients.3 Other effects in prostate cancer:

  • Decreased prostate cancer proliferation and decreased prostate tissue omega-6:omega-3 ratios, but no change in serum insulin-like growth factor I (IGF-1) in a small study of men undergoing radical prostatectomy4
  • Some evidence of decreased inflammatory markers in clinical trials5
  • Increased resistance to chemotherapy; not recommended on the days surrounding chemotherapy6

 Conflicting interactions with chemotherapy have been reported:

  • Improved outcomes with DHA added to chemotherapy in a small trial of metastatic breast cancer patients7
  • Increased resistance to chemotherapy has been found; use is not recommended on the days surrounding chemotherapy.8

Lab and Animal Evidence

Read more

Managing Side Effects and Promoting Wellness

Managing or relieving side effects or symptoms, reducing treatment toxicity, supporting quality of life or promoting general well-being

Omega-3 fatty acid (EPA and DHA) capsules or supplements with EPA have been associated with weight stabilization, gain in lean body mass, and improvement in quality of life markers in patients losing weight as a result of advanced pancreatic and head and neck cancers.15 The weight of patients with gastrointestinal cancer increased significantly with EPA supplementation.16 EPA and DHA Ameliorated muscle loss and myosteatosis (the presence of intermuscular and intramuscular adipose tissue) in clinical studies.17

 High-dose EPA inhibited bone resorption in breast cancer survivors taking aromatase inhibitors.1819

Omega-3s reduced paclitaxel-induced peripheral neuropathy in a small clinical study.20

Omega-3 supplements improved outcomes, especially body composition, in patients undergoing chemotherapy and/or radiotherapy.21

Dietary omega-3 fatty acids combined with guarana extract and a diet rich in whole foods, fruits and vegetables can treat cancer-related fatigue in patients with breast cancer.22


Nutritional supplementation with omega-3 fatty acids, arginine and nucleotides results in a marked improvement of immune functions in cancer patients undergoing surgery and a reduction in infectious complications, hospital stay and co-morbidities.23

Reducing Risk

Reducing the risk of developing cancer or the risk of recurrence

Clinical Evidence

Substantial data support the importance of omega-3 fatty acids for colorectal cancer prevention.24

Higher omega-6 to omega-3 ratios are associated with higher risk of breast cancer,25 while higher consumption of dietary marine omega-3 polyunsaturated fatty acids is associated with a lower risk of breast cancer.26 Higher levels from combined diet and supplements are associated with reduced risks of breast cancer.27 No impact of supplements on breast cancer recurrence and improved overall mortality in patients were found with early stage breast cancer, but marine omega-3s from food were associated with reduced risk of additional breast cancer events and all-cause mortality.28

Higher levels from combined diet and supplements are associated with reduced risks of breast cancer.29 No impact of supplements was found on breast cancer recurrence and improved overall mortality in  patients with early stage breast cancer, but marine omega-3s (DHA and EPA) from food were associated with reduced risk of additional breast cancer events and all-cause mortality.30

Data on omega-3 fatty acid supplementation for prostate cancer prevention are inconclusive. A 2017 review of the literature showed no clear relationship between fish-derived omega-3 fatty acids and risk of prostate cancer,31 but a separate review found that consumption of  omega-3 long-chain polyunsaturated fatty acids (LCPUFAs) and "an omega-6/omega-3 ratio of 2-4:1 are associated with a reduced risk of breast, prostate, colon and renal cancers."32

Lab and Animal Evidence

Read more


A few cautions are noted. Please see the Memorial Sloan Kettering Cancer Center’s About Herbs website for information.

  • High blood concentrations of omega-3s are associated with increased risk of prostate cancer (see the Foundation for Alternative and Integrative Medicine for an analysis of the study that found this).
  • A type of omega-3 fatty acid, 16:4(n-3), can reduce the activity of the chemotherapy drug cisplatin.34
  • 2018 review conclusions:
  • Four grams of supplementation may impair clotting; patients may want to eliminate omega-3 supplements before and immediately after surgery.35
  • A few adverse reactions and interactions with prescription and other drugs have been observed. 


BCCT does not recommend therapies or doses, but only provides information for patients and providers to consider as part of a complete treatment plan. Patients should discuss therapies with their physicians, as contraindications, interactions and side effects must be evaluated. Levels of active ingredients of natural products can vary widely between and even within products. See Quality and Sources of Herbs, Supplements and Other Natural Products.

Dosage recommendations are available from these sources:

Integrative Programs, Protocols and Medical Systems

For more information about programs and protocols, see our Integrative Programs and Protocols page.
  • Programs and protocols
    • Alschuler & Gazella complementary approaches36
      • Breast cancer
      • Colon cancer
      • Lung cancer
      • Pancreatic cancer
      • Prostate cancer
    • Block program37
      • Breast cancer case study
      • Lung cancer case study
      • Prostate cancer case study
      • Core diet plan
      • Remission support diet
      • Chemotherapy coupler
      • Radiation therapy coupler
      • Normalizing coagulation
      • Blocking inflammation
      • Blocking tumor-fueling enzymes
      • Boosting immune surveillance
      • Self-care program for stress chemistry and circadian rhythm
    • Chang strategies38
    • Lemole, Mehta & McKee protocols39
      • Breast cancer
      • Colorectal cancer
      • Endometrial cancer
      • Lung cancer
      • Prostate cancer
    • McKinney protocols40
      • Breast cancer
      • Depression
      • Fatigue
      • General cancer
      • Leukemia
      • Melanoma
      • Myelodysplastic syndrome
      • Prostate cancer
      • Sarcoma
      • Thyroid cancer
      • Weight loss
  • Traditional systems

Non-cancer Uses of Omega-3 Fatty Acids

BCCT has not reviewed the effectiveness of this therapy for non-cancer uses.

  • Depression
  • High cholesterol
  • Cardiovascular risk factors, including elevated triglyceride levels
  • Stroke
  • Rheumatoid arthritis
  • NSAID-associated gastroduodenal damage
  • Sunburn and sensitivity to ultraviolet radiation
  • Cystic fibrosis
  • Systemic lupus erythematosus (SLE)
  • Type 1 diabetes

Written by Nancy Hepp, MS, and reviewed by Laura Pole, RN, MSN, OCNS; most recent update on April 17, 2019. Note: BCCT has not conducted an independent review of research of Omega-3 fatty acids. This summary draws from the Memorial Sloan Kettering Cancer Center’s About Herbs and other sources as noted. 

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