Fish or Flax? Which Fat Should You Consume?

18015-1_nBy Monica Mollica.  While most people are aware of the health benefits of omegs-3 fat, there is still a lot of confusion regarding the different omega-3 fatty acids. It is important to clear this out because not all omega-3 fatty acids are of equal effectiveness.

The major sources of omegs-3 fats are fish oil and the cheaper flax oil. While they are both omega-3 oils, they provide different omega-3 fatty acids. Flax oil is a source of the parent omega-3 fatty acid alpha-linolenic acid (ALA), while fish oil is a source of the longer chain omega-3 fatty acids EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). The important distinction lies in the fact that it is EPA and DHA which are the “active” omega-3 fatty acids that give rise to the health benefits ascribed to omega-3 fats, especially fat loss, cardiovascular health and brain functioning 1-18.

While our bodies can convert ALA to EPA and DHA in the body, this conversion is extremely inefficient 19-25. It has been shown that the conversionof ALA to EPA is only between 0.3% and 8%, while  the conversion of ALA to DHA is often undetectable in men 21-24. Conversionof ALA to long-chain n–3 fatty acids appears is more efficient in women: up to 21% of consumed ALA is converted to EPA and up to9% is converted to DHA 19, 25. Even so, it is not enough to get an effective dose of EPA and DHA (2-3 g), which can only be obtained by consuming fish or supplementing with fish oil or algae oil. Algae oil is a vegetable source of DHA, while fish oil contains both EPA and DHA.

Apart from the low conversion efficiency of ALA to EPA and DHA, another concern with ALA is that it might cause prostate cancer 26, 27. This is another reason to supplement with fish oil instead of flax oil.

Therefore, to ensure adequate amounts of the active omega-3 fatty acids EPA and DHA, which is around 2-3 g, intake of these fatty acids via fatty fish and/or fish oil and algae oil is recommended, since we cannot rely on our body’s conversion of ALA.

References (As they say on ‘CSI,’ “Just Follow the Data”).

1. Couet C, Delarue J, Ritz P, Antoine JM, Lamisse F. Effect of dietary fish oil on body fat mass and basal fat oxidation in healthy adults. Int J Obes Relat Metab Disord. Aug 1997;21(8):637-643.

2. Delarue J, Couet C, Cohen R, Brechot JF, Antoine JM, Lamisse F. Effects of fish oil on metabolic responses to oral fructose and glucose loads in healthy humans. Am J Physiol. Feb 1996;270(2 Pt 1):E353-362.

3. Huffman DM, Michaelson JL, Thomas TR. Chronic supplementation with fish oil increases fat oxidation during exercise in young men. JEPonline. 2004;7(1):48-56.

4. Breslow JL. n-3 fatty acids and cardiovascular disease. Am J Clin Nutr. Jun 2006;83(6 Suppl):1477S-1482S.

5. Connor WE. Importance of n-3 fatty acids in health and disease. Am J Clin Nutr. Jan 2000;71(1 Suppl):171S-175S.

6. FDA. Qualified Health Claim for Omega-3 Fatty Acids, Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA) September 8, 2004 2004.

7. O’Keefe JH, Jr., Harris WS. From Inuit to implementation: omega-3 fatty acids come of age. Mayo Clin Proc. Jun 2000;75(6):607-614.

8. O’Keefe JH, Harris WS. Omega-3 fatty acids: time for clinical implementation? Am J Cardiol. May 15 2000;85(10):1239-1241.

9. Bourre JM. Roles of unsaturated fatty acids (especially omega-3 fatty acids) in the brain at various ages and during ageing. J Nutr Health Aging. 2004;8(3):163-174.

10. Dangour AD, Clemens F, Elbourne D, et al. A randomised controlled trial investigating the effect of n-3 long-chain polyunsaturated fatty acid supplementation on cognitive and retinal function in cognitively healthy older people: the Older People And n-3 Long-chain polyunsaturated fatty acids (OPAL) study protocol [ISRCTN72331636]. Nutr J. 2006;5:20.

11. Horrobin DF. A new category of psychotropic drugs: neuroactive lipids as exemplified by ethyl eicosapentaenoate (E-E). Prog Drug Res. 2002;59:171-199.

12. Johnson EJ, Schaefer EJ. Potential role of dietary n-3 fatty acids in the prevention of dementia and macular degeneration. Am J Clin Nutr. Jun 2006;83(6 Suppl):1494S-1498S.

13. Kidd PM. Omega-3 DHA and EPA for cognition, behavior, and mood: clinical findings and structural-functional synergies with cell membrane phospholipids. Altern Med Rev. Sep 2007;12(3):207-227.

14. Locke CA, Stoll AL. Omega-3 fatty acids in major depression. World Rev Nutr Diet. 2001;89:173-185.

15. Logan AC. Neurobehavioral aspects of omega-3 fatty acids: possible mechanisms and therapeutic value in major depression. Altern Med Rev. Nov 2003;8(4):410-425.

16. Logan AC. Omega-3 fatty acids and major depression: a primer for the mental health professional. Lipids Health Dis. Nov 9 2004;3:25.

17. Puri BK, Counsell SJ, Richardson AJ, Horrobin DF. Eicosapentaenoic acid in treatment-resistant depression. Arch Gen Psychiatry. Jan 2002;59(1):91-92.

18. Ross BM, Seguin J, Sieswerda LE. Omega-3 fatty acids as treatments for mental illness: which disorder and which fatty acid? Lipids Health Dis. 2007;6:21.

19. Burdge G. Alpha-linolenic acid metabolism in men and women: nutritional and biological implications. Curr Opin Clin Nutr Metab Care. Mar 2004;7(2):137-144.

20. Pawlosky RJ, Hibbeln JR, Novotny JA, Salem N, Jr. Physiological compartmental analysis of alpha-linolenic acid metabolism in adult humans. J Lipid Res. Aug 2001;42(8):1257-1265.

21. Burdge GC, Finnegan YE, Minihane AM, Williams CM, Wootton SA. Effect of altered dietary n-3 fatty acid intake upon plasma lipid fatty acid composition, conversion of [13C]alpha-linolenic acid to longer-chain fatty acids and partitioning towards beta-oxidation in older men. Br J Nutr. Aug 2003;90(2):311-321.

22. Burdge GC, Jones AE, Wootton SA. Eicosapentaenoic and docosapentaenoic acids are the principal products of alpha-linolenic acid metabolism in young men*. Br J Nutr. Oct 2002;88(4):355-363.

23. Emken EA, Adlof RO, Gulley RM. Dietary linoleic acid influences desaturation and acylation of deuterium-labeled linoleic and linolenic acids in young adult males. Biochim Biophys Acta. Aug 4 1994;1213(3):277-288.

24. Hussein N, Ah-Sing E, Wilkinson P, Leach C, Griffin BA, Millward DJ. Long-chain conversion of [13C]linoleic acid and alpha-linolenic acid in response to marked changes in their dietary intake in men. J Lipid Res. Feb 2005;46(2):269-280.

25. Burdge GC, Wootton SA. Conversion of alpha-linolenic acid to eicosapentaenoic, docosapentaenoic and docosahexaenoic acids in young women. Br J Nutr. Oct 2002;88(4):411-420.

26. Attar-Bashi NM, Frauman AG, Sinclair AJ. Alpha-linolenic acid and the risk of prostate cancer. What is the evidence? J Urol. Apr 2004;171(4):1402-1407.

27. Brouwer IA, Katan MB, Zock PL. Dietary alpha-linolenic acid is associated with reduced risk of fatal coronary heart disease, but increased prostate cancer risk: a meta-analysis. J Nutr. Apr 2004;134(4):919-922.


About Monica Mollica >

Monica Mollica has a Bachelor’s and Master’s degree in Nutrition from the University of Stockholm, Sweden, and is an ISSA Certified Personal Trainer. She works a dietary consultant, health journalist and writer for, and is also a web designer and videographer; Monica has admired and been fascinated by muscular and sculptured strong athletic bodies since childhood, and discovered bodybuilding as an early teenager. Realizing the importance of nutrition for maximal results in the gym, she went for a major in Nutrition at the University.  During her years at the University she was a regular contributor to the Swedish bodybuilding magazine BODY, and she has published the book (in Swedish) “Functional Foods for Health and Energy Balance”, and authored several book chapters in Swedish publications. It was her insatiable thirst for knowledge and scientific research in the area of bodybuilding and health that brought her to the US. She has completed one semester at the PhD-program “Exercise, Nutrition and Preventive Health” at Baylor University Texas, at the department of Health Human Performance and Recreation, and worked as an ISSA certified personal trainer. Today, Monica is sharing her solid experience by doing dietary consultations and writing about topics related to bodybuilding, fitness, health and anti-aging.