Both fish oil and flax oil are both used extensively as omega-3 fatty acid supplements. But which one should you choose? And is one better than another?
What are essential fatty acids?
The essential fats are two, relatively common fats found in the diet. The essential ‘omega 6’ fat is linoleic acid, found in abundance in the modern diet from vegetable oils (e.g. sunflower and safflower) and the ‘omega 3’ fat, found in far lesser amounts in the diet, is alpha-linolenic acid found in certain plant foods, most especially in flaxseeds, pumpkin seeds, hemp seeds, and chia.
Inflammation—friend and foe
Inflammation is a critical process in the body that helps us to heal and repair and signal appropriate immune responses (or dampen them down when needed). BUT excessive inflammation is linked to illnesses including autoimmune conditions, diabetes and insulin resistance, heart disease, cancer and neurological (brain) disorders. That’s why it has been suggested that the balance of omega 3 to omega 6 fats should be around 1 to less than 7. While a higher ratio (e.g. 1:1) of ALA to LA does result in the highest conversion to DHA and EPA,1 the latest evidence suggest that your total intake of omega 3 fats is more important than the ratio of omega 3 to 6.2 Suffice to say, our modern, western-style diet has a disproportionately high amount of omega 6 fats that can encourage inflammation.
Supplementing with either fish or flaxseed oil can help to redress the imbalance and provide omega-3 fatty acids that help to modulate inflammation.
What is flaxseed oil?
Flaxseed oil comes for the seeds of the common flax plant (Linum usitatissimum). Over 50% of the fatty acids in flaxseed oil come from alpha-linolenic acid (ALA), the ‘base’ omega 3 fat which can be converted to the ‘active’ omega-3 fatty acids in the body that help to modulate inflammation and immunity, especially docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA).
Flaxseed consumption is associated with benefits for the cardiovascular system with systematic reviews and meta-analyses showing significant reductions in blood pressure.3, 4 Other research suggests that flaxseed supplementation might help people to reduce weight and improve body composition (lean vs fat mass).5 Flaxseeds also help to regulate blood-sugar balance with reductions in blood glucose, insulin and insulin resistance models in those consuming supplemental flaxseed.6
What about fish oil?
Fish oil contains omega 3 fatty acids but unlike flaxseed oil, fish oil directly provides DHA and EPA. This can be beneficial because conversion rates of ALA to DHA and EPA are very poor for many people and are very variable.7 In fact, conversion rates can be as low as 5–10% for EPA and 2–5% for DHA8. Conversion rates of ALA to DHA and EPA might be even lower in men, and supplementation with ALA (from flax oil for example) may not always raise DHA effectively.9-11
Fish oil supplementation is likely to be generally cardioprotective12 and has several positive effects on health markers. For example, triglycerides are one of the best indicators of cardiovascular and metabolic health and you want these to be lower. Fish oil supplementation reduces triglycerides in a dose-dependent manner.13, 14 On the other hand, generally we want HDL cholesterol to be higher because this cholesterol carrier brings cholesterol back to the liver from peripheral tissue for processing and excretion. Fish oil supplementation increases HDL and improves the HDL to LDL ratio15 (sometimes referred to as the ‘good to bad cholesterol’ ratio), and fish oil also helps to reduce blood pressure.16
Overall, the scientific evidence suggests that increased consumption of omega 3 fats from fish or fish-oil supplements reduces all-cause mortality, cardiac and sudden death, and possibly stroke,17-19 reduces depression,20, 21 and joint swelling and pain.22
Note: These cardiometabolic benefits are not observed to the same degree from increased consumption of alpha-linolenic acid,23 the ‘base’ omega-3 fat found in plant-derived sources such as flaxseed oil.
Because of poor conversion rates and the importance of DHA for brain development, fish oils are considered very important to supplement during pregnancy and breast-feeding24
Which should I choose?
Choose flaxseed oil if:
- You are vegan or vegetarian
- You are using flaxseed oil as a supplemental oil in addition to fish oil
- You are from a population that has traditionally had a very low fish and meat intake (in which case you may be a better converter of the base alpha-linolenic acid to DHA and EPA.)
Choose fish oil if:
- You aren’t vegetarian or vegan
- You are from a population who have traditionally eaten a lot of fatty meats and fish (in which case, you may be a poorer converter of base omega-3 fats to DHA and EPA)
- You have a limited capacity (due to tolerance or dietary considerations) of taking in large amounts of flaxseed oil to meet your omega-3 fat requirements
References
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2. Goyens PL, Spilker ME, Zock PL, Katan MB, Mensink RP. Conversion of α-linolenic acid in humans is influenced by the absolute amounts of α-linolenic acid and linoleic acid in the diet and not by their ratio. The American Journal of Clinical Nutrition. 2006;84(1):44-53.
3. Khalesi S, Irwin C, Schubert M. Flaxseed Consumption May Reduce Blood Pressure: A Systematic Review and Meta-Analysis of Controlled Trials. The Journal of Nutrition. 2015;145(4):758-65.
4. Ursoniu S, Sahebkar A, Andrica F, Serban C, Banach M. Effects of flaxseed supplements on blood pressure: A systematic review and meta-analysis of controlled clinical trial. Clinical Nutrition. 2016;35(3):615-25.
5. Mohammadi‐Sartang M, Mazloom Z, Raeisi‐Dehkordi H, Barati‐Boldaji R, Bellissimo N, Totosy de Zepetnek J. The effect of flaxseed supplementation on body weight and body composition: a systematic review and meta‐analysis of 45 randomized placebo‐controlled trials. Obesity Reviews. 2017;18(9):1096-107.
6. Mohammadi-Sartang M, Sohrabi Z, Barati-Boldaji R, Raeisi-Dehkordi H, Mazloom Z. Flaxseed supplementation on glucose control and insulin sensitivity: a systematic review and meta-analysis of 25 randomized, placebo-controlled trials. Nutrition reviews. 2017;76(2):125-39.
7. Mantzioris E, James MJ, Gibson RA, Cleland LG. Dietary substitution with an alpha-linolenic acid-rich vegetable oil increases eicosapentaenoic acid concentrations in tissues. The American Journal of Clinical Nutrition. 1994;59(6):1304-9.
8. Davis BC, Kris-Etherton PM. Achieving optimal essential fatty acid status in vegetarians: current knowledge and practical implications. The American Journal of Clinical Nutrition. 2003;78(3):640S-6S.
9. Burdge GC, Calder PC. Conversion of $\alpha$-linolenic acid to longer-chain polyunsaturated fatty acids in human adults. Reprod Nutr Dev. 2005;45(5):581-97.
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11. Arterburn LM, Hall EB, Oken H. Distribution, interconversion, and dose response of n−3 fatty acids in humans. The American Journal of Clinical Nutrition. 2006;83(6):S1467-76S.
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15. Balk EM, Lichtenstein AH, Chung M, Kupelnick B, Chew P, Lau J. Effects of omega-3 fatty acids on serum markers of cardiovascular disease risk: A systematic review. Atherosclerosis. 2006;189(1):19-30.
16. Campbell F, Dickinson HO, Critchley JA, Ford GA, Bradburn M. A systematic review of fish-oil supplements for the prevention and treatment of hypertension. European Journal of Preventive Cardiology. 2013;20(1):107-20.
17. Wang C, Harris WS, Chung M, Lichtenstein AH, Balk EM, Kupelnick B, et al. n−3 Fatty acids from fish or fish-oil supplements, but not α-linolenic acid, benefit cardiovascular disease outcomes in primary- and secondary-prevention studies: a systematic review. The American Journal of Clinical Nutrition. 2006;84(1):5-17.
18. León H, Shibata MC, Sivakumaran S, Dorgan M, Chatterley T, Tsuyuki RT. Effect of fish oil on arrhythmias and mortality: systematic review. BMJ. 2008;337.
19. Rizos EC, Ntzani EE, Bika E, Kostapanos MS, Elisaf MS. Association between omega-3 fatty acid supplementation and risk of major cardiovascular disease events: A systematic review and meta-analysis. JAMA. 2012;308(10):1024-33.
20. Appleton KM, Rogers PJ, Ness AR. Updated systematic review and meta-analysis of the effects of n−3 long-chain polyunsaturated fatty acids on depressed mood. The American Journal of Clinical Nutrition. 2010.
21. Appleton KM, Hayward RC, Gunnell D, Peters TJ, Rogers PJ, Kessler D, et al. Effects of n–3 long-chain polyunsaturated fatty acids on depressed mood: systematic review of published trials. The American Journal of Clinical Nutrition. 2006;84(6):1308-16.
22. Miles EA, Calder PC. Influence of marine n-3 polyunsaturated fatty acids on immune function and a systematic review of their effects on clinical outcomes in rheumatoid arthritis. British Journal of Nutrition. 2012;107(SupplementS2):S171-S84.
23. Wendland E, Farmer A, Glasziou P, Neil A. Effect of α linolenic acid on cardiovascular risk markers: a systematic review. Heart. 2006;92(2):166-9.
24. Burdge G. α-Linolenic acid metabolism in men and women: nutritional and biological implications. Current Opinion in Clinical Nutrition & Metabolic Care. 2004;7(2):137-44.
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