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Omega-3 Fatty Acids: Fish or Supplements?

Long-chain omega-3 fatty acids from fish are known to have a variety of health benefits, but eating fish is not the healthiest method for getting these valuable fats.

There are three major omega-3 fatty acids that we get from our diets.  Alpha-linolenic acid (ALA) is a short-chain omega-3 found in flaxseeds, hemp seeds, walnuts, and other plant foods. ALA is an essential fatty acid – this means that the human body cannot synthesize it.  When we take in ALA from plant foods, the body can elongate it into long-chain omega-3s: docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), most commonly obtained by eating fish, whose tissues accumulate these fatty acids from algae or algae-consuming marine life.  EPA and DHA are important for human health, especially our brain.  Insufficiency of these valuable fats can cause a multitude of health issues.

Many health benefits are associated with adequate EPA and/or DHA levels or supplementation with these healthy fats:

  • Important for proper fetal and childhood brain and vision development
  • Reduced risk of ADHD and other childhood cognitive disorders
  • Improved memory; reduced risk of Alzheimer’s Disease and dementia
  • Improved lipid profile
  • Reduced risk of cardiovascular disease
  • Reduced risk of depression
  • Proper regulation of inflammation
  • Reduced risk of Parkinson’s disease

For vegetarians and vegans, are omega-3 supplements necessary? Or are walnuts and high omega-3 seeds enough?
EPA and DHA are considered “conditionally essential” fatty acids; even though the body is capable of making them from ALA (the “parent” omega-3 fatty acid found in walnuts, flax, hemp, chia, and leafy greens), they may be essential under some conditions because of inefficient conversion from ALA or insufficient ALA intake.1  Conversion of ALA to EPA and DHA varies based on dietary omega-6 to omega-3 ratio, other dietary fats, alcohol consumption, gender, age and individual genetic differences.2, 3   On average, less than 4% of ALA is converted to DHA in men and approximately 9% in women; less than 8% of ALA is converted to EPA in men and up to 21% may be converted in women.  Much of the ALA we take in from our diet is burned for energy, not converted to EPA and DHA.4  Because only ALA, not pre-formed DHA and EPA, is present in plant foods, vegans commonly have lower circulating levels of DHA than non-vegans.3, 5, 6   Unless eating lots of fatty fish, the typical modern diet is low in pre-formed EPA and DHA for omnivores, vegetarians, and vegans alike. Most people eat a diet rich in omega-6 fats, but deficient in omega-3s. Many vegetarians who consume sufficient flax, hemp, chia, walnuts, and greens as a source of ALA may manufacture sufficient long-chain omega-3s on their own. However, even with an ideal diet, conversion efficiency may not be sufficient for many people to achieve optimal long-chain omega-3 status, especially for DHA. 

One small study has suggested that vegans may have greater conversion efficiency than fish-eaters.7  However, the number of vegan participants was too small to come to any conclusions.  Vegan diets generally have a high ratio of omega-6 to omega-3 fatty acids, which inhibits conversion; a ratio of 2:1 to 4:1 is thought to result in adequate conversion, but vegetarian and vegan diets typically range between 10:1 and 20:1 (typical omnivorous diets are approximately 10:1), indicating that conversion is likely not optimal.  The low long-chain omega-3 blood levels found in vegans also indicate that conversion from ALA may not produce sufficient EPA and DHA to achieve their health benefits.3  It is often the case that consuming more ALA does not guarantee sufficient DHA.  For example, ALA supplementation of 2 grams/day (Adequate Intake of ALA recommended by the Institute of Medicine is 1.1 grams/day for women and 1.6 grams/day for men) was shown to produce only a very slight increase in long-chain omega-3 blood levels.8  I have found similarly when testing fatty acid levels in my patients that deficiencies of these fatty acids frequently exist, even in those who eat excellent diets with plenty of ALA-rich foods.  

As of yet, there is no data in the scientific literature investigating whether EPA and DHA supplementation specifically in vegetarians or vegans reduces disease risk similarly to the general population.9  However, at least two studies in vegetarians has shown that DHA supplementation improves serum lipids; triglycerides were reduced in both studies, and one study also saw a decrease in the total:HDL cholesterol ratio and the LDL:HDL ratio.  These results indicate that adding pre-formed EPA and DHA to a high-nutrient vegetarian or vegan diet would likely enhance the cardiovascular and other health benefits of the diet itself.10, 11

Fish, fish oil, or algae-based DHA+EPA?

Fish is an unfavorable source of EPA and DHA because most fatty fish contain harmful pollutants, such as dioxin and mercury. People also report difficulty digesting fish oils because of the fishy taste and foul odor. The bad taste, indigestion, and burping from these oils do not feel healthy. Purified fish oils are an option, but our oceans are in crisis. The claims about fish benefiting heart health have increased the demand for both fish and fish oils, and this demand cannot be met by the world's current supply. In 2003, it was estimated that the world's large predatory fish populations had declined 90% since the 1950s.15 Farmed fish are also problematic - they are fed a diet of smaller, wild fish, driving wild fish stocks down and adding chemicals and pollutants to local waters.16 DHA+EPA derived from lab-grown algae is a more sustainable option, a vegan source of long-chain omega-3s, and it is free of the environmental pollutants that accumulate in the fatty tissues of fish.

Since EPA and DHA have so many crucial functions and health benefits, it is imperative to maintain adequate levels of these fatty acids.

My experience has confirmed that for DHA levels sufficient to maintain brain health throughout life, a healthy diet (even with plenty of ALA-rich foods) simply may not be enough. This may be more important for males as they age. DHA deficiency carries dangerous risks and supplementation is the sensible choice.

Omega-3 supplement recommendations:

  • Take one tablespoon of hemp, chia, or ground flaxseeds each day.
  • Include additional plant sources of the omega-3 fatty acid ALA (walnuts, hempseeds or hemp milk, chia seeds) in your diet regularly.
  • Since only a limited amount of ALA can be converted to EPA and even less to DHA, take an algae-based DHA and EPA supplement each day.

To learn more:


  1. Higdon J: Essential Fatty Acids. In An Evidence-Based Approach to Dietary Phytochemicals. New York, NY: Thieme; 2006: 78-99
  2. Harnack K, Andersen G, Somoza V. Quantitation of alpha-linolenic acid elongation to eicosapentaenoic and docosahexaenoic acid as affected by the ratio of n6/n3 fatty acids. Nutr Metab 2009;6:8.
  3. Davis BC, Kris-Etherton PM. Achieving optimal essential fatty acid status in vegetarians: current knowledge and practical implications. Am J Clin Nutr 2003;78:640S-646S.
  4. Arterburn LM, Hall EB, Oken H. Distribution, interconversion, and dose response of n-3 fatty acids in humans. Am J Clin Nutr 2006;83:1467S-1476S.
  5. Sanders TA. DHA status of vegetarians. Prostaglandins Leukot Essent Fatty Acids 2009;81:137-141.
  6. Kornsteiner M, Singer I, Elmadfa I. Very low n-3 long-chain polyunsaturated fatty acid status in Austrian vegetarians and vegans. Ann Nutr Metab 2008;52:37-47.
  7. Welch AA, Shakya-Shrestha S, Lentjes MA, et al. Dietary intake and status of n-3 polyunsaturated fatty acids in a population of fish-eating and non-fish-eating meat-eaters, vegetarians, and vegans and the precursor-product ratio of alpha-linolenic acid to long-chain n-3 polyunsaturated fatty acids: results from the EPIC-Norfolk cohort. Am J Clin Nutr 2010;92:1040-1051.
  8. Fokkema MR, Brouwer DA, Hasperhoven MB, et al. Short-term supplementation of low-dose gamma-linolenic acid (GLA), alpha-linolenic acid (ALA), or GLA plus ALA does not augment LCP omega 3 status of Dutch vegans to an appreciable extent. Prostaglandins Leukot Essent Fatty Acids 2000;63:287-292.
  9. Mangat I. Do vegetarians have to eat fish for optimal cardiovascular protection? Am J Clin Nutr 2009;89:1597S-1601S.
  10. Conquer JA, Holub BJ. Supplementation with an algae source of docosahexaenoic acid increases (n-3) fatty acid status and alters selected risk factors for heart disease in vegetarian subjects. J Nutr 1996;126:3032-3039.
  11. Geppert J, Kraft V, Demmelmair H, et al. Microalgal docosahexaenoic acid decreases plasma triacylglycerol in normolipidaemic vegetarians: a randomised trial. Br J Nutr 2006;95:779-786.
  12. Myers RA, Worm B. Rapid worldwide depletion of predatory fish communities. Nature 2003;423:280-283.
  13. Jenkins DJA, Sievenpiper JL, Pauly D, et al. Are dietary recommendations for the use of fish oils sustainable? Can Med Assoc J 2009;180:633-637.
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