How to get enough omega-3 fatty acids on a vegan diet

In Blog, Fats, Nutrition by MurielLeave a Comment

Hold on tight! We’re uncovering some of the mysteries of essential fatty acids, why they’re important, where we can find them in foods, and whether we should supplement them. I’m rarely satisfied with a cursory overview and find myself digging into the details to understand as much as possible. This is a fascinating topic with still-evolving research, and I hope you’ll enjoy this piece. In case you want to skip ahead to the summary and takeaways, click here.

What are omega-3 and omega-6 fatty acids?

Omega-3 and omega-6 are two families of fatty acids that are crucial for good health. They’re called ‘essential fatty acids’ – essential, because they cannot be manufactured in our bodies, and they have to be obtained from food. And, you guessed it: fatty acids are the chemical structures that combine to form fats. Modern diets typically provide us with ample omega-6 fatty acids, but omega-3 fatty acids are a bit more limited (read on).

Short-chain fatty acids vs long-chain fatty acids

There are different forms of fatty acids in each of the two families. Short-chain fatty acids alpha-linolenic acid (ALA, an omega-3 fatty acid) and linoleic acid (LA, an omega-6 fatty acid) are generally abundant in the food supply. After we consume them, they undergo chemical processes in our bodies: a large portion is used for energy, a small percentage is converted to ‘long-chain’ (referring to a chain of carbon atoms) fatty acids called DHA and EPA (from ALA) and AA (from LA).

These long-chain fatty acids, in turn, are metabolised to compounds that are important for regulating various bodily processes including cell division, blood clotting, immune control, inflammation response and more…

Building brains

But the recent buzz around essential fatty acids concerns our brains: about 20% of the dry weight of our brains is made up of DHA and AA, the long-chain fatty acids from omega-3 and omega-6 (respectively)1O’Brien JS, Sampson EL. Lipid composition of the normal human brain: gray matter, white matter, and myelin. J Lipid Res. 1965 Oct;6(4):537-44. PMID: 5865382.. In early growth stages of human life, it’s critical to have adequate DHA levels so that the brain and central nervous system can form (which is why it’s strongly recommended that pregnant women take a DHA/EPA supplement)2Koletzko B, Lien E, Agostoni C, Böhles H, Campoy C, Cetin I, Decsi T, Dudenhausen JW, Dupont C, Forsyth S, Hoesli I, Holzgreve W, Lapillonne A, Putet G, Secher NJ, Symonds M, Szajewska H, Willatts P, Uauy R; World Association of Perinatal Medicine Dietary Guidelines Working Group. The roles of long-chain polyunsaturated fatty acids in pregnancy, lactation and infancy: review of current knowledge and consensus recommendations. J Perinat Med. 2008;36(1):5-14. doi: 10.1515/JPM.2008.001. PMID: 18184094.. As we age, our brains undergo a natural process where they slowly shrink in size from about the age of 20 – and if our omega-3 levels fall below a certain threshold, that brain loss can be accelerated (more on this later)3Greger M 2016, Should Vegans Take DHA to Preserve Brain Function?, viewed 14 Jan 2021, <>.

It’s about the ratio

Now, we need both omega-3 and omega-6 fatty acids. But the comparative amounts of omega-3 and omega-6 that we get in today’s food systems are very different to 150 years ago. It’s thought that in a bygone era, with pre-industrial food systems, we were getting about the same amount of omega-6 as omega-3 fatty acids, i.e. a 1:1 ratio. Today, our food system has changed dramatically, and the ratio of omegas in our diet ranges between about 8:1 to 18:14Davis, B., & Melina, V. (2014). Becoming Vegan: the complete reference to plant-based nutritionComprehensive Edition. Summertown, TN: Book Publishing Company.. In other words, we’re getting way more omega-6 than omega-3 from our foods. Why does this matter?

Competition for enzymes

Omega-3 and omega-6 compete for enzymes. The chemical processes that convert short-chain fatty acids (ALA and LA) to longer-chain fatty acids (e.g. DHA and AA), rely on a limited supply of enzymes (or biological catalysts). If there is too much of one type of fatty acid compared to another, there’s competition for those enzymes, and one of them wins out. In fact, a high intake of omega-6 can reduce the conversion of omega-3 by 40-60%5Simopoulos AP. An Increase in the Omega-6/Omega-3 Fatty Acid Ratio Increases the Risk for Obesity. Nutrients. 2016;8(3):128. Published 2016 Mar 2. doi:10.3390/nu8030128. A high omega-6 intake can result in higher inflammation and associated disease processes6Simopoulos AP. The importance of the omega-6/omega-3 fatty acid ratio in cardiovascular disease and other chronic diseases. Exp Biol Med (Maywood). 2008 Jun;233(6):674-88. doi: 10.3181/0711-MR-311. Epub 2008 Apr 11. PMID: 18408140. – we don’t want that!

We need to give our omega-3 fatty acids a better chance at competing for those enzymes, which means we need to reduce the ratio of omega-6 to omega-3 in our diets. That’s the first step: from there, we can look at increasing our intake of omega-3 to try and reach a ratio between 2:1 and 4:17Davis BC, Kris-Etherton PM. Achieving optimal essential fatty acid status in vegetarians: current knowledge and practical implications. Am J Clin Nutr. 2003 Sep;78(3 Suppl):640S-646S. doi: 10.1093/ajcn/78.3.640S. PMID: 12936959..

The big question: aren’t fish a good source of omega-3?

Fish and other seafood are widely accepted as a rich source of long-chain omega-3 fatty acids – and they are. People who eat fish do have a higher dietary intake of omega-3.

However, there are significant concerns about fish consumption. First, fish (and fish oil) are often contaminated with heavy metals such as lead and mercury, carcinogens that can induce organ damage and reduce mental function8Bosch AC, O’Neill B, Sigge GO, Kerwath SE, Hoffman LC. Heavy metals in marine fish meat and consumer health: a review. J Sci Food Agric. 2016 Jan 15;96(1):32-48. doi: 10.1002/jsfa.7360. Epub 2015 Sep 7. PMID: 26238481.. Second, fish-eaters have about the same rates of heart disease as meat-eaters (purportedly due to the saturated fat and cholesterol in their diets), whereas vegetarians (and vegans) have a considerably lower risk9Crowe FL, Appleby PN, Travis RC, Key TJ. Risk of hospitalization or death from ischemic heart disease among British vegetarians and nonvegetarians: results from the EPIC-Oxford cohort study. Am J Clin Nutr. 2013 Mar;97(3):597-603. doi: 10.3945/ajcn.112.044073. Epub 2013 Jan 30. PMID: 23364007.. Third, the oceans are steadily being stripped bare, which is having catastrophic effects on ecosystems globally10FAO Fisheries and Aquaculture Department, The State of World Fisheries and Aquaculture, 2006, Food and Agriculture Organization of the United Nations, Rome, 2007. Fourth, research has made it demonstrably clear that fish are highly social animals that experience pain when they are removed from their natural environments11Chandroo, K. P. et al. “Can fish suffer?: perspectives on sentience, pain, fear and stress.” Applied Animal Behaviour Science 86 (2004): 225-250..

With all this in mind, it’s a relief to know that fish don’t have to be a dietary source of omega-3 fatty acids. After all, fish don’t make their DHA and EPA, they get it from micro-algae – so if we want a direct source of long-chain omega-3, we can get it from micro-algae, just as the fish do. Moreover, research has shown that fish oil supplements don’t increase brain DHA levels (meanwhile, the supplement industry has been profiting for years)12Greger M 2014, Is Fish Oil Just Snake Oil?, viewed 14 Jan 2021, <>.

It’s worth bearing in mind that humans (and other animals) living far from coastal areas would not have had access to fish and seafood. Instead of getting a direct source of long-chain fatty-acids, they would have had to develop an ability to make the most of short-chain fatty acids for brain development. That’s another reason why seeds and nuts are such an important food source.

But long-chain omega-3 levels are lower in vegans…

There are mixed results from studies on omega-3 levels in vegans13Davis, B., & Melina, V. (2014). Becoming Vegan: the complete reference to plant-based nutritionComprehensive Edition. Summertown, TN: Book Publishing Company.. Most studies conclude that vegans typically have lower levels of DHA and EPA, but one study indicates that the conversion of omega-3 in non-fish eaters is higher than in fish-eaters14Welch AA, Shakya-Shrestha S, Lentjes MA, Wareham NJ, Khaw KT. 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 product-precursor ratio [corrected] of α-linolenic acid to long-chain n-3 polyunsaturated fatty acids: results from the EPIC-Norfolk cohort. Am J Clin Nutr. 2010 Nov;92(5):1040-51. doi: 10.3945/ajcn.2010.29457. Epub 2010 Sep 22. Erratum in: Am J Clin Nutr. 2011 Mar;93(3):676. PMID: 20861171.. It’s been hypothesised that the body limits the conversion to DHA when it’s not needed (after all, DHA is easily oxidised by free radicals, and oxidised fats can lead to disease)15Davis, B., & Melina, V. (2014). Becoming Vegan: the complete reference to plant-based nutritionComprehensive Edition. Summertown, TN: Book Publishing Company..

That said, there is concern about accelerated brain loss and dementia resulting from a DHA deficiency. As we age, our bodies’ ability to convert short-chain omega-3 tends to decline. If omega-3 levels fall below a certain threshold (an omega-3 index of 4.4), there is a risk of faster brain loss over time16Greger M 2016, Should Vegans Take DHA to Preserve Brain Function?, viewed 14 Jan 2021, <>.

What should a vegan do?

There are still gaps in knowledge and opportunities for further research – especially on omega-3 conversion in vegan diets. While it seems possible to attain a healthy omega-6 to omega-3 ratio with plant-based foods, many experts recommend taking a supplement, if only to err on the side of caution. But before you run out and buy that supplement, it’s important to get your foundations right first:

  1. Make sure you’ve got a varied diet with sufficient protein, vitamins, minerals and antioxidants, to maximise omega-3 conversion and protect the long-chain fatty acids from oxidation.
  2. Lower the ratio of omega-6 to omega-3 fatty acids in your diet, aiming for a 2:1 to 4:1 ratio. Reduce your use of oils high in omega-6 (e.g. sunflower, grapeseed and sesame oil), avoid refined convenience foods that rely on oils high in omega-6 (e.g. margarines, store-bought cookies and salad dressings), and limit your intake of high-omega-6 seeds (e.g. sunflower, pumpkin and sesame seeds).
  3. Be aware of factors that inhibit omega-3 conversion, and try to reduce them. Smoking, poor nutrition, high alcohol consumption, very high-fat diets, and trans-fatty acids all contribute to lower conversion rates.
  4. Make a point of adding sources of ALA (short-chain omega-3) to your daily diet. Instead of sunflower oil (which is high in omega-6), use canola oil or extra-virgin olive oil (high in omega-3), and eat a tablespoon or two of seeds rich in omega-3 (flaxseeds are great, but make sure to grind them first – whole flax tends to go right through your body without being digested).
  5. Finally, if you want to be extra safe, go and get a supplement. A combination of DHA and EPA is recommended, and it should be quality-controlled and toxin-free. 100 to 300 mg a few times a week should be adequate. (Pregnant women will need 200 to 300 mg per day.)17Davis, B., & Melina, V. (2014). Becoming Vegan: the complete reference to plant-based nutritionComprehensive Edition. Summertown, TN: Book Publishing Company.

The long and short of it all (sorry, couldn’t resist)

Eat whole, plant-based foods. Quit the junk. Eat seeds. Consider a supplement. And don’t forget other healthy brain-boosting activities: read books, spend less time on social media, solve puzzles. Brains need training, not just food!

Disclaimer: I’m vegan, and choose not to consume fish (or any other animals) for ethical and environmental reasons. I’m not a medical expert nor a dietician. The information in this article is sourced from a textbook on vegan nutrition by two widely-respected registered dieticians, and from scientific publications (references are included in the original article on my website). I’m fortunate to benefit from the hard work of respected scientists in the field of nutrition, and I’m glad to share my own learnings here. If anything’s unclear or if I’ve made any erroneous statements, please get in touch!

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