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).
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…
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). 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). 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).
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 18:1. In other words, we’re getting way more omega-6 than omega-3 from our foods. Why does this matter?
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%. A high omega-6 intake can result in higher inflammation and associated disease processes — 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 4:1.
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 function. 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 risk. Third, the oceans are steadily being stripped bare, which is having catastrophic effects on ecosystems globally. Fourth, research has made it demonstrably clear that fish are highly social animals that experience pain when they are removed from their natural environments.
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).
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.
There are mixed results from studies on omega-3 levels in vegans. 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-eaters. 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).
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 time.
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:
- 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.
- 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).
- 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.
- 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).
- 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.)
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!