Omega-3 and health- is it better to get from a supplement, fish or plant?


By Laurentia (Laura) Campbell

Omega-3’s are a type of polyunsaturated fatty acid that we can only get from our diet (our bodies cannot make them) which are essential for brain functioning (Kidd, 2007), glucose control and insulin sensitivity, as a source of energy and which reduce inflammation. They play a vital role in mental and physical health (Fairbairn et al., 2023). We have three types; ALA (alpha-linolenic acid), the “parent omega” which is from plants such as Brussel sprouts, green leafy veg, edamame beans, walnuts, cauliflower, almonds, chia, flax (Zhang et al., 2022) and hemp seeds and found in most vegetable oils and foods like Kale and Spinach. 6–8% of this, is then converted to EPA (eicosapentaenoic acid) which is found in oily fish like salmon, mackerel, tuna and sardines and in small doses of meat such as chicken and beef as well as algae and some seaweed, and docosahexaenoic acid (DHA), also found in oily fish and meat. DHA is a major structural component of the brain. Despite Brussel sprouts, edamame beans, walnuts and soya beans all being rich sources of Omega-3, we cannot get EPA and DHA solely from plant-based sources. Only less than 10% of plant-based sources convert to EPA and DHA. Most people are deficient in Omega-3, so what is the best source? Fish or fish oil supplement?

What are the benefits of Omega-3’s

Omega-3 increases neurogenesis (the formation of new brain cells and synaptic junctions (that link brain cells), (Liao et al., 2019), by impacting the formation of neurotropic factors which regulate the growth of new brain cells and play and important role in human cognition and emotion. Omega-3 fatty acids also have a low glycaemic index, which help stabilise blood sugar and keep emotions and energy levels balanced, helping contribute to sustained focus and concentration and optimising cognitive, creative, and educational performance. Evidence shows they also reduce symptoms of depression (Grosso et al., 2014) and help to reduce circulating LDL (low-density lipoproteins). LDL (Abdelhamid et al., 2018) move Cholesterol from our diet to the blood vessels where they can clump and block blood vessels, promoting high blood pressure and cardiovascular diseases such as Angina, heart attacks and strokes. Both plant and animal sources of Omega-3s have LDL-cholesterol reducing effects.

Figure 1: (Grosso et al., 2014)- Omega-3 fatty acids and depression: scientific evidence and biological mechanisms

Omega-6’s are also vital for health. They are structural lipids, made from linolenic acid (LA) “parent omega”, which are needed for immune function, reproduction, growth and brain development. Omega-6’s are found in nuts, seeds and vegetable oils and spreads (in some cakes, processed foods and biscuits). Omega-3 and Omega-6 fatty acids are made by the same enzymes, but the products of omega3 (DHA) are anti-inflammatory whilst the products of Omega6’s (Arachidonic Acid, AA) have been shown to be pro-inflammatory. Ideally, we want a high Omega3: low Omega-6 ratio (Simopoulos, 2002) as increased inflammation has been found to be associated with depression and other mood disorders, obesity and type 2 diabetes.

What is the best source of Omega-3?

The best traditional source of EPA and DHA Omega-3 has been algae, fish, seafood, and seaweed. This is because our prehistoric ancestors are believed to have turned to the (Stark et al., 2016) (Spiller et al., 2019) sea for essential nutrients and as they received sufficient from this source, our brains evolved to no longer make our own Omega-3. Fish meat is the ideal source of Omega-3 as the protein in the fish helps the Omega-3’s fatty acids be more easily digested from our gut into our blood and then taken up by tissues such as the brain. This helps reduce (Huang et al., 2020) inflammation in the tissues. It also helps reduce gut inflammation, improving the barrier function of the gut walls and helping reduce intolerances and allergy. The way the fish is cooked may also impact the amount and benefits of the Omega-3’s in fish. Fish are also rich in vitamin D, selenium antioxidant (which reduces inflammation) and Iodine mineral (which increases thyroid function and metabolism). The high protein content of fish also contributes to its benefits as the protein is broken down to amino acids in digestion, which are taken up by the blood and help to make muscle, collagen and keratin (skin and hair), neurotransmitters and neuropeptides. Therefore, fish consumption has numerous health benefits, which making it more advantageous to consume as part of a diet over taking fish oil supplements.

However, as many of you will have seen on the Netflix documentary “eating our way to extinction” about overfishing, regular fish eating is no longer sustainable, and there is a worry about the high levels of the toxin mercury in some fish. Small fish eat plant plankton containing mercury and then it moves its way up the food chain as the plankton are eaten by small fish, which are eaten by medium fish, which are eaten by larger fish. This is called Biomagnification (or bioamplification) when there is an increase in the concentration of a substance as you move up the food chain. Albacore tuna, swordfish and marlin are all large fish which are high in Mercury. Smaller fish such as anchovies, clams, shrimp, mussels, and medium fish such as cod, salmon, haddocks and crustaceans such as crab, contain omega3 but are low in mercury. Many people have chosen to reduce their fish intake for the environment and ethical reasons, and to turn to more plant based diets. In these cases, supplementation may be the easiest choice as alternatives, such as algae are hard to source and are not yet seen as a conventional dietary choice.

Plant based sources of Omega-3 include flaxseed, canola, soyabean oils, hemp and walnut oils which are rich in ALA. This is then converted to EPA and DHA in the liver. However, this conversion is limited in humans and factors such as stress, aging, illness, and diet can impair the process. Therefore those on plant-based diets are required to supplement their diet with algal oils which are a vegetarian source of DHA and some also contain EPA (Abdelhamid et al., 2018) or Flaxseed oil which contains ALA. Fish oil supplements contain EPA and DHA. Fish liver oil supplements, such as cod liver oil, contain EPA and DHA and they also contain vitamins A and D in small amounts that vary from product to product. Krill oil contains EPA and DHA. It is essential that if you want to buy a fish-based supplement that it says EPA and DHA Omega-3 and not simply “fish oils.” It is also important that you eat the supplement with a source of protein, to increase absorption and not with fibre (vegetables) as excess fibre can reduce the fatty acid absorption across the gut.

How much omega-3 should I have?

Excessive consumption of Omega-3 can lead to raised blood sugar levels and vitamin A and D toxicity, and so it is essential that you do not over-supplement and adhere to the required dosage. Whilst there is no UK recommended daily value (RDV) for Omega-3, it is advised to have 500–1000mg of Omega-3 per day. Examples of good sources include:

- A salmon fillet (240g) contains approximately 786mg DHA and 718mg EPA (1400mg omega3)

- A 240g tuna steak contains 330mg DHA

- A mackerel fillet 240g contains 1330mg DHA and EPA

- 15g of flaxseed contains 1500mg ALA

- 15g of chia seed contains 1250mg ALA

- 15g of walnuts contain 1125mg ALA

- Seaweed, nori, spirulina, and chlorella contain 600mg EPA and DHA (depending on source)

The exact Omega-3 dosage from a food depends on the source of the food (wild farmed fish contains more Omega-3 than mass farmed fish), the portion size, how the food is cooked (raw, steamed and fried fish have different Omega-3 profiles), and what you eat it with (protein increases Omega-3 absorption and fibre and saturated fats decrease it). With supplements (Nichols et al., 2014; Saini et al., 2021) it depends on the source of the type of Omega-3 (ALA/EPA/DHA), the source (which fish/how it is farmed) and how old the supplement is (as fish oil Omega-3 declines with time). Salted fish and salted seaweed decrease the Omega-3 absorption. If you are a vegan, it is essential for your health you supplement with DHA algae supplements to ensure you meet your brain and body Omega-3 requirements.

Omega-3 is food for the brain. It is essential. Feed your brain.


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Laurentia (Laura)Campbell

Neuroscience, mental health and nutrition academic and writer. Life-experimenter, trying to add value with an insatiable appetite for actioning positive change.