By Cordelia Woodward, Registered Dietitian
Marine foods are often promoted as important sources of nutrients such as omega-3 fatty acids and iodine. However, questions have been raised around their sustainability, ethics, accessibility and long-term role in healthy diets.
For people following predominantly plant-based diets, omega-3 is one nutrient worth exploring in more detail. Do we need to eat fish to get enough? How well does the body convert plant-based omega-3 into the longer-chain forms? And what role might algae-derived sources play?
These are some of the questions being explored in the Blue Foods: Are They Essential, Optional, or Obsolete? panel at Nutrition and Lifestyle Medicine Conference (NLMC) 2026, November 5-6th, which will bring together perspectives from nutrition science, public health, sustainability and food systems research.
What are omega-3 fatty acids?
Omega-3 fatty acids are a type of polyunsaturated fat that play an important role in supporting heart, brain and eye health.
There are different types of omega-3. The long-chain omega-3 fats EPA and DHA are mainly found in oily fish and marine algae.
Plant-based foods provide another type of omega-3 called ALA, or alpha-linolenic acid. The body can convert ALA into the longer-chain omega-3 fats EPA and DHA.
However, how much conversion takes place, why conversion may vary between people and which dietary factors might influence it are important considerations when looking at omega-3 intake in predominantly plant-based diets. These are among the questions being considered as part of the NLMC panel.
Where can you get omega-3 on a plant-based diet?
A range of plant foods can contribute ALA to the diet, including:
- Ground flaxseed or linseed – stir into porridge, easy to incorporate into baking
- Linseed oil – drizzle over cooked vegetables, stir into smoothies, or use as the oil in a salad dressing
- Rapeseed oil – a straightforward swap for salad dressings and everyday cooking
- Chia seeds – soak overnight for a simple chia pudding, or scatter over salads and cereal
- Hemp seeds – sprinkle over soups or salads
- Walnuts – a handful as a snack, or chopped over porridge
- Soya foods such as tofu, tempeh and edamame – tofu and tempeh in stir-fries and curries, edamame as a snack or salad addition
Some fortified foods, including certain dairy alternatives, spreads and other products, may also contain added omega-3.
The British Dietetic Association identifies foods such as flaxseed, rapeseed oil, walnuts, chia and soya as useful sources of ALA.1 The NHS also recommends foods including ground linseed, linseed oil, rapeseed oil, chia seeds, hemp seeds and walnuts as sources of omega-3 for people following vegan diets.2
These foods can therefore make an important contribution to omega-3 intake.
However, most plant foods provide ALA rather than EPA and DHA. Because conversion of ALA into these longer-chain fatty acids is limited, the overall dietary pattern and individual circumstances need to be considered rather than assuming that all sources of omega-3 are nutritionally interchangeable.3
What role could algae play?
Algae is particularly interesting when considering omega-3 intake in the context of plant-based diets. Fish obtain their omega-3 from marine algae, and algae-derived sources and supplements provide another way of obtaining DHA and EPA without relying on fish. As pressure on marine ecosystems increases due to factors including overfishing and climate change, microalgal oil (oils produced from microalgae) has emerged as a renewable and potentially scalable source of DHA and EPA. This makes algal oil a potentially useful option for people who do not eat fish.
There is also emerging human evidence supporting the bioavailability of algae-derived omega-3. A 2025 double-blind, placebo-controlled randomised controlled trial comparing microalgal oil with fish oil found that DHA and EPA from microalgal oil were non-inferior to those from fish oil .3 The authors concluded that “the current study supports the notion that microalgal oil is a sustainable, plant-based and bioavailable source of DHA and EPA that can help us meet the global nutritional needs for these essential macronutrients, similar to fish oil.”
Pregnancy is one area where this question may be particularly relevant. Long-chain omega-3, particularly DHA, has an important role in the development of the baby’s nervous system.4 For people who do not eat fish, algae-derived DHA may therefore be a particularly relevant source to consider.
However, bioavailability is only one consideration when evaluating the potential role of algal oil. Whether algae-derived omega-3 can provide comparable nutritional and health benefits to fish-derived omega-3, alongside considerations of sustainability, dosage and its practical role within plant-based diets, will be explored further in the NLMC discussion.
What about seaweed and iodine?
Iodine is another nutrient worth considering when discussing marine foods and plant-based diets, although it is separate from omega-3.
Seaweed can contain substantial amounts of iodine, but the concentration can vary considerably between different types and products. This means that seaweed should not simply be viewed as a consistent source of iodine without considering the particular product and quantity consumed.
The NHS advises that adults require around 140 micrograms of iodine per day and notes that people following vegan diets may need to consider iodine-fortified foods or supplementation. It also warns that excessive iodine intake can be harmful.5
For people following vegan or predominantly plant-based diets, iodine is therefore another nutrient that may warrant attention, rather than assuming that reducing or removing marine foods has the same nutritional implications for every nutrient.
What does the wider picture tell us?
The question of whether we need fish for omega-3 is part of a bigger conversation about what a healthy and sustainable diet could look like.
A 2019 EAT-commissioned scoping report, produced by researchers at the Stockholm Resilience Centre, highlights why seafood should not be treated as one single category. Different species and production methods can vary considerably in both their nutritional value and environmental impact. For example, fatty fish such as herring, mackerel, trout and salmon generally contain more EPA and DHA than lean fish, while lower-trophic species tend to be less dependent on animal-based feeds. The report also notes that carnivorous farmed species such as salmon, grouper and shrimp generally have larger environmental footprints, particularly in relation to feed.6
The report also highlights the particular importance of omega-3 from seafood for groups such as pregnant women and infants, while pointing to the need for further research into how seafood can contribute to healthy and sustainable diets.
This adds another layer to the question. It is not simply about whether fish can be replaced nutritionally, but about which foods provide which nutrients, for whom, and at what environmental cost.
So, do we need fish for omega-3?
No, fish are not essential for obtaining omega-3. Plant foods can provide ALA, while algae-derived oils can provide EPA and DHA directly. Emerging evidence suggests that DHA and EPA from microalgal oil can be as bioavailable as those from fish oil. However, bioavailability is only one part of the picture, and questions remain about whether different sources have the same longer-term health effects and how this evidence should inform dietary advice.
For people following predominantly plant-based diets, this means that meeting omega-3 needs does not necessarily require eating fish. Instead, the focus is on choosing appropriate sources of omega-3 and considering what those choices mean for health, sustainability and the wider food system.
These are the kinds of questions that the Blue Foods: Are They Essential, Optional, or Obsolete? panel at NLMC 2026 will explore, bringing together perspectives from nutrition, sustainability, public health and food systems research.
Want to hear the discussion in person?
The Nutrition and Lifestyle Medicine Conference (NLMC), organised by Plant-Based Health Professionals UK, takes place in London on 5th–6th November, bringing together experts in nutrition, planetary health and sustainable food systems.
The MyNutriWeb team will be there throughout so come and find us if you’d like to talk about the questions raised in this piece, or your own work in plant-based nutrition.
MyNutriWeb community members get 10% off with code MNW-NLMC26-D10.
The MyNutriWeb team at NLMC 2025
References
- British Dietetic Association. Vegetarian, vegan and plant-based diet. Published July 1, 2021. Accessed September 16, 2026. https://www.bda.uk.com/resource/vegetarian-vegan-plant-based-diet.html
- NHS. The vegan diet. Updated June 5, 2026. Accessed September 16, 2026. https://www.nhs.uk/live-well/eat-well/how-to-eat-a-balanced-diet/the-vegan-diet/
- Bailey E, Wojcik J, Rahn M, Roos F, Spooren A, Koshibu K. Comparative bioavailability of DHA and EPA from microalgal and fish oil in adults. Int J Mol Sci. 2025;26(19):9343. doi:10.3390/ijms26199343
- Hu R, Xu J, Hua Y, Li Y, Li J. Could early life DHA supplementation benefit neurodevelopment? A systematic review and meta-analysis. Front Neurol. 2024;15:1295788. doi:10.3389/fneur.2024.1295788
- NHS. Iodine—vitamins and minerals. Updated August 3, 2020. Accessed September 16, 2026. https://www.nhs.uk/conditions/vitamins-and-minerals/iodine/
- Troell M, Jonell M, Crona B. The Role of Seafood in Sustainable and Healthy Diets: The EAT-Lancet Commission Report Through a Blue Lens. Stockholm Resilience Centre; 2019. Accessed September 16, 2026. https://eatforum.org/wp-content/uploads/2025/09/Seafood_Scoping_Report_EAT-Lancet.pdf
