When is a fish not a fish?

The term fishless fish may seem like an oxymoron, but is there any value in consuming them as part of a healthy sustainable diet?

Consumers may be more accustomed to the term meat-less burgers and sausages as these plant-based (PB) meat replacements account for a greater proportion of the food market. As an example, an audit of products available in major supermarkets in Australia (in 2019) found that just 6.5% of products designed to mimic the taste and texture of animal products were categorised as seafood replacements. In contrast, burgers and sausages accounted for 36.5% and 21.2% of the market share, respectively. Consumers are also likely to be familiar with messages to reduce meat, specifically red and processed meat, due to the associated risk of cancer, and therefore, more amenable to introduce PB meat substitutes into their diets. Furthermore, there is growing awareness in the general population of the impact of meat consumption on the environment, in addition to animal welfare.

The lower availability of PB alternatives to fish may in part reflect the considerable challenges in producing a product that mimics the taste, texture and nutritional properties of fish. In addition, the demand may be lower for PB fish alternatives due to the proposed health benefits of including fish in the diet. Healthy eating guidelines in the UK recommend the consumption of two portions of fish per week, including one portion of oily fish. Oily fish, such as salmon, pilchards and sardines are good sources of the long chain omega 3 fatty acids, namely eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), along with iodine, which are important for heart health and thyroid function, respectively.

While there are PB sources of omega 3 (table 1), they are mainly comprised of alpha-linolenic acid (ALA), the precursor for EPA and DHA.  The conversion of ALA to the heart healthy EPA and DHA is low in humans, likely due to the high consumption of omega 6 fatty acids present in plant foods, which inhibits the process (Webb 2020). To help balance the ratio of omega 3 and omega 6, the Vegan Society recommend using vegetable oil (rapeseed) over sunflower, corn or sesame oil, and limiting the consumption of pumpkin and sunflower seeds to 30 g (1/4 cup) per day. In contrast, algal oil and seaweed provide a concentrated source of long chain omega 3 fatty acids (in the form of DHA) and iodine (Table 2), respectively, for people who exclude fish and other animal sources of iodine.

Table 1: Nutrient composition of foods containing good sources of omega 3

Food/IngredientPortion sizeOmega 3 (g)*
Algal oil Holland & BarrettHealthspan  1 capsule 1 Veg-omega 3  DHA 2.0 DHA 3.4, EPA 1.7
Chia seeds1 tablespoon (10g)1.9
Flax seed1 tablespoon (9 g)2.2
Rapeseed oil1 tablespoon (12.6g)1.2
Seaweed (Nori dried)10 gNo data
Walnuts6 whole nuts (24g)1.8
Mackerel1 medium fillet (80g)3.2
Mackerel1 can (tomato sauce) 125 g3.9
Sardines1 average portion (85g)1.1
Sardines1 can (oil) 120 g3.0
Salmon (farmed)1 small fillet (110g)3.6
Salmon (tinned)1 small can (79 g drained)1.3
Salmon (wild)1 small fillet (110g)2.4

* Data generated through dietary analysis software (Nutritics Education, v5.65)

**Manufacturers product information

Table 2: Nutrient composition of foods containing good sources of iodine

Food/IngredientPortion sizeIodine (μg)*
Chia seeds1 tablespoon (10g)No data
Flax seed1 tablespoon (9 g)0.0
Rapeseed oil1 tablespoon (12.6g)0.0
Seaweed (Nori dried)10 g147
Walnuts6 whole nuts (24g)2.2
Mackerel1 medium fillet (80g)23.2
Mackerel1 can (tomato sauce) 125 g59.0
Sardines1 average portion (85g)67.0
Sardines1 can (oil) 120 g27.6
Salmon (farmed)1 small fillet (110g)13.2
Salmon (tinned)1 small can (79 g drained)17.4
Salmon (wild)1 small fillet (110g)13.2

* Data generated through dietary analysis software (Nutritics Education, v5.65)

In recent years, there has been an increase in awareness of the impact of the fishing industry on the environment (microplastics and chemicals found in fish) and animal welfare (including marine mammals). While there have been efforts to reduce the impact of the fishing industry on marine life and biodiversity through certification of fisheries and industry that use sustainable fishing practices, the welfare of fish and seafood lacks the level of protection provided to other sentient beings. As an example, the Welfare of Farmed Animals at the Time of Killing Regulations (2015) include restrictions on the slaughter of birds, sheep, goats and bovine, but not aquatic animals. As awareness grows ethical consumers may drive the demand for PB fish alternatives.

The production and consumption of PB meat alternatives in general has increased considerably. These products provide a convenient way for people to transition to a vegetarian or vegan diet, as they allow consumers to continue to consume familiar meals using the meat substitute (e.g. spaghetti bolognaise or chilli con carnie). Despite this, the rise in consumption appears to be mostly in non-vegans, as it is estimated that with 92% of PB meals are eaten by non-vegans who want to consume less meat and dairy (Kantar, 2019).  But how do meat and fish alternatives measure up nutritionally?

Findings of a study conducted at Edge Hill University (data presented at the International Symposium on Nutrition, January 2022) indicates that PB alternatives to convenience foods available in UK supermarkets are generally lower in energy, total fat, and saturated fat than meat products, which may be beneficial to health. As an example, replacements could improve energy balance and lower saturated fat intake, and support efforts to reduce obesity and non-communicable diseases. Unsurprisingly, PB products were lower in protein, but contained significantly more fibre. This is interesting as data from the National Diet and Nutrition Survey, indicate that only 9% of the population meet current targets for fibre, while the majority of ‘developed’ nation populations exceed protein recommendations, and therefore may contribute to a more favourable nutritional status. Despite these positive attributes of PB products, both PB (0.83 ± 0.7 g per 100g) and meat (0.76 ± 0.44 g per 100g) products contain moderate amounts of salt and therefore indicate that convenience in general should be consumed in moderation.

As yet, there is limited data comparing the micronutrient content of PB meat and fish replacements to standard products. In contrast, comparisons of PB milks with animal milks are widespread.  A UK study comparing the nutrient profiles of these milks found that the majority of PB milks (n = 44 out of 47 sampled) were not fortified with iodine, and therefore provided just 1.7% of the iodine value of cow’s milk. Furthermore, PB milks fortified with iodine contained between 37 – 58 μg/kg and 151 – 172 μg/kg less iodine than the average organic and conventional milk, respectively. As such, consumers may need to be cautious when relying solely on PB replacements that may not provide a like for like nutrient profile. This is especially important for those following a vegan diet, as they exclude all animal products. At present, the best way to ensure a nutritionally balanced and sustainable diet is to carefully plan dietary intake, which may include the use of nutritional supplements.

Dr Claire Blennerhassett


Bath, S., Hill, S., Infante, H., Elghul, S., Nezianya, C., & Rayman, M. (2017). Iodine concentration of milk-alternative drinks available in the UK in comparison with cows’ milk. British Journal of Nutrition, 118(7), 525-532. http://doi:10.1017/S0007114517002136 

Curtain, F., & Grafenauer, S. (2019). Plant-Based Meat Substitutes in the Flexitarian Age: An Audit of Products on Supermarket Shelves. Nutrients. 30;11(11):2603. http://doi.org/10.3390/nu11112603

Kantar World Panel, 2019. Grocery Market Share. Available from:  https://www.kantarworldpanel.com/en/grocery-market-share/great-britain [Accessed 10 April 2021]

Stelfox, M., Hudgins, j. & Sweet, M. 2016. A review of ghost gear entanglement amongst marine mammals, reptiles and elasmobranchs, Marine Pollution Bulletin, 111 (1–2) pp 6-17. https://doi.org/10.1016/j.marpolbul.2016.06.034

Thiele, C.J., Hudson, M.D., Russell, A.E. et al. (2021) Microplastics in fish and fishmeal: an emerging environmental challenge?. Sci Rep 11, 2045. https://doi.org/10.1038/s41598-021-81499-8

Webb, G. P. 2020. Nutrition Maintaining and Improving Health. 5th ed. Florida: CRC Press