Nutrients in seafood
Fish and seafood provide energy (kilojoules), protein, selenium, zinc, iodine and vitamins A and D, as well as omega-3 long chain polyunsaturated fatty acids (omega-3s) to the Australian diet (NHMRC 2013, Australian Dietary Guidelines). Seafood is also an excellent source of fluoride. Some fish with edible bones (eg. canned salmon and sardines) also contribute significant amounts of calcium (FSANZ 2010).
Seafood is a major source of iodine in the Australian diet (ABS 2014). Saltwater seafood has approximately twice the amount of iodine as freshwater species (Oceanwatch Australia 2017). Iodine is required for thyroid hormone production, which is required for metabolism and growth throughout life. Iodine deficiency is the largest preventable cause of brain damage and mental impairment worldwide. Australia has been identified as having a mild iodine deficiency that has resulted in the mandatory iodine fortification of salt used in bread (Charlton et al 2016).
The Australian Seafood Cooperative Research Centre undertook laboratory testing on a range of fresh Australian wild and farmed seafood. Download the booklet from http://www.seafoodcrc.com/images/seafood/SFC_019_Super_Seafood_Consumer_Booklet_170x240_FINAL_WEB.pdf.
The Fisheries Research and Development Corporation (FRDC) are currently undertaking further nutritional profiling research to assess the composition of Australian species. As these are completed, they will be added to the species profiles on this website. A good starting point to understand this information is the FRDC publication What's so healthy about seafood?
Shellfish and cholesterol
While crustaceans (eg. prawns, crab, lobster) contain cholesterol, they need not be avoided by people with high blood cholesterol because the ready-made cholesterol present in all animal foods has little effect on blood cholesterol. In fact, rather than increasing heart disease risk; eating shellfish actually reduces it (Matheson et al 2009). The most important dietary influence on blood cholesterol is saturated fat, and seafood is naturally low in saturated fats (although take care not to add too much saturated fat from foods such as butter during cooking and preparation).
What are Omega-3's?
Omega-3s are a type of polyunsaturated fat important for good health.
There are two types of omega-3 fats:
- omega-3 fats known as alpha linolenic acid (ALA) mainly derived from plants, and
- long chain omega-3 fats docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and docosapentanoic acid (DPA) mainly derived from seafood.
Sources of long chain Omega-3s
Where are they found?
Oily fish, other fish and seafood are the main sources of long chain omega-3s. Pasture-fed beef provides smaller amounts, mostly DPA and EPA (Daley et al 2010). There is a vegetarian source of Omega-3 DHA, made from marine algae, which is used in a variety of omega-3 enriched foods and infant formulas. Interestingly, it is the marine algae that fish feed on which helps make them a rich source of long chain omega-3s.
Omega-3 ALA found in plant foods such as canola oil, linseeds and walnuts needs to be converted by the body to the long chain Omega-3s to be used effectively. While conversion of ALA to long chain omega-3s is possible, it occurs at a very low rate so including long chain omega-3s in the diet is recommended for optimal health (Burdge & Calder 2005).
The best source of long chain omega-3 fats (DHA, EPA) is fish, especially oily fish.
Recommended amounts of Omega-3s
The Nutrient Reference Values (NRVs) for Australia and New Zealand are as follows:
Adequate Intake (AI) for long chain omega-3s
- 90mg/day for women; 115mg in pregnancy; 145mg during breastfeeding
- 160mg/day for men
No recommended dietary intake (RDI) has been established.
However, the Suggested Dietary Target (SDT) to reduce chronic disease risk (Applicable to adolescents over 14 years of age and adults) is much higher:
SDT for long chain omega-3s:
- 430mg per day for women
- 610mg per day for men
Dietary modelling for the Australian Dietary Guidelines established that the recommended two serves of 100g cooked fish a week is enough for adults to meet the AI for long chain omega-3s. (Australian Government 2011).
To meet the SDTs, 2 servings of oily fish are needed per week (Fayet-Moore et al 2015).
Omega 3 intakes in Australia
The Australian Health Survey showed that, on average, adults are consuming an Adequate Intake of omega-3s (ABS 2014). The mean intake of long chain omega-3 fats (EPA and DHA) was:
- 260mg/day for men (vs 160mg AI)
- 180-240mg/day for women (vs 90-145mg AI)
However, Australians on average are not consuming the Suggested Dietary Target (SDT) of long chain omega-3 fats as recommended for chronic disease risk reduction. Only 20% of the population meets the SDT and only 10% of women of childbearing age meet the SDT. Intake patterns suggest some people are consuming high amounts of long chain omega-3s (primarily as supplements), but the majority of the population are consuming much lower amounts (Meyer 2016).
Omega-3 content of Australian seafood
All seafood is nutritious and contains a variety of nutrients including omega-3 fats, however some species contain more omega-3s than others. This data has been loaded into Microsoft Power BI to make it easy to analyze the omega-3 content of Australian seafood, classified into excellent, good and moderate sources. The species outlined below are rated as sustainable as part of the 2018 Status of Australian Fish Stocks Reports. Fishfiles provides omega-3 levels for all species covered on the site.
Omega-3 content of Australian sustainable seafood species
Blue eye trevalla
Blue Swimmer Crab
Big Eye Tuna
Canned seafood such as salmon, tuna, mackerel, herring and sardines are also excellent sources of omega-3 fats.
- Herring, canned in brine, drained: 3200mg/100g
- Australian salmon, canned in brine, drained: 2456mg/100g
- Sardines, canned in oil, drained: 2432mg/100g
- Red salmon, canned in brine, drained: 1969mg/100g
- Pink salmon, canned in brine, drained: 1830mg/100g
- Tuna, canned in brine, drained: 721mg/100g
*sourced from NUTTAB, except Herring sourced from pack nutrition information
Taking long chain omega-3 supplements alone doesn’t convey the full nutrition and health benefits that eating fish and seafood offer. A recent Cochrane Review concluded that increasing EPA and DHA has little or no effect on mortality or cardiovascular health, based on moderate to high quality evidence, mainly from supplement trials (Abdelhamid et al 2018).
The Heart Foundation Australia recommends all Australians aim to eat 2-3 serves of fish, including oily fish, per week to obtain 250-500mg long chain omega-3s EPA and DHA daily rather than relying on supplements. However, while routine supplementation with omega-3 fats is not recommended, people with hypertriglyceridaemia and heart failure may benefit from omega-3 supplementation in addition to including 2-3 serves of fish per week. (Nestel et al, 2015). You can read the Heart Foundation Position on Fish and Seafood at their website.
Their position is consistent with European, British and US guidelines (Heart Foundation 2018).