Fish, omega-3 fatty acids and cancer

Omega-3 fats are associated with a range of health benefits, such as lowering the risk of heart disease and relieving inflammatory conditions such as rheumatoid arthritis and inflammatory bowel disease.

Oily fish including swordfish, Atlantic salmon, gemfish, Spanish mackerel and canned fish such as sardines, salmon and tuna are rich sources of omega-3 fatty acids.

Plant foods and oils rich in omega-3 fatty acids include canola oil, canola margarine, soybeans, soybean oil, linseeds, linseed oil (flaxseed oil), walnuts, walnut oil and leafy vegetables.

Does eating fish reduce the risk of cancer?

Experimental studies and some studies in humans suggest that eating more fish and omega-3 fats may protect against cancer. Cancer Council analysis suggests there is limited suggestive evidence for an association between increased fish consumption and a reduced risk of breast, prostate cancer and bowel cancer risk. 

How much fish should I eat?
Because of the overall health benefits of fish and omega-3 fats, Cancer Council recommends people:

  • Eat fish (preferably oily) at least two times per week; and
  • Include some plant foods and oils rich in omega-3 fats in their diet.

Tips and ideas to boost fish and omega-3 fat intake
Practical and healthy ways to increase the intake of omega-3 fats in the diet include:

  • Have grilled or steamed fish with vegetables for dinner.
  • Use fish in mixed dishes such as curries, stews, casseroles, pastas and soups.
  • Use canned fish to make fish cakes and serve with vegetables.
  • Mix canned fish through salad.
  • Use canola oil in cooking, and canola based margarines on breads.
  • Eat soy and linseed bread.
  • Use whole soybeans in stews, casseroles and soups.
  • Eat a small handful of walnuts as a snack.
  • Include walnuts when making homemade breads, muffins and cakes.
  • Include green leafy vegetables such as broccoli, cabbage and spinach in mixed dishes like curries and stir fries.
  • Make a spinach pie.

Mercury and fish
Some types of fish can contain high levels of mercury. High levels of mercury are known to damage the nervous system. Therefore eating fish that contain high levels of mercury every day or in large quantities could be harmful. This is especially a concern for children and women who are pregnant or intending to become pregnant.

Cancer Council encourages all people to follow recommendations of Food Standards Australia New Zealand (FSANZ) about consumption of fish high in mercury.

FSANZ recommendations for consumption of fish species high in mercury

Pregnant women & women planning pregnancy
1 serve is 150g

Children (up to 6 years)
1 serve is 75g
Rest of the population
1 serve is 150g  
2-3 serves per week of any fish & seafood not listed below 2 – 3 serves per week of any fish & seafood not listed below
OR OR
1 serve per week of orange roughy (sea perch) or catfish and no other fish that week 1 serve per week of shark (flake) or billfish (swordfish/broadbill & marlin) & no other fish that week  
OR
1 serve per fortnight of shark (flake) or billfish (swordfish/broadbill & marlin) & no other fish that fortnight

A 150g serve for adults and older children is equivalent to approximately 2 frozen crumbed fish portions.

A 75g serve for children is approximately 3 fish fingers (hake or hoki is usually used in fish fingers).

Canned fish is sold in various sizes; for example, snack size cans of tuna are approximately 95 grams.

If you are in doubt about the type of fish you are purchasing, ask the retailer or restaurant for the name of the fish.

Read the full position statement:
Omega-3 fatty acids, fish and cancer prevention

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