Seafood and omega-3 fats

Wednesday, 31 March 2021

Research has shown people who eat more fish and seafood tend to have a reduced risk of a number of conditions including heart disease, stroke, heart failure, macular degeneration and dementia. We also know heart disease and stroke are common long term complications of diabetes, so we want to prevent them from occurring.

Omega-3 fats are the active ingredient in fish and seafood which is believed to reduce the risk of these health conditions from occurring. Our bodies cannot make our own omega-3 fats, therefore we need to obtain them from our food.

Omega-3 fats are a type of polyunsaturated fat (PUFA) found in many foods, including seafood. Different types of omega-3s come from different food sources.

Recommendations for omega-3s

The Heart Foundation recommends:

  • All Australians, including those with existing heart disease, aim to include 2–3 serves of fish (including oily fish) per week which provides about 250–500 milligrams of marine-sourced omega-3s, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), per day; and
  • All Australians include a variety of nuts, seeds and oils including soybean, canola, flaxseed/linseed, chia seeds and walnuts to provide 1 gram of plant-sourced omega-3 (ALA) per day.

But what about diabetes prevention and omega-3s?

Research shows that omega-3 fats don’t seem to have any effect on reducing the risk of developing type 2 diabetes and there is not enough research in the effects of omega-3 fats in preventing gestational diabetes to draw any conclusions.

However, novel research in animals and preliminary human trials shows that omega-3 fats may help to reduce the auto-immune degeneration of islet cells in type 1 diabetes, if caught early enough due to their anti-inflammatory effect. This is very exciting but is quite difficult to research.

How do they work?

Omega-3s work by:

  • Reducing triglycerides – a type of fat in the blood which in high levels contributes to heart disease
  • Decreasing LDL cholesterol – the unhealthy type of cholesterol
  • Increasing HDL cholesterol – the healthy type of cholesterol
  • Thinning the blood
  • Reducing inflammation in the body.

Are there different types of omega-3s?

There are three main types of omega-3 fats:

  1. ALA or alpha-linolenic acid
    • Protects the body against heart disease
      • Found in canola, linseed, chia, walnuts, soybean and soy products, and omega-3 enriched eggs
  1. EPA or eicosapentaenoic acid
    • Lowers triglycerides
      • Found in oily fish and some seafood, is the type of oil in fish oil, marine algae (spirulina) and krill supplements, plus is found in seaweed and omega-3 enriched eggs
  1. DHA or docosahexaenoic acid
    • Lowers triglycerides
      • Found in the same sources as EPA.

Interestingly, the EPA and DHA composition of fish sources has changed over time. This reflects that much of our fish and seafood is not caught wild but is now farmed. The fish and seafood fat composition depends on the diet the farmed fish and seafood are fed.

What about omega-3 supplements?

Over recent years international recommendations have leaned towards people eating foods containing omega-3s rather than taking supplements. However, supplementation with high grade marine oil, 2–4 g daily may be considered for those at high risk of cardiovascular disease and for treating high triglycerides. If you do want to take a supplement, talk to your doctor as a high intake of omega-3s can interact with some medications.

How much fish or seafood do I have to eat to get my omega-3s?

A serve of fish is considered to be 150g, while a serve of seafood is 100g.

Fish with the highest levels of omega-3 fats include:

  • Salmon: fresh or canned
  • Sardines: fresh or canned
  • Mackerel
  • Rainbow trout
  • Tuna: fresh and some canned varieties.

Other good marine sources of omega-3s are:

  • Barramundi
  • Bream
  • Flathead
  • Herring
  • Blue grenadier or hoki
  • Squid or calamari
  • Scallops (the fish ones, not the potato ones!)

What about mercury?

Some fish which are long lived or at the top of the food chain might have high levels of mercury in their flesh. Because of this, these types of fish should be limited, particularly for pregnant women.

The following fish should not be eaten very often:

  • If you have one serve per week of orange roughy (deep sea perch) or catfish then do not eat any other fish that week.
  • If you have one serve per fortnight of shark (flake) or billfish (swordfish/broadbill or marlin) then do not eat any other fish that fortnight.

How much plant food can I eat to get 1g of the omega-3 ALA?

Plant-sourced omega-3s are related, but slightly different, to marine-sourced omega-3s; however, both types are important in a healthy diet. One gram of ALA can be found in:

  • 30g walnuts
  • 2-3 teaspoons of ground linseed/flaxseed, chia seeds or LSA (linseed, sunflower and almond)
  • 1 tablespoon of canola oil or margarine
  • 200g tofu
  • 150g sprouted or cooked soybeans.

One part of the jigsaw

Don’t forget having a source of omega-3s in the diet is just one part of the healthy diet jigsaw.

To help manage your diabetes and keep your heart healthy eat plenty of fruit and vegies, wholegrains, legumes, lean meats and other unsaturated fats, drink water, and limit added sugars, saturated fats and over processed foods.


By Dale Cooke APD

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