Why fish is your heart’s best friend

More than just a tasty feed...

28 April 2023

As a coast-dwelling nation, we Australians are lucky to have access to an abundance of delicious, fresh fish.

And while there’s much to love about sitting down to a meal of grilled fish and salad, the benefits of this star of the seafood family are about more than just a tasty feed.

Fish is not only lower in saturated fat than red meat - and a good source of protein and iodine, among other essential vitamins and minerals - it also contains heart-friendly unsaturated fats known as omega-3 fatty acids.

What are omega-3 fatty acids?

There are three main types of omega-3 fatty acids:

• docosahexaenoic acid (DHA)
• eicosapentaenoic acid (EPA)
• alpha-linolenic acid (ALA)

These omega-3 fatty acids belong to a class of fats known as polyunsaturated fats (PUFAs), which also include omega-6 fatty acids.

DHA and EPA can be found in fish, while ALA is mainly found in plant sources.

How can fish improve heart health?

The omega 3s found in fish have been shown to have anti-inflammatory and other benefits to the heart that can help reduce the risk of heart disease and stroke.

These benefits include:

• lower triglyceride levels
• higher ‘good’ cholesterol
• reduced risk of blood clots
• slightly lower blood pressure

Which fish should I eat and how much?

After a scientific review of the evidence into the heart health benefits of fish, the Heart Foundation has recommended that all Australians consume two to three serves of fish (including oily fish, as fish with a higher fat content contain more omega 3s) per week. This serving recommendation provides around 250–500 milligrams (mg) of EPA and DHA per day.

A serving of fish is equivalent to 100g of cooked fish fillet, or one small can of fish.

Fish sources of omega 3 fatty acids include:

• salmon
• mackerel
• herring
• canned sardines
• canned salmon
• some varieties of canned tuna
• barramundi
• bream
• flathead
• snapper

When eating fish, it’s important to consider how it’s prepared. Baking, grilling, barbecuing, steaming, poaching and shallow frying (particularly when using heart-friendly oils like olive oil) are healthy choices, while options like deep fried battered fish should be eaten in moderation.

Can I have too much omega 3 in my diet?

When it comes to omega 3s and fish, there is an optimal amount to have in the diet. Not having enough omega 3s in the diet can increase the risk of heart disease. However, more is not necessarily better.

In fact, in an article by the Institute’s Professor Diane Fatkin, Dr Charles Cox and Professor Boris Martinac, it is noted that very high levels of omega-3 fatty acid supplements have been found to be associated with increased risk of atrial fibrillation.

What about mercury in fish?

Mercury is naturally present in the environment – including in water and soil. It can however accumulate in high levels in larger, predatory fish – aka fish that eat other fish.

Fish that can contain higher levels of mercury include:

• shark (also known as flake)
• orange roughy (also known as deep sea perch)
• billfish (eg. swordfish and marlin)
• catfish

Consumption of these fish should generally be limited to once a week, or once a fortnight, depending on the type of fish.

The Food Standards Australia New Zealand website provides guidance on the consumption of high mercury fish, including for children, pregnant women and those planning to become pregnant.

Fish that are low in mercury can be consumed two or more times a week.

What if I don’t eat fish or seafood, or I have a seafood allergy?

Even if you don’t eat fish, there are still ways to reap the heart-healthy benefits of omega-3s.

ALA (the type of omega-3 fatty acid found mainly in plants) can be found in foods such as:

• chia seeds
• hemp seeds
• flaxseeds/linseeds
• canola, soybean and flaxseed/linseed oils
• soy products
• walnuts
• edamame
• kidney beans

ALA is converted to DHA and EPA (the omega-3 fatty acids found in fish), but this conversion rate is low. This means you need to eat more plant sources to get the necessary omega-3 fatty acids in your diet.

The Heart Foundation recommends that all Australians should aim for 1 gram of ALA each day.