Omega-3. You've seen the word (and number) splashed across cereal boxes, tins of tuna and one of Australia's most popular supplements: fish oil.

These famous fatty acids are thought to have a vast range of health benefits.

So how can you make the most of them?

Omega-3 is short for omega-3 polyunsaturated fatty acids. They're a family of "essential fats" that play an important role in the way our cell membranes work.

"Omega-3 fats are 'essential'. What that means is that we are unable to synthesise them in our body … so we must obtain them from our diet," says Manohar Garg, professor of medical nutrition at the University of Newcastle.

Fats tend to get a bad rap, but polyunsaturated fats are the good guys. They help keep cholesterol balance in your body, decreasing the bad cholesterol and increasing the good cholesterol.

When it comes to the health benefits of omega-3, here's what you need to know.

Fatty acids linked to heart health

The strongest evidence for the benefits of omega-3 fats comes from studies of heart disease.

Research shows people who regularly consume fish (the best source of omega-3) tend to have lower rates of heart disease and stroke — and that may well be down to omega-3.

These fats are known to help lower your heart rate, reduce the risk of clotting, lower triglycerides (an unhealthy fat in the blood), decrease blood pressure, improve blood vessel function and delay the build-up of plaque in coronary arteries.

"Omega-3 fatty acids cut down the blood fat — blood cholesterol and blood triglycerides — and they also cut down inflammation in the body. These are the two underlying causes of cardiovascular disease," Professor Garg says.

Those anti-inflammatory properties of omega-3 have been used to help people with rheumatoid arthritis and diabetes.

But the evidence for omega-3's protective effects against other chronic diseases is less clear.

"In respect to the role of omega-3 in cognitive function and neuro-degenerative diseases, the evidence is building up," Professor Garg says.

"There is evidence that people with Parkinson's disease, Alzheimer's disease and people with dementia have low levels of omega-3 fatty acids … but we need to do more randomised clinical trials."

High-fish diet recommended

While omega-3 fats can be found in plants, seafood, and to a lesser extent, eggs and meat, the best way to boost your intake of fatty acids is to increase the amount of oily fish you consume.

The Heart Foundation recommends including two to three serves of fish (with the skin on) in your diet each week (150 grams per serve), as well as one gram of plant-sourced omega-3 fats each day.

"You can add fish to stir-fries, casseroles, pasta and soups, or simply have it in a sandwich or in a salad."

Good sources of marine omega-3s include salmon, blue-eye trevalla, blue mackerel, herring, canned sardines, canned salmon and some varieties of canned tuna.

When it comes to plant sources, walnuts, linseed, chia seeds, pumpkin seeds, tofu, leafy greens and vegetable oils such as canola and soybean are all good options.

Vegetarian alternatives on the horizon

If you don't eat fish, it's important to maximise your intake of plant-based sources of omega-3.

However, the type of omega-3 fatty acid found in plants (alpha-linolenic acid) is nowhere near as effective as the types found in marine sources (docosahexaenoic acid and eicosapentaenoic acid).

"From the plant sources, we do not get the fatty acids which are present in our body — we only get the precursors of those omega-3 fatty acids," Professor Garg says.

"So, they're not readymade … our body has to work hard, and the conversion of plant omega-3 fatty acids into docosahexaenoic acid is extremely slow.

"The conversion rate is almost less than 1 per cent."

Given the modest conversion rate, the Heart Foundation says it's important vegetarians and vegans still include marine-sourced omega-3 fats in their diet.

The foundation recommends omega-3 supplements derived from algae — which is actually where all marine-sourced omega-3 originates.

Professor Garg says there may be more omega-3 alternatives available for people who don't eat animal products in the near future.

"Tree nut oils, for example, are being genetically manipulated to contain long-chain omega-3 fatty acids. So that might be available in the next few years, but at the moment the choices are limited."

Little evidence for supplements

While some research shows fish oil supplements may help to reduce triglycerides in your blood, it's unclear whether they reduce your risk of cardiovascular disease.

Recent studies suggest the supplements may not be as helpful as previously thought in reducing the risk of heart attack or stroke.

  • Include 2–3 serves of fish a week (100–150g per serve).
  • Use nuts and seeds in your breakfast. Sprinkle ground linseed on cereal or try a handful of almonds sprinkled over yoghurt.
  • A handful of unsalted nuts make a healthy snack any time of the day.
  • Use oils and margarine spreads made from olive, sunflower, canola and safflower oils in cooking and on sandwiches and toast instead of butter.
  • Choose wholegrain bread with linseeds.

Source: The Heart Foundation

A 2012 meta-analysis of 20 studies found no association between omega-3 supplementation and risk of cardiac arrest, heart attack or stroke. And just recently, a study published in JAMA Cardiology found no association between omega-3 supplements and coronary heart disease.

Previously, the Heart Foundation recommended Australian adults consume fish oil every day, either by eating oily fish or taking supplements.

But that recommendation was updated in 2015 to say there was insufficient evidence to support the use of fish oil supplements in preventing heart attack.

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Look at the big picture

Although omega-3 fatty acids have been linked to good cardiovascular health, molecular nutritionist Emma Beckett says it's much more important to look at your diet overall, rather than focusing on individual nutrients.

"If you just focus on omega-3, that's really what we call a reductionist approach to nutrition … thinking about nutrients instead of food," she says.

Dr Beckett says the benefits of omega-3, as with most nutrients, are likely to come from consuming whole foods.

"It's not just the omega-3 you're getting with eating fish, it's the fact that the fish would be displacing something else potentially negative from your diet."