A high intake of the heart-healthy omega-3 fatty acid, alpha-linolenic acid (ALA), may significantly lower our risk of dying. But how much ALA do we need and what are the best food sources? Spoiler: walnuts are one of the few plant foods rich in ALA!

Omega-3s in a nutshell

Omega-3 fatty acids (also called omega-3 fats and n-3 fats) are a key ‘family’ of polyunsaturated fatty acids. Our bodies aren’t able to make omega-3 fats from scratch. Instead, we must get them from food. And for this reason, they are termed ‘essential’ fats.

There are three omega-3 fatty acids:

• Eicosapentaenoic acid (EPA)
• Docosahexaenoic acid (DHA)
• Alpha-linolenic acid (ALA)

The fatty acids EPA and DHA are found primarily in seafood (such as salmon, mackerel and sardines), so are sometimes called ‘marine omega-3s’.

ALA comes mostly from plant-based foods, likes nuts, seeds and plant oils. ALA is the precursor or ‘parent’ to EPA and DHA. That is, our bodies convert ALA to EPA and DHA.

Did you know? Walnuts are one of the few plant foods rich in omega-3 ALA.

Why are omega-3 fatty acids special?

They are a vital part of cell membranes throughout the body and impact the function of the cell receptors in these membranes (1).

The strongest evidence for the benefits of omega-3 fats is in reducing the risk of heart disease. And research suggests they have anti-inflammatory properties, and may help prevent and treat depression, and support immunity (1).

What about ALA?

The body of research to date shows beneficial effects of ALA on reducing atherogenic lipids and lipoproteins, blood pressure, and markers of inflammation [6], providing clues as to why ALA has cardiovascular benefits.

A major review, published in 2021, found a high intake of omega-3 ALA was linked with a significantly lower risk of dying (2).

This systematic review and dose-response meta-analysis collated the findings of 41 previously-published prospective cohort studies. Together, these studies involved almost 1.2 million people who were followed for up to 32 years.

A high intake of ALA (~1.6 grams/day), compared with a low intake (~<0.8 grams/day), was linked with:

• A 10% lower risk of dying from all causes
• An 8% lower risk of dying from cardiovascular disease
• An 11% lower risk of dying from coronary heart disease.

The researchers suggest ALA may have a unique role in heart health benefits, in addition to being a precursor to the beneficial EPA and DHA fatty acids. This includes ALA’s anti-coagulant and anti-inflammatory properties, and cholesterol, triglyceride and blood pressure lowering effects (2,6).

Did you know? Meta-analyses of observational studies show that increasing dietary ALA is associated with a 10% lower risk of cardiovascular disease. Three randomised controlled trials (AlphaOmega trial, PREDIMED, and Lyon Diet Heart Study) all showed benefits of diets high in ALA on cardiovascular-related outcomes (6).

How much ALA do we need?

The Nutrient Reference Values for Australia and New Zealand have set an adequate intake (AI) for ALA at 1.3g/day and 0.8g/day for men and women (19+ years), respectively (3).

And the 2021 review (2) concluded that:

• Intakes of ALA of 1g/day and higher are safe, and
• Intakes of ALA between 1g/day and 2.5g/day were found to be best for the prevention of heart disease mortality.

A 30g handful of walnuts (around ¼ of a cup, or 10 whole walnuts) contains 1.9g of omega-3 ALA.

Top sources of ALA

These five commonly-available foods are among the top sources of omega-3 ALA:

Reference: Heart Foundation – Sources of omega-3 (4)

All Australians should aim to include 2-3 serves of fish (including oily fish) per week as part of a heart-healthy diet. This provides around 250-500mg of marine-sourced omega-3s (EPA and DHA) per day. In addition, all Australians should aim for 1g of plant-sourced omega-3 (ALA) each day. – Heart Foundation

Which nuts are highest in omega-3 ALA?

While there’s no such thing as an unhealthy nut, they do vary in their nutritional make-up – including their omega-3 ALA content. Walnuts contain by far the most ALA.

The omega-3 ALA content of tree nuts:

Reference: Food Standards Australia New Zealand (2022). Australian Food Composition Database – Release 2. Canberra: FSANZ.

Include a handful of nuts every day to boost good fat (including ALA) intake. – Heart Foundation

A note on omega-6 fatty acids

Omega-6 is another type (or ‘family’) of polyunsaturated fatty acids. Linoleic acid (LA) is the most common form of omega-6, but there are other omega-6 fatty acids too (3). As with omega-3s, our body can’t make omega-6s, so we must get them from our diet.

Omega-6s are found naturally in plant foods like nuts (walnuts, pine nuts and Brazil nuts contain the most), seeds and plant oils (such as olive, corn, soy, safflower and sunflower oil) (3). Healthy, whole food sources of omega-6 are a good choice, especially when they replace foods rich in saturated fat.

But omega-6s are also found in highly-processed ‘discretionary’ foods, like cakes, biscuits, burgers, pizza and chips, which contain large amounts of processed seed and vegetable oils. Given these ‘discretionary’ foods are often high in saturated fats as well, they should be limited.

For the best health benefits, research suggests balancing our intake of omega-6s and omega-3s, with an ideal ratio of 1:1 (7). But in Australia, it’s estimated to be 8:1 of omega-6 to omega-3 (8). Health authorities suggest the best way to bring the two into balance is to boost omega-3 intake, and to limit ‘discretionary’ (or junk) foods (9). 

The bottom line

Including enough heart-healthy omega-3 fats into your day, as part of an overall healthy diet, makes good sense. And this helps achieve the ideal balance of omega-3s to omega-6s in our diet. Intake of ALA – the omega-3 fatty acid in nuts (particularly walnuts) and other plant-based foods, has been linked with a lower risk of dying from all causes. Another good reason to include a 30g handful of nuts in your day, every day!