Despite science proving fat just ain’t the devil, The Australian Dietary Guidelines still recommend a low-fat diet…
… and even the fats they recommend are not good for us (we’re talking to you, vegetable oils). This edited extract from The Conversation breaks it down.
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How do fats contribute to our health?
Apart from contributing energy that our bodies need to work properly, fats have numerous important health benefits including healthy skin and hair, absorbing fat-soluble vitamins (A, D, E and K), and insulation to keep us warm.
Omega-3 and omega-6 polyunsaturated fatty acids are important for brain development. Docosahexaenoic acid is particularly concentrated in our brains, where it has multiple important roles in healthy brain function, cognition and mental health.
Furthermore, omega-3 polyunsaturated fatty acids produce important chemicals that reduce inflammation and blood clotting, and improve blood vessel dilation. Conversely, omega-6 polyunsaturated fatty acids promote inflammation, clotting and constriction of blood vessels.
A diet low in omega-3 and rich in omega-6 can therefore create a range of problems, including chronic inflammation and poor blood flow. These changes are associated with chronic diseases such as obesity, heart disease, stroke, mental illness and dementia.
What sorts of fats do Australians eat?
In traditional societies, humans consumed a ratio of roughly 2-1:1 of omega-6 to omega-3 polyunsaturated fatty acids. This came about due to diets rich in fish, plant foods and free grazing animals, and eggs from chickens that ate plants high in omega-3 fats.
In industrialised regions such as Europe and the United States, the dietary ratio of omega-6 to omega-3 is very different, being closer to 16:1. In Australia it is estimated to be 8:1.
Therefore Australians are not meeting recommended guidelines for omega-3 intake, eating high levels of processed and takeaway foods, a lot of fatty red meat and not enough fish or vegetables.
This diet is associated with high levels of obesity and chronic disease in adult Australians.
Furthermore, one in four Australian children is overweight or obese. This age group also consumes excess saturated fat – largely through processed foods – and not enough omega-3 fats.
Confusion around dietary fat: polyunsaturated fatty acids.
Guidelines in America and Australia recommend replacing saturated fat with polyunsaturated fat. In practice, this translates to recommending vegetable oils and margarines instead of butter, and thus replacing saturated fat with omega-6 polyunsaturated fatty acids. Little heed is paid to dietary content of omega-3 in this approach.
However, omega-3 and omega-6 polyunsaturated fatty acids are not the same. Recently uncovered data from a study conducted in Sydney in the 1960s showed that margarine containing linoleic acid (omega-6 fat) was associated with increased risk of early death.
When data across a range of studies investigating polyunsaturated fats and heart disease were re-analysed, study outcomes changed when omega-3 and omega-6 were separated rather than treated as a single factor. When separated, omega-6 was found to be a risk factor for mortality, while omega-3 was protective.
This supports good evidence linking omega-3s with heart health. Although some recently published research questions the importance of omega-3s in fish oil for prevention of heart disease, this interpretation has been professionally critiqued due to methodological flaws.
So where are we now?
Australian dietary guidelines continue to recommend low-fat diets, polyunsaturated fats in place of saturated fats (without segregating omega-6 and omega-3), and no longer specifically recommend omega-3s for preventing heart disease.
Encouragingly, the recent Nutrition Australia food pyramid has incorporated some significant changes reflecting evidence around the health benefits of a Mediterranean-style diet.
These changes include the placement of vegetables, fruit and legumes at the base of the pyramid, indicating the importance of high intake of plant foods, and extra virgin olive oil is depicted as a healthy fat.
In light of current evidence and consistent with the recent editorial, Australians can improve their health and maintain a healthy weight by aiming for an equal balance of omega-6 to omega-3 intake.
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