A recent editorial in the journal Open Heart suggests that many of us have it all wrong when it comes to balancing the fats we eat.
The authors urge a return to equal amounts of specific types of fats known as omega-6 and omega-3 polyunsaturated fatty acids to help fight global obesity.
The paper reflects a recent surge of evidence supporting a review of dietary fat guidelines, including in Australia.
What are dietary fats?
Fats – more correctly called fatty acids – are a major source of food energy, along with carbohydrates and proteins. Fats can be saturated or unsaturated, terms that refer to the composition and structure of fat molecules.
Polyunsaturated fatty acids include omega-6 and omega-3 fatty acid groups. Omega-6 linoleic acid and omega-3 alpha-linolenic acid are called essential fatsbecause humans cannot produce them: we must obtain them from food sources.
The main sources of omega-6 polyunsaturated fatty acids are seeds that are used extensively in vegetable oils such as safflower and sunflower oil. These oils are commonly used to make margarines. Processed foods such as cakes, cookies, burgers, pizzas and fries are therefore rich in omega-6s.
Plant sources of omega-3 alpha-linolenic acid are nuts (like walnuts), seeds (like flax seeds), and green leafy vegetables. The longer-chain, more highly unsaturated omega-3s, known as eicosapentaenoic acid and docosahexaenoic acid come from algae and fatty fish such as salmon, tuna, mackerel and sardines.
There is good evidence of the health benefits of monounsaturated fatty acids: they are found in olive oil, macadamia oil, avocado and certain nuts such as almonds and peanuts.
Excessive amounts of saturated fatty acids in the diet have been linked to an increased risk of clogged arteries and heart disease (although this is complicated and may depend on their source). Saturated fatty acids come mainly from red meat and processed foods, but dairy products, coconut and palm oil also contain it.
Highly processed foods also contain trans fatty acids that occur as a result of the hydrogenation of vegetable oils for margarine, commercial baking and manufacturing. This process changes the structure of fat, and these are associated with an increased risk of heart disease.
How do fats contribute to our health?
In addition to providing the energy our body needs to function properly, fats have many important health benefits including healthy skin and hair, absorption of 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 brain, where it plays multiple important roles in health brain function, cognition and mental health.
otherwise, 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-3s and high in omega-6s can therefore create a range of problems, including chronic inflammation and poor blood circulation. These changes are related to chronic diseases such as obesity, heart disease, stroke, mental illness and dementia.
What kinds of fats do Australians eat?
In traditional societies, humans consumed a report approximately 2-1:1 omega-6 to omega-3 polyunsaturated fatty acids. This is due to diets high in fish, plant foods and free grazing animals, as well as eggs from hens that ate plants high in omega-3 fatty acids.
In industrialized 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 at 8:1.
As a result, Australians do not meet the recommended guidelines for omega-3 intakeeating high levels of processed and take-out foods, lots of fatty red meat, and not enough fish or vegetables.
This diet is associated with high levels of obesity and chronic disease in adults. Australians.
Otherwise, 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 fatty acids.
The recent Open-hearted editorial suggests that these statistics may reflect poor food policy:
It is the responsibility of governments and international organizations to establish science-based nutrition policies and not continue down the same path of focusing exclusively on calories and energy expenditure, which have failed miserably over the past 30 last years.
Confusion around dietary fat: low-fat diets
Since the 1960s, the focus has been on low-fat diets to improve health. However, recently retrieved documents imply a role for sugar industry fraud in this area. A sponsored research program has cast doubt on the links between sugar and heart disease and instead pointed the finger at fat.
There is now a growing body of high-quality evidence that a Mediterranean-style diet high in monounsaturated fats from extra virgin olive oil is superior to a low-fat diet in preventing heart disease and reversing foie graswhich is associated with metabolic syndrome and the risk of type 2 diabetes.
Not only that, but a high-fat Mediterranean diet is superior to a low-fat diet for weightlossand especially for the long-term maintenance of weight loss.
This may be due at least in part to the fact that not all calories are created equal: processed foods are believed to provide energy in a form that is more accessible to our bodies than raw or unrefined foods.
Fats are also more satiating, which may explain why a Mediterranean-style diet is more sustainable. Extra virgin olive oil is not only very palatable, but its antioxidant properties have been linked to weightloss.
Confusion around dietary fats: polyunsaturated fatty acids
Guidelines in America and Australia recommends replacing saturated fats with polyunsaturated fats. In practice, this translates into the recommendation of vegetable oils and margarines instead of butter, and therefore the replacement of saturated fats with omega-6 polyunsaturated fatty acids. Little attention is paid to dietary omega-3 content in this approach.
However, omega-3 and omega-6 polyunsaturated fatty acids are not the same. Recently data not covered from a study conducted in Sydney in the 1960s showed that margarine containing linoleic acid (omega-6 fatty acid) was associated with an increased risk of premature death.
When data from a series of studies looking at polyunsaturated fats and heart disease were reanalyzed, the results of the studies changed when omega-3s and omega-6s were separated rather than treated as a single factor. When separateomega-6s were found to be a risk factor for mortality, while omega-3s were protective.
This supports good proof linking omega-3s to heart health. Although some recently published research questions the importance of omega-3s in fish oil for the prevention of heart disease, this interpretation has been professionally critical due to methodological flaws.
So where are we now?
Australian dietary guidelines continue to recommend low-fat diets, polyunsaturated fats instead of saturated fats (without separating omega-6s and omega-3s), and no longer specifically recommend omega-3s to prevent heart disease .
Encouragingly, the recent Food Australia The food pyramid has incorporated significant changes reflecting evidence of the health benefits of a Mediterranean-style diet.
These changes include the placement of vegetables, fruits and legumes at the base of the pyramid, indicating the importance of a high consumption of plant foods, and extra virgin olive oil is described as a healthy fat.
In light of current evidence and in line with recent editorialAustralians can improve their health and maintain a healthy weight aiming for a balanced balance between omega-6 and omega-3 intakes.
