Why we need healthy fats in our diet

There is often confusion around which types of fat are healthy for us and which types are not. You couldn’t be blamed for feeling confused, as there is conflicting evidence for both sides of the argument. Unfortunately, there is still a lot of fear of gaining weight from consuming fat, however, contrary to many people’s beliefs, when eating the right types of fat (healthy fats), considerable weight loss can be achieved.

Saturated Fat Myth?

Ancel Keys was a physiologist who set out to prove his theory that saturated fat was responsible for heart disease, in his Seven Countries study in the late 1950’s. He concluded that there was a correlation between cardiovascular disease, total cholesterol and saturated fat. Low fat diets were recommended following his findings, which in fact, increased cardiovascular disease occurrence as a result of this advice. This study has since been discarded as a seriously flawed study.

A systematic review from 2010 showed that there was no significant evidence to conclude that dietary saturated fat was associated with an increased risk of cardiovascular disease (1).

A paper was published in 2013 in The British Medical Journal stating that saturated fat does not cause heart disease, trans fats do (2). Unfortunately, this advice is still not getting to the general public 6 years later.

What is important about fats in the diet is not the ‘amount’ of fat but the ‘type’ of fat. The problematic fats linked to chronic diseases are industrial trans fats, found in hydrogenated vegetable oils and processed foods.

When combined with an insufficiency of monounsaturated fats, found in olive oil, avocados, nuts and seeds; and omega-3 fatty acids, found in oily fish, walnuts, flaxseeds, and chia seeds, disease processes may ensue.

Dietary fat is necessary for cell membrane composition, and a high consumption of trans fats reduces the membrane fluidity, which decreases the binding of insulin to receptors on cell membranes, decreasing insulin action (3). Studies have shown trans fats to be associated with all cause mortality, cardiovascular disease, coronary heart disease mortality, type 2 Diabetes, and ischemic stroke. These diseases and disease processes were not associated with saturated fats; however, there were methodological limitations to the studies (4).

Cholesterol Myth?

We have been told that cholesterol causes heart disease. This theory was also based on the highly flawed Seven Countries study by Ancel Keys.

Ancel Keys took data from 22 countries; however, he only used the data from the seven countries whose evidence supported his view. He discounted the rest. It was from this data that we were told to cut out or seriously reduce butter, animal fats, eggs and dairy from our diets.

There is no study that connects consuming high cholesterol foods with increased cholesterol in the body. Your body makes cholesterol, if you eat more, then your body makes less.

We need cholesterol:

• To produce our cell membranes

• To make important hormones

• To make vitamin D

• To help us digest fats

• For healthy brain function

Good fats (anti-inflammatory) Monounsaturated fats, polyunsaturated fats, saturated fats, and omega-3 oils.

Good sources include extra virgin olive oil, extra virgin coconut oil, nuts and seeds, nut and seed butters, avocado, flaxseed oil, sesame oil, tahini, wild caught oily fish (salmon, trout, sardines, mackerel, herring, anchovies etc.), olives, ghee, hemp seed, and MCT oils.

Also found from grass-fed animal fats such as beef, chicken, turkey, and dairy products such as cheese, butter and cream. Saturated fats mainly found in animal products such as butter, ghee, and lard are good cooking fats as they have a higher smoke point than unsaturated fats, meaning they are less likely to be damaged by oxidation. Coconut oil is also a saturated fat with a high smoke point.

It’s important to note that while we have been told that we shouldn’t use extra virgin olive oil for cooking, recent studies found it to be one of the most stable oils (followed by coconut oil) when heated. This is due to its’ fatty acid profile and antioxidant content (5). The Mediterranean diet, high in extra virgin olive oils, has been shown to be heart protective, especially when compared to low fat diets.

These healthy fats are essential for our bodies to function efficiently. We need them for our hormone balance, a healthy brain and mood, our skin health, healthy joints, and our organs; in fact every cell in our body is composed of a fatty cell membrane, essential to good health. Did you know our brain is composed of around 60% fat?

Fat-soluble nutrients such as vitamins A, D, E & K rely on fat in the diet for their absorption. This is why we should always have an oily dressing with our salad or vegetables. Healthy fats slow down the absorption of glucose from carbohydrates, helping to balance our blood sugar levels. They can also help with weight loss because they are very satiating, leaving us feeling full for longer and less likely to want to snack.

Bad fats (inflammatory) – Trans fats, hydrogenated and partially hydrogenated vegetable oils (omega-6 oils).

These come in the form of hydrogenated and partially hydrogenated fats and oils (canola, soy, corn, sunflower, cottonseed, peanut, safflower, vegetable). Trans fats are found in many processed foods, baked goods and fried foods such as crisps, shop bought cakes, biscuits, pastry, margarine, frozen pizzas, commercial salad dressings, sunflower, soybean, and corn oil.

These are man-made trans fats (unsaturated), and we should avoid them as much as possible, especially if they are genetically modified (GM). These fats interfere with the body’s ability to use important essential fatty acids and studies have shown them to be directly involved in multiple disease processes (6).

In conclusion, what we need to know is that it is important for our health to avoid man made trans fats, these are the partially hydrogenated oils found in refined cooking oils and many processed foods. Saturated fats from animals and animal products are safe to consume in moderation, however, it is important to choose quality meat and dairy that is grass-fed, free range and organic, as much as is possible.

Healthy polyunsaturated fats and monounsaturated fats from nuts, seeds, olive oil, and avocados should be consumed regularly. The omega 3 fats found in oily fish are essential to our health, and most people should be consuming wild caught oily fish around twice a week, or should consider a daily good quality omega-3 supplement. Please bear in mind that cheaper fish oil supplements may include refined vegetable oils high in omega-6.

Vegan and vegetarian omega-3 alternatives are available, however, these short chain ALA omega-3 fats, are not so well converted in the body to the long chain fats that the brain requires (EPA and DHA), and this conversion may only be around 10% efficient (7).

It’s also important to note that there is no one size fits all when it comes to dietary advice and fish oils can be contraindicated for people on certain medications. Therefore it is important to get personalised advice from a registered nutritional therapist, as they can help to tailor advice specific to your needs.


1. Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease. Siri-Tarino et al.

2. Malhotra, A., 2013. Saturated fat is not the major issue. BMJ (Online), 347(7930).

3. Murray, M. and Pizzorno, J. The Encyclopedia of Natural Medicine. Third edition. 2014.

4. De Souza, R.J. et al., 2015. Intake of saturated and trans unsaturated fatty acids and risk of all cause mortality, cardiovascular disease, and type 2 diabetes: Systematic review and meta-analysis of observational studies. BMJ (Online).

5. De Alzaa, F. & Ravetti, L., 2018. Evaluation of chemical and physical changes in different commercial oils during heating. Acta Scientific Nutritional Health.

6. Dhaka, V. et al., 2011. Trans fats-sources, health risks and alternative approach - A review. Journal of Food Science and Technology, 48(5), pp.534–541.

7. Davis, B.C. & Kris-Etherton, P.M., 2003. Achieving optimal essential fatty acid status in vegetarians: Current knowledge and practical implications. In American Journal of Clinical Nutrition.

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