Fats get a constant wrap for being just that, good, bad and ugly. It tends to be overdone at times but lately certain media manipulators are on the pro-fat bandwagon. So what does research actually tell us?
- Fat is essential for protection of organs, hormone production, as an energy source and for absorption of some vitamins and minerals.
- Per gram fat provides more than double the energy of carbohydrates and protein (9 calories per gram).
- There are many types of fats and oils, they are grouped into categories based on their structure.
- These structural differences affect how we digest and metabolise them, and subsequently how they affect our health.
- We should aim to consume about 30% of our calories from fat, although this vary between 25 and 40% depending on your goals.
- This intake should be fairly evenly distributed between monounsaturated, polyunsaturated and saturated fat sources.
Saturated fats (The bad?). These are mainly animal sources of fat although a few plant sources provide saturated fat too. Saturated fats are the most stable under high heat and are usually solid at room temperature. They are in fact the best choice for cooking with. Some critics will say that these fats are evil, which has some truth but is not entirely so. Saturated fats do impact blood cholesterol levels and certain cholesterol markers are a risk factor for heart disease. This is not cause and effect entirely however. Saturated fats are natural fats that we have eaten since man-in-cave learnt to sharpen stones and hunt buffalo. The Inuit have survived on saturated fat (whale blubber) without heart disease for ages so perhaps the link is not so straight forward. Reviews of research have shown that there is limited evidence of a link between saturated fat intake and chronic diseases and you may have come across headlines to this recently.
The studies reviewed there were not necessarily great quality and there are a myriad of issues with how the studies are conducted and which end-points have been measured. Another major limitation has been that all saturated fats have been placed in one basket where we are beginning to learn that not all saturated fats are the same. For example, medium chain triglycerides which are saturated fats found in coconut oil, cocoa butter and dairy appear to increase HDL cholesterol (the good one) and reduce LDL:HDL favourably. They do however increase blood triglyceride levels, possibly due to the fact that they are absorbed directly into the blood, which is a different mechanism to other fats. This can be a good thing if we are active and exercising because we can use this as fuel immediately. However if combined with a high carbohydrate meal it may not be so great and these two factors could contribute to fat gain.
The prudent point on saturated fats is this: Do not fear them but do not add them unnecessarily to your diet or replace other healthy fats with the saturated kind. For a great article on all of this read this by Dr David Katz.
Examples of saturated fats are the visible fat we see on meat and poultry, as well as butter, milk, cream and coconut oil.
Trans fats (The ugly!!). These are predominantly man-made fats, produced by hydrogenating unsaturated fats to resemble saturated fats. This processing usually occurs in a factory under high heat. These fats are used to improve the stability of foods, increase the shelf life or to make unsaturated fats solid at room temperature. We cannot metabolise these fats efficiently and this has dire consequences for our wellbeing by negatively impacting cardiovascular health, blood cholesterol and inflammation.
Trans fats are common in margarine, refined oils and baked goods where these plant oils or margarine are used as an ingredient. This includes pastries, biscuits, cakes and chips. Read your labels and avoid all trans fats (aka hydrogenated fats) like the plague.
We do get a small amount of non-evil, natural trans fats from dairy products and meat. These fats differs in structure from the man-made variety and appear to have no harmful impact.
Unsaturated fats (The Good?). In this group we have some animal and some plant sources of fat. They are liquid at room temperature.
Monounsaturated fats are present in meat, milk, nuts, olives, avocados and canola oil. These fats are “heart-healthy”, beneficial to cardiovascular health. They have a slightly lower smoking point than saturated fats which means they don’t take to heating as well but are better options than polyunsaturated oils for cooking purposes. Monounsaturated fats can be found in olive oil and olives, avocado, nuts and seeds and their respective oils too. Look to include these daily as your main source of fat.
Polyunsaturated fats are found in some seeds (sunflower, flaxseed), walnuts, soy beans, fish, algae and krill. There are different classes of polyunsaturated fats and some are essential fats like omega 3’s found in oily fish. Omega 3 fats are associated with improved cardiovascular health, reduced inflammation, improved cognitive function and they are helpful for the development of the fetus. We should be including omega 3 foods daily from oily fish (salmon, tuna, mackerel, sardines, pilchards), grass fed beef and dairy or from flaxseed.
Other polyunsaturated fats include omega 6 and omega 9 fats, found predominantly in other plant oils like palm oil, soy bean oil, sunflower oil and canola oil. A diet high in these polyunsaturated fats from vegetable sources may worsen inflammation, chronic disease and cancer risks, particularly when they are highly processed or used repeatedly. The imbalance in our current diet between omega 3 and omega 6 fats is argued to be one of the contributing factors to many health issues that are on the rise today. Aim to keep your intake of these plant based oils to a minimum by avoiding processed foods.
The bottom line with fat is this:
- Don’t be afraid of saturated fats; cook with them and choose dairy (including butter), coconut and palm kernel as your saturated fats of choice but don’t let them dominate your diet
- Avoid trans fats religiously
- Include unsaturated fats daily from olive oil, nuts and seeds, avocado and oily fish
- Limit refined polyunsaturated fats from plant oil