Sometimes trying to be healthy can be difficult. There’s so much info out there, it can be hard to know what to do. Fats are especially confusing in this way. So I’ve put some info together to help add some clarity.
Firstly we need fats in our diet, in fact dietary fat should provide between 15-20% of our total energy intake. The human brain is about 60% fat. Fats are a component of every cell in the body and are essential for hormone and neurotransmitter production. However not all fats are created equal. Some are very good for us, some very bad, some are very good but can easily become bad. So lets try and clarify some of the facts about fats.
There are three main types of fats;
- Saturated fats
- Monounsaturated fats
- Polyunsaturated fats
The fats are defined by their structure in relation to a covalent bond which attaches the carbons. You can see the unsaturated fat has a double bond in the middle, while the saturated fat has no double bond.
No double bond makes the saturated fat more stable in relation to temperature and light. Saturated fats are solid at room temperature and found in animal fats, coconut oil and palm oil.
Most oils are made up of a composition of each of these types of fats. For example;
- Beef fat (lard): 47% monounsaturated, 11% polyunsaturated, 44% saturated
- Butter: 30% monounsaturated, 4% polyunsaturated, 52%saturated
- Olive oil: 72% monounsaturated, 9% polyunsaturated, and 14% saturated fats
- Coconut Oil: 6% monounsaturated, 2% polyunsaturated and 86% saturated fat
A monounsaturated fat has one covalent bond, it is less stable than a saturated fat but more stable than a polyunsaturated fat. Examples of monounsaturated fats are butter and ghee. Peanut oil, olive oil and avocado oil are all high in monounsaturated fats. In fact
Polyunsaturated fats (PUSF) have numerous covalent bonds and therefore are not stable when heated, exposed to light or oxygen. They become rancid very easily and when heated turn from a healthy oil to an unhealthy trans fat.
Polyunsaturated fats are very good for heart health, as well as brain function, mood and skin. Polyunsaturated fats are found in nuts, seeds and smaller amounts in vegetables and fruits (such as olive and avocado). Popular PUSF’s include sunflower oil, canola oil, almond oil, sesame oil, macadamia oil. Enjoy these oils on a salad, as a mayonnaise or anyway that does not involve heating them. Polyunsaturated fats also include a special group of oils called essential fatty acids. These are oils we can not produce inside the body and therefore need to be consumed. Essential fatty acids are found in fish, krill, calamari, flax seed, nuts and hemp seeds. If you are not eating these foods regularly it is a good idea to supplement.
Saturated fats are non-essential as our body can produce them from other fats if required. Excessive amounts of saturated and monounsaturated fats have been linked to increased incidence of heart disease and dementia so they should be enjoyed in moderation in conjunction with a diet high in heart and brain healthy fruits, vegetables, legumes, wholegrains, nuts, seeds, fish and uncooked polyunsaturated fats. However the consensus is that saturated fats are better for your health than trans fats (14). Breast milk is 50% saturated fat. Saturated fats help us to feel full and satisfied after we eat. Saturated fats are much more stable than PUFA’s and are an excellent choice for cooking. Try roast potatoes in duck fat and buy a tasteless coconut oil for regular use in the frying pan. When coconut oil is not available your next choice is olive oil, butter, ghee, avocado oil or peanut oil.
Polyunsaturated fats which are so so so good for you raw, unheated and stored well are not good once they are heated and turn into trans fats. Trans fats were noted as a public health threat in the 1990’s (14). The most commonly consumed trans fat is in the form of partially hydrogenated vegetable fat (most commonly made from soy oil). Partial hydrogenation raises the melting temperature of vegetable oils, so that they remain solid or semi-solid at room temperature, and also increases their shelf life (14). Historically, margarine and vegetable shortening products, using partially hydrogenated oils, replaced butter and lard in the 1950s and ’60s. Partially hydrogenated soybean oil replaced palm oil in many processed food products, such as biscuits and crackers, beginning in the 1970s, in part due to a belief that it was more healthful than palm oil, which has a very high saturated fat content (14).
We have known for a while that trans fats are bad for our cardio vascular system, but as healthy fats are essential for healthy brain function much new evidence is linking intake of trans fats to poor neurological function. Because these trans fats still look like healthy polyunsaturated fats they attach to receptor sites on cells. Whilst there, they provide no function but block other polyunsaturated fats and essential fatty acids from attaching and actually providing a function. Here are some of the negative effects of trans fats;
- Development of atherosclerotic plaques and increased cholesterol. Which essentially increases your risk of cardio vascular disease and dementia (9, 12, 14).
- Increasing systemic inflammation (14).
- Increased risk of type 2 diabetes.(14)
- Increased likelihood toward drug addiction (due to neurological changes in the hippocampus and reduced neurological anti-oxidation due to trans fats) (8)
- Increased likelihood to be damaged by UV radiation and have poor skin quality which ages more rapidly (10)
- Anxiety or less ability to cope with stress (due to oxidation damage in the brain) (11).
- Poor memory retention. In this study on rats, the group being fed the saturated fat lard scored much higher than the trans fat group. The negative effects of the trans fats were improved with exercise (13).
- Studies on humans have also found that the higher the trans fat intake the lower the score on memory tests
- The Institute of Medicine of the National Academy of Sciences recommended in their 2002 Dietary Reference Intake report that trans fatty acids in the diet be as low as possible, as any intake above zero was associated with increased health risks (14).
- Recent studies show that rats fed high trans fats give birth to rats that are more likely to be hyperactive, prone to drug addiction and anxiety in stressful situations (15).
When looking at heating oils much of the emphasis has been on the saturated, monounsaturated and polyunsaturated content. This is easy to analyse and important to be aware of due to the detrimental effects of trans fats. However fats have many components. For example consumption of heated sunflower oil has been linked in the pathogenesis of cancer and of some degenerative diseases such as Alzheimer, Parkinson and atherosclerosis. This is due to the formation of toxic compounds (and not only the trans fats), when these oils are heated or even stored inappropriately (6).
There are two factors that make some oils safer than others to heat. They are
- Level of saturation
- Level of anti-oxidants
Our favourite oils to cook with are
- Olive oil which has a high MUFA content and is also high in phenolic antioxidants.
- Coconut oil which is 90% saturated fat and has a high antioxidant content.
- Olive oil has been compared to other PUFA’s and has been found to be more stable and less toxic once heated (7).
- Animal fats including ghee, duck fat, goose fat, lard etc.
Although these oils are far better to cook with than a canola, vegetable or sunflower oil they still lose many of their health benefits when heated and the hotter they get the more toxic they become. Also if the oil gets reused it losses more and more of its good properties and begins to generate toxic metabolites which – Increase cholesterol, lipid peroxidation, blood pressure and all of those nasty cardiovascular symptoms (3), in short behaving like a trans fat. A study conducted by Hamsi et al, 2014 found that heating coconut oil once to 180C and cooking with it did not greatly change the positive properties of the oil or contribute any ill effects to the consumers. However if the oil was heated 5 or 10 times the positive properties were lost and consumption of foods fried in it caused significant increases in blood pressure, inflammatory markers prostacyclin 2 and troboxane A2, as well as inflammatory marker C reactive protein.
So ditch the deep fat fryer and ditch oils after you have used them for shallow frying. Don’t allow your frying pan to smoke away while you chop your onions. Add oil to a hot pan and add your ingredients to the oil straight away, this will help cool the oil while still giving your food that hot oil start.
I hope this has helped clear up a few myths and clarified some facts about fats. In my next post I will share some info about coconut oil. As although it is a saturated fat it has special properties that make it a very healthy option that should be consumed and used regularly. If you have any questions post them on my Facebook page and I will try to answer them.
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13. Teixeira, A. Exercise affects memory acquisition, anxiety-like symptoms and activity of membrane bound enzyme in brain of rats fed with different fats: Impairments of trans fats, Neuroscience 195 (2011) 80–8
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