Cooking Oils & Fats: Clearing up the Confusion

If you’re interested in nutrition and healthy eating then the chances are that you’ve read conflicting reports in the media regarding which cooking oils are the healthiest.

Whole aisles in supermarkets are dedicated to the huge variety of oils available to us. These oils are often promoted as being a healthy alternative to butter and animal fats which are very high in saturated fat. Recent media coverage and scientific studies appear to be challenging these claims, citing that some of these cooking oils are in fact more harmful than natural animal fats.

The history

In 1955, an American researcher called Ancel Keys put forward his lipid theory to the World Health Organisation (WHO), stating that the consumption of saturated fat was directly related to heart disease. This theory was quickly embraced by leading health authorities who warned that eating meat, eggs, butter and foods rich in saturated fat, increased risk of heart disease and recommended that people eat a low fat diet.

The demonising of saturated fats contributed to a boom in the production and sale of processed vegetable oils that were considered to be the superior health choice for cooking and frying due to their composition of polyunsaturated fats. This belief, in conjunction with a fearsomely successful marketing campaign from Procter & Gamble, the US manufacturers of Crisco vegetable shortening, contributed to a rapid increase in the amount of vegetable oils and spreads used in cooking.

A booming market

Today you can find hundreds of different cooking oils for sale. Vegetable oil, olive oil, sunflower oil and coconut oil, are all commonly used in the UK. Determining which oil is best to cook with depends on several factors. Firstly, the nutritional value of the oil or fat, does it contribute to good health? Secondly, the smoke point of the fat or oil, is it safe to expose to very high temperatures before consumption?

Not all fat is created equal

Let us look at the nutritional value of cooking fats first. Most people are aware that there are two different types of fat. Unsaturated fats are liquid at room temperature and are generally considered to be good for you; saturated fats are solid at room temperature and are considered to be harmful to health. Most foods containing fat have both saturated and unsaturated fat in varying ratios. Animal fats such as butter and lard contain very high levels of saturated fats, vegetable oils contain high levels of unsaturated fat.

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Polyunsaturated fats are essential fatty acids that are either omega-3 or omega-6 in structure. Neither of these fats can be produced by the human body, so we must consume them in our diet. The ratio of these polyunsaturated fatty acids (PUFA) is key to good health. Although the exact optimal ratio of PUFA’s in the body is a matter for much debate (ranging from 1-4:1, omega-6: omega-3), it is generally agreed that a lack of omega-3 in the western diet, and massive overconsumption of omega-6 contributes significantly to a range of illnesses1. The average ratio of omega-6: omega-3 in the western diet is approximately 15-16:11.

Commercial vegetable oils are exposed to a series of harsh processing steps that first extract the oil and then refine it using procedures such as distilling, bleaching, degumming and preservation. This produces an oil that has a long shelf life and is neutral in taste. These refined oils are typically very high in omega-6 polyunsaturated fatty acids and are used in a wide range of commercially available processed foods. The high consumption of omega-6 from commercial vegetable oils, putting our omega ratio’s so out of balance, has been implicated as a contributing factor in breast cancer2, prostate cancer3, cardiovascular disease, inflammation and autoimmune disorders4.

The best way to correct the imbalance is to reduce the amount of processed food that you eat and increase the amount of omega-3 containing food such as raw nuts and seeds, egg yolks and oily fish. You do still need some omega-6 to achieve that healthy ratio. This omega-6 can be consumed in non-processed foods such as eggs, nuts, poultry and avocado.

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Smoke-points matter

Finally, in order to make the best choice of cooking fat or oil, you need to know about the smoke-point. Fats and oils all have varying temperature points at which they start to smoke; when a fat exceeds its smoke-point it undergoes molecular changes that produce toxins and harmful free radicals. For this reason, you should choose fats and oils with high smoke-points for frying, searing and browning. For baking, oven-cooking and stir-frying you can choose fats with medium smoke-points. Oils and fats with low smoke-points should be used for dressings, dips and marinades that do not require the application of heat.

On the whole, the more refined the oil, the higher the smoke-point. However, as we have discussed previously, highly refined vegetable oils should be avoided due to their high omega-6 content. So which fats and oils should you use?

Almond oil, rapeseed oil and high quality ghee all have a high enough smoke-point to be suitable for cooking at high temperatures. Butter, lard, olive oil (not extra-virgin), sesame and coconut oil have a medium smoke-point and can be used for baking and stir-frying. Flaxseed, walnut and extra-virgin oils should not be used for cooking as they have a low smoke-point5,6.

In summary

A healthy diet consists of adequate levels of essential PUFA’s but consuming too many omega-6 and too few omega-3 PUFA’s could be harmful to health. Highly processed vegetable oils contain high levels of omega-6 PUFA and are not the optimal cooking choice. Less processed fats and oils should be used for cooking, the type you choose should be dependent on the cooking method to be used due to varying smoke-points. Superior quality ghee is a good choice for high-temperature cooking and olive oil is a good choice for baking and oven-cooking. All fats contribute calorie intake to your diet and should be eaten in moderation for a healthy diet.

If you want help to remove processed food from your diet, join our community at The Green Apple Club and receive your free E-book: Getting Started on Your Clean Eating Journey.

Article references:

    1. http://www.ncbi.nlm.nih.gov/pubmed/12442909
    2. https://www.ncbi.nlm.nih.gov/pubmed/18636564
    3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1890998/
    4. http://www.sciencedirect.com/science/article/pii/S0753332206002435
    5. http://health.clevelandclinic.org/2014/10/heart-healthy-cooking-oils-101/
    6. http://culinaryarts.about.com/od/culinaryreference/a/smokepoints.htm


About the author: 

Sonia Nicholas is a Biomedical Scientist and Freelance Clinical Science Writer & Editor. She has been working in the field of clinical science for fifteen years.

Sonia believes that everyone can improve their health by eating a clean diet – a claim that scientific research increasingly supports. Sonia also believes that healthy, clean eating is accessible to all and doesn’t have to be an expensive lifestyle choice.

All of the information on The Green Apple Club website is in line with current, recommended Government guidelines. All of the articles are evidence based and fully scientifically referenced.


Article tags: cooking fats, omega 3, omega 6, healthy fats

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