Why healthy oils are essential

Posted on 28 August 2013

People have been consuming oils since biblical times – but are they actually good for us? Irene Labuschagne, part-time dietitian at the Nutrition Information Centre of the University of Stellenbosch, explains.

Do we need oil at all?
Yes we do. Oils are essential to our health. Good fats such as plant oils are cardio-protective and will raise the good cholesterol level in your body, helping to prevent blocked arteries, heart disease and other diseases. They also bring moisture to our cell membranes, help with fluidity of the brain and delay gastric emptying, which keeps us fuller for longer. Although this is good news to anyone who thinks a fat-free diet is the only way to slim down, it’s still advisable to use oils sparingly. A tablespoon of oil, for example, has twice the number of kilojoules than a tablespoon of milk.

What are the healthy oils?
Vegetable oils, which include monounsaturated and polyunsaturated fats, are great for improving our good cholesterol level. Olive oil has always been pitched as the healthiest option because it’s a great source of essential fatty acids and can help to raise the antioxidants in your body that fight disease. ?The South African Olive Industry Association conducted a study that proved local olive oils to be the best on the market when it comes to quality, value for money and truthful labelling. Other good oils include the more affordable canola, grapeseed and sunflower oils, as well as nut oils such as macadamia and sesame. Don’t forget fish oils are high in omega-3 fatty acids – try to eat fatty fish such salmon, pilchards, sardines, mackerel and tuna twice a week.

What oils should I avoid?
Not all vegetable oils are necessarily good for us. It depends on the quality of the oil and the effect it has on our bodies. For example, if you buy olive oil you need to get the pure, cold-pressed kind – it’s more expensive but also less refined (or altered). Avoid blends of oils: rather buy pure oils so you know exactly what you’re getting. Other oils to avoid include palm-kernel oil, which is used in many processed foods, is high in saturated fat and increases our bad cholesterol level, as well as partially hydrogenated canola oil, which undergoes a process turning it into a trans fat that increases the risk of heart disease.

I’ve heard that I shouldn’t heat oil past its smoke point and I shouldn’t cook with olive oil. Why is that?
It’s always best to use alternative cooking methods such as baking, steaming, boiling and grilling to avoid adding fats and oils to food and recipes. Recipes that require frying and deep fat frying should be limited and preferably only eaten on special occasions and in small quantities. Polyunsaturated and monounsaturated liquid vegetable and seed oils like sunflower, canola and olive oil should be used for cooking. A variety of these can be selected based on cost, personal preference and flavour.

The smoke point of cooking oil refers to the temperature at which oil begins to break down to glycerol and free fatty acids, and marks the beginning of both flavour and nutritional degradation. So it’s an important consideration when selecting oil for frying, with the smoke point of the specific oil dictating its maximum unstable temperature and therefore its possible applications. For instance, since deep fat frying is a high temperature process, it requires a fat with a high smoke point. The more refined an oil, the higher the smoke point. Refining removes the impurities that can cause the oil to smoke, so unrefined oils such as cold-pressed oils should be used for milder applications and not for frying. The longer the oil is exposed to heat, the lower its smoke point becomes. Fresher oil will have a higher smoke point than the very same oil after it has been heated in a deep-fryer for several hours. Presence of food particles also decreases the smoke point of oil.

Aldehydes, compounds that form when oil cools down, are a concern. Precautions should be taken to avoid temperatures less than 190°C and the repeated use of frying oil should be limited between five and 10 cycles (also depending on what you are frying). Make sure you remove all food particles from the oil before reusing it.

I’ve had a bottle of olive oil in my cupboard for ages. Can oil go off?
Oil can become rancid even if it’s kept in a cool dark cupboard. Rancid oil not only smells and tastes foul but also changes structure and develops harmful free radicals. The rate at which oil turns rancid depends on factors such as the storage temperature, exposure to light and air, and the amount of natural antioxidants in the oil. Generally the higher an oil is in polyunsaturated fat, the faster it will spoil. So nut and seed oils, which are high in these fats, are best bought in small bottles and stored in the fridge. Oils such as olive and canola oil are fine stored in a cool cupboard. Even so, don’t keep them for too long – they’re best enjoyed fresh!

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The information provided in this article was correct at the time of publishing. At Mediclinic we endeavour to provide our patients and readers with accurate and reliable information, which is why we continually review and update our content. However, due to the dynamic nature of clinical information and medicine, some information may from time to time become outdated prior to revision.

Published in Nutrition