There is an abundance of information on dietary fats out there. But if we wish to better understand why and which type our bodies need, there are some basic facts that we should know about their functions, classification and characteristics. If you too strive to understand why your body needs this valuable macronutrient, this article is for you.
What are dietary fats?
Dietary fats are naturally occurring molecules that are part of our diet and belong to a larger group of compounds named lipids, which also include waxes, sterols (for example cholesterol) and fat-soluble vitamins. They originate from both plants and animals. Common plant sources are seeds (rapeseed, sunflower, soybean, corn and others), fruits (olive, palm fruit) and nuts (almonds, walnuts). Common animal sources on the other hand, are meat, (oily) fish such as salmon, eggs and milk. Both vegetable and animal fats can be consumed as they naturally occur or, indirectly, with other foods, where they are used to improve texture and taste, for example in pastries and sauces.
Dietary fats are, as our other articles on fats state, the main source of energy in our diet and have a number of important biological functions. They are structural components of our cells and membranes, are carriers of fat-soluble vitamins, are involved in neural development and, when stored, body fat also provides energy, cushions and protects vital organs and helps insulate the body.
How are dietary fats built?
Understanding the basic chemistry of fats helps us understand the role they play in our health and food technology. Over 90% of dietary fats are in the form of triglycerides, with a glycerol backbone and fatty acids. The latter are classified according to the presence and number of double bonds in their carbon chain. More specifically, saturated fatty acids contain no double bonds, monounsaturated contain one and polyunsaturated contain more than one double bond. You can read more about how this distinction changes their effect on our bodies in our article The Functions of Fats in the Human Body.
Unsaturated fatty acids can also be classified as “cis” or “trans”, the first being a bent form and the latter a straight form. But their molecular structure aside, what you should know about them is that most naturally occurring unsaturated fatty acids are found in cis form, while trans fatty acids can either be natural or artificial. The later is produced by humans and can be found in products containing vegetable oils/fats that have undergone hydrogenation - a hardening process where hydrogen atoms are added to the oils to increase their firmness and spreadability. The consumption of trans fats is linked to adverse health effect. You can read more on the topic in our articles Fats and their Facts and The Functions of Fats in the Human Body.
Polyunsaturated fatty acids can be further categorised into three categories: omega-3, omega-6 and omega-9. More on the omega fatty acids is written in our article Omega-3 and Omega-6 Fatty Acids – Why are They Important?
What is their role in food-technology?
Fats are used in food technology because they can make food more pleasant by enhancing its texture, mouth feel and appearance, and by carrying fat-soluble flavours. They also have physical characteristics that are important in food manufacturing and cooking.
But the suitability of a fat for food manufacturing depends on many things, among others its physical properties, such as the melting temperature and thermal stability. Saturated fatty acids tend to be solid at room temperature and have a relatively high melting temperature (such as butter or lard), while most vegetable oils, which contain higher levels of unsaturated fatty acids, are usually liquid at room temperature.
Vegetable oils are obtained by crushing the seeds, fruits or nuts, using heat to separate the oil, which is then refined to remove any unwanted taste, smell or colour. However, some oils (for example extra virgin olive oil, walnut or grapeseed oil) are pressed straight from the seed or fruit, without further refining.
The desired characteristics of an oil are also gained through technical processes, such as hydrogenation and interesterification (or fatty acid rearrangement). The former was mentioned above, while the latter is an alternative to the hydrogenation process, where different oils are blended, without actually modifying the fatty acid molecules. This results in the alternation of the fat’s properties, such as hardness, plasticity and heat resistance, without turning them into trans fatty acids.
Dietary fats are an important part of our diet, supplying from 20 and up to 35% of our daily energy needs. But there are many different types of fatty acids, and we should be careful which type we put into our bodies, as some are vital and good for our health, while others will do more harm than good if consumed in greater amounts. Furthermore, we should strive to understand which type of fatty acid is present in the food we buy, to best be able to avoid harmful fatty acids, such as trans fatty acids.
Adapted from www.eufic.org