Lipids include simple lipids or triglycerides, complex lipids or phospholipids, and cholesterol or cyclic lipids. The term “fats” is used primarily for triglycerides, which are made up of three fatty acid molecules and glycerol. In the daily diet, fats account for 95–98% of lipids. That is why the term “fats” is used in the sense of food energy. Dietary lipids or fats are an indispensable component of food, a source of energy, plastic material for humans, and a supplier of essential substances.
Dietary lipids contain three types of fatty acids: saturated, monounsaturated, and polyunsaturated. Saturated fatty acids predominate in animal fats such as lard or butter. Animal fats are usually solid at room temperature. Mono- and polyunsaturated fatty acids are predominantly present in vegetable fats, such as olive oil. The human body is unable to synthesize two polyunsaturated fatty acids, linoleic (Omega-6 fatty acid) and linolenic (Omega-3), so they must be obtained from food. The content of these three types of acids in different fats varies.
Dietary lipid is a concentrated source of energy for the human body: 1 g of it provides approximately 9 kcal of energy. Lipids are important building material for cells; they participate in the processes of growth and regulation of vital activity and supply the human body with fat-soluble vitamins. They are needed for their absorption and transportation in the body. Phospholipids are found in all tissues and cells, most of them in nerve tissues and brain cells. The fatty layer that forms around the organs protects them from bruises. They are needed to remove bile into the intestines; otherwise, it accumulates in the gallbladder, and there is a risk of gallstones formation. Dietary lipid is essential because it carries the flavor of food and creates a feeling of fullness.
The recommended caloric content of fat in the human diet is 30 – 33% or 90 – 107 g per day. A balanced composition of the daily human diet should contain 10-20% polyunsaturated, 50-60% monounsaturated, and 30% saturated fatty acids. This is achieved when one-third of vegetable and two-thirds of animal fats are used in the diet. Lipids should not provide less than 20% of dietary energy; otherwise, there may be problems with the amount of essential fatty acids and the receipt of fat-soluble vitamins. In the case of a lack of fat, the development of the whole organism can be inhibited and resistance to environmental influences can decrease. On the other hand, fats provide too much energy, and when energy intake and expenditure are not balanced, they can be stored as fat in adipose tissue, leading to overweight or obesity.
The sources of dietary lipid in food are fats used in food preparation and those contained in food. To assess the amount of dietary lipid, a person needs to monitor both visible and hidden fat. The amount of the latter is difficult to estimate since it is not visible. Therefore, it is important to read the composition of the product on the packaging and monitor the fat content. Latent fat can, for example, be present in cheeses, sausages, and buns. It is recommended that the number of lipids used in cooking should not exceed half the daily amount of fat.
To conclude, unsaturated fatty acids are involved in the breakdown of lipoproteins, and cholesterol, prevent the formation of blood clots and reduce inflammation. Lipids affect the metabolism in cells, are part of cell membranes, affect blood pressure, and remove cholesterol from the body, while increasing the elasticity of the walls of blood vessels. Vegetable oils are the richest in polyunsaturated fatty acids among food products. Therefore, for health to be strong, it is not necessary to avoid the fats contained in the food and used in its preparation. However, it is important to choose which fats to give preference to and which ones to use as rarely as possible.