What Are Macronutrients: Fats

What Are Fats Or Lipids?

Let us immediately specify that there are no “good” or “bad” fats, even if often to simplify it is used to define them like this. Fats (or lipids) are part of the macronutrients together with proteins (or proteins) and carbohydrates (or sugars). Their main function is energy (i.e., providing energy to the body) and providing 9 kcal per gram. Lipids are widespread: we find them in animal and plant kingdoms and are the essential constituents of almost all organisms. 

Fats are present in foods both in liquid and solid form. In the food pyramid, we classify them in:

1. visible: those contained in seasoning fats, both of animal origin such as butter (83% of lipids), and vegetable origins such as margarine (84% of lipids), olive or seed oil in general (99% lipids);
2. Not visible: present in different percentages in individual foods. Absent or in small traces in fresh fruit and vegetables, in small quantities in legumes and cereals, especially whole grains, in high quantities in oily nuts, coconut, and avocado. In foods of animal origin (meat, fish, milk and derivatives, eggs, etc.), fats have very variable concentrations, from very small quantities (less than 1% of lipids) to quite high (over 35% of lipids).

Classification of fats

Based on their chemical composition, we can divide fats or lipids into:

Saturated Fats

They are almost always of animal origin, usually present in solid form, and are mainly contained in meat, offal, sausages, eggs, seafood (crustaceans and mollusks such as shrimp, mussels, lobsters, oysters, etc.), in lard, cream, butter and even in cheeses. Furthermore, they can be visible (e.g., ham fat) and invisible (e.g., beef fillet, lamb chops, etc.). 

However, saturated fats are not only found in animal foods but are also found in abundant quantities in some types of plant foods such as palm oil (47% saturated lipids) or coconut oil. (86% of saturated lipids), in fair quantities in condiments such as some margarine (26% of saturated lipids) and small quantities in nuts such as peanuts (7% of saturated lipids).

Unsaturated Fats

They are almost always of vegetable origin, usually present in liquid form, and are mainly contained in olive oil, corn, sunflower, and other types of seeds; in nuts such as walnuts, almonds, peanuts; in single-seed margarine and also in some foods of animal origin such as milk and its derivatives, fish oil (e.g., cod liver oil) and fish in general. Unsaturated fats are in turn divided into: – monounsaturated fats: they are found mainly in oils, such as olive, soy, and monoseme, but also milk and derivatives such as Grana Padano PDO; –

Polyunsaturated Fats

present in both the plant and animal world, such as fish, nuts, and oils. Among the main polyunsaturated fats are Omega-3, which is contained in excellent quantities in fish, especially bluefish, salmon, and fish oil, and Omega-6, which is contained in oils, particularly corn and sunflower. Omega-3, -6, and -9 are called essential fatty acids because our body cannot produce them autonomously, and we must therefore take them through these foods. They also play a fundamental role in the prevention of cardiovascular diseases.

Milk Fats And Meat Fats

It should be noted that there is a difference between the fats in milk and those contained in the meat of animals. About 70% of total milk fats are saturated but different from those of meat: they result from the secretory activity of the cow’s mammary gland. The fats secreted by the breast are made up of globules coated with a special lipoprotein membrane, which includes various layers containing polar lipids and numerous bioactive proteins with metabolic, transport, and protection functions from infections. 

Lipase acts rapidly on this membrane, breaking down fats by transforming triglycerides, responsible for cardiovascular risk, into glycerol and fatty acids. Meat fats, on the other hand, despite the extreme variability due to the species, cut, age, and breeding of the animal, are mainly represented by triglycerides. In other words, the main difference between milk fats and meat fats is that the latter does not belong to a secretory moment; they are not exocrine substances, i.e., secreted by a gland in the lumen of a duct (breast) and are not anatomically constitutive. 

And they are structured in the edible muscle tissue of the animal carcass. Therefore, the consumption of milk and derivatives, such as Grana Padano PDO, does not change the values ​​of triglycerides and HDL (“good” cholesterol). Therefore these foods can be consumed, as part of a balanced diet, even by those who have an excess of triglycerides or cholesterol in the blood. 

Furthermore, intervention studies on middle-aged women and men have shown that a diet with milk, cheese, and ice cream fats for 20% of the daily energy reduced the LDL cholesterol values ​​(the “bad” one) from 4.3 to 5.3%. It can therefore be deduced that milk fat as an “aggregate molecule” is, from a biological and nutritional point of view, a different fate, that is, not burdened by the cardiovascular risk typical of the saturated fats of other foods.

Trans Fats

Another type of fat, this time not present in nature, is trans fats. They arise from an industrial process called hydrogenation through which low-cost vegetable fats (palm, coconut, etc.) are chemically “broken up and reassembled” together, giving shape to trans fats. This process allows obtaining a more compact fat, more easily spreadable, with greater palpability and a longer storage time. , all at very low costs for the food industries. 

It should be noted that this type of fatty acid causes an increase in “bad” cholesterol (LDL lipoproteins), accompanied by a decrease in “good” cholesterol (HDL lipoproteins). Therefore, a diet rich in trans fats increases the risk of developing serious cardiovascular diseases such as atherosclerosis, thrombosis, stroke, etc. 

It also seems that trans fatty acids have a pro-inflammatory action. That is, they favor the onset of inflammation and that they produce an alteration of the normal function of the endothelium. This tissue covers the inside of the blood and lymphatic vessels of the heart (endothelial dysfunction). The WHO guidelines recommend limiting calories derived from trans fats, which should represent a maximum of 1% of calories in the diet, and emphasize how a diet rich in this type of fat increases the risk of heart disease: 21% and 28% death.

The Main Functions Of Fats

1. Energy function: 1 gram of lipids provides 9 Kcal. They are our main source of energy. Proteins and sugars provide less than half of them.
2. Reserve energy: the lipids consumed in excess with the diet are stored in the fatty tissue in triglycerides. This “accumulation” represents for the organism the reserve from which to draw if a lack of energy occurs. Since the reserves accumulated in our body can be unlimited, it is essential to remember that an excessive introduction of lipids is associated with an increased risk of overweight and obesity with possible serious consequences and cardiovascular risk.
3. Structural function: lipids are an important component of cell membranes, of the hydrolipidic film that covers the skin, and of myelin, a substance that lines the nerve fibers. In infants, a lack of essential fatty acids can impair the normal development of the visual and nervous systems.
4. Protective function:
5. moderate accumulations of fat around the joints and vital organs serve to protect them from trauma and to keep them in their physiological position;
6. Fat, especially brown adipose tissue, is a thermal insulator for our body. If necessary, it can produce heat to maintain an adequate body temperature;
7. unsaturated omega-3 and -6 fats (ω-3 and ω-6) are useful in preventing cardiovascular diseases and in some cancers. The ω-3, in particular, are involved in the control of LDL (or “bad”) cholesterol and the reduction of triglyceride levels in the blood.
8. Fats are essential for absorbing fat-soluble vitamins A, D, E, K.

Fat Requirement

The daily lipid requirement is evaluated as a percentage of the daily calories consumed. The highest values, justified by neuronal development, occur in infants (6-12 months) with 40% of total calories and children (1-3 years) with 35-40%. In children aged four years, adolescence, and adulthood, including pregnancy and breastfeeding, the requirement ranges from 20 to 35%. In addition to quantitative considerations, a qualitative assessment is required. Saturated fats consumed in high quantities negatively affect the LDL cholesterol values. 

Basically, in a correct diet, it is essential to respect the lipid requirement compared to the total calories but, given the different chemical and functional structure of the fatty acids, it is important that saturated fats do not exceed 10% of the total energy of the diet and that the remaining percentage is distributed equally between mono and polyunsaturated fatty acids. About the latter, their needs increased up to 2 years of age and during pregnancy and lactation for neuronal and visual development.

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