Let's consume only the necessary fat

In the previous presentation we referred to the main components of fats or lipids, their fundamental nutritional characteristics and the fatty foods rich in each of these components. We also learned that the differences between fats depend fundamentally on the fatty acid composition of each one.

In this presentation we will refer to the functions that fats perform in the organism; we will also know which types of fats are healthier; we will expose the intakes of fats recommended by specialists and we will provide general recommendations to include in the diet only the necessary fat.

Why should we include fats in our diet?

As we studied in presentation number one, fats are one of the three macronutrients essential for life. We will now discuss the main functions they perform in the body:

• They are indispensable in the formation and maintenance of various structural components of the organism. For example: cholesterol, phospholipids and glycolipids form the lipid bilayers of cell membranes.

• They constitute a concentrated source of energy since one gram of fat metabolized produces 9 kilocalories, which is more than double the amount provided by one gram of carbohydrates or proteins.

• They protect and coat different parts of the body. For example: the triglycerides in adipose tissue cover the organs, giving them consistency and mechanical protection. Fats also coat the hair and skin, protecting them from the negative effects of external agents.

• They intervene as regulatory elements in some cellular processes. For example: In the synthesis of steroid hormones and bile salts.

• They contain certain acids that man cannot synthesize (essential acids) that play an important role in certain structures, mainly in the nervous system. For example: linoleic acid and alpha-linolenic acid.

• They transport and participate in the absorption of fat-soluble vitamins (A, D, E, and K).

• They intervene in the regulation of the concentration of lipids and lipoproteins in the blood.

• Fats improve the taste, smell and texture of foods and therefore their acceptance, an essential element for the diet to be consumed.

Let us first consider the quality of fats, then the quantity to be ingested.

In all the foods that contain fats, there are mixtures of the three types of fatty acids (saturated, monounsaturated and polyunsaturated), but in some the saturated fatty acids predominate, while in others the monounsaturated or polyunsaturated ones.

The quality of the fat contained in food depends on the type of fatty acid predominant in it, as these acids have different effects on health.

The healthiest fats

The healthiest fats are monounsaturated and polyunsaturated fats:

• Moderate consumption of monounsaturated fats helps lower blood levels of "bad cholesterol" (LDL) and increase "good cholesterol" (HDL). They also protect against oxidation and lower blood pressure. Monounsaturated fats are found in olive oil and nuts.

• Moderate consumption of polyunsaturated fats of the omega-3 and omega-6 types reduce blood pressure, prevent arrhythmias and prevent the formation of blood thrombi.

The omega-3 polyunsaturated fatty acids are found in the tissues of certain oily blue fish such as salmon, sardines, anchovies, tuna, mackerel, etc. It is also contained in some vegetable sources such as walnuts, flaxseed, olive, canola and soybean oils.

Omega-6 polyunsaturated fatty acids are present in many vegetable oils, such as sunflower, corn and soybean oils, as well as in foods such as walnuts and avocado.

Less healthy fats

Although some label saturated fats as "unhealthy," it has been proven that when consumed in limited amounts, they can keep us healthy.

However, when consumed in higher than recommended amounts, they increase the levels of "bad cholesterol in the blood," increase the risk of developing heart disease and cerebrovascular disease, and promote weight gain and obesity, disorders that contribute to the onset of other chronic diseases.

To avoid the negative effects of saturated fats, it is recommended to eat only occasionally the following foods: fatty meats, sausages, butter, fatty cheeses, ice cream, coconut and palm oils, cakes, industrial pastries and other foods rich in saturated fats.

Harmful fats

Hydrogenated fats (known as "trans fats") are considered harmful for the following reasons:

• They lower the levels of "good cholesterol" in the blood and promote an increase in "bad cholesterol," which accelerates the progression of atherosclerosis.

• They increase the risk of myocardial infarction more than any other nutrient.

• They increase the risk of type 2 diabetes mellitus.

To avoid their consumption we should consume as little as possible foods made with partially hydrogenated oils and some margarines. It is recommended to check the labels of cakes, cookies, potato chips, snacks, popcorn and industrial bakery products, in order to discover the presence of trans fats in their preparation.

What amounts of fat should we ingest daily?

The consumption of fat should be moderate, it should never exceed 30% of the total calories of the diet, nevertheless, in Spain it is admitted up to 35%, given the habitual consumption of olive oil as culinary fat.

It is recommended that the total lipid intake be obtained from the different types of fats, in the following proportions:

• Around 15 to 20% monounsaturated fatty acids, coming mostly from olive oil.

• Between 7% and 8% of polyunsaturated fatty acids come mainly from oily fish, nuts and seed oils such as sunflower, corn and soybean.

• No more than 8% of saturated fatty acids, coming from whole milk, lean meats, eggs, fish, etc.

• Less than 300 mg of cholesterol per day should be consumed.

• Avoid consumption of trans fats.