Lipids

Description

Lipids are the fats living beings and constitute a wide group of compounds that are generally soluble in organic solvents and generally insoluble in water.

They are an essential component of cell membranes whose functioning depends on the quality of the fat consumed.

The lipids can be either solid or liquid at room temperature, depending on their structure and composition. Although the words "oils", "fats" and "lipids" are all used to refer to fats, the term "oil" is usually used to refer to fats that are liquid at normal room temperature, while the term " fat "is generally used to refer to fats that are solid at room temperature. The word "Lipids" is used to refer to fats both liquid and solid, and other related substances, usually in medical or biochemical contexts. They are broken down in the body by enzymes called lipases produced in the pancreas.

Examples of edible animal fats or oils are lard, fish oil, butter and blubber. They are obtained from fats in milk and meat, as well as under the skin of an animal. Examples of edible plant fats or oils include peanut, soybean, sunflower, sesame, coconut oil and olive oil, and cocoa butter.

These examples of fats can be categorized into saturated and unsaturated. Unsaturated fatty acids can be divided into cis fatty acids, which are the most common in nature, and trans fats, which are rare in nature, but present in partially hydrogenated vegetable oils.

The main role of fatty acids is to form membranes and secondarily to serve as an energy source when reserves of sugars (carbohydrates) are exhausted.

These fatty acids are divided into two categories: saturated fats (which are very rigid and too much consumed in developed countries) and unsaturated fats (omega 3, 6 and 9), which are more flexible and less frequently consumed. Roughly, the first rather have a negative effect on health and the second a rather positive effect except omega-6 (arachidonic acid), which is often present in excess in the diet (especially fatty meats) promoting inflammation and allergy. Those who are the most beneficial are unfortunately the least consumed namely omega 3.

Omega-3 liplids are mainly present in fatty fish: sardines, mackerel, tuna, salmon, sea trout, eel, halibut, etc.. and to a lesser extent in rapeseed, walnut, hazelnut, wheat germ, flax and camelina. Omega 3 lipids have a preventive effect on degenerative diseases (especially cardiovascular but also inflammation, allergy, immunity, cancer and certain dementias).

Omega 6 lipids, for simplicity, are of two types: one originating from plants (rapeseed, walnut and borage and common evening primrose), the other mainly from animal fats. The first have a positive effect on health because they are the only sources of a an important fatty acid, gamma-linolenic acid, which has a positive effect on cardiovascular diseases and immunity. The second (fatty meats) has a rather negative effect it induces an excess of arachidonic acid that promotes inflammation, allergy and cardiovascular diseases.

Omega-9 lipids are mainly present in olive oil, they increase, as does omega-3, the "good" cholesterol. In reality there is no good cholesterol (HDL) and bad cholesterol (LDL). LDL brings cholesterol to the cell that needs to make its membranes as well as some hormones, vitamin D. HDL transports the cholesterol that has not been used to the liver. If LDL for reasons we shall see, is not absorbed correctly into the cell, it will accumulate in the blood and may participate in the formation of atherosclerotic plaques (hence the name "bad" cholesterol). In comparison the more HDL is present, the more cholesterol is transported to the liver thus avoiding an excess of cholesterol in the blood, hence the name of "good" cholesterol.

Hydrogenation is the conversion of liquid vegetable oils into solid or semi-solid form, such as those present in margarine. Changing the degree of saturation of the fat changes some important physical properties such as melting points. This explains why liquid oils become semi-solid. The solid or semi-solid oils are preferred for cooking due to the way in which the fat is mixed with the flour to obtain a more desirable texture in the baked product. Because partially hydrogenated vegetable oils are cheaper than animal fats and are more readily available and have other desirable characteristics (eg, increased oxidative stability / shelf life), they are the ones most used in industrially prepared foods including baked goods. Hydrogenation converts unsaturated fatty acids to saturated with the effect of making them less good for health.

Sources of lipids

See the list of foods that provide the most fat

Needs

For scientists, it seems that given the increasing incidence of obesity, it is useful for the general population to limit fat intake to 30-35% of energy needs. Value RNI fat 100% on the graph of Nutritiomètre ® corresponds to approximately 33% of energy needs.

The distribution of fatty acids (SFA, MUFA and PUFA) which are followed with the base CIQUAL should ideally correspond to the following :

  • SFA: 8% of energy needs
  • MUFA: 20% of energy needs
  • PUFA: 5% of energy needs (and 5.8% for pregnant or lactating women)

100% RNI values on the graph of Nutritiomètre ® for SFA, MUFA and PUFA are the ideal distribution recommended by scientists based on the profile of individuals.

(Source: "Recommended dietary allowances for the French population," the CNERNA-CNRS. Edition coordinated by Ambroise Martin.)

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