Lipids and fatty acids in our diet

Lipids are macronutrients made up of fatty acids, essential to our body. They represent approximately 20% of the body weight and constitute a good source of energy for the body by providing 9 Kcal per gram of lipids. The recommended nutritional intakes of lipids represent approximately 35 to 40% of total calories provided (Kcal) daily.

Often compared to fat, lipids have a bad reputation. However, they are nutrients essential to the functioning of the body, notably thanks to fatty acids. They are essential for the functioning of the circulatory, hormonal, immune and nervous systems. However, we must be careful with the quantity and types of fatty acids consumed because some can be harmful to our health if consumed in excess.

Fatty acids are part of the lipid category. Most dietary lipids are triglycerides, molecules composed of 3 fatty acids attached to a glycerol molecule. It is precisely these fatty acids that have an important nutritional benefit for our body. They are therefore the main components of lipids and are hydrophobic. There are more than 40 different fatty acids.

A fatty acid is made up of a chain of atoms of carbon (C) and D'hydrogen (H), with at one end a cOOH carboxylic acid function. This forms a more or less long chain depending on the type of fatty acid. Depending on the number of hydrogen atoms found on these carbons, we distinguish several configurations of fatty acids, mainly saturated and unsaturated. Unsaturated fatty acids can take two different geometric forms: cis or trans, which gives them different properties. Trans fatty acids are often the result of numerous agri-food industrialization processes.

Unsaturated fatty acids are divided into two groups : fatty acids monounsaturated (MUFA) with omega 9 and fatty acids polyunsaturated (PUFA) which are themselves divided in two with omega 3 and omega 6. Certain polyunsaturated fatty acids are also called essential fatty acids because they cannot be synthesized by the body, this is particularly the case for linoleic acid and linolenic acid. It is therefore necessary to provide them through food. Polyunsaturated fatty acids should be favored as part of a balanced diet, since they protect against cardiovascular diseases. However, they provide as many calories as saturated fatty acids, be careful not to overdo them!

The best known unsaturated fatty acids are:

• oleic acid (omega 9)
• linoleic acid (omega 6)
• alpha-linolenic acid or ALA (omega 3)
• eicosapentaenoic acid or EPA (omega 3)
• docohexaenoic acid or DHA (omega 3)

Saturated fatty acids are synthesized by the body and they are also found in foodsanimal or plant origin. They are in solid form at room temperature and generally resist heat and oxidation well. Saturated fatty acids have a rather negative image for health since they tend to increase the risk of cardiovascular diseases and the level of bad cholesterol in the blood. However, this information needs to be qualified because not all saturated fatty acids are bad for your health.

The best known saturated fatty acids are:

• palmitic acid
• stearic acid
• lauric acid
• myristic acid
• butyric acid
• arachidic or eicosanoic acid
• caprylic acid

Trans fatty acids, or hydrogenated fats, are part of the category of unsaturated fatty acids. They can benatural origin, but most of the time they areartificial origin and obtained by partial hydrogenation vegetable oils. This partial hydrogenation will modify the molecular structure of fatty acids and therefore their properties.

Indeed, trans fatty acids are composed of the same atoms as cis fatty acids, but they are less present in the natural state than cis fatty acids. Their geometry in space differs from cis fatty acids, so they will have a straight shape instead of being curved at the level of the double bonds between carbon atoms. This configuration makes trans fatty acids less fluid and more solid at room temperature, which is generally sought after by food industries.

The action of these hydrogenated fats on the body is dangerous, they are mainly found in canned soups, industrial pastries or biscuits and other processed products.

Fatty acids mainly constitute a source of energy (1 g of lipids = 9 kcal) and participate in the proper functioning of the body and the various metabolic systems. In addition to having an energetic role, fatty acids will also have a structural, metabolic, anti-inflammatory and protective role for the cardiovascular and cerebral system.

• Metabolic role: fatty acids initially play a metabolic role, since they are an important source of energy. Indeed, during physical effort, the body will draw on its reserves and break down fatty acids. This degradation will make it possible to produce energy in the form of ATP, which is essential for the various metabolic reactions.

• Anti-inflammatory role: lhe anti-inflammatory role of fatty acids is played at the level of fatty acids precursors of molecules essential for the regulation of inflammation, we find in particular omega 3 such as alpha-linolenic acid, precursor of anti-inflammatory eicosanoids. 
  

• Structural role: saturated and polyunsaturated fatty acids will also have a structural role by allowing the synthesis of other lipids useful in the formation of cell membranes. They will notably play a role in the fluidity of membranes, cell growth, the integrity of the skin or the regeneration of damaged tissues.

• Protective role: fatty acids play a protective role in the cardiovascular system and the brain. Monounsaturated fatty acids such as omega 9 will allow cholesterol to be used properly and promote the proper functioning of the cardiovascular system. Omega 6 is particularly involved in the nervous and cardiovascular systems. Omega 3 will participate in the development and proper functioning of the brain, nervous system and heart.

  Recommended nutritional intakes (anc)

The recommended share of lipids in total energy intake is 30 to 40%.

• This lipid intake must consist ofsaturated fatty acids up to 25%, or 8 to 10% of the total energy intake.

• THE monounsaturated fatty acids like omega 9, must represent approximately 50% of lipid intake, or 20% of total energy intake.

• THE polyunsaturated fatty acids such as omega 3 and 6 must represent 25% of lipid intake, with a good omega 6/omega 3 ratio. The omega 6/omega 3 balance is important and must be equal to 5.

  Where can we find them in our food?

• Saturated fatty acids: animal fats such as red meat, butter, cheese, milk but also palm oil or coconut oil.

• Omega 9: olive oil, nuts, avocado and peanuts.

• Omega 6: vegetable oils such as sunflower, safflower, grape seed, soy or corn oil.

• Omega 3: flax seeds and oil, hemp, chia, fatty fish, green vegetables but also algae such as spirulina.

 Recommendations 

Saturated fatty acids tend to increase bad cholesterol levels, so it is preferable to favor unsaturated fatty acids. Indeed, omega 3, 6 and 9 make it possible, for example, to reduce the level of bad cholesterol in the blood. However, although these fatty acids are good for our health, consuming too much of them can cause problems. In fact, our diet provides twice as much omega 6 as omega 3. A deficiency in omega 3 contributes to the increase in inflammatory and cardiac pathologies and certain cancers.

Cholesterol is a lipid essential for the proper functioning of the body, but we know it cholesterol also increases the risk of cardiovascular problems. This is why it is important to take stock. And no, not all cholesterol is bad! 

In fact, there are two types of cholesterol:

• the bad one says LDL for Low Density Lipoprotein (low density lipoproteins) tends to be deposited on the walls of the arteries, which leads to atherosclerotic plaques or fatty plaques.

• the good one says HDL for High Density Lipoprotein (high density lipoproteins) will capture cholesterol molecules in the arteries to transport them to the liver and then be eliminated by the digestive tract. 

Ideally we should have an amount less than 1.6 g/L of LDL cholesterol and an amount greater than 0.35 g/L of HDL cholesterol in our body. A diet high in saturated or trans fat significantly increases LDL cholesterol levels. Therefore, it is preferable to consume unsaturated fatty acids in reasonable quantities to regulate blood cholesterol levels and to have a varied and balanced diet.