Fatty acids, a central family of lipids
Fatty acids are the largest family of lipids. Their structure is based on a carbon chain of varying length, between 4 and 36 carbons, a hydrophilic head carrying a carboxyl group, and a hydrophobic tail formed by the carbon chain.
This chain can have zero, one or several double bonds. Their number determines two properties: how flexible the fatty acid is and how fragile it is in the face of oxidation. The more double bonds a fatty acid has, the more flexible it becomes, but also the more sensitive to oxidation.
The main families of fatty acids
Saturated fatty acids
Saturated fatty acids have no double bonds, which makes their structure rigid. They are found in meat, charcuterie, butter, cheese, coconut oil and palm oil.
According to Pauline Chambon, they do not disappear from the diet but should be limited: excessive consumption is associated with metabolic syndrome and an increase in LDL cholesterol. In practice, they account for around 10% of calorie intake, no more.
Monounsaturated fatty acids: omega-9 and omega-7
Monounsaturated fatty acids have a single double bond. The main omega-9 is oleic acid, found in olive oil, olives, avocado and some nuts such as almonds and walnuts. Omega-9s are associated with favourable effects on the cardiovascular system.
Omega-7s are rarer. They are found mainly in macadamia nuts and macadamia oil, as well as in sea buckthorn oil. Their main representative is palmitoleic acid, whose properties concern the skin and mucous membranes.
Polyunsaturated fatty acids: omega-6 and omega-3
Omega-6s and omega-3s belong to this family. They are the most sought-after fatty acids in nutrition and supplementation.
The lead omega-6 is linoleic acid, found in sunflower, corn, grapeseed and evening primrose oils. It is then converted into GLA, then into DGLA. DGLA is the precursor of series 1 prostaglandins, involved in the resolution of inflammation.
The lead omega-3 is alpha-linolenic acid, found in linseed, rapeseed and camelina oils, and to a lesser extent in walnut and hazelnut oils. Omega-3s are also found in small oily fish.
From alpha-linolenic acid, the body produces EPA and DHA, but the conversion rate remains low. According to Pauline Chambon, a spoonful of linseed oil on a salad is not enough to cover EPA and DHA needs.
What fatty acids do in the body
Fatty acids are not only an energy store, even though they provide 9 kilocalories per gram, twice as much as carbohydrates or proteins.
First, they play a structural role. They are incorporated into cell membranes, whose quality therefore depends directly on the fatty acids consumed. They influence membrane fluidity, transmembrane exchanges, the efficiency of receptors and transporters, and cell deformability. This fluidity matters particularly for red blood cells and for immune cells during diapedesis.
Next, they are precursors of several biochemical mediators: prostaglandins, leukotrienes and thromboxanes. They also take part in certain immune cascades.
Finally, they have an epigenetic role: fatty acids can bind to PPAR receptors, open up the DNA molecule and activate certain genes, notably genes involved in carbohydrate metabolism.
The omega-6 / omega-3 ratio, the central marker
The body makes some fatty acids in the liver, but this pathway remains secondary. Diet remains essential, especially for the essential fatty acids the body cannot make: linoleic acid on the omega-6 side, and alpha-linolenic acid on the omega-3 side.
The delta-desaturase enzyme is involved in converting omega-6s and omega-3s. It works slowly, and several factors slow it down further: ageing, alcohol consumption, hyperthyroidism, high cholesterol and an unbalanced omega-6 / omega-3 ratio.
According to Pauline Chambon, the ideal ratio lies between 2 and 4, at most 5, whereas the average diet shows a ratio closer to 15. One point is worth remembering: the population is often short of both omega-6 and omega-3, and above all of omega-3. The goal is therefore twofold: increase omega-6 intake and increase omega-3 intake even more.
Rebalancing dietary intake
Industrial trans fatty acids should be avoided. They are found in processed foods: industrially made pizzas, viennoiseries, pastries and biscuits.
Saturated fatty acids found in dairy products, cheese, charcuterie and animal products should, for their part, be limited.
On the omega-3 side, Pauline Chambon recommends favouring small oily fish, with at least two portions of fish a week, rapeseed oil, cold-pressed linseed oil as a dressing, and products from animals fed an omega-3-enriched diet.
For cooking, omega-9s, and olive oil in particular, remain better suited. Omega-3s are fragile and do not tolerate heating.
Supplement forms and their bioavailability
Choosing a supplement does not depend only on the amount of omega-3 or omega-6 on the label. The form used matters just as much.
Triglycerides are the natural form of fatty acids. They offer good bioavailability and good stability, but require digestion by pancreatic lipases. This form is therefore less suitable when digestion is disrupted.
Re-esterified triglycerides concentrate EPA and DHA further, while retaining good bioavailability and good stability. They also require pancreatic digestion.
Ethyl esters are an industrial, synthetic form with an unfavourable profile: poor bioavailability, poor oxidative stability, often mediocre digestive tolerance and a higher risk of adverse effects. According to Pauline Chambon, this form is also associated with a warning about the risk of atrial fibrillation in some people with an unfavourable cardiovascular background. A product that is highly concentrated in EPA and DHA but inexpensive should make you think of an ethyl ester form.
Phospholipids offer very good bioavailability and are incorporated directly into cell membranes. They have very good oxidative stability and require no prior digestion. Krill oil provides this form.
Free fatty acids also offer very good bioavailability without requiring digestion. Their weak point remains their fragility when exposed to oxygen.
Oxidation and the Totox index
Oxidation is the main enemy of fatty acids. An oxidised fatty acid loses its benefits and can become harmful. An oxidised oil can generate oxidative stress, cause digestive disorders and develop a rancid smell or taste. An oil that smells or tastes rancid should not be consumed.
The Totox index measures the overall degree of oxidation of an oil. It combines the peroxide value, which measures primary oxidation, and the anisidine value, which measures secondary oxidation. An index below 26 is acceptable, an index below 10 indicates very good quality, and for some oils the peroxide value should stay below 5.
The quality criteria to look for are cold extraction, no solvents, capsules sealed against water and oxygen, filling under nitrogen, opaque packaging, the presence of natural antioxidants such as tocopherols or rosemary extract, and a Totox index check on every batch.
Spotting an imbalance in consultation
Assessment starts with the case history. A few questions are enough to frame intake: which cooking fat, which dressing oil, how much fish and in particular oily fish, how often, and what place for walnuts, almonds and seeds.
Physical signs often show first on the skin, hair and nails, with dry skin, and then sometimes as difficulty concentrating or emotional imbalances.
Some situations reduce fatty acid absorption and are worth looking for: exocrine pancreatic insufficiency, hepatic stasis, bariatric surgery and other digestive disorders.
On the laboratory side, several tests are available: total cholesterol, LDL, HDL, triglycerides, oxidised LDL, free fatty acids and the red blood cell fatty acid profile. The latter makes it possible to assess the omega-6 / omega-3 ratio, the omega-3 index, the arachidonic acid / EPA ratio, inflammatory status and cardiovascular risk.
Choosing the fatty acid according to the goal
Cardiovascular system
The cardiovascular system calls for at least 250 mg of EPA and DHA a day, with EPA to be favoured. Krill oil has a 2 to 1 ratio in favour of EPA in phospholipid form, with excellent bioavailability. For a vegetarian or vegan profile, a plant-based omega-3 in triglyceride form, with DHA and EPA from microalgae, is the alternative. It is taken with a fatty meal, for a minimum period that is often three months.
Nervous system and cognition
DHA is the most abundant fatty acid in the brain. It is involved in neurotransmission and synaptic plasticity. According to Pauline Chambon, it is particularly suited to cognitive functions and intellectual performance, as well as to pregnancy and breastfeeding, where it supports the development of the brain and eyes of the foetus and infant.
The dosage markers mentioned are at least 250 mg a day for a general action on the brain, and at least 450 mg a day during pregnancy or breastfeeding.
Mood and emotional balance
EPA acts on certain lipid mediators and notably modulates dopamine and serotonin. It can be combined with magnesium bisglycinate, and with saffron in situations of mild to moderate low mood.
Vision
DHA is the main fatty acid of the retina, with a marker of 250 mg a day. It can be combined with lutein, zeaxanthin or bilberry depending on the context.
Skin and mucous membranes
Two families stand out here, omega-6s and omega-7s. Borage oil provides GLA, which strengthens the skin's barrier function, is converted into DGLA and helps soothe skin irritation. The skin converts linoleic acid poorly into GLA and then DGLA, so GLA needs to be provided directly.
Sea buckthorn oil stands out for its richness in omega-7. It acts on barrier function, mucin secretion and the hydration of mucous membranes, which makes it relevant in situations of skin, vaginal or eye dryness. The combinations mentioned are sea buckthorn oil and hyaluronic acid for dry skin, borage oil and black seed oil for reactive skin, and sea buckthorn oil and bilberry for dry eyes.
Joint comfort
For the joints, EPA remains the reference: it promotes a pro-resolving action on inflammation. Krill oil is favoured thanks to its ratio in favour of EPA. Borage oil is a less attractive alternative, but useful thanks to DGLA. Depending on the situation, curcumin and devil's claw can be combined.
Points of caution
Linseed oil, very rich in alpha-linolenic acid, must be stored away from light and in the cold, used quickly, and never cooked.
Sea buckthorn oil contains vitamin K and beta-carotene. It is not suitable for people on anticoagulants or for smokers. In smokers, beta-carotene can become pro-oxidant, and this precaution for use applies whatever the amount stated on the supplement.
DHA usefully supports pregnancy and breastfeeding, and can pass into breast milk. Finally, krill oil is not suitable for people allergic to shellfish and fish.
Key takeaways
Fatty acids play a major role in the body's balance. They are involved in energy, cell membranes, signalling, inflammation, the brain, vision, the skin, mucous membranes and the joints.
Three markers structure the advice: favour good dietary sources, choose forms that are highly bioavailable and well protected from oxidation, and adapt the choice of fatty acid to the clinical situation. EPA, DHA, GLA, omega-7 or omega-9: each family has its value, provided you select the right form, the right quality and the right context.
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