Omega-3 fatty acids are polyunsaturated fatty acids.
The group of omega-3 fatty acids includes:
- Alpha-linolenic acid – (ALA) – C18:3, of plant origin – vegetable oils and green leafy vegetables.
- Eicosapentaenoic acid – (EPA) – C20:5, oil of oily marine fish and cold water mammals.
- Docosahexaenoic acid – (DHA) – C22:6, oil of fatty marine fish and cold–water mammals.
Alpha-linolenic acid is metabolized (metabolized) to EPA and DHA by elongation and desaturation (conversion of saturated to unsaturated compounds) in the leukocytes (white blood cells) and liver of humans.
Alpha-linolenic acid (ALA)The only known function of alpha-linolenic acid is as a precursor (precursor) for the synthesis of the long-chain omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).Caution! Due to the suboptimal enzyme equipment of humans, i.e. the limited ability to convert alpha-linolenic acid into EPA, about 20 g of pure alpha-linolenic acid – corresponding to about 40 g of linseed oil – must be ingested to reach the required amount of 1 g EPA. This is an amount that is not practical. Only the intake of a diet rich in deep-sea fish ensures optimal concentrations of EPA and DHA in the human body.
Eicosapentaenoic acid (EPA)
Eicosapentaenoic acid is formed in the healthy human organism from alpha-linolenic acid. To ensure endogenous synthesis of EPA, sufficient alpha-linolenic acid must be available. Alpha-linolenic acid is an essential fatty acid and can be found in pumpkin, flaxseed and walnuts, for example. In addition, a sufficient concentration of both delta-6 and delta-5 desaturase is necessary for the self-synthesis of EPA. These enzymes convert alpha-linolenic acid to EPA by inserting double bonds.Alpha-linolenic acid, unlike oleic and linoleic acid, has the highest affinity for both delta-6-desaturase and cyclooxygenase and lipoxygenase. Regular intake of alpha-linolenic acid-rich foods eventually leads to an increase in the synthesis of EPA and a decrease in the turnover of arachidonic acid.To maintain the activity of delta-6 and -5 desaturase, an adequate intake of magnesium, calcium, vitamin B6, biotin, and zinc and magnesium and biotin, respectively, is necessary. If the activity of these desaturases is impaired, endogenous synthesis of EPA cannot occur.The activity of the enzyme delta-6-desaturase is inhibited by:
- Increased intake of saturated fatty acids.
- Micronutrient deficiencies of calcium, magnesium, zinc, vitamin B6 and biotin.
- Alcohol consumption in high doses and over a long period of time, chronic alcohol consumption.
- Elevated cholesterol levels
- Insulin-dependent diabetes mellitus
- Viral infections
- Stress – adrenaline/cortisol
- Aging
Since the conversion of alpha-linolenic acid to eicosapentaenoic acid is very slow, the intake of fatty marine fish or direct administration of EPA is essential.
Docosahexaenoic acid (DHA)
Synthesis
The biosynthesis of docosahexaenoic acid occurs in the healthy human organism starting from the essential alpha-linolenic acid via eicosapentaenoic acid (EPA), which is also important for metabolism. EPA is metabolized by elongation (extension of the fatty acid chain by 2 C atoms) and desaturation (insertion of double bonds) to a fatty acid with 24 C atoms and 6 double bonds. Subsequent ß-oxidation (oxidative shortening of fatty acids by 2 C atoms each) in the peroxisomes (cell organelles in which fatty acids and other compounds are oxidatively degraded) ultimately produces docosahexaenoic acid (DHA).However, the conversion of alpha-linolenic acid to docosahexaenoic acid occurs only to a small extent. Therefore, the intake of fatty marine fish or the direct administration of DHA is exceedingly important.