DHA: STRUCTURE, BIOLOGICAL FUNCTION, BENEFITS, FOOD - BIOLOGY - 2025

The docosahexaenoic acid (DHA, from the English Docosahexaenoic Acid) is a fatty acid long chain of the group of omega-3 is present especially in brain tissue, so it is essential to normal neuronal development and learning and memory.

It has recently been classified as an essential fatty acid belonging to the group of linoleic acid and arachidonic acid. To date, it has been recognized as the unsaturated fatty acid with the largest number of carbon atoms found in biological systems, that is, the longest.

Chemical structure of docosahexaenoic acid (Source: D.328 2008/11/22 03:47 (UTC) via Wikimedia Commons)

Various experimental studies have revealed that DHA has positive effects in a large number of human conditions such as cancer, some heart diseases, rheumatoid arthritis, liver and respiratory diseases, cystic fibrosis, dermatitis, schizophrenia, depression, multiple sclerosis, migraine, etc.

It is found in foods from the sea, both in fish and shellfish meat and in seaweed.

It directly influences the structure and function of cell membranes, as well as the processes of cell signaling, gene expression and the production of messenger lipids. In the human body it is very abundant in the eyes and in brain tissue.

Its consumption is necessary, especially during fetal and neonatal development, since it has been proven that an insufficient amount of it can negatively impact the development and mental and visual performance of children.

Structure

Docosahexaenoic acid is a long chain unsaturated fatty acid composed of 22 carbon atoms. It has 6 double bonds (unsaturations) located at positions 4, 7, 10, 13, 16 and 19, so it is also said to be a polyunsaturated omega-3 fatty acid; all its unsaturations are in the cis position.

Its molecular formula is C22H32O2 and it has an approximate molecular weight of 328 g / mol. The presence of a large number of double bonds in its structure makes it not "linear" or "straight", but has "folds" or is "twisted", which makes packing more difficult and lowers its point of melting (-44 ° C).

DHA conformation (Source: Timlev37 via Wikimedia Commons)

It is found predominantly in the membrane of the synaptosomes, the sperm and the retina of the eye, and can be found in proportions close to 50% of the total fatty acids associated with the constituent phospholipids of the cell membranes of these tissues.

DHA can be synthesized in animal body tissues by desaturation and elongation of the fatty acid of 20 carbon atoms known as eicosapentaenoic acid or by the elongation of linoleic acid, which has 18 carbon atoms and which enriches flax seeds, chia, walnut and others.

However, it can also be obtained from foods ingested in the diet, especially the meat of different types of fish and seafood.

In the brain, endothelial cells and glial cells can synthesize it from alpha-linoleic acid and another triunsaturated precursor, but it is not known with certainty how much it supplies the necessary demand for this fatty acid for neuronal tissue.

Synthesis from linoleic acid (ALA)

The synthesis of this acid can occur, both in plants and in humans, from linoleic acid. In humans, this occurs mainly in the endoplasmic reticulum of liver cells, but it also seems to occur in the testes and the brain, from ALA from the diet (consumption of vegetables).

The first step in this route consists of the conversion of linoleic acid into stearidonic acid, which is an acid of 18 carbon atoms with 4 double bonds or unsaturations. This reaction is catalyzed by the enzyme ∆-6-desaturase and is the limiting step of the entire enzymatic process.

Subsequently, stearidonic acid is converted into an acid with 20 carbon atoms thanks to the addition of 2 carbons by means of the elongase-5 enzyme. The resulting fatty acid is then converted to eicosapentaenoic acid, which also has 20 carbon atoms, but 5 unsaturations.

This last reaction is catalyzed by the enzyme ∆-5-desaturase. Eicosapentaenoic acid is elongated by two carbon atoms to produce n-3 docosapentaenoic acid, with 22 carbon atoms and 5 unsaturations; the enzyme responsible for this elongation is elongase 2.

Elongase 2 also converts n-3 docosapenanoic acid to a 24-carbon acid. The sixth unsaturation, characteristic of docosahexaenoic acid, is introduced by the same enzyme, which also has ∆-6-desaturase activity.

The precursor of 24 carbon atoms thus synthesized is translocated from the endoplasmic reticulum towards the peroxisome membrane, where it undergoes a round of oxidation, which ends up removing the additional carbon pair and forming DHA.

Biological function

The structure of DHA provides it with very particular properties and functions. This acid circulates in the bloodstream in the form of an esterified lipid complex, is stored in adipose tissues, and is found in the membranes of many cells in the body.

Many scientific texts agree that the main systemic function of docosahexaenoic acid in humans and other mammals lies in its participation in the development of the central nervous system, where it maintains the cellular function of neurons and contributes to cognitive development.

In gray matter, DHA is involved in neuronal signaling and is an antiapoptotic factor for nerve cells (it promotes their survival), while in the retina it is related to the quality of vision, specifically to photosensitivity.

Its functions are mainly related to its ability to affect cell and tissue physiology through modification of the structure and function of membranes, the function of transmembrane proteins, through cell signaling and lipid production. messengers.

How does it work?

The presence of DHA in biological membranes significantly affects their fluidity, as well as the function of the proteins that are inserted into them. Similarly, the stability of the membrane directly influences its functions in cell signaling.

Therefore, the DHA content in the membrane of a cell directly influences its behavior and response capacity to different stimuli and signals (chemical, electrical, hormonal, antigenic in nature, etc.).

Furthermore, this long-chain fatty acid is known to act on the cell surface through intracellular receptors such as those coupled to G-protein, for example.

Another of its functions is to provide bioactive mediators for intracellular signaling, which it achieves thanks to the fact that this fatty acid functions as a substrate for the cyclooxygenase and lipoxygenase pathways.

Such mediators are actively involved in inflammation, platelet reactivity, and smooth muscle contraction, therefore DHA serves in lowering inflammation (promoting immune function) and blood clotting, to name a few.

Health benefits

Docosahexaenoic acid is an essential element for the growth and cognitive development of neonates and children in the early stages of development. Its consumption is necessary in adults for brain function and processes related to learning and memory.

In addition, it is necessary for visual and cardiovascular health. Specifically, cardiovascular benefits are related to lipid regulation, modulation of blood pressure, and normalization of the pulse or heart rate.

Some experimental studies suggest that the regular intake of foods rich in DHA may have positive effects against various cases of dementia (Alzheimer's among them), as well as in the prevention of macular degeneration related to the progress of age (loss of the vision).

Apparently, DHA reduces the risks of suffering from heart and circulatory diseases, since it reduces the thickness of the blood and also the content of triglycerides in it.

This omega-3 fatty acid has anti-inflammatory and

Foods rich in DHA

Docosahexaenoic acid is transmitted from a mother to her child through breast milk and among the foods that have the highest amount of it are fish and seafood.

Tuna, salmon, oysters, trout, mussels, cod, caviar (fish roe), herring, clams, octopus, and crabs are some of the foods richest in docosahexaenoic acid.

Eggs, quinoa, Greek yogurt, cheese, bananas, seaweed, and dairy creamers are also foods high in DHA.

DHA is synthesized in many green leafy plants, it is found in some nuts, seeds and vegetable oils and, in general, all milks produced by mammalian animals are rich in DHA.

DHA dietary supplement (Source: Mr. Granger via Wikimedia Commons)

Vegan and vegetarian diets are normally associated with low plasma and body levels of DHA, so people who undergo these, especially pregnant women during pregnancy, should consume dietary supplements high in DHA to meet the body's demands.

References

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