The human body cannot produce linoleic acid, and it is found mainly in food. Intriguingly, LA plays a significant role in inflammation and immune modulation, which are key elements of the COVID-19 infection. Aside from that, these fatty acids are also essential to maintain cell membranes in the lungs to promote ventilation. LA also helps in the production of prostaglandins that protect against inflammation in the cardiovascular system.
Linoleic acid is a small molecule and a free fatty acid essential for many cellular functions. Two fatty acids are essential in the diet – linoleic or omega-6 fatty acid and alpha-linolenic or omega-3 fatty acid. Both are polyunsaturated fatty acids, which means that they contain two or more double bonds
Studies have shown that infection, excessive coagulation, cytokine storm, leukopenia, lymphopenia, hypoxemia and oxidative stress have also been observed in critically ill Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) patients
Several clinical trials are being conducted to investigate the most appropriate treatment for SARS-CoVDue to its anti-inflammatory, immunomodulatory, and other various beneficial properties, omega-3 FA is a natural, inexpensive, and could play a role as a healthier choice of supplement during this ongoing pandemic situation.
Omega-3 fatty acid acting on different elements of the immune response.
Omega-3 fatty acids, through their anti-inflammatory mechanism, inhibit the production of pro-inflammatory mediators like interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α and prevent cytokine storm. Some studies also suggest that they dampen the inflammatory response through regulatory T cells (Treg) differentiation. They also exert an anti-viral effect by enhancing the phagocytic activity of cells of the innate immune system- Neutrophils and Macrophages.
https://doi.org/10.3947/ic.2020.52.4.478 Copyright © 2020 by The Korean Society of Infectious Diseases, Korean Society for Antimicrobial Therapy, and The Korean Society for AIDS
one review paper suggest that omega-3 PUFA dietary supplementation may be beneficial to reduce the risk of coronavirus complications, progressing to serious outcomes like ARDS, with the need for artificial ventilation in ICU. The rational for such Hypothesis is based on the following data. An increased intake level (long-term supplementation for prevention against infection or short-term supplementation in acute inflammation phase) of omega-3 PUFAs, including both α-linolenic acid (ALA) as precursor and long-chain derivatives (EPA, DPA docosapentaenoic acid and DHA) may increase their overall tissue storage. This higher cell and tissue omega-3 status could lead to a better conversion to SPMs, leading in turn to a more rapid resolution of inflammation, improving the severity of the cytokine storm, and improving finally the outcome of Covid-19 infected patients.(1)
In 2018, the European Society for clinical nutrition and metabolism (ESPEN) expert group recommended the use of omega-3 rich fish oil in enteral and parenteral nutrition, for its general clinical benefits due to its anti-inflammatory and immune-modulating effects : reduction in infection rate, and length of hospital stay in medical and surgical patients admitted to the ICU.
Indeed, in humans, supplementation with EPA and DHA was shown to lead to the incorporation of both omega-3 LC-PUFA in body lipid pools . The rate of incorporation varied between sample types, with the time to maximal incorporation ranging from days (plasma phosphatidylcholine) to months (mononuclear cells), and higher for adipose tissue . In addition, several plasma EPA- and DHA-derived SPMs were shown to respond linearly with the increased intake of EPA and DHA .
In connection with these interesting results, various SPMs synthesized from EPA and DHA have already shown protection and resolution of acute lung lesions in ARDS . Omega-3 PUFA, in the form of fish oil, mostly rich in EPA and DHA, have also been used as a treatment in several clinical trials in enteral and parenteral nutrition with ARDS patients. Recent meta-analyses [, , ] demonstrated a beneficial impact of these omega-3 supplementation, especially when the supplementation was limited to enteral nutrition . Even if the doses were different and if various other supplementation (such as antioxidants) occurred in the different trials, the authors highlighted significant benefits obtained in only a few days (28 days) on mortality (−36%), as well as on the duration of ventilation, the length of stay in ICU  with enteral supplementation of omega-3 [21,44,45]. In these trials, omega-3 PUFA was provided at high doses to patients with ARDS (from 5 to 20 times the recommended nutritional intake for EPA and DHA).
Considering all these results, administering omega-3 PUFAs appears a reasonable strategy in ARDS. A recent review suggested the systematic use of omega-3 LC-PUFAs if enteral or parenteral nutrition is indicated in the Covid-19 patients admitted in the ICU . In addition to EPA and DHA, recent epidemiological and mechanistic data also suggest a specific role for omega-3 DPA in lung tissue [27,36,48]. Indeed, little studied so far, omega-3 DPA seems to be the starting point for specific routes of synthesis of pro-resolution mediators at the level of the lung .
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