Influenza and other respiratory viral infections, the most common type of acute respiratory infection, are likely to be a major concern for a long time.

Approaches should be taken to ensure that people's immune systems are well supported, to restore some of the physiological functions involved, which may not be there at the end of the illness, and to minimise the complications associated with such conditions.

Nutrition should be at the forefront of these approaches in order to make up for deficits or avoid excesses.

A number of vitamins (A, B6, B12, B9, D and E) and trace elements (zinc, copper, selenium, iron) have been shown to play key roles in supporting the human immune system and reducing the risk of infections: zinc and selenium appear to be particularly important for the latter.

An excessive inflammatory response can lead to deficiencies in acquired immunity. There is evidence that the cytokine storm can be controlled by omega-3 fatty acids.

The intestinal mucosa is the largest site of immune tissue in humans.

The gut microbiota plays a role in the education and regulation of the immune system. Gut dysbiosis is a hallmark of disease, including many infectious diseases and has been described in COVID-19.

Your good gut bacteria are also capable of creating actual drugs (metabolome), such as butyrate, and synthesising certain vitamins essential to your defences.

Dietary approaches to achieving a healthy microbiota can also benefit the immune system.

The Essential COVID Balance Sheet:

SOD and GPX: two antioxidant enzymes: if their value is high you are under oxidative stress. This must be stopped in order to avoid further damage.

SELENIUM: its insufficiency :

- Decreases: antibody production, number of killer cells

- Increases susceptibility to infections and mycobacterial disease.

Poor selenium status could lead to the emergence of more pathogenic strains of the virus, increasing the risks and burdens associated with viral infection.

COPPER: Copper is an antimicrobial and supports the function of the rapid immune response (or innate immunity).

ZINC: Zinc plays a key role in host defence against RNA viruses by inhibiting the arn polymerase required by RNA viruses, such as coronaviruses, to replicate.

 Zinc deficiency impairs many aspects of innate immunity. There are also marked effects of zinc deficiency on acquired immunity.  

Zinc supports the proliferation of cytotoxic T lymphocytes, key cells in antiviral defence.

It is also an essential cofactor for antioxidant enzymes and is involved in the loss of taste and smell.

Nutritional covid balance: ZINC+SELENIUM.

FERRITINE: its insufficiency induces

-Atrophy of the thymus, reducing the production of naive T lymphocytes.

-weakening of innate and acquired immune responses.

- increase susceptibility to infection.

But excess iron promotes damaging inflammation and microorganisms need iron. Excess iron can promote the growth of the pathogen.

Vitamin A: important for barrier function and for the maturation and function of immune cells, especially innate.

Vitamin A deficiency can impair the response to vaccination.

B vitamins are involved in intestinal immune regulation, thus contributing to the intestinal barrier function.

Vitamins B6, B9 and B12 also support the activity of killer cells and cytotoxic T8 lymphocytes: effects that would be important in antiviral defence.

Vitamin D

- Improves the integrity of epithelial barriers (lungs, intestines) and induces the synthesis of antimicrobial and immune molecules, directly enhancing host defence.

- Improves the effectiveness of the adaptive (vaccine) response by promoting antigen presentation.

- Appears to increase the number of regulatory T cells for control of the immune response.

- Prevents the multiplication of infected cells via inhibition of the Renin Angiotensin system. SARS-CoV-2 requires angiotensin converting enzyme 2 (ACE2) as a receptor to enter cells.

People with low vitamin D status have a higher risk of respiratory tract viral infections.

Lower seroprotection rates to influenza A virus and influenza B virus in vitamin D deficient people.

Vitamin E: Vitamin E deficiency reduces :

- Lymphocyte proliferation,

- Natural killer cell activity and elimination of infected cells.

- Specific antibody production after vaccination.

Vitamin E promotes the adaptive immune response (vaccination). 

Fatty acids: omega fatty acids Epa and DHA have anti-inflammatory properties. Administration of n-3 fatty acids has led to reductions in the duration of mechanical ventilation and length of stay in the intensive care unit, as well as improved oxygenation.

It appears that patients with acute respiratory distress syndrome can be treated favourably with n-3 fatty acids, which act to reduce inflammation and cytokine storm.

Nutritional covid+AGCC balance: butyrate, acetate, propionate, valerate.

New biomarker discoveries related to respiratory viral infections repeatedly report deficiencies in certain metabolites from the gut microbiota, notably short chain fatty acids (SCFAs).

SCFAs derived from the microbiota's processing of fermentable carbohydrates are capable of releasing patrol monocytes from their hibernation in the marrow and immediately attracting them to the lungs, all to protect and repair suffering lung tissue. They also accelerate the maturation and proliferation of cells capable of eliminating lung viruses and reducing lung damage.

Thus, SCFAs have been primarily associated with the regulation of the immune system and the prevention of exacerbated inflammation.

SCFAs are not limited to the gastrointestinal tract, but can diffuse through the bloodstream, influencing cells in peripheral tissues.

Propionate promotes haematopoiesis of dendritic cell precursors in the bone marrow.

In case of a deficit in acetate production, supplementation corrects the susceptibility to pulmonary bacterial superinfection.

Butyrate imparts an anti-inflammatory and antibacterial programme, leading to improved barrier function.

Broad spectrum antibiotics cause butyrate deficiency, a dysfunction of the immune system usually sensitised by butyrate.

The restoration of macrophage antibacterial function via butyrate may be a universal mechanism for preventing or treating chronic mucosal inflammation.


The gut microbiota is a modulator of the immune response and plays an important role in immune-mediated diseases.

A healthy, rich microbiota is able to create a barrier that will prevent the start of virus replication in the lung epithelium and allow time for the immune system to specialise to fight the virus effectively.

The depletion of intestinal bacterial diversity leads to a veritable inflammatory storm causing respiratory distress syndrome and eventual organ failure.

Dysbiosis of the gut microbiota is also thought to contribute to increased mucosal permeability leading to microbial translocation and second infection.

For example, it has been found in deceased patients that the proportion of Bifidobacterium, Lactobacillus and Eubacterium was reduced, and that that of pathogenic bacteria, such as Corynebacterium of the Actinobacteria and Ruthenibacterium of the Firmicutes was increased.

Furthermore, any viral or microbial infection leads to a depletion of the gut microbiota, thus increasing the vulnerability to future infections.

Finally, it has been shown that a depleted microbiota reduces or even cancels out vaccine effectiveness.

It is essential to know the state of one's microbiota in order to prevent, cure and restore viral infections with respiratory tropism.

The transition from a diseased to a healthy microbiota requires specific and individual dietary advice.

Sébastien JEAN

Nutrition et biologie préventive

Clinique de nutrition physiologique