Gastric viruses

In July, it was reported that due to the easing of restrictions following the Covid19 pandemic, gastric viruses such as norovirus, which have been supressed due to social distancing, may become a  significant issue this winter, with numbers already increasing. Human noroviruses in the family Caliciviridae are a major cause of epidemic gastroenteritis, and pre-pandemic they were responsible for at least 95% of viral outbreaks and over 50% of all outbreaks worldwide. Norovirus infections can sweep through families and communities. They are especially likely to spread among people in confined spaces, causing fever, vomiting, diarrhoea and gastritis. In most cases, you pick up the virus from contaminated food or water, although person-to-person transmission also is possible.

The delivery of infection has meant that norovirus incidence has declined due to lockdowns etc, however, as there has been a decline in infections there is also a decline in natural immunity, which tends to be relatively short lived in these types of infections. Although the infection is self-limiting (recovery occurs in 12-72 hours) in most healthy people, immunocompromised, the elderly and infants can be susceptible to severe illness following a gastric virus infection. It is therefore an important time to protect ourselves against the occurrence of these types of infection as well as Covid19 and the flu.

Skip to Key Takeaways

We have been aware of the importance of handwashing and hygiene during the pandemic, and this is also essential for helping to ameliorate the spread of gastric viruses, with particular importance with regards to food hygiene.

It is also important to consider healthful interventions which support the health of both the immune and the gastro-intestinal systems. The more robust these systems are, the less likely for the infection to take hold and cause symptoms or disease severity.

Stomach Acid

Stomach acid is essential for the digestion of food, particularly activation of protease enzymes and the cleavage of minerals from carrier molecules. It also possesses functions including the neutralisation and destruction of pathogens as they enter the body. Gastric viruses enter the body via the digestive system and are mainly ingested by contaminated foods stuff or hands that are then put into the mouth. If stomach acid levels are insufficient, not only can this impair digestion and therefore essential nutrient absorption but can also render the individual more susceptible to gastric infections. It has been hypothesised that reduced levels of gastric acid are, in part, responsible for the increased prevalence of infections in the very young and the elderly, who tend to have reduced gastric output1.

If stomach acid levels are low, you can experience bloating, discomfort and a feeling of fullness following a meal, due to delayed gastric emptying. Other symptoms include undigested food in the stool, food intolerances and nutrient deficiencies including B12 and iron. Therefore, if you are experiencing any of these it may be prudent to support stomach acid production. To help support stomach acid production you should:

  • Ensure adequate zinc intake, zinc is a cofactor for the production of hydrochloric acid.
  • Use a supplement containing betaine HCl, preferably with additional digestive enzymes – note; these are contraindicated in cases of gastritis, hiatus hernia and stomach ulcers.
  • Avoid using over the counter antacid medication where possible.
  • Avoid drinking 30 minutes before food as can dilute stomach acid.
  • Use apple cider vinegar or lemon in water with / during meals to help stimulate gastric acid.

Secretory IgA

The gut is one of our first lines of defence against infection and contains secretory IgA or sIgA, which lines the digestive tract. SIgA acts as an anti-septic paint in order to neutralise pathogens before they can enter the blood stream and is therefore a member of the adaptive secretory immune system. A deficiency of sIgA is one of the most common types of primary immune deficiency and people with reduced sIgA have an increased prevalence of many conditions, including infectious disease and autoimmunity2. Protective IgA responses to gastrointestinal viruses are thought to be comprised of high affinity antibodies that recognize and neutralize the viruses3-4.

Secretory IgA is significantly depleted by chronic stress. Therefore, stress management is essential for helping to support defence against pathogens. The duration of the stressful situation is particularly important: acute stress enhances sIgA levels, in contrast to prolonged stress, which diminishes sIgA levels

The balance of gut flora (mentioned later) is also really important for supporting sIgA and immune function and therefore should always be considered when looking at preventative strategies. You can support sIgA production by:

  • Stress management (e.g. yoga, mindfulness, gentle exercise and breathing techniques)
  • Sacchromyces Boulardii – a prebiotic, commensal yeast which stimulates the production of sIgA5
  • Supporting healthy balance of gut flora with a probiotic6, prebiotics or fermented foods7

Gut Health

Evidence has been growing for the role that the microbiota plays in interactions between the host and various pathogens, including norovirus. Pro-viral and antiviral effects of the microbiota have been observed for both human and murine noroviruses, and it has become clear that direct effects of microbes and their metabolites, as well as indirect effects of commensals on the host, are key in modulating pathogenesis. The gut microbiota has been  shown to possess the ability to regulate the host interferon response, thereby modulating norovirus infection8,9.

Immune Support

It is well understood that the gut plays an essential role in the health of the immune system and therefore when supporting immunity, the gut should also be considered. The digestive system is home to 70% of our immune tissue, known as the gut associated lymphoid tissue or GALT. GALT is comprised of lymphocytes in the mucosal epithelium and in the underlying connective tissue, mesenteric lymph nodes and Peyer’s patches (aggregates of lymphoid tissue). It is essential that such a large part of the immune system resides here as the lumen (inside) of the gut is in effect the external environment. The gut lining has an extremely large surface area, approximately the size of a tennis court, and therefore is the largest area of the body that is exposed to the outside world. The lumen is separated from the GALT by a single layer of epithelial cells which are infiltrated by B cells, T cells, macrophages, dendritic cells and M cells, all poised to ward off infection. It is also important to consider the microbiome (gut bacteria) which play an essential role in supporting and stimulating the immune system.10

Supporting gut health post-infection is also essential as it has been shown that viruses can enter the enterocytes and Peyer’s patches in the gut where viral replication occurs, this can affect both the immune tissue and the microbiome, as well as increasing gastrointestinal permeability.

Healthy digestive function can be supported by:

  • maintaining adequate zinc levels, zinc is very important for the production of stomach acid as well as for maintenance of epithelial tissue which lines the digestive system
  • eating prebiotic foods such as baked apples, chicory and artichoke
  • eating fermented foods such as kefir, sauerkraut and kimchi to support gut flora
  • consider taking a multi-strain probiotic
  • using digestive enzymes to improve nutrient digestion, if this is impaired
  • drinking bone broths – make a broth from meat carcass (ideally organic) – this is high in the amino acid glutamine which supports the repair of the digestive lining
  • increasing foods that support the liver such as brassicas, onions, garlic, rocket and watercress

Other immune supporting nutrients

Beta glucans are not synthesised by the human body and therefore are recognised as foreign. As they are found in the cell walls of fungi and bacteria, the innate immune system recognises them as a potential pathogen, although they themselves do not possess the ability to cause an infection. The recognition of these specific molecules triggers the upregulation of the immune system12.

  • 1-3, 1-6 beta glucans stimulate cells of our innate immune system, have anti-microbial properties, and have therefore been shown to help support immune function.
  • Studies have shown that 1-3, 1-6 beta glucans are able to prevent and reduce infections in both healthy and susceptible individuals.

Micronutrients which play specific roles in immune function include vitamins A, C and D and the minerals zinc, iron and selenium.

Anti-viral Nutrients

Selenium – Selenium is an essential antioxidant and supports the production of the master intracellular antioxidant, glutathione. Dietary selenium deficiency that causes oxidative stress in the host can alter a viral genome so that a normally benign or mildly pathogenic virus can become highly virulent in the deficient host under oxidative stress14.

Vitamin C – Vitamin C contributes to immune defence by supporting various cellular functions of both the innate and adaptive immune system. It additionally supports epithelial barrier function against pathogens. Vitamin C deficiency results in impaired immunity and higher susceptibility to infections15.

Zinc – Zinc is involved in multiple aspects of immune function and a deficiency is associated with reduced:16

  • T cell and B cell function
  • Lymphoproliferative response to mitogens
  • Thymic hormone levels
  • Phagocytosis
  • Chemotaxis
  • Cytotoxic activities

Zinc deficiency therefore increases susceptibility to infectious diseases.

Although the symptoms caused by human norovirus infection typically resolve within several days, virus particles can be shed from asymptomatic individuals for weeks after exposure. Furthermore, symptomatic infection has been documented in immunosuppressed individuals with symptoms lasting for over 2 years and in immunocompetent children with symptoms lasting for up to 6 weeks9.

While these case reports provide only anecdotal evidence that norovirus infection can have varied clinical outcomes, they do suggest that noroviruses should be considered as potential etiological agents of diseases other than gastroenteritis. This highlights  the need to ensure immune and gut function is working optimally to help ameliorate the impact of gastric viruses.

Key Takeaways

  • Gastric viruses, including norovirus, are predicted to become a significant problem this winter, following previous suppression due to the Covid19 pandemic
  • Stomach acid plays an important role in protecting against gastric infections by neutralising or destroying pathogens as they enter the gastrointestinal tract following oral ingestion. Supporting the stomach acid, if necessary, with adequate zinc and potentially a betaine HCl supplement may be useful if stomach acid levels are suboptimal
  • Secretory IgA is the first line of defence for the gastro-intestinal tract and is significantly depleted by stress. The microflora help to support normal secretory IgA levels as well as other methods of immunity by supporting the GALT (gut associated lymphoid tissue). Therefore, supporting the gut microflora and using specific probiotics such as saccharomyces Boulardii, as well as stress management, are important for helping to protect against infection
  • Supporting immune function by supporting the gut flora is also important to ensure a robust response to infections. Other immune supporting nutrients may play a beneficial role in protection including beta glucans, Vitamins A, C and D, iron, zinc and selenium
  • Other nutrients possess specific antiviral capabilities such as vitamin C, zinc and selenium

If you have questions regarding the topics that have been raised, or any other health matters, please do contact me by phone or email at any time.
01684 310099

Amanda Williams and the Cytoplan Editorial Team


  4. Stier H, Bischoff SC. Influence of Saccharomyces boulardii CNCM I-745on the gut-associated immune system. Clinical and Experimental Gastroenterology. 2016;9:269-279. doi:10.2147/CEG.S111003.
  8. Walker FC, Baldridge MT. Interactions between noroviruses, the host, and the microbiota. Curr Opin Virol. 2019 Aug;37:1-9. doi: 10.1016/j.coviro.2019.04.001. Epub 2019 May 13. PMID: 31096124; PMCID: PMC6768699.
  10. Forchielli ML, Walker WA. The role of gut-associated lymphoid tissues and mucosal defence. Br J Nutr. 2005 Apr;93 Suppl 1:S41-8.
  11. Hoffmann PR, Berry MJ. The influence of selenium on immune responses. Molecular nutrition & food research. 2008;52(11):1273-1280.
  12. Stier H, Ebbeskotte V, Gruenwald J. Immune-modulatory effects of dietary Yeast Beta-1,3/1,6-D-glucan. Nutr J. 2014;13:38. doi:10.1186/1475-2891-13-38
  13. Calder, P. C. et al. (2020) ‘Optimal Nutritional Status for a Well-Functioning Immune System Is an Important Factor to Protect against Viral Infections’, Nutrients. MDPI AG, 12(4), p. 1181. doi: 10.3390/nu12041181.
  14. Guillin, O. M. et al. (2019) ‘Selenium, selenoproteins and viral infection’, Nutrients. MDPI AG. doi: 10.3390/nu11092101.
  15. Carr, A. C. and Maggini, S. (2017) ‘Vitamin C and immune function’, Nutrients. MDPI AG. doi: 10.3390/nu9111211.
  16. Read, S. A. et al. (2019) ‘The Role of Zinc in Antiviral Immunity.’, Advances in nutrition (Bethesda, Md.), 10(4), pp. 696–710. doi: 10.1093/advances/nmz013.

Last updated on 2nd February 2022 by cytoffice


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