Here, Jessica English, RD, takes a look at what has been in the spotlight since the pandemic and whether we really can influence immunity through nutrition.

Immunity has become an understandably hot topic in the past two years; a time when many would have done anything to increase their natural protection against COVID-19 and seasonal illnesses that have run rampant after our prolonged social isolation.

One variable that people may try to take control over when all else is taken out of their hands is, of course, nutrition.

A quick Google search will show a multitude of options for ‘boosting’ your immunity with food and/or supplements, and food manufacturers have been eager to jump on this particular bandwagon. However, as we know, ‘boosting’ your immune system is not actually a desirable outcome. It is also not possible to directly measure an individual’s immune function, nor is it clear how it can actively be improved.¹

What we aim for instead is a way to support immunological homeostasis.

HAS THE PANDEMIC CHANGED HOW WE VIEW NUTRITION AND IMMUNITY?

Historically, people have looked for ways to support immunity with nutrition through cold and flu seasons, but recent research from Taiwan²  used Google Trends data to look at search volume for specific terms related to nutrition, immunity and coronavirus since the start of the pandemic. This research has highlighted an increase in relevant Google searches and the search terms most frequently used.

POPULAR SEARCH TOPICS COMPARED BETWEEN COUNTRIES

The research found the following most popular search topics used in certain world areas:

• European countries: ‘Vitamin D and coronavirus’
• Asia, Middle East, African countries: ‘Vitamin C and coronavirus’
• Central and South America and Caribbean countries: ‘Zinc and coronavirus’

Caribbean and African countries also had high search volumes for specific herbs, such as turmeric and garlic.

This gives an interesting overview and some insight into the differences in the way that nutrition and immunity is perceived worldwide. Such research is limited, however, as these keywords can’t be directly correlated with real-life shopping and eating habits.

IMMUNITY: A QUICK REFRESH

Our immune system can be separated into two different areas: innate and acquired immunity. These work together to provide a host immune response to viruses, fungi, bacteria and parasites.

Functions of the immune system:

• Barrier to prevent microbes entering the body
• Recognise and identify microbes and assessing their potential to cause harm
• Elimination of harmful microbes
• Generation of immunological memory

Nutrition is only one of the many factors that have an effect on our immune function. Additional factors include: genetics, illness, age, stress, smoking, sleep, alcohol consumption, PAL, vaccination, and gut microbiota, amongst others.³

Key nutrients to support immune function:

These are:³

• Vitamins: A, C, D, E and K
• B vitamins
• Zinc
• Copper
• Iron
• Selenium
• Magnesium

Deficiencies in any of these may lead to an impaired immune response and repletion can lead to improved outcomes.³

Functions of nutrition in the immune response include:

• Nutrients with specific immune functions, such as zinc and potentially vitamin D, possess antibacterial/antiviral properties.
• Provision of essential nutrients for each aspect of the immune response to function correctly.
• Regulators of inflammatory and oxidative stress: vitamins C and E, plant polyphenols and LC omega-3s.
• Essential amino acids which help to form proteins key in the immune response: antibodies and acute phase proteins, etc.
• Provision of substrates, such as arginine, for immune-specific metabolites.

Poor nutrient status may, therefore, increase the probability of a poor immune response, greater impact of illness and death.³

GUT HEALTH AND OUR IMMUNE SYSTEM

Our gut mucosa plays an important part in maintaining immune homeostasis, walking a tightrope between preventing entry of harmful bacteria and pathogens and preventing an autoimmune response.⁴

The relationship between commensal bacteria in our gut and our immune function is based around both cell-to-cell communication and the release of lactic acid and antimicrobial proteins that serve to inhibit pathogen growth. Therefore, it’s proposed that some probiotic organisms – specifically certain lactobacilli and bifidobacteria – may also provide our immune function with a helping hand.^5,6

Conversely, intestinal dysbiosis has been observed in many illnesses and appears linked to reduced immune function, though it remains difficult to determine cause and effect.

Disruption of the gut microbiome as a result of dietary changes or antibiotic use can also have a direct effect on immunity, resulting in increased susceptibility to invading pathogens and even systemic dissemination of these commensal bacteria.⁷

HOW CAN WE HELP AS DIETITIANS AND NUTRITIONISTS?

Diets in general appear to have changed since COVID-19 – for better, or worse. There’s evidence to suggest that we ate more fresh fruit and vegetables during the pandemic; however, at the same time, we also increased our snack food and alcohol intake.⁸ The public are also likely to be more alert to the potential positive impact of nutrition on immunity and brands are taking advantage of this by plastering foods with ‘immune-boosting’ claims.

Malnutrition can have a detrimental effect on our immune system, and as such it’s important to ensure that people are eating a well-balanced diet and supplementing where needed. This includes the recommended vitamin D supplementation, attention to gut health, including adequate fibre and diversity of intake and considering use of appropriate pre/probiotic supplements.

As always, there’s no magic bullet to be found in a single pill or meal, but working with clients/patients to support their overall health is likely to have a positive effect on supporting their immune function.

Jessica English, RD

Jess is a self-employed private practice dietitian with interests
in IBS, maternal and child health and public health.

Instagram: @meals.for.motherhood
Website: www.mealsformotherhood.com

 References:

1. Cummings JH, Antoine JM, Azpiroz F et al. PASSCLAIM--gut health and immunity. Eur J Nutr. 2004; 43 Suppl 2:II118-II173. doi:10.1007/s00394-004-1205-4
2. Mayasari NR, Ho DKN, Lundy DJ, Skalny AV, Tinkov AA, Teng I-C, Wu M-C, Faradina A, Mohammed AZM, Park JM, Ngu YJ, Aliné S, Shofia NM, Chang J-S. Impacts of the COVID-19 Pandemic on Food Security and Diet-Related Lifestyle Behaviors: An Analytical Study of Google Trends-Based Query Volumes. Nutrients. 2020; 12(10): 3103. https://doi.org/10.3390/nu12103103
3. Calder PC. Nutrition and immunity: lessons for COVID-19. Eur J Clin Nutr 75, 1309-1318 (2021). https://doi.org/10.1038/s41430-021-00949-8
4. Wu HJ, Wu E. The role of gut microbiota in immune homeostasis and autoimmunity. Gut Microbes. 2012; 3(1): 4-14. doi:10.4161/gmic.19320
5. Powell N, MacDonald TT. Recent advances in gut immunology. Parasite Immunol. 2017; 39(6): 10.1111/pim.12430. doi:10.1111/pim.12430
6. Wiertsema SP, van Bergenhenegouwen J, Garssen J, Knippels LMJ. The Interplay between the Gut Microbiome and the Immune System in the Context of Infectious Diseases throughout Life and the Role of Nutrition in Optimising Treatment Strategies. Nutrients. 2021; 13(3): 886. https://doi.org/10.3390/nu13030886
7. Zheng D, Liwinski T, Elinav E. Interaction between microbiota and immunity in health and disease. Cell Res. 2020; 30(6): 492-506. doi:10.1038/s41422-020-0332-7
8. Food Standards Agency. The Covid-19 Consumer Research: Behaviour and perception. Version last updated: 24 February 2022. Available online: https://www.food.gov.uk/research/behaviour-and-perception/the-covid-19-consumer-research (accessed 28/10/2022)