Boost your immune system this winter

As the weather gets colder, days shorter and with Christmas just around the corner it tends to be the beginning of the flu season. Flu not only affects people’s health, and in some cases can be life threatening, but also places a strain on the economy and not to mention the already much stretched NHS. Flu vaccines do not protect against all strains of the virus, therefore the best way to protect yourself from being stricken with flu is to support your body’s ability to fight off infection.

Unfortunately, modern day life tends to be detrimental to normal immune function. Stress, pollution, nutritional deficiencies, poor digestive and liver function and inflammation, among others, can all put a strain on the immune system, leaving it more vulnerable to attack. So when supporting immune function it is also important to help support certain body systems and remove some of the factors that may be contributing to reduced immune function.

Skip to Key Takeaways

Gut Health

First line of defence

The digestive system is home to 70% of our immune tissue, known as 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.

Every day we are bombarded with challenges to our immune system that have the potential to initiate an infection whether it be from food, airborne pathogens, environmental toxins and contact with other people. Therefore, this large area of digestive tissue needs to act as a first line of defence.

B cells within the Peyer’s patches secrete an antibody known as secretory IgA (sIgA) which is a little bit like an anti-septic paint across the gastrointestinal mucosa, it is designed to neutralise invading bacteria and viruses. It is therefore protective against infections, and can be influenced by many factors including stress, inflammation and the gastrointestinal microbiome (commensal bacteria within the gut).

Some probiotic species, including the probiotic yeast Saccharomyces boulardii, have been shown to increase sIgA(11). “The gastrointestinal tract is the primary site of interaction between the host immune system and microorganisms, both symbiotic and pathogenic.”(7)

The GALT and the microbiome in the gut have a very intimate relationship and have the ability to affect each other, the understanding of this relationship is developing all of the time. Studies have shown that the microbiota is important for the development and regulation of innate and adaptive immune systems and that the host-microbial symbiosis and the balance of bacteria within the gut seems necessary for gut homeostasis(8).

Although it is also recognised that the precise mechanisms have not fully been elucidated. It has, however, long been understood in functional medicine that a healthy balance of digestive flora is fundamental to the adequate function of the immune system. “Germ-free animals are more susceptible to infection by certain bacterial, viral and parasitic pathogens.”(7)

The use of live bacteria supplements (also known as probiotics) has been gaining respect as a therapy for many conditions as they aim to help rebalance the flora within the gut and also inhibit the adherence of pathogenic microbes to the digestive lining. Studies have also shown benefits to immune function, demonstrating that, probiotics can stimulate the synthesis and secretion of sIgA, and therefore protect mucosal surfaces against harmful bacterial invasion(2).

Prebiotics are dietary fibres which act as food for the microbiota and stimulate the growth of beneficial bacteria. The digestion, or fermentation, of these “prebiotics” produces short chain fatty acids (SCFAs), which act as a fuel for the cells lining the digestive system, known as enterocytes, and support the integrity of the digestive lining. The SCFAs enhance mucin production which can support immunity.

“Animal and clinical studies have shown that inulin-type fructans will stimulate an increase in probiotics (commensal bacteria) and these bacteria have been shown to modulate the development and persistence of appropriate mucosal immune responses.”(2)

Healthy digestive function can be supported by:

  • drinking lemon in hot water first thing in the morning – to stimulate bile production
  • 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
  • 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

Stress and Adrenal Function

Chronic stress has been associated with the suppression of the immune system. Many studies have shown an association between stress and reduced immune function. One study looked at students at the beginning of term and during exam time and found that there was a reduction of B lymphocytes, an essential part of immunity, during periods of increased stress(6).

The relationship between stress and immunity is a complicated one as it has also been shown that prolonged levels of the stress hormone cortisol can lead to both a decreased resistance to infection and also over activation of immune function and inflammation leading to auto-immune conditions. Therefore, supporting a healthy stress response and adrenal function is essential for maintaining immune homeostasis.

So clearly when supporting immune function, it is important to look at the health of the adrenal (stress) glands. Nutrients that are important for a healthy stress response include:

Vitamins C, B5 and B6 – support normal adrenal function and cortisol production.

Magnesium – an essential cofactor for many enzymes involved in the production of adrenal hormones and therefore depleted in times of stress; it is also a muscle relaxant of both skeletal and smooth muscle.

Phosphatidyl serine – has inhibitory effects on HPA (stress) axis – it has been shown to lower cortisol levels.

Adaptogenic herbs – such as Ashwagandha, Siberian gingseng, Panex gingseng and Rhodiola may be used to modulate the stress response.

Lifestyle – many lifestyle factors can help to reduce cortisol levels and calm the mind and body, here are a few examples:

  • Meditation or mindfulness
  • Moderate, enjoyable exercise
  • Yoga
  • Reading

Nutrients to support Immune Function

There are nutrients and molecules which have been shown to specifically support immune function:

Beta Glucans are naturally occurring polysaccharides found in the cell walls of plants such as oats, yeast, seaweed and mushrooms, particularly shitake and reishi. The healing properties of mushrooms in Eastern medicine are attributed in part to their beta glucan content. Beta glucans found in yeast and mushrooms been shown to have immune modulating abilities, therefore they stimulate the immune system’s resistance to infection whilst preventing over activity of immune function and inflammation.

Immune-stimulatory properties of beta glucans (1,4): Research into beta glucans’ (extracted from yeast) has shown that they:

  • Increase phagocytosis (increased phagocytic activity of granulocytes and monocytes and the percentage of phagocytic cells)
  • Simulate production of chemokines and cytokines
  • Stimulate macrophages
  • Increase intraepithelial lymphocytes

Double-blind randomised controlled clinical trials have found that daily oral administration of 1,3-1,6 beta-glucans reduces the incidence of common cold episodes during the cold season in otherwise healthy subjects(4).

Vitamin C, which has multiple benefits for supporting immunity as it stimulates neutrophils and increases lymphocyte production, increases interferon production and has antioxidant and antihistamine properties. Vitamin C is found in most fruits, particularly berries and vegetables particularly dark leafy greens.

Zinc improves cell mediated immunity by increasing production of T-lymphocytes and regulating the function of white blood cells. Zinc can be found in eggs, wholegrains and pumpkin seeds.

Vitamin D is known to support healthy immune function and has been shown to be deficient in the majority of the population particularly over the winter months. Vitamin D can be manufactured in sunlight by the skin and obtained from the diet although it can be difficult to get enough from the diet; vitamin D is found in oily fish, butter and eggs. The government recommends supplementing 10ug of vitamin D all year round although requirements may increase depending on vitamin D status.

Vitamin A is important for the function of neutrophils, macrophages, and natural killer cells. Deficiency impairs innate immunity by impeding normal regeneration of mucosal barriers damaged by infection. Vitamin A is also required for adaptive immunity and plays a role in the development of T both-helper (Th) cells and B-cells(9).

It is also essential for the maintenance and repair of epithelial tissue and therefore helps to maintain the integrity of the gastrointestinal lining. Vitamin A is rich in oily fish, eggs and also as beta-carotene (which can be converted to vitamin A) in orange and yellow vegetables.

Selenium – studies have demonstrated an enhancement of both cell-mediated and humoral immune responses by increasing levels of selenium intake. Sources of selenium depend on the selenium content of soil and food but can be found in Brazil nuts, oily fish, eggs and seaweed.

So when aiming to protect against flu, coughs and colds it is important to consider digestive health, stress and adrenal function. Increasing intake of specific nutrients such as beta-glucans, vitamins A, C and D as well as zinc and selenium may also be warranted – a good all-round multivitamin and mineral is a good place to start.

Key Takeaways

  1. The health of the gut is essential for immune function as 70% of our immune tissue is found in the gut. Gut health is heavily influenced by the microbiota, therefore, supporting a good balance of microflora is essential for immune function.
  2. Stress can deplete immune function, therefore stress relieving techniques and adrenal support can indirectly support healthy immune response.
  3. Beta-Glucans have been shown to possess immune-stimulatory properties and therefore can be a useful intervention when immune function is reduced or under stress.
  4. Nutrients which play specific roles in immune function include vitamins A, C and D and the minerals zinc and selenium.

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

Helen Drake and the Cytoplan Editorial Team

Relevant Cytoplan Products:

Immunovite – contains beta-glucans, vitamin C, zinc and selenium.

Cytobiotic Active – contains 9 strains of commensal bacteria as well as prebiotic inulin

Saccharomyces Boulardii – contains probiotic yeast.

CoQ10 Multi – comprehensive multi vitamin and mineral, additionally contains CoQ10 and beta glucans.

Vitamin D3 Drops – comes in the form of vitamin D3 Drops with 2 drops = 5mcg.

Vitamin A – comes in the form of Retinol Palmitate and is a vegan-friendly product.

Wholefood Zinc– made from hydroponically-grown brassica (a member of the broccoli family).

Cherry C – contains vitamin C derived from Acerola Cherries.

Adrenal Support – contains vitamin B5, selenium, chromium, Kelp, Rhodiola, Liquorice, Tienchi Root, Suma Root, Siberian Ginseng and Chinese Red Ginseng.

Biofood Magnesium – has a 100mg per tablet potency combined in a probiotic culture.


1. Akramiene D, Kondrotas A, Didziapetriene J, Kevelaitis E. Effects of beta-glucans on the immune system. Medicina (Kaunas). 2007;43(8):597-606.
2. Forchielli ML, Walker WA. The role of gut-associated lymphoid tissues and mucosal defence. Br J Nutr. 2005 Apr;93 Suppl 1:S41-8.
3. Frei, Remo; Akdis, Mübeccel; O’Mahony, Liam (2015). Prebiotics, probiotics, synbiotics, and the immune system: experimental data and clinical evidence. Current Opinion in Gastroenterology, 31(2):153-158.
4. Heike Stier, Veronika Ebbeskotte, and Joerg Gruenwald. Immune-modulatory effects of dietary Yeast Beta-1,3/1,6-D-glucan. Nutr J. 2014; 13: 38.
5. Lehtoranta L, Pitkäranta A, Korpela R. Probiotics in respiratory virus infections. Eur J Clin Microbiol Infect Dis. 2014 Aug;33(8).
6. McGregor BA, Murphy KM, Albano DL, Ceballos RM. Stress, cortisol, and B lymphocytes: a novel approach to understanding academic stress and immune function. Stress. 2016;19(2):185-91
7. Round, J. L., & Mazmanian, S. K. (2009). The gut microbiome shapes intestinal immune responses during health and disease. Nature Reviews. Immunology, 9(5), 313–323.
8. Min YW, Rhee PL. The Role of Microbiota on the Gut Immunology. Clin Ther. 2015 May 1;37(5):968-75.
9. Stephensen CB. Vitamin A, infection, and immune function. Annu Rev Nutr. 2001;21:167-92.
10. Hoffmann PR, Berry MJ. The influence of selenium on immune responses. Molecular nutrition & food research. 2008;52(11):1273-1280.
11. 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.

Last updated on 16th November 2017 by cytoffice


1 thoughts on “Boost your immune system this winter

We'd love your comments on this article
It's easy, just post your questions, comments or feedback below

Names will be displayed as entered. Your email address will not be published. Required *