It’s no myth that we get ill more in winter and that the number of deaths rises during the cold months.1 But why?
Well, we know that vast numbers of viruses exist, and just as there is a wide variety of plant species, viruses themselves are also very diverse. Plus, they can mutate very quickly. Around 219 known species of virus can infect humans, but there are also plenty yet to be discovered.2 Each virus has its preferred climates, hosts and routes of transmission. Viruses do not have the proteins needed to reproduce, so they have to invade cells in order to multiply.
A number of theories have been put forward to explain why we get ill during the winter cold snaps. For example, our tendency to stay indoors in poorly ventilated and overcrowded places, the low temperatures and humidity helping viruses to spread,3 the lack of UV rays to kill off viruses, and immune systems often being less responsive and defences being weaker (e.g. irritated mucous membranes). Learn more about how immune system works…
Certain nutrients play a role in the functioning of our immune system.
The benefits of vitamin C are well known, as reflected by health claims authorised by the European Food Safety Authority (EFSA) stating that vitamin C contributes to ‘the normal function of the immune system’, to ‘the protection of cells from oxidative stress’ and to ‘the reduction of tiredness and fatigue’. Indeed, a large number of studies have shown that vitamin C promotes the maturation of T-cells and enhances immune function.4 It is also a key antioxidant that neutralises free radicals (ROS).5 Rosehip is a plant rich in vitamin C (even more so than citrus fruits!) as well as antioxidants, galactolipids, minerals and other vitamins.6
Vitamin D is an essential element that ‘contributes to the normal function of the immune system’. It can bind to receptors on immune cells (dendritic cells, B-cells, T-cells, etc.) and modulate innate and adaptive immune responses.7,8 Vitamin D also enhances the cells’ ability to resist stress.9 According to a study, the incidence of flu was reduced in children taking vitamin D3 supplements.10 Meanwhile, vitamin D deficiency has been linked to an increase in autoimmune diseases and a susceptibility to infection.
B vitamins, including biotin
Since their discovery around a century ago, B-complex vitamins have been the subject of extensive study. They influence a large number of cellular processes, and vitamin B deficiency has been linked to a range of dysfunctions, including immune, inflammatory and nervous system dysfunctions.11,12 Taking vitamin B6, for example, improves immune function,13 while taking vitamin B5 can limit the growth of bacteria by stimulating the immune system.14 Biotin (vitamin B7) is also essential for proper cell function. It is a cofactor of many key enzymes for cellular metabolism, especially lymphocyte metabolism. Biotin deficiency causes the immune system to stop functioning properly (thymus and dendritic, T- and NK cell impairment) and develop inflammation (inflammatory cytokine secretion).15,16,17
Vitamin E supplementation brings clear benefits in terms of boosting our immune system, for example, promoting the proper maturation of T-cells. Its beneficial effects are even more significant in elderly people who have weaker immune defences. Vitamin E can also reduce susceptibility to infections, limit the effects of oxidative and immune stress on cells, and facilitate the elimination of certain pathogens.18–22
Q10, or ubiquinone, is a coenzyme that participates in aerobic cellular respiration (in the mitochondria), which in turn generates the molecule ATP, a vital energy source in our cells and tissues. Q10 is also a very powerful antioxidant, preventing the generation of free radicals along with the potential damage they cause and the modification of proteins, lipids and DNA. In particular, Q10 supports and stimulates our immune system.23
Beta-glucans are polysaccharides found in the bran of cereals, and in certain fungi and bacteria. These substances enhance the immune response by activating the complement system (macrophages and NK cells) and stimulating the production of cytokines (IL-2, IL-4, IL-5, IFN-γ).24,25 Studies have shown that taking beta-glucans can reduce the risk and duration of respiratory infections in adults, the elderly, and children under the age of four, while also improving mood, increasing vigour, and reducing tension and fatigue.26,27,28
Choline is essential for the synthesis of phospholipids and for maintaining homeostasis of inflammatory molecules. It also regulates immune system activation and macrophage and lymphocyte response. Likewise, it helps to protect against pathogens and has a role in reducing oxidative stress. 29–31
Zinc is a molecule known to contribute to the ‘normal function of the immune system’ and to the ‘protection of cells from oxidative stress’, among its many roles. Zinc is needed, for example, to enable neutrophils to form NETs (neutrophil extracellular traps) and eliminate pathogens. It plays a significant part in the modulation of the pro-inflammatory response (NF-κB, TLR4, IL-2Rα, etc.), regulation of pro-inflammatory cytokines (e.g. TNF-α, IL-2, IL-1β, IL-8) and oxidative stress control. It is therefore useful against viral (colds, diarrhoea, HIV, etc.), bacterial and parasitic infections.32–35
Zinc deficiency is very common, however, especially in children, pregnant women and the elderly.36 It has been linked to skin problems, stunted growth, hypogonadism, childhood diarrhoea, macular degeneration, and could potentially be connected to the progression of many chronic diseases involving inflammation and oxidative stress (rheumatoid arthritis, diabetes, arthrosclerosis, cognitive impairment, allergies, autoimmune diseases, etc.). 32-35
Calcium and magnesium
Calcium appears to play a key role in the activation of immune cells. It acts as a messenger between cells, including lymphocytes, regulating the various stages of their development and maturation.37,38
Magnesium also has a close relationship with both innate and adaptive immune responses. It is essential for the synthesis of immunoglobulins, cell adhesion molecules, receptors and antibodies. It is also needed for the proliferation and proper function of lymphocytes and for certain immune responses. Magnesium deficiency can also lead to inflammation (IL-6, TNF-α, IL-2, IL-4, IL-5, IL-10, IL-12, IL-13 and IFN-γ cytokines), cell death and impairment of immune cell functions.39–41
Selenium plays a crucial role in the development of various physiological processes, including immune response. Around 50% of the Swiss population could have a selenium deficiency (intake of less than 100 µg/day), which can cause a number of health problems, such as metabolic, nervous system, immune system and allergy-related disorders. We have to be careful, though, as taking over 850 µg/day could lead to selenium toxicity. Taking selenium supplements can stimulate the immune system (e.g. activating the proliferation and functions of T- and NK cells and macrophages) and can modulate respiratory tract inflammation thanks to its antioxidant capacities. A number of studies in rodents have shown that an optimum selenium intake helps to eliminate a range of pathogens more easily, thus giving selenium an antiviral effect.42,43,44
Curcuma (turmeric extract)
Curcuma is a powerful antioxidant that helps to protect cells and organs, including the liver, from the damage caused by oxidative stress. It also has anti-inflammatory and immunomodulatory properties, such as monocyte stimulation and enhancement of immune surveillance.45–52
Thanks to its sulphur-based composition, MSM protects against inflammation and oxidative stress. It can disrupt cellular mechanisms and transcriptional signalling in order to limit chronic inflammation. It has strong antioxidant properties, regulating the balance of free radicals, in particular by stimulating antioxidant enzymes and inhibiting cytokines, enzymes and other cellular processes involved in the generation of free radicals.53
Creatine, arginine and citrulline
Creatine is involved in the renewal of ATP molecules, which are the main energy source in our cells.54 It has also been shown to interact with the nervous system (neuroprotection) and immune system (modulation of macrophage and T-cell activity).55–57
Citrulline malate helps to promote energy production, reduce the sensation of fatigue and support recovery.58,59 Arginine is an important initiator of immune responses. Arginine supplementation can therefore improve the efficiency of the immune system, in particular, by activating T-cells and macrophages.60,61 The same effects have also been observed with citrulline supplementation.62,63
There are 22 amino acids, which are the building blocks of proteins and vital for the functioning of our cells and therefore our body. They play a role in the regulation of immune response by activating the various immune cells, and they regulate the proliferation of lymphocytes and their protein, antibody and cytokine production. They also modulate cellular redox state and gene expression. Amino acids are essential to the optimisation of the intestinal immune system. Each amino acid has certain properties that help to maintain the integrity of the intestine, and normalise cytokine secretion and T-cell function.64–66 Branched-chain amino acids (BCAAs) – leucine, isoleucine and valine – have been shown to play a particularly important role.64 Leucine, for example, appears to be essential to T-cell activation and metabolism.67 Methionine, a precursor of cysteine, is a key amino acid in oxidative stress reduction, and a sulphate and methionine donor to many proteins.68 Lysine can be used to counter the replication mechanism of oral herpes, which causes cold sores,69 and appears to be involved in the activation of antiviral innate immunity70 as well as having an effect on inflammation.71 An increased utilisation of threonine has been observed during immune system stimulation.72 Supplementation could therefore help to strengthen our immune defences.
Collagen, chondroitin, glucosamine, hyaluronic acid
Collagen, chondroitin, glucosamine and hyaluronic acid are building blocks for the structure of our connective tissue. A large portion of our physical barriers (skin, mucous membranes, digestive tract) is composed of connective tissue. It therefore makes sense to strengthen the tissue’s structure to protect against potential damage to our physical barriers.
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