Coronavirus (44) Nutrients help to combat COVID-19
Since the outbreak of COVID-19 in the UK, which led to the first national lockdown in March 2020, the pandemic has already lasted for more than 15 months. During this period of time, many countries in the world experienced several waves of COVID-19 outbreaks, and quite a few major variants of the SARS-CoV-2 virus emerged. For the UK, the country has been attacked by the wild type, the variant from South Africa (Beta variant, B1.351), the variant from Kent (Alpha variant, B.1.1.7), and recently the variant that originated from India (Delta variant, B1.617.2).
The existing therapies and vaccines against COVID-19 were designed based on the SARS-CoV-2 virus first identified. The longer the virus spread among people, the higher the chances that the virus would mutate. The mutated variants that later become dominant are usually more virulent, and they are more resistant, to various degrees, to the existing therapies and vaccines. Unless we could produce a specific therapy or vaccine in time for an emerged variant, a good immune system, which is able to respond promptly and appropriately to different challenges, is very important to protect us against any SARS-CoV-2 variants.
Optimal nutritional status and lifestyle habits are essential to keeping our immune systems working properly. Here in this blog post, I would like to share with you findings from two review articles on how different nutrients can help us protect ourselves from infectious diseases.1,2 This might give us an idea of what we could prepare for our meals in order to strengthen our health to combat coronavirus-related diseases.
Vitamin A
Vitamin A has been called an “anti-infective vitamin”. It is essential for body's defences against infection as it is important for normal differentiation of epithelial tissue.*1,2 Lack of vitamin A is associated with increased susceptibility to respiratory infections, diarrhoea and severe measles.
Moreover, vitamin A is important for immune cell maturation and function: Vitamin A controls maturation of neutrophils, macrophages, natural killer cells, dendritic cells, and CD4+ T lymphocyte, which are involved in the killing of pathogens.1
As we are undergoing a national vaccination program in the UK, it is also relevant to note that vitamin A deficiency can impair the body’s response to vaccination. Vitamin A’s metabolite, retinoic acid, is required for normal functioning of B lymphocytes, including antibody generation. An example from Indonesian children with vitamin A deficiency showed a higher antibody response to tetanus vaccination after providing them with vitamin A, suggesting that lack of vitamin A can impair the response to vaccination.1
B group vitamins
B vitamins are water-soluble vitamins and work as part of coenzymes.2 B vitamins are generally involved in intestinal immune regulation, thus contributing to gut barrier function.1 Vitamins B6 and B12 and folate (Vitamin B9) all support the activity of natural killer cells and CD8+ cytotoxic T lymphocytes, effects which would be important in antiviral defence.1 Lack of vitamin B6 deficiency causes thymus and spleen atrophy, low blood T lymphocyte numbers, and impaired lymphocyte proliferation and T lymphocyte-mediated immune responses,1 while vitamin B12 deficiency decreases phagocytic** and bacterial killing capacity of neutrophils. In general, shortage of B vitamins weakens the host immune response.
Other B vitamins also has their special functions.1 Vitamin B2 (riboflavin) and UV light effectively reduced the amount of MERS-CoV in human plasma products.2,3 Vitamin B3 (nicotinamide) could enhance the killing of Staphylococcus aureus (bacteria which often cause skin infections, pneumonia, heart valve infections, and bone infections). Moreover, lung injury during mechanical ventilation is usually seen in the severe cases of COVID-19 who need ventilators to get oxygen into body. Vitamin B3 treatment to these patients has a strong anti-inflammatory effect as it significantly inhibits neutrophil infiltration into the lungs.2 Neutrophil infiltration in inflamed lung causes damage to the lung, and is a hallmark of Acute Respiratory Distress Syndrome in severe COVID-19 cases.
Vitamin C
Vitamin C is involved in collagen biosynthesis in connective tissues and is important for maintaining epithelial integrity (tissue in glands and linings).***1,2
Its roles in immunity include leucocyte migration to sites of infection, phagocytosis** and bacterial killing, natural killer cell activity, T lymphocyte function (especially of CD8+ cytotoxic T lymphocytes) and antibody production1 (similar to the function of vitamin A).
Vitamin C supplementation has been shown to decrease the duration and severity of upper respiratory tract infections such as the common cold.1 People deficient in vitamin C are susceptible to severe respiratory infections such as pneumonia.1 This suggests that vitamin C might prevent the susceptibility to lower respiratory tract infections. Furthermore, vitamin C may also protect against infection caused by a coronavirus, as vitamin C increased the resistance of cultures of chick embryo tracheal organ to avian coronavirus infection.2 As COVID-19 is related to lower respiratory tract infection, the Chinese researchers of a review article even suggest vitamin C could be one of the choices for COVID-19 treatment.2
Vitamin D
Vitamin D receptors are found in most immune cells. Vitamin D stimulates the maturation of many immune cells, and enhances epithelial integrity. Vitamin D also induces antimicrobial peptide synthesis in epithelial cells and macrophages, directly enhancing host defence.1 Moreover, vitamin D increases phagocytosis, superoxide# production and bacterial killing by innate immune cells.1
A study from Taiwan found that people with vitamin D deficiency has lower antibody response, after vaccination with influenza A virus subtype H3N2 and B strain, than the group of people with normal vitamin D levels.1 Studies using data from British and American populations suggested that vitamin D levels is inversely correlated with respiratory infection. This means the lower the vitamin D levels, the higher the risk of viral respiratory tract infection.1
Vitamin D can be synthesized in our body with the help of sunlight. Summer is the time with sufficient sunlight, but over a year it is only a short time, so a high proportion of healthy adults in the UK are reported to have low levels of vitamin D. Moreover, the reduced outdoor journies due to the COVID-19 pandemic, further decreases the chance of people to absorb sunlight. Therefore, in addition to absorbing vitamin D from food, vitamin D deficient patients in the UK are usually prescribed vitamin D supplements by a GP. Meanwhile, a study in Japan found that supplementation of Japanese schoolchildren with vitamin D for 4 months during winter reduces the risk of influenza A by about 40%.1
Vitamin E
Vitamin E is a lipid-soluble antioxidant that plays an important role in reducing oxidative stress through binding to free radicals.2
Vitamin E also plays a role in immune response and enhances antibody production.1 The effect of vitamin E is especially obvious in healthy adults over 60 years of age. Research found a positive association between plasma vitamin E and cell-mediated immune response, and a negative association between plasma vitamin E and the risk of infections in this age group.1 Studies by the Nutrition Research Center on Ageing at Tufts University in Boston demonstrated that vitamin E supplementation at high doses (800 mg/day) enhanced T helper 1 cell-mediated immunity (lymphocyte proliferation and IL-2 production), and improved vaccination response to the hepatitis B virus.1 The same research group also reported that a daily intake of vitamin E supplement (135mg/day) for a year decreased upper respiratory tract infections, particularly the common cold, in elderly residents of a nursing home.1 A study from Spain provided further evidence that supplementation of older adults with vitamin E improved their immunity defences.1
Information on other nutrients to protect ourselves from infectious diseases will be presented in my next blog post.
*Epithelial tissue covers most of the external and internal surfaces of the body and its organs. These tissues serve as the first line of defence against inorganic, organic, and microbial intruders. Epithelial cells are the main cell type of these tissues.4
**Phagocytosis is a process of ingesting harmful foreign particles, bacteria, and dead or dying cells.
***Epithelial cells are the main cell type of epithelial tissues, which cover most of the external and internal surfaces of the body and its organs.4 Epithelial integrity is very important as a first line of defence against inorganic, organic, and microbial intruders.
#Superoxide is a reactive oxygen species. It is generated by the immune system to kill invading pathogens in oxygen-dependent killing mechanisms.
References
1. P.C. Calder. Nutrition, immunity and COVID-19. Review. BMJ Nutrition, Prevention & Health. 2020, May 20;3(1):74-92.
2. L. Zhang, and Y. Liu. Potential interventions for novel coronavirus in China: A systematic review. Journal of Medical Virology, 2020, May 92(5):479-490.
3. S.D. Keil, R. Bowen, and S. Marschner. Inactivation of Middle East Respiratory Syndrome coronavirus (MERS-CoV) in plasma products using a riboflavin-based and ultraviolet light-based photochemical treatment. Transfusion. 2016;56:2948-2952.
4. J. Gunther, & H-M. Seyfert. The first line of defence: insights into mechanisms and relevance of phagocytosis in epithelial cells. Semin Immunopathol. 2018; 40(6): 555–565.
Since the outbreak of COVID-19 in the UK, which led to the first national lockdown in March 2020, the pandemic has already lasted for more than 15 months. During this period of time, many countries in the world experienced several waves of COVID-19 outbreaks, and quite a few major variants of the SARS-CoV-2 virus emerged. For the UK, the country has been attacked by the wild type, the variant from South Africa (Beta variant, B1.351), the variant from Kent (Alpha variant, B.1.1.7), and recently the variant that originated from India (Delta variant, B1.617.2).
The existing therapies and vaccines against COVID-19 were designed based on the SARS-CoV-2 virus first identified. The longer the virus spread among people, the higher the chances that the virus would mutate. The mutated variants that later become dominant are usually more virulent, and they are more resistant, to various degrees, to the existing therapies and vaccines. Unless we could produce a specific therapy or vaccine in time for an emerged variant, a good immune system, which is able to respond promptly and appropriately to different challenges, is very important to protect us against any SARS-CoV-2 variants.
Optimal nutritional status and lifestyle habits are essential to keeping our immune systems working properly. Here in this blog post, I would like to share with you findings from two review articles on how different nutrients can help us protect ourselves from infectious diseases.1,2 This might give us an idea of what we could prepare for our meals in order to strengthen our health to combat coronavirus-related diseases.
Vitamin A
Vitamin A has been called an “anti-infective vitamin”. It is essential for body's defences against infection as it is important for normal differentiation of epithelial tissue.*1,2 Lack of vitamin A is associated with increased susceptibility to respiratory infections, diarrhoea and severe measles.
Moreover, vitamin A is important for immune cell maturation and function: Vitamin A controls maturation of neutrophils, macrophages, natural killer cells, dendritic cells, and CD4+ T lymphocyte, which are involved in the killing of pathogens.1
As we are undergoing a national vaccination program in the UK, it is also relevant to note that vitamin A deficiency can impair the body’s response to vaccination. Vitamin A’s metabolite, retinoic acid, is required for normal functioning of B lymphocytes, including antibody generation. An example from Indonesian children with vitamin A deficiency showed a higher antibody response to tetanus vaccination after providing them with vitamin A, suggesting that lack of vitamin A can impair the response to vaccination.1
B group vitamins
B vitamins are water-soluble vitamins and work as part of coenzymes.2 B vitamins are generally involved in intestinal immune regulation, thus contributing to gut barrier function.1 Vitamins B6 and B12 and folate (Vitamin B9) all support the activity of natural killer cells and CD8+ cytotoxic T lymphocytes, effects which would be important in antiviral defence.1 Lack of vitamin B6 deficiency causes thymus and spleen atrophy, low blood T lymphocyte numbers, and impaired lymphocyte proliferation and T lymphocyte-mediated immune responses,1 while vitamin B12 deficiency decreases phagocytic** and bacterial killing capacity of neutrophils. In general, shortage of B vitamins weakens the host immune response.
Other B vitamins also has their special functions.1 Vitamin B2 (riboflavin) and UV light effectively reduced the amount of MERS-CoV in human plasma products.2,3 Vitamin B3 (nicotinamide) could enhance the killing of Staphylococcus aureus (bacteria which often cause skin infections, pneumonia, heart valve infections, and bone infections). Moreover, lung injury during mechanical ventilation is usually seen in the severe cases of COVID-19 who need ventilators to get oxygen into body. Vitamin B3 treatment to these patients has a strong anti-inflammatory effect as it significantly inhibits neutrophil infiltration into the lungs.2 Neutrophil infiltration in inflamed lung causes damage to the lung, and is a hallmark of Acute Respiratory Distress Syndrome in severe COVID-19 cases.
Vitamin C
Vitamin C is involved in collagen biosynthesis in connective tissues and is important for maintaining epithelial integrity (tissue in glands and linings).***1,2
Its roles in immunity include leucocyte migration to sites of infection, phagocytosis** and bacterial killing, natural killer cell activity, T lymphocyte function (especially of CD8+ cytotoxic T lymphocytes) and antibody production1 (similar to the function of vitamin A).
Vitamin C supplementation has been shown to decrease the duration and severity of upper respiratory tract infections such as the common cold.1 People deficient in vitamin C are susceptible to severe respiratory infections such as pneumonia.1 This suggests that vitamin C might prevent the susceptibility to lower respiratory tract infections. Furthermore, vitamin C may also protect against infection caused by a coronavirus, as vitamin C increased the resistance of cultures of chick embryo tracheal organ to avian coronavirus infection.2 As COVID-19 is related to lower respiratory tract infection, the Chinese researchers of a review article even suggest vitamin C could be one of the choices for COVID-19 treatment.2
Vitamin D
Vitamin D receptors are found in most immune cells. Vitamin D stimulates the maturation of many immune cells, and enhances epithelial integrity. Vitamin D also induces antimicrobial peptide synthesis in epithelial cells and macrophages, directly enhancing host defence.1 Moreover, vitamin D increases phagocytosis, superoxide# production and bacterial killing by innate immune cells.1
A study from Taiwan found that people with vitamin D deficiency has lower antibody response, after vaccination with influenza A virus subtype H3N2 and B strain, than the group of people with normal vitamin D levels.1 Studies using data from British and American populations suggested that vitamin D levels is inversely correlated with respiratory infection. This means the lower the vitamin D levels, the higher the risk of viral respiratory tract infection.1
Vitamin D can be synthesized in our body with the help of sunlight. Summer is the time with sufficient sunlight, but over a year it is only a short time, so a high proportion of healthy adults in the UK are reported to have low levels of vitamin D. Moreover, the reduced outdoor journies due to the COVID-19 pandemic, further decreases the chance of people to absorb sunlight. Therefore, in addition to absorbing vitamin D from food, vitamin D deficient patients in the UK are usually prescribed vitamin D supplements by a GP. Meanwhile, a study in Japan found that supplementation of Japanese schoolchildren with vitamin D for 4 months during winter reduces the risk of influenza A by about 40%.1
Vitamin E
Vitamin E is a lipid-soluble antioxidant that plays an important role in reducing oxidative stress through binding to free radicals.2
Vitamin E also plays a role in immune response and enhances antibody production.1 The effect of vitamin E is especially obvious in healthy adults over 60 years of age. Research found a positive association between plasma vitamin E and cell-mediated immune response, and a negative association between plasma vitamin E and the risk of infections in this age group.1 Studies by the Nutrition Research Center on Ageing at Tufts University in Boston demonstrated that vitamin E supplementation at high doses (800 mg/day) enhanced T helper 1 cell-mediated immunity (lymphocyte proliferation and IL-2 production), and improved vaccination response to the hepatitis B virus.1 The same research group also reported that a daily intake of vitamin E supplement (135mg/day) for a year decreased upper respiratory tract infections, particularly the common cold, in elderly residents of a nursing home.1 A study from Spain provided further evidence that supplementation of older adults with vitamin E improved their immunity defences.1
Information on other nutrients to protect ourselves from infectious diseases will be presented in my next blog post.
*Epithelial tissue covers most of the external and internal surfaces of the body and its organs. These tissues serve as the first line of defence against inorganic, organic, and microbial intruders. Epithelial cells are the main cell type of these tissues.4
**Phagocytosis is a process of ingesting harmful foreign particles, bacteria, and dead or dying cells.
***Epithelial cells are the main cell type of epithelial tissues, which cover most of the external and internal surfaces of the body and its organs.4 Epithelial integrity is very important as a first line of defence against inorganic, organic, and microbial intruders.
#Superoxide is a reactive oxygen species. It is generated by the immune system to kill invading pathogens in oxygen-dependent killing mechanisms.
References
1. P.C. Calder. Nutrition, immunity and COVID-19. Review. BMJ Nutrition, Prevention & Health. 2020, May 20;3(1):74-92.
2. L. Zhang, and Y. Liu. Potential interventions for novel coronavirus in China: A systematic review. Journal of Medical Virology, 2020, May 92(5):479-490.
3. S.D. Keil, R. Bowen, and S. Marschner. Inactivation of Middle East Respiratory Syndrome coronavirus (MERS-CoV) in plasma products using a riboflavin-based and ultraviolet light-based photochemical treatment. Transfusion. 2016;56:2948-2952.
4. J. Gunther, & H-M. Seyfert. The first line of defence: insights into mechanisms and relevance of phagocytosis in epithelial cells. Semin Immunopathol. 2018; 40(6): 555–565.
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