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 Table of Contents  
REVIEW ARTICLE
Year : 2021  |  Volume : 14  |  Issue : 3  |  Page : 297-301

Nutrition insights in COVID-19


1 Department of Physiology, JN Medical College, KLE Academy of Higher Education and Research, Belagavi, Karnataka, India
2 Cosmos Institute of Mental Health and Behavioral Sciences, New Delhi (CIMBS), New Delhi, India

Date of Submission21-May-2021
Date of Acceptance20-Sep-2021
Date of Web Publication30-Sep-2021

Correspondence Address:
Dr. Harpreet Kour
Department of Physiology, JN Medical College, KLE Academy of Higher Education and Research, Nehru Nagar, Belagavi - 590 010, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/kleuhsj.kleuhsj_131_21

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  Abstract 

The COVID-19 is compromising individuals' immunity to a larger extent, it becomes imperative to strengthen and support the immune system with the right nutrition. Immune functioning can be improved through the right nutrition. Hence, adequate nutrition becomes paramount in leveling up the immune functioning through higher and wider Immunoglobulin generation. This review article is attempted to highlight the importance of nutrition during compromised immunity as in the case of COVID-19.

Keywords: COVID-19, macronutrients, micronutrients, nutrition


How to cite this article:
Kour H, Shrivastava R. Nutrition insights in COVID-19. Indian J Health Sci Biomed Res 2021;14:297-301

How to cite this URL:
Kour H, Shrivastava R. Nutrition insights in COVID-19. Indian J Health Sci Biomed Res [serial online] 2021 [cited 2021 Dec 8];14:297-301. Available from: https://www.ijournalhs.org/text.asp?2021/14/3/297/327246


  Introduction Top


With the impending effects of COVID-19 infection in the first wave and then again, more severely, in the second wave, the biggest realization across the general and scientific community that has emerged is the importance of our body's innate immunity in facing and fighting such rapidly mutating the virus. In October 2020, the WHO warned of the unprecedented challenge of COVID-19 on disrupting socioeconomic conditions and its effect on people's health, nutritional status, and food systems.[1]

The COVID-19 or SAR-CoV2 is compromising individuals' immunity to a larger extent, it becomes imperative to strengthen and support the immune system with the right nutrition. The immune system is activated to produce and release antibodies (to replace-becomes more functional) with the invasion of any pathogen to prevent the damage. This process needs energy and essential cofactor yielding substrates including macro and micronutrients to work optimally through a variety of pathways in both innate and adaptive immune responses.[1]

The immune system works through several mechanisms of which the four key areas identified are:[2]

  1. Barrier to the invasion of the pathogen
  2. Identification of pathogen, if barrier crossed
  3. Elimination of pathogen
  4. Creating a memory, to fight infection in the future.


For all these mechanisms to occur at all levels of immune functioning, the presence of the right substrates becomes vital. These substrates are mostly peptide chains that require cofactors to get activated to initiate an adequate response.

It clearly implies that adequate nutrition becomes important to develop innate immunity. Identification of the relevance of nutrition in immune function has opened up a new avenue of nutritional Immunology and has recently gained a huge amount of interest.


  Nutrients and their Role in Immunity Top


Macronutrients

Carbohydrates

Alongside the main objective of providing energy, carbohydrate sources play another important role of sparing the proteins for their primary function in the body. Another important role of a type of carbohydrate that we call complex carbohydrates (or fiber) is to provide substrate to the gut microbiota, which has now been established as one of the key players in establishing immune function. Low glycemic index carbohydrate sources like whole grains of cereals like millets, Jowar, multigrain wheat bajra, or a mix of different grains is advisable owing to high fiber and improved micronutrient profile. The study by Monnier et al. has reported that consumption of refined and processed carbohydrates leads to increased inflammatory cytokines such as C-reactive protein, Interleukin 6, and tumor necrosis factor. Refined carbohydrates, coming from all-purpose flour, cornflour, or other refined flours should be restricted in COVID-19 patients, as they have been reported to increase mitochondrial overload, production of free radicals and also trigger inflammatory responses and elevate circulating blood sugar levels.[2],[3]

Proteins

Activation of immune response initiates the production of several amino acid-based active molecules such as immunoglobulins, chemokines, cytokines, cytokine receptors, adhesion molecules, and acute-phase proteins. 2 Hence, for the identification and for the elimination of SARS CoV-2 like pathogens, the presence of substantial amounts of amino acids becomes vital to produce the right, chemically active compounds that may be able to initiate and carry forward the suitable immune activity. High-quality dietary proteins that can provide substantial amounts of all the essential and non-essential amino acids in good amounts, therefore, become important. Almost all of the amino acids have been found to play potentially important roles in the immune system at various levels of innate and adaptive immunity. Key ones are arginine, glutamine, glycine, methionine, lysine, threonine, tyrosine, tryptophan. Histidine promotes vasodilation and likewise, Phenylalanine, lysine, and methionine are important substrates for NO metabolism.[4] Therefore, a moderately high intake of protein-rich food items is recommended to improve the immune functioning of the body.

Fats

Saturated fatty acts like toll-like receptor 4, a sensor that binds bacterial lipopolysaccharide to produce innate immune responses. As a result, a high intake of saturated fatty acids favors low-grade inflammation. The mono and polyunsaturated fatty acids act as antioxidant, antimicrobial, and antiviral agents by activating cells for both innate and adaptive immune responses and thus known as immunomodulators. Synthesis of prostaglandins and leukotrienes, immunoglobulins, chemokines, cytokines and its receptors, acute phase proteins, etc., – Fatty acids and Proteins. Both the total fat intake and the ratios between fatty acids of different classes influence the activity of immune cells. Essential fatty acids are required for the growth and maintenance of the immune cells, and free fatty acids are produced and secreted during the activation of these cells. So overall reduction in fat intake with an improved ratio of unsaturated and saturated fats is recommended to enhance immune functioning.[5],[6],[7],[8]

Having said that, since the physical barriers are the first line of defense, maintenance of their structural integrity becomes paramount. Phospholipids are an important part of the cellular structure, so optimum quantity of good quality fats in the diet is recommended.

Micronutrients

The studies have highlighted the importance of minerals and vitamins in the development of both innate and adaptive immune responses. Vitamins A, C, D, E, B6, and B12, Zinc helps to maintain structure and function of Physical barriers, differentiation, and proliferation of innate immune cells and it also acts as antioxidants. Vitamins C and E, along with zinc and selenium protect against free radical damage during increased oxidative stress. Vitamins A, C, D, E, B6, and B12 and zinc and selenium support the adaptive immune response by influencing the differentiation, proliferation, and normal function of T and B cells. These nutrients also affect antibody production and function, contribute to cell-mediated immunity, and support the recognition and destruction of pathogens. Lastly, they have antimicrobial activity and regulate the inflammatory response.[9],[10]

Vitamin A is needed for maturation of the immune cells of neutrophils, dendritic cells and CD4+ T-lymphocyte and have a role in the maintenance of gut barrier.[11] Studies have reported that supplementation of Vitamin A, C, D (1,25-dihydroxyvitamin D3) has decreased pneumonia morbidity and mortality, increased the clinical response rate, shortened clearance time of signs, and shortened length of hospital stay among the study population.[12],[13],[14] Vitamin D also induces antimicrobial peptide synthesis in epithelial cells and macrophages, promotes differentiation of monocytes to macrophages and increases phagocytosis, superoxide production and thus enhances host defense.[15],[16] Vitamin E also helps in lymphocyte proliferation, natural killer cell activity, specific antibody production following vaccination, and phagocytosis by neutrophils. A negative association was established between decreased plasma Vitamin E and increased risk of infections in healthy adults.[17] The group of Vitamin B complexes contributing in gut barrier functions, intestinal immunity, regulation of functions of thymus and spleen, functions of white blood cells, natural killer cells, and CD8+ cytotoxic T-lymphocytes would be important in antiviral defense.[18] Vitamin C is needed for the synthesis of collagen and thus maintains epithelial integrity, regulates natural killer cell activity, T-lymphocyte function, and antibody production. Vitamin C supplementation has also been shown to decrease the duration and severity of upper respiratory tract infections.[19],[20] B group vitamins are involved in intestinal immune regulation, thus contributing to gut barrier function. Vitamins B6 and B12 and folate all support the activity of natural killer cells and CD8+ cytotoxic T-lymphocytes, effects which would be important in antiviral defense.[2] Studies have reported a significant reduction in the risk of pneumonia with vitamin C supplementation in people who have low dietary intakes.[21],[22]

Vitamin C is required for collagen biosynthesis and is vital for maintaining epithelial integrity. It also has roles in several aspects of immunity, including leukocyte migration to sites of infection, phagocytosis and bacterial killing, natural killer cell activity, T-lymphocyte function (especially of CD8+ cytotoxic T-lymphocytes), and antibody production.[2]

The findings of the study by Mayo et al. reported that children with recurrent respiratory tract infections had lower hair levels of zinc, copper, and iron. The mineral acts as an adjunct therapy to decrease mortality from pneumonia.[23] A study by Read et al. has reported the role of zinc in antiviral immunity as host defense against RNA viruses. Zinc inhibits the RNA polymerase required by RNA viruses for replication, as same in the case of COVID-19 infection, suggesting that zinc may play a key role.[24],[25]

Alongside the antimicrobial effect that Copper shows, it also supports neutrophil, monocyte, and macrophage function and natural killer cell activity. It promotes T-lymphocyte responses such as proliferation and interleukin-2 (IL-2) production.[2] Lower Selenium concentrations in humans have also been linked with diminished natural killer cell activity and increased mycobacterial disease. Observations suggest that poor Selenium status could result in the emergence of more pathogenic strains of the virus, thereby increasing the risks and burdens associated with viral infection.[2] Therefore, the deficiencies of both macro and micronutrients alter immune responses and increased susceptibility to infections.

Gut Microbes

As we know that the human body is a host to organisms. The community of organisms in a particular location is referred to as the microbiota which shows a high degree of variability among individuals. It has been reported in a series of papers that microbiota is strongly influenced by habitual diet. A diseased condition and prolonged use of antibiotics can destroy microbiota which favors the growth of pathogenic organisms. The use of probiotic organisms which are readily found in fermented foods including conventionally cultured dairy products and some fermented milks are of immense help. These organisms can colonize the gut temporarily, making their regular consumption necessary. Lactobacilli or bifidobacterial probiotics have most often been used in various studies.[26],[27],[28],[29]


  Cytokine Storm and Nutritional Therapy Top


COVID-19 viruses cause respiratory system damage. A significant inflammatory reaction is evoked as response to an immunogenic reaction by the host's immune cells which leads to leakage from the small blood vessels and the fluid enters alveoli. This, in turn, hampers the diffusion and transport of oxygen and patients land with dropping oxygen saturation levels and needs ventilatory support. During the process, there is increased production of reactive oxygen species, inflammatory eicosanoids and inflammatory chemokines and cytokines such as tumor necrosis factor-alpha (TNF-α), IL-1β, and IL-6. This pro-oxidative and proinflammatory state is referred to as a cytokine storm. This condition is like Acute Respiratory Distress Syndrome. It also included suppression of acquired immune response, decrease in numbers of CD4+ and CD8+ T-lymphocytes, and CD4+ T lymphocytes. This is the reason elevated inflammatory markers have been reported with COVID-19. The report from randomized controlled trials has reported the use of Omega 3 fatty acids, eicosapentaenoic acid, and docosahexaenoic acid in combination with other bioactive nutrients like, antioxidant and γ-linolenic acid formulation decreases the duration of mechanical ventilation and intensive care unit length of stay by controlling cytokine storm.[30],[31],[32],[33],[34],[35]

Hydration

As per the guidelines given by Indian Dietetic Association, Hydration is very important in COVID-19 patients. It helps relieve symptoms of congestion, helps flushing toxins, and maintain mucous membrane of the nose and paper respiratory tract intact.

The review paper by Jodi et al. hypothesized that sub-optimal hydration in the weeks before exposure to COVID-19 increases the risk of COVID-19 mortality via multiple possible pathways that favor fluid accumulation in the lungs. Chronic hypertonicity, total body water deficit and/or hypovolemia cause multiple intracellular and/or physiologic adaptations that preferentially retain body water and favor positive total body water balance when challenged by infection. Via effects on serum/glucocorticoid-regulated kinase 1 signaling, aldosterone, TNF-α, vascular endothelial growth factor, aquaporin 5 (AQP5) and/or Na+/K+-ATPase, chronic sub-optimal hydration in the weeks before exposure to COVID-19 may conceivably result in: (a) greater abundance of angiotensin-converting enzyme 2 (ACE2) receptors in the lung. This further can increase the likelihood of COVID-19 infection as lung epithelial cells are pre-set for exaggerated immune response. (b) Increased capacity for capillary leakage of fluid into the airway space, and/or (c) Reduced capacity for both passive and active transport of fluid out of the airways.[36],[37]


  Recommendations Top


Immune functioning can be improved through the right nutrition. Hence, adequate nutrition becomes paramount in leveling up the immune functioning through higher and wider immunoglobulin generation. The battery of studies from 2018 to 2020 on COVID-19 and nutrition have encouraged the consumption of

  1. Small and frequent meals evenly distributed over the day
  2. Balanced meals with all the major macro and micronutrients, fiber, and probiotics
  3. Low GI foods with restricted simple sugars
  4. 5-6 servings of fresh fruits, vegetables per day
  5. Omega 3 fa sources regularly
  6. Good quality proteins evenly distributed over the day
  7. Enough fluids to maintain fluid and electrolyte balance
  8. Moderate amounts of spices and herbs, to render the beneficial effects of potentially active phytochemicals in supporting the immune system owing to their antimicrobial properties.


As a general recommendation, well-balanced meals with adequate portions of all the major food groups daily are advisable. Including whole grains, legumes, pulses, nuts and seeds, fruits, vegetables, eggs, chicken and fish, and low-fat dairy products along with probiotics and enough hydration should be adopted as a general practice to keep the immune functioning optimum, in health and illness. Adequate supplementation of Vitamin D, Vitamin A, Ca, Zn, and folic acid can be considered to fulfill the micronutrient requirements.

Disclaimer

Individuals with comorbidities should follow the advise of their Consulting doctors and dieticians for specific dietary modifications.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
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