Diet and immunity have an age-old link, as the deficiencies in the natural diet may impact the immune system to a greater extent. An adequate intake of essential minerals like selenium, iron, and zinc and the vitamins A, C, D, E, B6, and B12 are crucial to maintain a healthy immune function [1]. Commercial dietary products containing a mixture of some of the above-mentioned; nutrients may suffice the specific requirements in definitive groups of populations. In India, an inclination towards commercial dietary products was the recent trend. The comprehensive impact on the Indian population with consumption of commercial dietary products in addition to natural dietary products; during the COrona Virus Disease (COVID) pandemic was assessed. The presence of adulterants and contaminants of both biological and chemical nature in supplements was challenging and notable. [2]. Immunity was not a precise or reliable indicator of nutritional status yet functionally dependent. [3]. Immunity can be physiologically maintained with a natural diet rich in nutrients. [4]. During the COVID pandemic need for improvement in knowledge regarding diet plays a substantial role. The natural dietary patterns followed by the public and additional dietary products consumed may influence the scenario a lot. The need for commercial dietary products in specified groups of the population was predictable.

There were three main groups of constituents in foods viz., carbohydrates, proteins, fats, and their derivatives. Water along with varied organic & inorganic substances like enzymes, minerals, anti-oxidants from other constituents. [5]. The basal metabolic rate describes the obligatory energy expenditure required to maintain metabolic functions in tissues and hence to sustain life. It is most closely predicted by lean body mass (i.e., total body mass - fat mass). [6]. The need for dietary nutrients to run the tissue metabolism smoothly for maintenance of immunological functions and the multitude of obesity affecting the immunological function was notable.

Vitamins were organic substances that were not synthesized in the body. They are broadly divided into fat-soluble A, D, E, K vitamins and water-soluble vitamins lie B-complex and Vitamin C. [7]. Malnutrition is associated with defective immune function. Assessment of immunity is not a practical method in routine clinical practice. [8].

Available literature was reviewed on nutritional elements to be consumed in view of COVID 19 infection, natural dietary products rich in those particular nutritional elements, the nutritive value of commercial dietary products, and their cost. The collected data were summarized as tables and graphs to study and to compare the nutritive value of natural dietary products with commercial dietary products.

Inclusion criteria: All the subjects in the age group between 10 to 80 years old, who were willing to participate were included in the study. Six commercial dietary products which were specified by subjects & available in the Indian market were studied. Their names were kept confidential and they have numbered accordingly from one to six. Six natural dietary products from different sections namely meat products, egg&milk products, fruits, vegetables, leafy vegetables, and freshwater&marine products available in the Indian market were selected randomly and studied.

Exclusion Criteria: All the subjects who were not willing to participate in the study were excluded.

* Cal - calcium, CDP - Commercial Dietary Product, Gm - Gram, Mcg - Microgram, Mg - Milligram, Prot - Proteins, Vit - Vitamin, Se – Selenium.

Table 1 depicts animal meat products as were the richest source of Vitamin A, Vitamin B12, and Folic

Acid. Folic acid is adequately available in eggs and milk products next to animal meat products. Egg and milk products were rich in calcium & vitamin D while aquatic products were a good source of Vitamin E.

*Cal - calcium, Gm - Gram, Mcg - Microgram, Mg - Milligram, Prot - Proteins, Se – Selenium, Vit - Vitamin, Zn - Zinc.

Table 2 depicts leafy vegetables as were a rich source of Vit A, calcium, and selenium while

* CDP - Commercial Dietary Products.

In our study nutritive patterns of 3699 subjects were analyzed, which resulted in age, gender, and population-specific consumption of commonly available commercial dietary products while vegetables and egg, milk products were commonly consumed natural dietary products. During the COVID pandemic, the trend expected was a shift

from consumption of meat products to fruits and egg, milk products.

Table 4: chart representing the gender wise consumption of dietary products with in our population.

*Chi-Square value :47.4152 ; p- value <0.00001; significant at p <0.05

Chi-Square value with Yates correction: 46.7911; p- value <0.00001; significant at p <0.05

Table 4 shows that there was a significant association between gender and consumption of commercial dietary products along with natural dietary products. This can be possibly explained by gender-specific needs like pregnancy, lactation, and postmenopausal state. The nutritive needs vary in these states while the impending risk of Coronary Artery Disease after menopause possibly might urge the consumption of commercial dietary products. 15.865% of the population were consuming commercial dietary products in addition to natural dietary products. The composition of proteins in the dietary product has to be considered along with the availability and composition of essential amino acids. Age and gender-appropriate proteins have to be consumed through a judicious mixture of varied natural dietary products.

Figure 1: Bar chart representing protein and other nutritive elements available in Commercial Dietary Products from one to six.

Figure 2: Bar chart representing protein and other nutritive elements available in natural meat products

Natural meat products serve the purpose of provision of nutrient-rich diet to be consumed during the COVID pandemic.

Fruits were rich in Vitamin C and Vitamin K. Egg and milk products were rich in calcium & vitamin D while aquatic products were a good source of Vitamin E. This suggests that balanced consumption of animal meat products, aquatic products, fruits in addition to egg& milk products may cater to the need for maintenance of immune system healthier to fight the COVID pandemic in the economy. The other way of dietary nutritional enrichment was optimal consumption of specified fruits that were rich in Vitamins A, C, D, K, folic acid, magnesium in addition to grains that were good sources of selenium, proteins, calcium, vitamin D. Specified vegetables, leafy vegetables have to be consumed as a source of Iron and eggs for vitamin E.

Commercial dietary products may provide multiple micronutrients in varied quantities to cater to specified populations. For example, CDP 5 was rich in calcium, iron, and vitamin A while CDP 4 was rich in Folic acid and selenium. The vividity of available natural dietary products for consumption may cater to the need for personalized palatability of the person at a lower cost. The reasons for not opting for such a diet were lack of nutritional knowledge at the population level and influence of media through advertising commercial products.

An adequate intake of zinc, iron, and vitamins A, B 12, B6, C, and E is essential for the maintenance of immune function, as they impact the immune system through gene expression, cell activation, and signaling molecules modification. In addition, various dietary ingredients are determinants of gut microbial composition and subsequently shape the immune responses in the body. [11]. Both the immune impairments and the susceptibility to infection can be reversed by correcting the deficiency showing a causal relationship between the availability of specific nutrients and immune defenses.

This is recognized by the European Food Safety Authority which permits claims of 'maintenance of functions of the immune system' for vitamins A, B6, B12, C, D, and folate (vitamin B9) and for the trace elements zinc, iron, selenium, and copper. [12]. Zinc deficiency may affect both humoral and cell-mediated immunity. Zinc deficiency may result in decreased Natural Killer cells activity, T Lymphocyte proliferation, InterLeukin 2 (IL2) production, which can be corrected with supplementation. [13]. Hence, daily intake of Zinc at low doses <25mg/day on a long-term basis was recommended. [14].

Vitamin D Stimulates Thelper2 (Th2) cells and attenuates Th1 cells which evolve to reduce pro-inflammatory cytokines like Tumor Necrosis Factor α (TNFα) and Interferon γ (IFNγ) thereby decreasing the risk of ARDS. [12] With regards to COVID, vitamin D prevents a Tumor Growth Factor β1 (TGF-β1)-induced profibrotic phenotype of lung cells. [14]. Vitamin E supplementation reduces the production of superoxides thereby maintaining the balance between oxidants and antioxidants. Failure of biological membranes due to excessive lipid peroxidation may result in diffuse alveolar damage and ARDS. [16]. Vitamin K is an essential "switch" in balancing the coagulation and anti-coagulation process. The anticoagulant role of Vitamin K can be recognized through the activation of protein C, S and Z. Vitamin K-dependent protein C activation can inhibit clotting factors V and VIII which were responsible for clot generation. K2 acts as an immunosuppressive compound to modulate the expression of a multitude of pro-inflammatory cytokines such as TNF, InterLeukin-1α (IL-1α), IL-1β and suppresses IL-6 release which was implicated in the pathogenesis of COVID.

Thus, vitamin K administration may reduce the risk for ARDS development in COVID-19 patients. [17]. As stated by Heiman and Greenway, “The more diverse the diet, the more diverse the microbiome and the more adaptable it will be to perturbations.” This suggests the dietary intake of varieties of plant-based foods to modify the gut microflora, in turn, affects immunity.[15]. When fecal samples of COVID patients were collected and compared to that of healthy individuals, opportunistic pathogens and depleted commensals were observed in COVID patient samples while healthy subjects maintained a higher prevalence of Eubacterium, Roseburia, Lachnospiraceae Eubacterium, Faecalibacterium prausnitzii, Roseburia, and Lachnospiraceae. [18]. Indeed, the consumption of foods that are a source of fiber has been related to lower levels of inflammatory cytokines (CRP, TNF-α, and IL-6), as well as enhanced levels of short-chain fatty acids (SCFAs).SCFAs (acetate, propionate, and butyrate) exert their anti-inflammatory effect by inhibiting the release of pro-inflammatory molecules and by decreasing the expression of nuclear factor-kB (NF-kB). [18].

Limitations: The complete composition of proteins present in commercial dietary products in comparison to natural dietary products was not studied in detail.