Acta agriculturae Slovenica, 117/2, 1–7, Ljubljana 2021 doi:10.14720/aas.2021.117.2.1980 Review article / pregledni znanstveni članek Nutrition and Covid-19 epidemic Tanja PAJK ŽONTAR 1 , Rajko VIDRIH 1,* Received November 30, 2020; accepted March 19, 2021. Delo je prispelo 30. novembra 2020, sprejeto 19. marca 2021. Nutrition and Covid-19 epidemic Abstract: Proper nutrition is an essential part of an in- dividual’s defence against numerous diseases including coro- navirus disease SARS-CoV-2 (Covid-19). Nutritional status of individual is affected by several factors such as age, sex, health status, physical activity, life style and medications. Optimal nu- trition and dietary nutrient intake impact the immune system, therefore the sustainable way to survive in current context is to strengthen the immune system. Inadequate intake of energy, protein, and specific micronutrients are associated with de- pressed immune function and increased susceptibility to infec- tion. Predominantly vital for the encouraging of immune func- tion are elements selenium, iron and zinc and vitamins A, D, C, E, B 6 , B 9 (folate) and B 12 as well as omega-3 polyunsaturated fatty acids. Thus, during this time it is important to take care of nutritional habits, following a healthy and balanced nutritional pattern containing a high amount of elements, antioxidants and vitamins. It is also recommended, that individuals should be mindful of physical activity, known to be associated with all- cause mortality. Regular physical activity also improves men- tal health and overall feelings of wellbeing. Thus, now in the time of epidemic, more than ever, wider access to healthy foods should be a top priority for governments around the world Key words: nutrition; Covid-19; immune system; nutri- ents; vitamins; elements; antioxidants; omega-3 polyunsatu- rated fatty acids 1 University of Ljubljana, Biotechnical Faculty, Department of Food Science and Technology, Ljubljana, Slovenia * rajko.vidrih@bf.uni-lj.si Prehrana in epidemija Covid-19 Izvleček: Pravilna prehrana je pomemben del posamezni- kove obrambe pred številnimi boleznimi, vključno pred koro- navirusno boleznijo SARS-CoV-2 (Covid-19). Na prehranski status posameznika vpliva več dejavnikov, kot so starost, spol, zdravstveno stanje, telesna dejavnosti, življenjski slog in uživa- nje zdravil. Optimalna prehrana in z njo vnos hranil vplivata na imunski sistem, zato je trajnostni način preživetja v seda- njih okoliščinah krepitev imunskega sistema. Neustrezen vnos energije, beljakovin in določenih mikrohranil je povezan z osla- bljenim delovanjem imunskega sistema in povečano dovzetno- stjo za okužbe. Za spodbujanje imunske funkcije so pomembni predvem elementi selen, železo in cink ter vitamini A, D, C, E, B 6 , B 9 (folati) in B 12 ter večkrat nenasičene maščobne kisline omega-3. V obdobju epidemije je zato še toliko bolj pomembno skrbeti za zdravo in uravnoteženo prehrano, ki vsebuje dovolj elementov, antioksidantov in vitaminov.Priporočljivo je tudi, da se posamezniki zavedajo pomena redne telesne dejavnosti, za katero je znano, da zmanjšuje tveganje za smrtnost zaradi raz- ličnih vzrokov. Redna telesna dejavnost ima tudi ugoden vpliv na duševno zdravje in splošno počutje. Širši dostop do zdrave hrane bi v danih okoliščinah morala biti ena izmed prednostnih nalog vlad po vsem svetu. Ključne besede: prehrana; Covid-19; imunski sistem; hranila; vitamin; elementi; antioksidanti; večkrat nenasičene maščobne kisline omega-3 Acta agriculturae Slovenica, 117/2 – 2021 2 T. PAJK ŽONTAR, R. VIDRIH 1 INTRODUCTION At the time of this writing, the Covid-19 pandemic will have infected more than 125 million people and tak- en the lives of nearly 2,800,000 individuals world-wide. Data for Slovenia (2 million inhabitant) in the moment are not encouraging, nearly 210,000 infected since the beginning and 4,280 lives taken till 25 th of March, 2021. Proper nutrition, with the aim to maintain immune function is an essential part of an individual’s defence against Covid-19. Optimal nutrition and dietary nutri- ent intake impact the immune system through gene expression, cell activation, and signalling molecules modification. In addition, various dietary ingredients are determinants of gut microbial composition and subsequently shape the immune responses in the body (Aman & Masood, 2020). Adequate intake of energy, protein, and specific micronutrients are associated with depressed immune function and increased susceptibility to infection. Predominantly vital for the strengthening of immune function are elements selenium, iron and zinc and vitamins A, D, E, C, B 6 and B 12 and omega-3 polyun- saturated fatty acids (Naja & Hamadeh, 2020) Therefore, the key to maintaining an effective im- mune system is to avoid deficiencies of the energy and nutrients that play an essential role in immune cell trig- gering, interaction, differentiation, or functional expres- sion (Barazzoni et al., 2020). Covid-19 does not treat the whole population equal- ly, differences are due to genetics and lifestyle. World Health Organization exposed, that people who eat a well- balanced diet tend to be healthier with stronger immune system and lower risk of chronic noncommunicable diseases and infectious diseases (WHO, 2020a). Under- nourished people have weaker immune system, and may be at greater risk of severe illness due to the virus. At the same time, poor metabolic health, including obesity and diabetes, is strongly linked to worse Covid-19 outcomes, including risk of hospitalisation and death (Global ..., 2020). The high consumption rate of diets high in satu- rated fats, sugars, and refined carbohydrates (collectively called Western diet), and low levels of dietary fibre, un- saturated fats and antioxidants worldwide, contribute to the prevalence of obesity and type 2 diabetes, and could place these populations at an increased risk for severe Covid-19 pathology and mortality. Typical western diet consumption activates the innate immune system and impairs adaptive immunity, leading to chronic inflam- mation and impaired host defence against viruses (Butler et al., 2020) There is not enough scientific evidence whether people with diabetes are more likely to get Covid-19 than the general population. General opinion is that people with diabetes are more likely to have serious complica- tions from Covid-19. As seen from observations from Italy 30 % of deceased people due to Covid-19 had dia- betes (Antonio et al., 2020). Reports from Lombardy also suggest that anti diabetes medicines worsen the course of Covid-19 disease (Antonio et al., 2020). In a future virus pandemic, we might face a “double burden” of malnutrition, when both undernutrition and overnutrition will promote severity of disease (Barazzoni et al., 2020). This article explores the importance of nutrition to boost immunity and gives some professional and authen- tic dietary guidelines about nutrition and food safety to better withstand Covid-19. The food safety, food man- agement, access to food and many other important topics related to Covid-19 and nutrition are not the issue of this article. 2 NUTRITION AND COVID-19 Nutritional deficiencies of energy, protein, and specific micronutrients are associated with depressed immune function and increased susceptibility to infec- tion. A proper planned diet, comprised of well-balanced nutrients is crucial to health, supports normal B and T immune cell functions for optimal disease-reducing im- munity. In the case of Covid-19, the goal of nutrition is to reduce infection and disease progression while improv- ing recovery during the course of the disease (Jaggers et al., 2020). 2.1 FRUITS AND VEGETABLES Food and Agriculture Organization put down seven healthy eating tips to face the Covid-19 crisis, first of them is dedicated how to strengthen our immune system through a proper diet. Focus should be put in consump- tion of at least five servings a day of fruits and vegetables, because they contain a lot of micronutrients, which can boost immune function. Some of these micronutrients such as vitamin C, A, C, E and beta-carotene are antioxi- dants that increase the number of T-cell subsets, enhance lymphocyte response to mitogen, increase interleukin-2 production, potentiate natural killer cell activity, and in- crease response to influenza virus vaccine compared with placebo (FAO, 2020; Muscogiuri et al., 2020). 2.2 FATS AND OILS World Health Organization recommended to con- sume unsaturated fats, which are found in oils (sunflow- Acta agriculturae Slovenica, 117/2 – 2021 3 Nutrition and Covid-19 epidemic er, olive, soy, canola and corn), fish, avocado and nuts, rather than saturated fats from fatty meat, butter, coconut oil, cream, cheese, ghee and lard (WHO, 2020a). Excessive saturated fats consumption can induce a lipotoxic state and activate the innate immune system via activation of toll-like receptor 4 expressed on mac- rophages, dendritic cells, and neutrophils. This triggers activation of canonical inflammatory signalling path- ways that produce proinflammatory mediators and other effectors of the innate immune system (Rogero et al., 2020). Furthermore, consumption of a high fat diet in mice increased macrophage infiltration to lung tissue, specifically in the alveoli, which is especially relevant to Covid-19 patients given the high rate of infection among lung alveolar epithelial cells and the involvement of lung tissue inflammation and alveolar damage in Covid-19 pathology (Butler & Barrientos 2020). 2.2.1 Role of omega-3 fatty acids in immune system Omega-3 fatty acids are unsaturated long chain fatty acids known to decrease inflammation, which seems to be critical also for Covid-19 patients. Among them, ei- cosapentaenoic (EPA) and docosahexaenoic (DHA) are considered the most potential in inhibiting inflamma- tion, could ameliorate some patients need for intensive care unit admission and have stimulating effect on im- mune system (Shakoor et al., 2020). Omega-3 fatty acids might inhibit growth of influenza virus, they are sug- gested to increase the oxygenation in Covid-19 patients (Barazzoni et al., 2020). From that point of view, patient therapy must consider omega-3 fatty acids as a co-thera- py in Covid-19 (Rogero et al., 2020). Both, EPA and DHA are found in fish and fish oils. Cod liver oil is of special interest from nutritional point of view due to the high content of natural vitamin D 3 and vitamin A (retinol). 2.3 VITAMINS AND ELEMENTS There is currently no guidance on micronutri- ent supplementation for the prevention of Covid-19 in healthy individuals or for the treatment of Covid-19. Wherever possible, micronutrient intakes should come from a nutritionally balanced and diverse diet, includ- ing fruits, vegetables and animal source foods (WHO, 2020b). 2.3.1 Vitamin A and carotene Vitamin A has been defined as “anti-infective” vita- min since many of the body’s defences against infection depend on its adequate supply. Vitamin A deficiency is involved in measles and diarrhoea and measles can be- come severe in vitamin A-deficient children (Barazzoni et al., 2020; Solomons, 2012). In experimental models, the effect of infection with infectious bronchitis virus, a kind of coronaviruses, was more pronounced in chick- ens, fed with a diet marginally deficient in vitamin A than in those fed a diet adequate in vitamin A. It has also been reported that vitamin A supplementation in hu- mans reduced morbidity and mortality in different infec- tious diseases, such as measles, diarrheal disease, measles related pneumonia, malaria and HIV/AIDS infection (Barazzoni et al., 2020). The richest animal sources of vitamin A in the human diet are fish liver oils, liver, other organ meats, cream, butter, and fortified milks. Certain tropical fatty fruits are the richest sources of provitamin A (Solomons, 2012). Beta carotene (provitamin A) is most abundant in sweet potatoes, carrots and green leafy vegetables (Muscogiuri et al., 2020). 2.3.2 Role of vitamin C in immune system There is no evidence found that supplements can cure or »boost« the immune system except vitamin C, which is one of the best way to improve immune system. Vitamin C is one of the major constituents of water solu- ble vitamins which tends to contribute to a strong im- mune system (Aman et al., 2020). The daily recommend- ed dietary allowance for vitamin C is 110 mg/day for men and 95 mg/day for women (NIJZ, 2020). Vitamin C, water soluble antioxidant acts by scav- enging damaging reactive oxygen species, thus protect- ing the tissues from oxidative damage and dysfunction. It is known for long as a protective factor for infectious diseases acting as an antioxidant through inactivation of free radicals and thus protecting proteins, lipids and nu- cleotides against oxidative damage (Shakoor et al., 2020). It accumulates in leucocytes reaching 50-100 fold higher concentration as compared to its plasma content, but it is depleted fast in case of infection (Shakoor et al., 2020). Patients with asthma and pneumonia are known to have low vitamin C content in plasma (Hunt et al., 1994). Among others, vitamin C also reduces pro-inflammatory cytokines and increases anti-inflammatory cytokines; administration of 1 g of vitamin C per day increases the anti-inflammatory cytokines (Shakoor et al., 2020). Covid-19 patients are very susceptible to pneumonia, in- travenous administration of high vitamin improved in- flammatory respiration parameters (Hiedra et al., 2020). Sources of vitamins C include red peppers, oranges, strawberries, broccoli, mangoes, lemons, and other fruits and vegetables (Muscogiuri et al., 2020). 2.3.3 Role of vitamin D in immune system Vitamin D deficiency in winter has been reported to be associated to viral epidemics. Adequate vitamin Acta agriculturae Slovenica, 117/2 – 2021 4 T. PAJK ŽONTAR, R. VIDRIH D status reduces the risk of developing several chronic diseases such as cancers, cardiovascular disease, diabe- tes mellitus, and hypertension that significantly increase risk of death from respiratory tract infections than oth- erwise healthy individuals. Further, vitamin D protects respiratory tract preserving tight junctions, destroying enveloped viruses through induction of cathelicidin and defending, and decreasing production of proinflamma- tory cytokines by the innate immune system, therefore reducing the risk of a cytokine storm leading to pneumo- nia (Muscogiuri et al., 2020). Vitamin D seems to be tightly connected to the out- come of Covid-19 disease (Shakoor et al., 2020). Short- age of vitamin D is more pronounced in older people, at increased body weight, at men, hypertension, in higher geographic latitude and under conditions of higher coag- ulation (Shakoor et al., 2020). Older population is known to have chronic increased pro-inflammatory condition which render older people more susceptible to chronic diseases (Ferrucci et al., 2018). Vitamin D shortage pose a higher risk of community acquired pneumonia as has been reported in 8 studies including a total of 20966 pa- tients as cited by Zhou et al., (2019). Sufficient consump- tion of vitamin D inhibits the synthesis of pro-inflamma- tory cytokines and limit the respiration stress connected to fatal outcome due to Covid-19 (Shakoor et al., 2020). In the future, investigations will confirm whether insufficient vitamin D status more specifically character - izes Covid-19 patients and is associated to their outcome. In support to this hypothesis, decreased vitamin D levels in calves have been reported to enhance risk for bovine coronavirus infection (Barazzoni et al., 2020). Since the time spent outdoor and consequently to the sun exposure is limited, especially during winter, it is encouraged to get more vitamin D from diet. Foods con- taining vitamin D include fish, liver, egg yolk and foods with supplemented vitamin D and food supplements (Muscogiuri et al., 2020). 2.3.4 Role of zinc in immune system Essential trace element that is crucial for the main- tenance of immune function is zinc. It has been reported that zinc inhibited severe acute respiratory syndrome (SARS) coronavirus RNA-dependent RNA polymer- ase template binding and elongation in Vero-E6 cells. Although oysters contain the most zinc per serving, the most common food to get zinc include poultry, red meat, nuts, pumpkin seeds, sesame seeds, beans, and lentils (Muscogiuri et al., 2020). The primary, relatively rich, plant source of zinc are whole-grain cereals. Zinc is mostly contained in the bran and germ portions, thus, nearly 80 % of the total zinc in these foodstuffs can be lost in the wheat milling process (Holt et al., 2012). Zinc is a microelement involved in numerous bio- logical processes including the immune response to vi- rus infections (Shakoor et al., 2020). Shortage of zinc increases pro-inflammatory cytokines, permeability of epithelial cells in lungs (Shakoor et al., 2020). Increased intake of zinc results in higher number of T cells that in- hibit synthesis, replication and transcription of coronavi- rus (Te Velthuis et al., 2010). Due to the above mentioned facts, administration of zinc to Covid-19 patients resulted in an improved in- fection symptoms of lower respiration tract (Finzi 2020). 2.3.5 Role of Vitamin B 12 in immune system Serum vitamin B 12 also called as cobalamin is a cru- cial micronutrient in many aspects of healthy metabo- lism. It plays an important role in maintaining nerve tis- sue health, brain function and red blood cell synthesis (Naik et al., 2020). In Singapore cohort study, Tan et al. (2020) reported that a combination of vitamin D, magnesium and vita- min B 12 lessen the need for oxygen therapy and/or inten- sive care support. Humans obtain vitamin B 12 from products of ani- mal origin including meat, fish, shellfish, dairy products and eggs (Naik et al., 2020). 2.3.6 Role of vitamin E and selenium in immune system Vitamin E and selenium play an important role in antioxidative system, shortage of any of them might change immune response against viruses (Shakoor et al., 2020). The content of selenium in the diet is influ- enced by geographical location of production (Terry & Diamond, 2012). Chinese researchers have proved the correlation between the content of selenium in soil from Chinese provinces and the course of the Covid-19 dis- ease (Zhang et al., 2020). From that point of view the cure rate of Covid-19 patients inside Hubei Province, known as province with low soil selenium content, was signifi- cantly lower as compared to other provinces (Zhang et al., 2020). Selenium intake in humans originates princi- pally from the consumption of meat, eggs and fish, which contain high levels of selenium in relation to other foods, ranging from 180 to 800 ng/g. Most plants do not accu- mulate high levels of selenium, with some exceptions like the crops from Brassica genus, which includes broccoli and kale, garlic, mushrooms and brazil nuts, which con- tain the highest levels of bioavailable selenium (Terry & Diamond, 2012). Beside selenium alone, administration of selenium combined with vitamin E improved the immune re- sponse against respiratory infections (Wu et al., 2019). Rather than any of vitamin E isomers alone, the mix- ture of all four isomers proved to be more efficient than Acta agriculturae Slovenica, 117/2 – 2021 5 Nutrition and Covid-19 epidemic α-tocopherol alone due to the availability of more recep- tors (Liu et al., 2002). The major dietary sources of vitamin E are vegetable oils (soybean, sunflower, corn, wheat germ, and walnut), nuts, seeds, spinach, and broccoli (Muscogiuri et al., 2020). 2.3.7 Role of folate in immune system Folate play an important role in the synthesis, re- pair and methylation of DNA, cellular division and in the maturation of red blood cells. Inadequate supplementation of folic acid results in abnormally large red blood cells that do not work prop- erly. This results in an increased red cell distribution width (RDW), a blood parameter associated with folate deficiency anaemia, which can cause tiredness and other symptoms (Batool et al., 2013; Im et al. 2020). Studies investigating folate concentration in plasma are scares. A significantly lower serum folate has been re- ported in Israel for patients with severe Covid-19 infec- tion (Itelman et al., 2020). In their review authors Acosta-Elias et al., (2020) hypothesize that pregnant women are less likely to ac- quire Covid-19 infection while those infected have a higher chance of being asymptomatic (Acosta-Elias & Espinosa-Tanguma 2020). Wiltshire et al. (2020) recommend a supplementa- tion of folic acid at 5 mg as a therapeutic option for pul- monary hypertension and severe hypoxaemia as well as for patients affected by severe Covid-19 pneumonia. A number of plant and animal foods are rich sourc- es of folate, including spinach, kale, broccoli, avocado, citrus fruits, eggs, and beef liver. 2.4 HYDRATION World Health Organization and Food and Agricul- ture Organization recommended to drink at least two li- tres of water a day, as the best choice, to stay hydrated and support our immune system. Water transports nutrients and compounds in blood, regulates our body tempera- ture, gets rid of waste, and lubricates and cushions joints (WHO, 2020a; FAO, 2020). 3 RECENT FINDINGS REGARDING THE MOST COMMON NUTRITIONAL DEFFICIENCIES OF COVID-19 PATIENTS Im et al. (2020) investigated the contents of vitamin B 1 , B 6 , B 12 , vitamin D (25-hydroxyvitamin D), folate, se- lenium and zinc levels in 50 hospitalized patients with Covid-19. Covid-19 patients were deficient primarily in vitamin D (76.0 %) and selenium (42.0 %), while 6.0 % of patients showed deficiency in both vitamin B 6 and folate. Mechanically ventilated patients showed even higher deficiency in vitamin D (80.0 %) and 100 % deficiency in selenium (Im et al., 2020). Haematological parameter RDW is an indicator of red blood cells size, normal refer- ence range of RDW-CV (Red Cell Distribution Width) in human red blood cells is 11.6–14.8 %. RDW is con- sidered as biomarker indicative of cardiovascular disease (Borné et al., 2011). Higher RDW values are indication for inflammation and oxidative stress (Emans et al., 2011). Authors Batool et al., (2013) investigated the rela- tionship between RDW and anaemia. They found 88.0 % of older people with iron deficiency to have RDW higher than 14.8 %. On the other hand 44.0 % of patients with vitamin B 12 deficiency and 57 % with folate deficiency had RDW higher than 14.8 %. In their recent investiga- tion authors Foy et al. (2020) found elevated RDW(>14.5 %) associated with an increased mortality risk in patients of all ages in 4 hospitals in Boston, USA. They found mortality rate of 11 % for patients with normal RDW and 31 % of patients with an elevated RDW. The literature data regarding the control of RDW by healthy lifestyle are scarce. In their attempt to clarify the impact of life- style on RDW , Loprinzi et al., (2015) studied dietary data collection and accelerometer-determined physical activ- ity. They found physical activity inversely associated with RDW but not healthy eating. The limitation of this study is that nutritionally important components were not ana- lysed precisely but it was estimated using 2 recall surveys. However, there are sufficient indications that food rich in iron, vitamin B 12 and folate and probably other nutrients lower the RDW. Regarding physical activity, endurance sport seems to be beneficial in lowering RDW (Alis et al., 2015). Like for overall mortality, RDW seems to be a val- uable predictor of mortality also for Covid-19 patients. 4 CONCLUSION Individuals should be aware of healthy eating habits to reduce susceptibility to and long-term complications from Covid-19. Thus, now more than ever, wider access to healthy foods should be a top priority since people nu- tritional status strongly impact the outcome of Covid-19 patients. Recent nutritional status of Covid-19 patients shows a substantial deficiency in some nutritionally im- portant compounds. Eating a variety of nutritionally dense food is the recommended way to get nutrients we need. In some circumstances adding dietary supplements are recom- mended for specific groups like babies, pregnant women, Acta agriculturae Slovenica, 117/2 – 2021 6 T. PAJK ŽONTAR, R. VIDRIH elderly and the people with weak immune system on one side as well as for people diagnosed with specific diseases. Dietary supplements are also recommended for people with inadequate nutrition or when nutrition is not the adequate source of specific nutrients. Before taking di- etary supplements it is recommended to talk with the doctor or pharmacist. It seems that Mediterranean diet pattern could rep- resent a healthy nutritional pattern to be followed under Covid-19 circumstances. Key ingredients of Mediter- ranean cuisine include fresh fruits and vegetables, fish, protein-rich legumes, olive oil and whole grains with moderate amounts of wine and red meat. 5 REFERENCES Acosta-Elias, J., & Espinosa-Tanguma, R. (2020). The folate concentration and/or folic acid metabolites in plasma as factor for COVID-19 infection. Frontiers in pharmacology, 11, 1062. https://doi.org/10.3389/fphar.2020.01062 Alis, R., Romagnoli, M., Primo-Carrau, C., Pareja-Galeano, H., Blesa, J. R. & Sanchis-Gomar, F . (2015). Effect of exhaustive running exercise on red blood cell distribution width. Clin- ical Chemistry and Laboratory Medicine (CCLM), 53(2), e29-e31. https://doi.org/10.1515/cclm-2014-0749 Aman, F., & Masood, S. (2020). How Nutrition can help to fight against COVID-19 Pandemic. Pakistan Journal of Medical Sciences, 36(COVID19-S4), S121-S123. https://doi. org/10.12669/pjms.36.COVID19-S4.2776 Antonio, S. G., Matteo, M., Achille, C., Enrica, V., Valentina, G., Salvatore, S., … Edoardo, M. (2020). Are diabetes and its medications risk factors for the development of COV- ID-19? Data from a population-based study in Sicily. Nutri- tion, Metabolism and Cardiovascular Diseases, 31(2), 396- 398. https://doi.org/10.1016/j.numecd.2020.09.028 Barazzoni, R., Bischoff, S. C., Breda, J., Wickramasinghe, K., Kr- znaric, Z., Nitzan, D., … Singer, P . (2020). ESPEN expert statements and practical guidance for nutritional manage- ment of individuals with SARS-CoV-2 infection, Clini- cal Nutrition, 39(6), 1631-1638. https://doi.org/10.1016/j. clnu.2020.03.022 Batool, S., Wang, Q., Qureshi, S. & Chua, E. (2013). The red cell diameter width distribution, the forgotten haemato- logical parameter for anaemia in the older person. Euro- pean Geriatric Medicine, 4, 1-4. https://doi.org/10.1016/j. eurger.2012.02.001 Borné, Y., Smith, J. G., Melander, O., Hedblad, B. & Engström, G. (2011). Red cell distribution width and risk for first hos- pitalization due to heart failure: a population‐based cohort study. European Journal of Heart Failure, 13(12), 1355- 1361. https://doi.org/10.1093/eurjhf/hfr127 Butler, M. J., & Barrientos, R. M. (2020). The impact of nutri- tion on COVID-19 susceptibility and long-term conse- quences. Brain, Behavior, and Immunity, 87, 53-54. https:// doi.org/10.1016/j.bbi.2020.04.040 Emans, M. E., van der Putten, K., van Rooijen, K. L., Kraaijen- hagen, R. J., Swinkels, D., van Solinge, W. W., … Gaillard, C. A. (2011). Determinants of red cell distribution width (RDW) in cardiorenal patients: RDW is not related to erythropoietin resistance. Journal of Cardiac Failure, 17(8), 626-633. https://doi.org/10.1016/j.cardfail.2011.04.009 FAO. (2020). 7 healthy eating tip to face the COVID 19 crisis. Retrived from http://www.fao.org/americas/noticias/ver/ en/c/1267852/ Ferrucci, L., & Fabbri, E. (2018). Inflammageing: chronic in- flammation in ageing, cardiovascular disease, and frailty. Nature reviews. Cardiology, 15(9), 505-522. https://doi. org/10.1038/s41569-018-0064-2 Finzi, E. (2020). Treatment of SARS-CoV-2 with high dose oral zinc salts: A report on four patients. International Journal of Infectious Diseases, 99, 307-309. https://doi.org/10.1016/j. ijid.2020.06.006 Foy, B. H., Carlson, J. C., Reinertsen, E., Valls, R. P. I., Lopez, R. P., Palanques-Tost, E., … Higgins, J. M. (2020). Asso- ciation of red blood cell distribution with mortality risk in hospitalized adults with SARS-CoV-2 infection. JAMA Net- work Open, 3(9), e2022058-e2022058. https://doi:10.1001/ jamanetworkopen.2020.22058 Global Nutrition Report. (2020). 2020 Global Nutrition Re- port. Retrived from https://globalnutritionreport.org/ reports/2020-global-nutrition-report/ Hiedra, R., Lo, K. B., Elbashabsheh, M., Gul, F., Wright, R. M., Albano, J., …Aponte, G. P . (2020). The use of IV vitamin C for patients with COVID-19: a single center observation- al study. Expert Review of Anti-Infective Therapy, 18(12), 1259–1261. https://doi.org/10.1080/14787210.2020.17948 19 Holt, R. R., & Uriu-Adams J. Y ., & Keen C. L. (2012). Zinc. In J. W . Erdman & I. A. Macdonald & S. H. Zeisel (Eds.), Present knowledge in Nutrition (pp. 521 – 539). Hong Kong, A John Wiley & Sons, Ltd., Publication. Hunt, C., Chakravorty, N., Annan, G., Habibzadeh, N. & Scho- rah, C. (1994). The clinical effects of vitamin C supplemen- tation in elderly hospitalised patients with acute respiratory infections. International Journal for Vitamin and Nutrition Research, 64(3), 212-219. Im, J. H., Je, Y. S., Baek, J., Chung, M.-H., Kwon, H. Y. & Lee, J.-S. (2020). Nutritional status of patients with COVID-19. International Journal of Infectious Diseases, 100, 390-393. https://doi.org/10.1016/j.ijid.2020.08.018 Itelman, E., Wasserstrum, Y., Segev, A., Avaky, C., Negru, L., Cohen, D., … Lasman, N. (2020). Clinical characterization of 162 COVID-19 patients in Israel: preliminary report from a large tertiary center. The Israel Medical Association Journal: IMAJ, 22(5), 271-274. Jaggers, G. K., Watkins, B. A. & Rodriguez, R. L. (2020). COV- ID-19: repositioning nutrition research for the next pan- demic. Nutrition Research (New York, NY), 81, 1-6. https:// doi: 10.1016/j.nutres.2020.07.005 Liu, M., Wallin, R., Wallmon, A. & Saldeen, T. (2002). Mixed tocopherols have a stronger inhibitory effect on lipid perox- idation than α-tocopherol alone. Journal of Cardiovascular Pharmacology, 39(5), 714-721. Loprinzi, P. D., & Hall, M. E. (2015). Physical activity and di- etary behavior with red blood cell distribution width. Phys- Acta agriculturae Slovenica, 117/2 – 2021 7 Nutrition and Covid-19 epidemic iology & Behavior, 149, 35-38. https://doi.org/10.1016/j. physbeh.2015.05.018 Muscogiuri, G., Barrea, L., Savastano, S. & Colao, A. (2020). Nutritional recommendations for CoVID-19 quarantine. European Journal of Clinical Nutrition, 74, 850-851. https:// doi.org/10.1038/s41430-020-0635-2 Naik, S. R., Gupta, P., Khaitan, T. & Shukla, A. K. (2020). Re- duced levels of serum vitamin B12 in symptomatic cases of oral lichen planus: A cross-sectional study. Journal of Oral Biology and Craniofacial Research, 10(4), 578-582. https:// doi.org/10.1016/j.jobcr.2020.07.010 NIJZ. (2020). Referenčne vrednosti za energijski vnos ter vnos hranil. Retrived from https://www.nijz.si/sites/www.nijz.si/ files/uploaded/referencne_vrednosti_2020_3_2.pdf Rogero, M. M., Leão, M. d. C., Santana, T. M., de MB Pimentel, M. V ., Carlini, G. C., da Silveira, T . F ., … Castro, I. A. (2020). Potential benefits and risks of omega-3 fatty acids supple- mentation to patients with COVID-19. Free Radical Biol- ogy and Medicine, 156, 190-199. https://doi.org/10.1016/j. freeradbiomed.2020.07.005 Shakoor, H., Feehan, J., Al Dhaheri, A. S., Ali, H. I., Platat, C., Ismail, L. C., … Stojanovska, L. (2020). Immune-boosting role of vitamins D, C, E, zinc, selenium and omega-3 fatty acids: Could they help against COVID-19? Maturitas, 143, 1-9. https://doi.org/10.1016/j.maturitas.2020.08.003 Solomons, N. W. (2012). Vitamin A. In J. W. Erdman & I. A. Macdonald & S. H. Zeisel (Eds.), Present knowledge in Nu- trition (pp. 149 – 184). Hong Kong, A John Wiley & Sons, Ltd., Publication. Tan, C. W., Ho, L. P., Kalimuddin, S., Cherng, B. P. Z., Teh, Y. E., Thien, S. Y., … Nagarajan, C. (2020). A cohort study to evaluate the effect of combination Vitamin D, Magnesium and Vitamin B12 (DMB) on progression to severe outcome in older COVID-19 patients. Nutrition, 79-80, 111017. htt- ps://doi.org/10.1016/j.nut.2020.111017 Terry, E. N., & Diamond A. M. (2012). Selenium. In J. W . Erd- man & I. A. Macdonald & S. H. Zeisel (Eds.), Present knowl- edge in Nutrition (pp. 521 – 539). Hong Kong, A John Wiley & Sons, Ltd., Publication. Te Velthuis, A. J., van den Worm, S. H., Sims, A. C., Baric, R. S., Snijder, E. J. & van Hemert, M. J. (2010). Zn 2+ inhibits coro- navirus and arterivirus RNA polymerase activity in vitro and zinc ionophores block the replication of these viruses in cell culture. PLOS pathogens, 6(11), e1001176. https:// doi.org/10.1371/journal.ppat.1001176 Wiltshire, E., Peña, A. S., MacKenzie, K., Shaw, G. & Couper, J. (2020). High dose folic acid is a potential treatment for pulmonary hypertension, including when associated with COVID-19 pneumonia. Medical Hypotheses, 143, 110142. https://doi.org/10.1016/j.mehy.2020.110142 WHO. (2020a). Nutrition advice for adults during the COV- ID-19 outbreak. Retrived from: http://www.emro.who.int/ nutrition/nutrition-infocus/nutrition-advice-for-adults- during-the-covid-19-outbreak.html WHO. (2020b). Coronavirus disease (COVID-19): Food safety and nutrition. Retrived from https://www.who.int/news- room/q-a-detail/coronavirus-disease-covid-19-food-safe- ty-and-nutrition Wu, D., & Meydani, S. N. (2019). Vitamin E, Immune Function, and Protection Against Infection. Vitamin E in Human Health, In: Weber P ., Birringer M., Blumberg J., Eggersdor- fer M., Frank J. (Eds) Vitamin E in Human Health. Nutri- tion and Health. Humana Press pp. 371-384. Humana Press, Cham. https://doi.org/10.1007/978-3-030-05315-4_26 Zhang, J., Taylor, E. W ., Bennett, K., Saad, R. & Rayman, M. P . (2020). Association between regional selenium status and reported outcome of COVID-19 cases in China. The Ameri - can Journal of Clinical Nutrition, 111(6), 1297-1299. https:// doi.org/10.1093/ajcn/nqaa095 Zhou, Y.-F., Luo, B.-A. & Qin, L.-L. (2019). The associa- tion between vitamin D deficiency and community- acquired pneumonia: A meta-analysis of observational studies. Medicine, 98(38), e17252. https://doi: 10.1097/ MD.0000000000017252