Comment on"The association between dairy products and the risk of COVID-19"

Cagri Baris Gunec

1Sun Yat-sen University,Zhongshan School of Medicine,Guangzhou 510080,China.

Dubbed SARS for its severity,the Acute Respiratory Syndrome Named after the 2019 new coronavirus (COVID-19),coronavirus 2 (SARS-CoV-2) is a fast-spreading viral illness that emerged in late 2019 in Wuhan City,Hubei Province,China [1].There are 207 million persons infected with coronavirus globally as of August 16,2021,with 4.36 million dying as a result.A total of 97,828 Iranians have perished due to the coronavirus outbreak.The health community noted the rapid development of the coronavirus disease 2019 (COVID-19) outbreak and its high fatality,as cited in Darand et al.[2].Consuming dairy products as part of a balanced diet has improved immunity and reduced the risk of contracting infectious diseases.The relationships between dairy product intake and COVID-19 incidence are thoroughly explored in research published in the "European journal of clinical nutrition" by Darand et al.[2].

Darand et al.[2] conducted a thorough multivariate analysis to investigate the links between milk and its product consumption and the occurrence of COVID-19 in a large sample of the adult population.To the authors' knowledge,this is the first research to examine the possible link between dairy and COVID-19.Larger consumption of low-fat dairy products was shown to have a protective function against COVID-19,and a moderate intake of total dairy was found to lessen the risk of contracting COVID-19.On the other hand,increased consumption of whole milk,high-fat milk,and yogurt with added sugar,cheese,and butter was associated with a greater risk of contracting COVID-19.The results showed no statistically significant connection between consuming other types of dairies and COVID-19[2].According to a gender-based examination of butter consumption,women who eat more of it are more likely to get COVID-19 than men.

These diseases may be influenced by dietary and nutritional factors and food security as a modifiable factor [3-5].It is well known that consuming dairy products as part of a balanced diet may boost immunity and protect against illnesses,particularly viruses [6].Proteins in milk,namely caseins and whey proteins,have been shown to mitigate inflammation and oxidative stress [2].Another fatty acid found in dairy products called conjugated linoleic acid (CLA) had been shown to decrease inflammatory markers [7].According to the study,dairy products have been speculated to lower the chance of contracting COVID-19 [8] because of their anti-inflammatory,antioxidant,and immune-boosting properties.

Dairy intake and the risk of COVID-19 have only been studied seldom [8].Single research cited in Darand et al.[2] found that consuming bread and yogurt decreased the risk of contracting COVID-19.Yogurt,which contains probiotics and bioactive peptides,has been shown to reduce COVID-19 symptoms,according to a narrative review by Gouda et al.[9].In contrast,another research found that drinking more milk was linked to a greater COVID-19 infection rate [4].Milk and its derivatives,which include some traditional Eastern products,can be effectively applied in the community to reduce COVID-19.However,the health effects of these products depend on several complex specifications,such as the presence of probiotics in yogurt,kashk,and dough,and the fermentation of cheese,among others.That is why Darand et al.[2] set out to see whether there was a connection between dairy intake and the occurrence of COVID-19 in the current investigation.

The link between dairy and the risk of COVID-19 has only been investigated in a few of research [4].Animal protein,particularly milk,was shown to have a protective effect on recovery from COVID-19,according to an analysis of the impact of meals and nutrients on the recovery process conducted by Cobre et al.[8].Inconsistently,nations with higher infection rates between 1500 and above also had greater total milk intake [4].This was found in research examining the relationship between dietary variables and the risk of infection and death from COVID-19 across 158 countries.The publication by Darand et al.[2] looked at the link between high-and low-fat dairy products and the spread of COVID-19 in further depth.Consuming modest amounts of dairy may lower one's risk of contracting COVID-19.Those who drank more low-fat dairy products and milk were less likely to get COVID-19.

In addition,there was a correlation between greater yogurt intake and an increased risk of COVID-19.In contrast,higher consumption of low-fat dairy products was associated with a reduced chance of contracting the virus [2].In contrast,different Iranian research found that low-fat,medium-fat,and high-fat dairy did not affect the prevalence of COVID-19.Still,intake of yogurt and doogh (yogurt drink) dramatically decreased the incidence of COVID-19.However,this research mostly credited probiotics for yogurt's health benefits [10].Furthermore,the research results are at odds with a narrative review study [9] that theorizes the advantages of probiotics and peptides generated from yogurt for patients with COVID-19.Variations in the frequency and severity of COVID-19 symptoms in various regions of the globe,variances in the kind of dairy products tested (milk,yogurt,or low-fat vs.high-fat),and differences in the quantity of dairy intake are all plausible but unprovable explanations.

According to Darand et al.[2],the gap may also be attributed to the study's adjusted confounding variables being different from those used in earlier research.According to a gender-based examination of butter intake and COVID-19 risk,men and women generally vary in these areas.The risk of contracting COVID-19 was higher for women who consumed much butter than for males.Possible explanations include variations in study length,butter consumption,and physiological factors across sexes,such as changes in the immune system and gut microbiota [11].As cited in Darand et al.[2],sex hormones,nutrition,medications,body mass index,and colonic transit time are all factors that influence sex-based variations in the gut microbiota.

The origin of the link between dairy consumption and COVID-19 is a topic of speculation.Dairy products and milk provide several health benefits,including being high in protein,zinc,selenium,and vitamins A,D,and B12 [12,13].T lymphocytes,macrophages,and other immune cells rely heavily on the antioxidant enzymes glutathione peroxidase and thyroxine reductase,composed of dietary selenium.There is essentially little evidence that selenium helps with DNA viruses [14].Many enzymes and immune cell growth rely on zinc as a necessary cofactor.An adequate zinc intake from dietary sources aids immune cell maintenance and lowers susceptibility to many illnesses,including pneumonia [15].Vitamin A is a key regulator of monocyte and T cell development and function.The vitamin D levels of the host may influence the immunological response.

Supplemental vitamin D3 has been,according to Darand et al.[2],shown to promote recovery from respiratory infections such as COVID-19,influenza,recurrent pneumonia,and TB.Furthermore,casein and whey protein,as well as peptides generated from them,exhibit antioxidant,anti-viral,anti-inflammatory,and immune-regulatory effects in lung cells [6].Conjugated linoleic acid is only one example of a fatty acid found in milk that has been hypothesized to have antiinflammatory effects in the stomach and,by extension,boosts immune function [16].However,many Iranians consume traditional yogurt,which is strong in fat and saturated fatty acids.The consumption of high-fat dairy products has been linked to an increase in the number of pathogenic bacteria in the digestive tract and the generation of inflammatory endotoxin molecules [17].It is suggested that each individual have 2-3 servings of low-fat dairy products per day,even though in the current investigation,ingesting more low-dairy products showed a protective impact in reducing COVID-19.

There are several advantages to the study by Darand et al.[2].First,the authors make sure no other factors are influencing the correlation.Second,the study's power was bolstered by including a large sample size across many age groups.Finally,the study separately analyzed the correlation between low-and high-fat milk,yogurt,cheese,and yogurt drinks and COVID-19.A professional reviewer also created the questionnaire for the research.The currently available research by Darand et al.[2] is not without its limitations,which must also be considered.Despite the author's best efforts,there are still certain remaining elements that cannot be ruled out as the cause of the problem.Examining a person's eating habits will always be susceptible to measurement bias.The outcomes of the research indicated,in a nutshell,that a diet abundant in low-fat dairy products,and low-fat milk,in particular,served as a protective factor against COVID-19.On the other hand,consuming a diet heavy in dairy products with a highfat content was connected to an increased chance of developing COVID-19.Despite the optimistic results of our research,further research is necessary to confirm these hypotheses before we can offer any sound suggestions about food.