ABSTRACT
Dietary quality and patterns may influence SARS-CoV-2 infection and outcomes, but scientific data and evidence to support such a role are lacking. Therefore, this meta-analysis aims to elucidate the effect of prepandemic diet quality on the risk of COVID-19 infection and hospitalization. PubMed/MEDLINE, CENTRAL, Scopus, and EMBASE were systematically searched for articles published up to September 1, 2022. A systematic review and meta-analysis were performed to calculate each outcome's risk ratio (RR) and 95% confidence interval (CI). Five studies including 4 023 663 individuals (3 149 784 high-quality diet individuals and 873 881 controls) were included in the present meta-analysis. The effectiveness of high-quality dietary pattern against SARS-CoV-2 infection and hospitalization was 28% (95% CI 19%-36%) and 62% (95% CI 25%-80%); respectively. Subgroup analysis based on different levels of diet quality showed no difference between middle and high levels of diet quality in reducing the risk of COVID-19 infection. Interestingly, subgroup analysis based on the different types of high-quality diets and the risk of COVID-19 infection revealed that the effectiveness of plant-based diet against SARS-CoV-2 infection was 50% (95% CI 30%-65%); while the effectiveness of Mediterranean diet against SARS-CoV-2 infection was 22% (95% CI 12%-31%). Adherence to a high-quality dietary pattern is associated with a lower risk of COVID-19 infection and hospitalization. More studies are required to confirm these findings, and future studies should determine the biological mechanisms underlying the association between diet quality and risk of COVID-19 infection.
ABSTRACT
The emergence of the COVID-19 virus and the subsequent pandemic have driven a great deal of research activity. The effects of COVID-19 are caused by the severe respiratory syndrome coronavirus 2 (SARS-CoV-2) and it is the underlying actions of SARs-CoV-2 virions on the endothelial glycocalyx that we consider here. One of the key factors in COVID-19 infection is its almost unique age-related profile, with a doubling in mortality every 10 years after the age of 50. The endothelial glycocalyx layer is essential in maintaining normal fluid homeostasis, but is fragile and prone to pathophysiological damage. It is physiologically significant in capillary microcirculation and in fluid distribution to the tissues. Human serum albumin (HSA), the most abundant protein in plasma, is created in the liver which also maintains its concentration, but this reduces by 10-15% after 50 years of age. HSA transports hormones, free fatty acids and maintains oncotic pressure, but SARS-CoV-2 virions bind competitively to HSA diminishing its normal transport function. Furthermore, hypoalbuminemia is frequently observed in patients with such conditions as diabetes, hypertension, and chronic heart failure, i.e., those most vulnerable to SARS-CoV-2 infection. Hypoalbuminemia, coagulopathy, and vascular disease have been linked in COVID-19 and have been shown to predict outcome independent of age and morbidity. Hypoalbuminemia is also known factor in sepsis and Acute respiratory distress syndrome (ARDS) occurs when fluids build-up in the alveoli and it is associated with sepsis, whose mechanism is systemic, being associated with the fluid and logistic mechanisms of the circulation. Glycocalyx damage is associated with changes plasma protein concentration, particularly HSA and blockage of albumin transport can produce the systemic symptoms seen in SARS-CoV-2 infection and sepsis. We therefore conclude that albumin binding to SARS-CoV-2 virions may inhibit the formation of the endothelial glycocalyx by inhibition of albumin transport binding sites. We postulate that albumin therapy to replace bound albumin might alleviate some of the symptoms leading to sepsis and that clinical trials to test this postulation should be initiated as a matter of urgency.