Correction to: Is diet partly responsible for differences in COVID-19 death rates between and within countries?

[This corrects the article DOI: 10.1186/s13601-020-00323-0.].

Available and affordable complementary treatments for COVID-19: From hypothesis to pilot studies and the need for implementation.

Vaccination is a highly effective preventive measure against COVID-19. However, complementary treatments are needed to better control the disease. Fermented vegetables and spices, agonists of the antioxidant transcription factor nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and TRPA1/V1 channels (Transient Receptor Potential Ankyrin 1 and Vanillin 1), may help in the control of COVID-19. Some preliminary clinical trials suggest that curcumin (spice) can prevent some of the COVID-19 symptoms. Before any conclusion can be drawn and these treatments recommended for COVID-19, the data warrant confirmation. In particular, the benefits of the foods need to be assessed in more patients, through research studies and large trials employing a double-blind, placebo-controlled design.

Differentiation of COVID-19 signs and symptoms from allergic rhinitis and common cold: An ARIA-EAACI-GA2 LEN consensus.

BACKGROUND: Although there are many asymptomatic patients, one of the problems of COVID-19 is early recognition of the disease. COVID-19 symptoms are polymorphic and may include upper respiratory symptoms. However, COVID-19 symptoms may be mistaken with the common cold or allergic rhinitis. An ARIA-EAACI study group attempted to differentiate upper respiratory symptoms between the three diseases. METHODS: A modified Delphi process was used. The ARIA members who were seeing COVID-19 patients were asked to fill in a questionnaire on the upper airway symptoms of COVID-19, common cold and allergic rhinitis. RESULTS: Among the 192 ARIA members who were invited to respond to the questionnaire, 89 responded and 87 questionnaires were analysed. The consensus was then reported. A two-way ANOVA revealed significant differences in the symptom intensity between the three diseases (p < .001). CONCLUSIONS: This modified Delphi approach enabled the differentiation of upper respiratory symptoms between COVID-19, the common cold and allergic rhinitis. An electronic algorithm will be devised using the questionnaire.

Potential Interplay between Nrf2, TRPA1, and TRPV1 in Nutrients for the Control of COVID-19.

In this article, we propose that differences in COVID-19 morbidity may be associated with transient receptor potential ankyrin 1 (TRPA1) and/or transient receptor potential vanilloid 1 (TRPV1) activation as well as desensitization. TRPA1 and TRPV1 induce inflammation and play a key role in the physiology of almost all organs. They may augment sensory or vagal nerve discharges to evoke pain and several symptoms of COVID-19, including cough, nasal obstruction, vomiting, diarrhea, and, at least partly, sudden and severe loss of smell and taste. TRPA1 can be activated by reactive oxygen species and may therefore be up-regulated in COVID-19. TRPA1 and TRPV1 channels can be activated by pungent compounds including many nuclear factor (erythroid-derived 2) (Nrf2)-interacting foods leading to channel desensitization. Interactions between Nrf2-associated nutrients and TRPA1/TRPV1 may be partly responsible for the severity of some of the COVID-19 symptoms. The regulation by Nrf2 of TRPA1/TRPV1 is still unclear, but suggested from very limited clinical evidence. In COVID-19, it is proposed that rapid desensitization of TRAP1/TRPV1 by some ingredients in foods could reduce symptom severity and provide new therapeutic strategies.

Spices to Control COVID-19 Symptoms: Yes, but Not Only .

There are large country variations in COVID-19 death rates that may be partly explained by diet. Many countries with low COVID-19 death rates have a common feature of eating large quantities of fermented vegetables such as cabbage and, in some continents, various spices. Fermented vegetables and spices are agonists of the antioxidant transcription factor nuclear factor (erythroid-derived 2)-like 2 (Nrf2), and spices are transient receptor potential ankyrin 1 and vanillin 1 (TRPA1/V1) agonists. These mechanisms may explain many COVID-19 symptoms and severity. It appears that there is a synergy between Nrf2 and TRPA1/V1 foods that may explain the role of diet in COVID-19. One of the mechanisms of COVID-19 appears to be an oxygen species (ROS)-mediated process in synergy with TRP channels, modulated by Nrf2 pathways. Spicy foods are likely to desensitize TRP channels and act in synergy with exogenous antioxidants that activate the Nrf2 pathway.

Nrf2-interacting nutrients and COVID-19: time for research to develop adaptation strategies.

There are large between- and within-country variations in COVID-19 death rates. Some very low death rate settings such as Eastern Asia, Central Europe, the Balkans and Africa have a common feature of eating large quantities of fermented foods whose intake is associated with the activation of the Nrf2 (Nuclear factor (erythroid-derived 2)-like 2) anti-oxidant transcription factor. There are many Nrf2-interacting nutrients (berberine, curcumin, epigallocatechin gallate, genistein, quercetin, resveratrol, sulforaphane) that all act similarly to reduce insulin resistance, endothelial damage, lung injury and cytokine storm. They also act on the same mechanisms (mTOR: Mammalian target of rapamycin, PPARγ:Peroxisome proliferator-activated receptor, NFκB: Nuclear factor kappa B, ERK: Extracellular signal-regulated kinases and eIF2α:Elongation initiation factor 2α). They may as a result be important in mitigating the severity of COVID-19, acting through the endoplasmic reticulum stress or ACE-Angiotensin-II-AT1R axis (AT1R) pathway. Many Nrf2-interacting nutrients are also interacting with TRPA1 and/or TRPV1. Interestingly, geographical areas with very low COVID-19 mortality are those with the lowest prevalence of obesity (Sub-Saharan Africa and Asia). It is tempting to propose that Nrf2-interacting foods and nutrients can re-balance insulin resistance and have a significant effect on COVID-19 severity. It is therefore possible that the intake of these foods may restore an optimal natural balance for the Nrf2 pathway and may be of interest in the mitigation of COVID-19 severity.

Efficacy of broccoli and glucoraphanin in COVID-19: From hypothesis to proof-of-concept with three experimental clinical cases.

COVID-19 is described in a clinical case involving a patient who proposed the hypothesis that Nuclear factor (erythroid-derived 2)-like 2 (Nrf2)-interacting nutrients may help to prevent severe COVID-19 symptoms. Capsules of broccoli seeds containing glucoraphanin were being taken before the onset of SARS-CoV-2 infection and were continued daily for over a month after the first COVID-19 symptoms. They were found to reduce many of the symptoms rapidly and for a duration of 6-12 h by repeated dosing. When the patient was stable but still suffering from cough and nasal obstruction when not taking the broccoli capsules, a double-blind induced cough challenge confirmed the speed of onset of the capsules (less than 10 min). A second clinical case with lower broccoli doses carried out during the cytokine storm confirmed the clinical benefits already observed. A third clinical case showed similar effects at the onset of symptoms. In the first clinical trial, we used a dose of under 600 µmol per day of glucoraphanin. However, such a high dose may induce pharmacologic effects that require careful examination before the performance of any study. It is likely that the fast onset of action is mediated through the TRPA1 channel. These experimental clinical cases represent a proof-of-concept confirming the hypothesis that Nrf2-interacting nutrients are effective in COVID-19. However, this cannot be used in practice before the availability of further safety data, and confirmation is necessary through proper trials on efficacy and safety.

Cabbage and fermented vegetables: From death rate heterogeneity in countries to candidates for mitigation strategies of severe COVID-19.

Large differences in COVID-19 death rates exist between countries and between regions of the same country. Some very low death rate countries such as Eastern Asia, Central Europe, or the Balkans have a common feature of eating large quantities of fermented foods. Although biases exist when examining ecological studies, fermented vegetables or cabbage have been associated with low death rates in European countries. SARS-CoV-2 binds to its receptor, the angiotensin-converting enzyme 2 (ACE2). As a result of SARS-CoV-2 binding, ACE2 downregulation enhances the angiotensin II receptor type 1 (AT1 R) axis associated with oxidative stress. This leads to insulin resistance as well as lung and endothelial damage, two severe outcomes of COVID-19. The nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is the most potent antioxidant in humans and can block in particular the AT1 R axis. Cabbage contains precursors of sulforaphane, the most active natural activator of Nrf2. Fermented vegetables contain many lactobacilli, which are also potent Nrf2 activators. Three examples are: kimchi in Korea, westernized foods, and the slum paradox. It is proposed that fermented cabbage is a proof-of-concept of dietary manipulations that may enhance Nrf2-associated antioxidant effects, helpful in mitigating COVID-19 severity.

Is diet partly responsible for differences in COVID-19 death rates between and within countries?

Reported COVID-19 deaths in Germany are relatively low as compared to many European countries. Among the several explanations proposed, an early and large testing of the population was put forward. Most current debates on COVID-19 focus on the differences among countries, but little attention has been given to regional differences and diet. The low-death rate European countries (e.g. Austria, Baltic States, Czech Republic, Finland, Norway, Poland, Slovakia) have used different quarantine and/or confinement times and methods and none have performed as many early tests as Germany. Among other factors that may be significant are the dietary habits. It seems that some foods largely used in these countries may reduce angiotensin-converting enzyme activity or are anti-oxidants. Among the many possible areas of research, it might be important to understand diet and angiotensin-converting enzyme-2 (ACE2) levels in populations with different COVID-19 death rates since dietary interventions may be of great benefit.