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Dr. Ron Brown – Opinion Editorial
July 22, 2021
The following excerpts are based on my latest paper published in Medicina, “Sodium Toxicity in the Nutritional Epidemiology and Nutritional Immunology of COVID-19.” Referenced sources for the excerpts are cited in the peer-reviewed paper, which is available for free at: Medicina | Free Full-Text | Sodium Toxicity in the Nutritional Epidemiology and Nutritional Immunology of COVID-19 (mdpi.com).
Modifiable dietary and nutritional factors for COVID-19 prevention remain relatively under-investigated. The need for novel interventions is especially urgent for older adults in the high-risk category for morbidity and mortality from COVID-19. Emerging evidence suggests that sodium toxicity, the toxic effect in the body caused by dysregulated amounts of the micronutrient sodium, has potential causal influences in the etiology of influenza-like illnesses like COVID-19.
High sodium intake is a dietary risk factor associated with multiple diseases, and it is estimated to have caused a mean of 3 million deaths globally in 2017. Several of these diseases, like hypertension, stroke, and kidney disease, have also been identified as underlying conditions associated with increased risk for COVID-19 morbidity and mortality. Importantly, World Health Organization listed nutritional status among factors that increase susceptibility to infection.
After receiving sodium chloride infusions during a medical experiment in 1969, some patients rapidly developed severe pulmonary congestion and fluid retention in the lungs, or pulmonary edema, which blocked respiration and lowered arterial oxygen pressure. More recently, the gummy yellow fluid in the lungs of COVID-19 patients appears identical to the yellow fluid identified in pulmonary edema.
Sodium toxicity adversely affects the nasal mucosal immune system, which may lead to respiratory viral infection. COVID-19 patients were found to have prolonged mucociliary clearance of microorganisms through nasal passages compared with healthy ear, nose, and throat outpatients with non-nasal symptoms.
Animal studies have shown that injected sodium chloride acts as a pyrogen that causes fever, and adverse effects of pharmaceutical sodium chloride tablets include fever and rashes. Skin rashes are dermatologic manifestations of COVID-19, and higher salt concentrations were found in the skin of people with atopic dermatitis. Migraine is also associated with COVID-19, and researchers demonstrated increased sodium permeability through the blood−brain barrier and blood cerebral spinal fluid barrier during migraine. Thus, sodium toxicity potentially accounts for many of the symptoms of influenza-like illnesses like COVID-19.
Research has also found that people consume more sodium chloride in the winter, while excreting less sodium chloride by sweating less compared to warmer temperatures, coinciding with increased incidence of respiratory infections in colder seasons. Moreover, a recent systematic review and meta-analysis found that people of lower socioeconomic status consume 14% more sodium than people of a higher socioeconomic status, coinciding with increased COVID-19 risk in lower groups with lower socioeconomic status.
The research literature on infectious disease outbreaks associated with sea voyages and with the 1918 pandemic also infers a potential causative role played by excessive sodium chloride intake. Of relevance, U.S. Navy experiments in 1918 could not demonstrate transmission of influenza infection in healthy subjects exposed to the coughs, breath, and sputum of influenza patients, implying reverse causality between the infection and the disease. That is, disease determinants like sodium toxicity may cause infections by compromising immune system clearance of viruses. Excess sodium has also been found to stimulate inflammatory macrophages of the immune system.
More research is needed to investigate sodium toxicity as an etiologic determinant of COVID-19. In particular, interventions to reduce COVID-19 morbidity and mortality through reduced-sodium diets should be explored, particularly targeting long-term care homes with vulnerable populations.