Which Fermented Food Bacteria can Mitigate Viral Infections?
A Review of 3 Scientific Papers
Recent scientific research papers have confirmed the potency of probiotic bacteria such as lactobacilli (available in traditional fermented food) in mitigating viral infections (such as COVID-19) in severity and outcome. A summary of the papers follows. Also, in my just-published book, I list a longer list of beneficial nutrients and lifestyles and discuss the latest brain research as a practical guide to understanding imbalances, anxiety, depression, bad habits, pain, sleep disorder, low libido, etc.
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Kefir: A protective dietary supplementation against viral infection
The paper reviwes several studies that demonstrate Kefir and its probiotic contents can modulate the immune system to suppress infections from viruses (e.g., Zika, hepatitis C, influenza, rotaviruses). The antiviral mechanisms of kefir involve enhancement of macrophage production, increasing phagocytosis, boosting production of cluster of differentiation-positive (CD4+), CD8+, immunoglobulin (Ig)G+ and IgA+ B cells, T cells, neutrophils, as well as cytokines (e.g., interleukin (IL)-2, IL-12, interferon gamma-γ). Kefir can act as an anti-inflammatory agent by reducing expression of IL-6, IL-1, TNF-α, and interferon-γ. Hence, kefir might be a significant inhibitor of the ‘cytokine storm’ that contributes to 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.
Methods Single-center, quadruple-blinded RCT. Symptomatic Covid 19 outpatients (aged 18 to 60 years) with positive SARS-CoV2 nucleic acids test were randomized to active (n=150; ≥2×109 colony-forming units (CFU) of probiotic strains Lactiplantibacillus plantarum KABP022, KABP023 and KAPB033, plus strain Pediococcus acidilactici KABP021) or placebo (n=150), take orally once daily for 30 days. Oral acetaminophen was allowed and controlled as co-intervention. Primary endpoint included: i) proportion of patients in complete remission (both symptoms and nucleic acids test) or progressing to moderate or severe disease with hospitalization; ii) death rate and duration on Intensive Care Unit (ICU). Safety was assessed in all patients. This study is registered at ClinicalTrials.gov (NCT04517422).
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Findings 300 subjects were randomized (median age 37.0 years [range 18 to 60], 161 [53.7%] women, 126 [42.0%] having known metabolic risk factors), and 293 completed the study (97.7%). Remission was achieved by 78 of 147 (53.1%) in the active group compared to 41 of 146 (28.1%) in placebo (P<0.0001; ARR=25.0% [95%CI 14.1-35.9%]), still significant after multiplicity correction for the primary endpoint. No hospitalizations or deaths occurred during the study, precluding the assessment of efficacy on these endpoints. No serious adverse events occurred during the study. Replication studies with this probiotic formula are warranted.