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22 Nutrients to Support Immunity Against SARS-CoV-2

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Disclaimer: This article is intended for informational purposes only. None of the following is intended as medical advice. Please consult your doctor or nutritionist before starting a new diet, in case of food sensitivities, allergies, drug interactions, or other precautions. Please consult with an expert herbalist or mycologist before attempting to consume any foraged foods.

This review of the literature highlights a variety of naturally occurring vitamins, minerals, and polyphenols that may reduce the risk of contracting COVID-19 and/or reduce disease severity. On a biochemical level, nutrients play irreplaceable physiological roles as hormones, antioxidants, enzyme cofactors, and more. Nutrient deficiencies present real risk factors in all-cause morbidity and mortality; as such, nutrition is a critical cornerstone of any preventive lifestyle regimen.

1. Vitamin D3

Vitamin D deficiency is associated with greater susceptibility to and severity of COVID-19[1]. Vitamin D has been shown to decrease the incidence of viral respiratory tract infections and pneumonia and lower viral replication. Sufficient Vitamin D reduces your risk of catching COVID-19 by modulating the angiotensin-converting enzyme 2 (ACE2) receptor that SARS-CoV-2 uses to infiltrate cells. Specifically, it is thought to bind to ACE2 and downregulate its expression. ACE2 expression is high in the lung, heart, ileum, kidney and bladder.

Vitamin D also suppresses cytokine release and pro-inflammatory pathways, including NF-kB, IL-6, and TNF, and promotes neurotrophic factors like nerve growth factor (NGF) that help neurons survive[2].

The majority of your Vitamin D comes from UVB sunlight, not dietary sources. Vitamin D deficiency is more common in winter months. Your best bet is to spend at least 5-30 minutes in the sun every day. The most significant dietary sources are cod liver oil, wild caught salmon, mackerel, dairy products, and eggs, but vitamin D is also found in trace amounts in wild mushrooms.

Vitamin D needs vitamin K2 and magnesium to function most optimally[3]. Vitamin D is also beneficial for individuals with existing conditions fighting COVID-19, such as cardiovascular disease, acute respiratory distress, cancer, and kidney disease[4].

  • Prevention: Maybe, by downregulating ACE2

  • Treatment: Maybe

2. Melatonin

Melatonin is a neurotransmitter and potent antioxidant. It’s immunomodulatory, meaning it can be either pro-inflammatory or anti-inflammatory, with the pro-inflammatory effects associated with antiviral activity.

In terms of anti-inflammatory effects, melatonin inhibits the NLRP3 inflammasome and activates Nrf2. In the respiratory system, melatonin blocks NF-kB, upregulates C-Fos, and downregulates matrix metalloproteases-3 (MMP-3), making it anti-fibrotic and vasodilating in activity. Melatonin indeed protects against lung injury and pulmonary fibrosis in animal models, reducing swelling, pneumonitis, collagen deposition, inflammatory cell infiltration, and vascular and alveolar thickening in the lungs. Melatonin can reduce damage to lung parenchyma and increases SIRT-1 expression, giving it anti-apoptotic effects[5].

Children seem to be less affected by COVID-19, and children also have the highest secretion of melatonin.

Melatonin’s promotion of lung health warrants featuring it on this list, as the majority of melatonin in the body is produced by the pineal gland and is associated with deep, restorative sleep and glymphatic system activity. I’m not saying you should go pop some melatonin, but try to get at least 7 hours of sleep per night and take care of your sleep hygiene. Get dark shades if you need to, and turn off electronic devices after 9pm, which is around the time when pineal melatonin secretion starts. At minimum, turn off electronic devices 2 hours before bed.

  • Protection: Maybe

  • Lessen disease severity: Maybe

3. Oranges

Hesperidin and ascorbic acid (vitamin C) found in oranges fight COVID-19. Specifically, out of 1066 natural substances screened by Wu et. al against COVID-19, hesperidin was the most suitable to bind to the spike protein. Hesperidin was found to disrupt the ACE2-RBD (receptor binding domain) complex and the main SARS-CoV-2 viral protease Mpro; hesperidin had a better interaction with the Mpro enzyme than the reference drug lopinavir in a clinical trial[6].

Vitamin C-rich foods increase white blood cell production, which is key to fighting infection. Vitamin C functions in hormonal regulation, metabolic energy, and increasing collagen, promoting barrier integrity. Vitamin C inhibits NLRP3 inflammasome activation. Clinical trials have found that vitamin C shortens the frequency, duration and severity of the common cold and the incidence of pneumonia[7].

Foods rich in Vitamin C include:

  • Green and red bell peppers

  • Tomatoes

  • Cruciferous vegetables: broccoli, Brussels sprouts, cauliflower, and cabbage

  • Leafy greens: spinach and turnip greens

  • Citrus, papaya, kiwi, pineapples

  • Sweet and white potatoes

  • Winter squash

  • Reduce incidence: Maybe

  • Reduce severity: Maybe

4. Quercetin

Quercetin could prevent COVID-19 infection, specifically by inhibiting the binding of the virus to human cells. Quercetin binds readily to the viral S-protein–human ACE2 receptor interface–ligand-binding complex. These molecules significantly alter human gene expression involved in attachment of the virus to host cells. Quercetin and vitamin C have synergistic antiviral activity. Quercetin was also able to block entry of SARS-CoV-2 into Vero E6 cells in vitro[8, 9].

Rutin, which contains quercetin and the disaccharide rutinose, also bound readily to Mpro (the main, SARS-CoV-2 serine protease, also known as 3CLpro). Rutin is found in figs.

Elderberries. Image via Getty Images

Foods rich in quercetin include elderberries, lettuce, asparagus, onions, green pepper, apples[10], berries, cilantro (coriander), capers, lovage, and dill.

Another paper using in silico data argues that oral quercetin is “unlikely to be effective in clinical trials” because of its low bioavailability during digestion, specifically its biotransformation, absorption, and metabolism. The authors instead suggest researchers focus their efforts on developing and testing nasal or throat sprays for direct administration to treat COVID-19[11].

  • Prevention: Maybe

  • Treatment: Maybe, with optimized delivery

5. Black Cumin and Parsley

Polyphenols display anti-inflammatory, antioxidant, anti-cancer, and antiviral activities. Apigenin, quercetin, amentoflavone, daidzein, puerarin, epigallocatechin, epigallocatechin gallate, and gallocatechin gallate were found to inhibit the proteolytic activity of SARS-CoV-2 3C-like protease, which is vital for viral replication.