COVID-19 Vitamin D is involved in the body’s immune function. Vitamin D deficiency results in a higher rate of upper respiratory tract infections, especially in people with asthma and COPD. A deficiency of this vitamin is also associated with several autoimmune diseases. Our bodies obtain vitamin D through UVB (ultraviolet B) light exposure to our skin and orally through our diet. Vitamin D is then converted to an active form by the liver, kidney and our immune cells. Recommended daily exposure to UVB light varies by skin colour and geographic location. White skin types are recommended to have about 10 minutes of exposure to the sun midday, while darker skin types should increase exposure to about 30 minutes. There are no age parameters attached to these UVB recommendations. As we age, our skin has a decreased ability to manufacture vitamin D. Seniors are, therefore, more likely to require oral supplementation. Recommendations for oral supplementation vary as well. Some health authorities recommend people at risk of influenza and/or COVID-19 take 10,000 IU per day for a few weeks, followed by 5,000 IU per day. Other health authorities recommend regular supplementation of 800 IU per day with a limit of 4000 IU per day. There are no clear, specific guidelines and the varying recommendations will also depend on your underlying vitamin D levels. Short-term (a fewweeks), high-level vitamin D supplementation is not toxic to most individuals. Remember that it is possible to get too much of a good thing. It is not necessary to get a sunburn to obtain your recommended dose of vitamin D from the sun, and long-term, highdose oral supplements can cause problems. Vitamin D, via its active metabolites, influences more than 200 genes. Receptors for vitamin D are extensively distributed throughout the cells lining the respiratory tract and in immune cells. Cells in both the upper and lower airways secrete antimicrobial peptides that also inhibit viruses from entering the body. Vitamin D can increase the production of these peptides. Vitamin D also regulates the expression of ACE 2 in lung tissue. Vitamin D doesn’t just appear to play a role in the infective stage of COVID-19. It also influences the subsequent inflammatory stage, which is responsible for disease severity. Vitamin D inhibits inflammatory molecules and is believed to be involved in balancing the immune system. Other dietary components which have been studied in influenza and other human coronaviruses are plant-based polyphenols and flavonoids found in a wide variety of foods. Edible plants with high polyphenol levels include berries, plums, cherries and apples. Black beans and white beans also have high levels of polyphenols, as do such nuts as hazelnuts and pecans. Foods high in flavonoids include citrus fruit, blueberries, spinach, dark chocolate and nuts, to name but a few. This list of beneficial foods is not exhaustive and you can check the polyphenol content of your favourite fruits, vegetables, nuts and legumes online to ensure that your diet is rich in these important substances. Extracts from a species of elderberry have been shown to have anti-viral properties against a different type of coronavirus by blocking attachment of the virus and inhibiting replication. A pomegranate polyphenol extract was found to have other beneficial effects against the influenza virus. Although plant extracts have been shown to be beneficial in the study of viruses other than COVID-19, the best way to obtain the benefits of polyphenols and flavonoids is to maintain a diet rich in plant-based food. This is not our first pandemic, nor is it going to be our last. We know that the interaction of COVID-19 with our immune system is complex and can involve immune suppression as well as hyper-activation. With no effective, universal treatment for COVID19 and no current vaccine, the best defence against this disease is minimizing your risk of exposure and maintaining a balanced, healthy immune system. Supplements and COVID-19 CSANews | SUMMER 2020 | 37
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