Coronavirus Pandemic, part 2 : how to support your immune system
Updated: Apr 25
Given widespread concern for the growing coronavirus pandemic, I want to share my medical advice as a physician who treats medical conditions that affect the immune system. As a rheumatologist who has seen conditions characterized by an immune system that is out of control, I am well aware of the kind of critical illness and lung inflammation that the coronavirus may unleash (also called ARDS = Acute Respiratory Distress Syndrome). To date, there is very limited research regarding interventions to prevent the immune system from having an auto-inflammatory response to the virus and therefore prevention is more important than anything else we do (see my previous blog post here). However, given many readers of this article have already stocked up on supplements and are now wondering what do with them and how much to take safely, I have posted some of my insights below.
Recommendations to support your immune system:
1) Eat a diet rich in fruits and vegetables
A number of research articles have established that the phytonutrients and flavonoids which are present in every fruit and vegetable have unique antiviral and antibacterial properties. Eating a wide variety of high-quality fruits, vegetables, and grains is arguably more important than any number of supplements out there.
As a single example, cited in this article luteolin was found to have antiviral activity against the previous coronavirus which caused SARS:
Xu et al.  tested 400 highly purified natural compounds for inhibition of EV71 and coxsackievirus A16 infections and found that luteolin exhibited the most potent inhibition through disruption of viral RNA replication. Besides these antiviral activities, luteolin or luteolin-rich fractions showed antiviral effects against severe acute respiratory syndrome coronavirus (SARS-CoV), rhesus rotavirus, CHIKV and Japanese encephalitis virus (JEV)
Dietary sources of luteolin include celery, broccoli, green pepper, parsley, thyme, dandelion, perilla, chamomile tea, carrots, olive oil, peppermint, rosemary, navel oranges, and oregano.
2) Get exercise
Within reason and while maintaining appropriate physical distance, get exercise (outdoors if your location is not on lock-down). In multiple studies going back decades, moderate physical exercise has been linked to a lower risk of respiratory viral infection, likely due to its positive impact on immune surveillance and immune regulation.
It is well-established that sleep is important for multiple systems in the body including immune health and infection prevention. Try your best to get 8 hours of sleep per night as there is an association with increased likelihood of respiratory viral infection with 5 or less hours of sleep per night.
4) Stay in touch with friends and family:
One study shows that maintaining social ties is protective of respiratory viral illness
5) Can supplements help?
One of my physician colleagues shared with me the International Society for Orthomolecular Medicine's supplement recommendations which have been circulating for the prevention of Coronavirus infection. Given that I disagree with their dosing of vitamin C based on possible harm, I have listed a few widely used supplements with my caveats below.
Although it is plausible that taking extra ascorbic acid (vitamin C) may be beneficial for preventing severe infection, clinical results to date have not been supportive for the common cold. Moreover, mega-doses of Vitamin C (10 grams per day) can cause kidney stones that can permanently damage the kidneys as well as gastrointestinal side effects (stomach discomfort)
For critically ill patients (e.g., on a ventilator), there is also limited evidence for IV ascorbic acid - with some small studies showing a benefit and other small studies not showing any benefit beyond IV hydrocortisone. Clinical benefits specific to COVID-19 remain anecdotal and theoretical. Moreover, the same kidney toxicity noted with oral vitamin C has been noted with IV vitamin C and this should cause hesitation.
How much to take? It would be reasonable to eat citrus fruits and not take any supplemental Vitamin C. Moreover, you will be obtaining other possible antiviral benefits from the flavonoids present in the citrus fruits! If you absolutely want to use vitamin C, I will acquiesce. You may take 500 mg twice a day which may be increased* to 2000 mg daily if you have mild respiratory symptoms that Vitamin C could address. This could be beneficial in patients with diabetes and other inflammatory or autoimmune conditions who may have chronic vitamin C deficiency.
*Avoid higher doses if you have an underlying kidney problem
Vitamin D exposure leads to a "shift from a proinflammatory to a more tolerogenic immune status" so it is plausible that this could be helpful to impede the excessive inflammatory response to COVID-19 infection.
Update 04/25/2020: I reviewed more recent Vitamin D data indicating a benefit for prevention of acute respiratory tract infections, most notable among people who are vitamin D deficient and those receiving daily doses (not high-dose weekly doses).
How much to take ? In my estimation, doses ranging from 1000 to 4000 IU daily are reasonable. Mega-doses of vitamin D are not advisable based on a possible negative impact on bone health. (unless the dose is justified by vitamin D deficiency)
Though zinc deficiency is common in the elderly who get pneumonia and supplementation with 30 mg/day has been shown to lead to an increase in blood zinc levels, there is no consistent effect of zinc supplementation on preventing or treating infection. In childhood lung infection, one study using a 10 mg per day dose did not show a benefit while a meta-analysis (an analysis of the results of multiple studies) did show zinc supplementation (doses as high as 20 mg per day) was effective in reducing the mortality of severe pneumonia in children. Additional studies in adults are needed.
Nutritional sources of zinc should be considered as the daily intake can usually be met with no risk of zinc toxicity.
How much zinc to take? Fifteen to 30 mg daily is reasonable (toxicity only occurs at prolonged doses above 100 mg per day).
Selenium: 100 mcg (micrograms) daily
Similar to zinc, it is important to avoid selenium deficiency (excerpt from article below) but mega-doses are unnecessary in people who have a well-balanced diet.
Selenium promotes proliferation and favors differentiation of naive CD4-positive T lymphocytes toward T helper 1 cells, thus supporting the acute cellular immune response.
In summary, I want to emphasize the link between healthy diet/lifestyle and immune health. We should favor prevention with the pillars of long-term human health, as opposed to a "quick fix" approach and supplements.
Dr. Yousef Zarbalian is a rheumatologist, internist, and acupuncturist at East-West Rheumatology which he founded in 2019.