• Cristina Montoya, RD

Supporting Your Immune System When You Are Immunocompromised: COVID-19 Edition

Amid the first wave of the COVID-19 pandemic, I posted a blog Should You Take Immune Boosters If You Are Immunocompromised?. It's been ten months of ups and downs; as someone who is immunocompromised and inadvertently was in close contact with a person who tested positive for COVID-19, I know the general stress and anxiety that comes with the flu season and rising COVID-19 cases in Canada and across the globe. Here is an update on a few vitamins, minerals, supplements and foods that can help support your immune system:

Vitamin D

Vitamin D, the sunshine vitamin, helps to maintain your immune system but can be hard to come by in Canada during the cold and flu season. This amazing vitamin also helps to regulate immune function and reduce inflammation!

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What is new?

There is promising research on vitamin D concerning the prevention and treatment of COVID-19. A recent study looked at 489 individuals who received a COVID-19 test and had their vitamin D levels assessed the previous year. Researchers found that 19% of the vitamin D deficient individuals tested positive for COVID-19 versus only 12% of patients who tested positive but had adequate vitamin D levels.

Another study found a positive correlation between living in northern countries (associated with less vitamin D absorption from the sun) and an increased risk of death from COVID-19. A study conducted in Spain found that out of 216 COVID-19 patients, 82.2% of them had a vitamin D deficiency. These patients were more likely to have more extended hospital stays. No recommendations have been made for vitamin D levels and COVID-19, but research has shown that having adequate levels is essential to support the immune system's adequate functioning.

Osteoporosis Canada recommends that those taking medications affecting vitamin D absorption should supplement with 800 – 2,000 IU daily. Make sure you are purchasing vitamin D3 (cholecalciferol) supplements in oil or oil-based capsules for optimal absorption. Always speak to your healthcare provider for advice that fits best with you. For instance, my rheumatologist suggested taking between 3000 - 4000 IU per day, which is right below the upper limit daily intake.

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When it comes to fighting colds, Zinc gets a lot of attention, for a good reason! Your immune system relies on Zinc for optimal functioning and it may help to shorten the duration of colds if taken at the onset of symptoms. It also helps with tissue development and helps to support cartilage regeneration, both are very important for those with inflammatory arthritis.

Supplementation is usually not needed if you eat a varied diet that includes high protein foods such as seafood, legumes or lean meats. However, studies have shown that people with Rheumatoid Arthritis may have lower levels of zinc. Additionally, people with short bowel syndrome and inflammatory bowel disease (i.e. Crohn’s Disease) are at risk of Zinc deficiency due to malabsorption.

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So how much zinc should you take?

You may have heard of the UL (aka the Tolerable Upper Intake Level), it is the highest level of a nutrient that can be ingested each day without having any adverse effects for most healthy individuals. For Zinc, that UL is 20mg a day for healthy adults, so mega-doses of Zinc over long periods of time should be avoided. Taking more than 50mg/day can not only cause toxicity, it can block the absorption of copper. Copper is an essential mineral that has anti-inflammatory effects, and low levels of it may lead to irreversible anemia. Speak to your healthcare provider to decide what dose is right for you

Regarding zinc and COVID-19, a study in Spain looked at 249 hospitalized COVID-19 patients. The researchers noted that those patients with low blood levels of zinc had more difficulty recovering from the illness than patients who had normal levels. They also identified increased mortality. No recommendation has been set based on these results.


Omega-3 fatty acids provide excellent support for your immune system during the cold and flu season, and it can help to reduce inflammation. The best dietary sources of Omega-3s are from fatty fish such as salmon, tuna and sardines or from plant sources such as walnuts, soybeans and flaxseeds. If you are concerned that you may not be consuming enough through your regular diet, speak to your healthcare provider to find out which Omega-3 supplements could be of most benefit to you.

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In vitro and in vivo experiments have shown that omega-3 fatty acid supplementation can reduce the severity of COVID-19 but that was only with small doses, high doses need further research. They noted that the reduction in severity is because eicosapentaenoic acid EPA and docosahexaenoic acid DHA have anti-inflammatory effects. When they are oxidized by enzymes, they help synthesis less inflammatory eicosanoids and lipid mediators, which reduces inflammation caused by infections and viruses.