MONTREAL -- Two Montreal researchers believe the well-documented anti-inflammatory properties of vitamin D could make it an important addition to the arsenal against the novel coronavirus.

They're investigating the question with the PROTECT study, be led by Doctors Francine Ducharme, from CHU Sainte-Justine, and Cecile Tremblay, from the Center hospitalier de l'Universite de Montreal (CHUM).

"Is this a valid approach? Is it effective? And if it's effective, then perfect, we can add a string to our bow," said Ducharme. "Theoretically, it's likely to work, but it has to be proven."

The study will investigate whether high doses of vitamin D could decrease the risk of infection in people who do not yet have COVID-19 and whether it could decrease the duration and intensity of the disease in those patients already infected.

The study will also look at the potential impact of vitamin D on the vaccine response.

The researchers are therefore recruiting 2,414 health-care workers in the greater Montreal area, since people in the region have a higher risk of coming into contact with the virus.

Up to 20 per cent of COVID cases identified in Canada since the start of the crisis have been among health-care workers.

Several previous studies lead to the conclusion that vitamin D has a protective effect against viral infections such as the common cold and influenza.

"There is a prevention effect of about 10 to 20 per cent that has been shown, so we reduce the risk of a person developing a common cold," said Ducharme.

"The question remains, could it work with COVID?"

Additionally, as people who develop a severe form of COVID-19 exhibit an inordinate inflammatory response, she added, "the anti-inflammatory properties of vitamin D may help."

Vitamin D is involved in the regulation of some 200 genes, several of which are involved in the body's defence against infections in general and in the regulation of inflammation.


The study has been adapted to the COVID-19 pandemic context so that participants take part from the comfort of their homes. For one of the very first times, everything can be done remotely.

The researchers will also take advantage of the new availability of COVID-19 vaccines to study how vitamin D could contribute to the vaccination campaign.

"It is all the more interesting and important that given the 'shortage' of vaccines, we must have a longer-than-recommended timeframe," explained Ducharme.

"If vitamin D has an adjuvant effect that increases protection in the interim of the two doses, I think that could be very interesting."

The first results of the study should be available in about 20 weeks. Until then, those curious about the effects will have to resist the temptation to go to the local pharmacy to stock up on vitamin D.

Ducharme said the previous studies that have shown vitamin D's protective or preventive effect had been carried out on people who consumed little or none at all.

In addition, all governments that have spoken on the issue have recommended not to take additional vitamin D supplements, beyond the recommended daily dose.

Health Canada's Dietary Reference Intakes for vitamin D range from 400 international units per day for babies under one year to 800 international units per day for adults over 70 years of age.

"We do not know if it will help or not," said Ducharme. "We don't want people to rush into it; there may be side effects to taking vitamin D. It's very safe, but rushing for a vitamin when you don't know if it's going to work is not worth it."

The main source of vitamin D comes from exposure to the sun. It is also found in foods such as certain fish, cow's milk, margarine and egg yolks. 

This report by The Canadian Press was first published Feb. 10, 2021.