Researchers in Norway are expanding a major ongoing study to determine whether cod liver oil can help fight off Covid-19 and reduce its mortality rate or whether those who take the nutrient simply lead healthier lives in general. Recent studies have postulated the lower rates of Covid-19 contagion and mortality in Northern Europe compared to Southern Europe may be partially explained due to the high consumption of cod liver oil in the north.

In line with this analysis, a previous major national Covid-19 study in Norway that began this spring, found that cod liver oil users had a lower risk of catching the virus.

“Preliminary data from our ongoing COVID-19 study suggest that cod liver oil users may have a reduced risk of COVID-19 and a lower risk of severe disease outcomes if they are infected,” says Arne Søraas, physician-scientist at the Department of Microbiology, Oslo University Hospital.

Now researchers want to expand the study into a “randomized, parallel-group treatment, quadruple masked, two-arm study” to test cod liver oil’s mettle and determine if it can help prevent or reduce both Covid-19 infections as well as other seasonal viral diseases like flu and the common cold. A properly structured study will yield more definitive conclusions.

The research team is calling for 70,000 volunteers to participate, half of whom will be dosed with cod liver oil and the other given a placebo (corn oil) from November until April next year.

This hypothesis is in line with current prevailing findings in the scientific literature regarding omega-3 fatty acids and vitamin D, both found in cod liver oil, and how they help prevent respiratory tract infections and Covid-19.

Cod liver oil is one of the few natural sources of vitamin D for most Norwegians, whose dark winters usually limit the body’s natural production of the substance through exposure to sunlight. 

The randomized study aims to determine whether cod liver oil might be a cheap but effective weapon that could easily be distributed worldwide with life-saving consequences for limited cost.

The researchers are also hoping to gain further insight into demographic-specific Covid-19 infections and whether cod liver oil doses might be of particular use to certain sections of the population.

“The target group is those who have a vitamin D deficiency. We know that people with darker skin more often have such a deficiency. So it’s very important that the study recruits as many people with a vitamin D deficiency, or with dark skin, so we can see the effects more clearly,” Saumia Shankar, a doctor at Oslo University Hospital, said.

In North America it is known that over 70% of the population is deficient in vitamin D, which is essential for supporting barrier tissues that prevent the entry of viruses into the body and also controlling the immune response to an infection. Most fatalities from Covid-19 result from an immune over reaction, or an unbalanced immune response. The active form of vitamin D is used by the immune system to ensure balanced, healthy immune activity that will kill invaders but not attack the hosts tissues.

Cod liver oil also contains naturally formed vitamin A, which is essential for optimal white blood cell activity. Various white blood cells are required to clear viruses from the human body.