Can cod liver oil supplementation prevent COVID-19 and other acute respiratory infections?

Numerous studies have been conducted to determine treatment options for combating the 2019 coronavirus disease (COVID-19) pandemic. Much attention has been focused on the role of vitamin D in the prevention and treatment of COVID-19. Several preclinical studies have shown that vitamin D metabolites play an important role in the immune response to respiratory viruses.

Additionally, low levels of 25-hydroxyvitamin D3 (25(OH)D3) have been observed to increase the risk of acute respiratory infections. A recent meta-analysis suggested that vitamin D supplementation may reduce the risk of respiratory infections compared to placebo.

Severe cases of COVID-19 are associated with uncontrolled immune cell activation, increased inflammation, and excessive release of proinflammatory cytokines. Long-chain omega-3 fatty acids, such as docosahexaenoic acid and eicosapentaenoic acid, have been shown to have anti-inflammatory properties. Ensuring sufficient levels of vitamin D and these fatty acids can therefore serve as a cost-effective way to prevent severe COVID-19 and SARS-CoV-2 infections.

Cod liver oil is a low-dose vitamin D supplement containing docosahexaenoic acid and eicosapentaenoic acid. Consuming cod liver oil in winter is a long tradition in Norway to prevent vitamin D deficiency.

New research published in British Medical Journal (BMJ) We aimed to analyze whether cod liver oil could prevent severe COVID-19, SARS-CoV-2 infections, or other acute respiratory infections during the winter of 2020-2021.

About research

The study was a randomized, two-arm, and quadruple-mask parallel-arm treatment consisting of participants aged 18 years or older, who had a Norwegian personal identification number, and who had access to the government’s secure digital government ID service. It was an exam. Participants were randomized in her 1:1 ratio to receive placebo or 5 ml of cod liver oil daily. Both the placebo and cod liver oil were subjected to blind testing by an experienced taste panel who could not distinguish between the two.

Randomization was performed without stratification or blocking at the Research Support Unit of Oslo University Hospital. Data collection, storage and analysis were also carried out by the University of Oslo.

Participants were required to complete a baseline questionnaire, including questions about personal data, vitamin D, etc., before taking placebo or cod liver oil. They were followed up 6 months later for intervention adherence, SARS-CoV-2 infection, COVID-19 vaccination, acute respiratory infections, and experience of side effects.

Compliance was described as strict if 5ml or more of placebo or cod liver oil was taken for more than 2-3 months. Compliance was described as gradual when ingested. Side effects were graded and classified according to the Common Terminology Criteria for Adverse Events (CTCAE).

Four primary endpoints were evaluated. The first was positive for SARS-CoV-2 oropharynx or pharynx. Nasopharyngeal swab The test was detected by reverse transcriptase quantitative polymerase chain reaction in a Norwegian laboratory and reported to the Mandatory Norwegian Surveillance System for Communicable Diseases (MSIS). The secondary endpoint was her outbreak of severe COVID-19 associated with hospitalization or death. A third endpoint was the incidence of participants with one or more of her negative SARS-CoV-2 test results documented in MSIS. A fourth endpoint was the occurrence of participants who reported one or more acute respiratory infections.

The number of participants admitted to a hospital or intensive care unit for COVID-19 constituted a pre-defined secondary endpoint. Exploratory endpoints included self-reported changes in blood levels of 25(OH)D3 and omega-3 indices, blinding to study supplements, and side effects. Blood samples were taken from participants before and during supplementation to analyze levels of omega-3 fatty acids and 25(OH)D3. Finally, baseline SARS-CoV-2 antibody analysis was performed.

Survey results

Results showed that a total of 34,741 participants participated in the study, more than half of the participants were female, had a mean age of 44.9 years, and had a baseline body mass index of 26.1. 17,278 participants received cod liver oil and 17,323 received placebo.

Most of the participants reported not using vitamin D supplements prior to the study, while 39.8% reported being exposed to approximately 30 hours of sun exposure from July to October 2020, and 61.5% reported eating less fat. reported that they ate fish with a lot of Additionally, 35.6% found that he had received her COVID-19 vaccine more than once.

A total of 455 participants reported positive SARS-CoV-2 test results, evenly distributed between locations and cod liver oil groups. reported by 121 participants in the cod liver oil group. A total of 17 participants were hospitalized, 8 of whom were in the intensive care unit. Additionally, the relative risk of severe COVID-19 was observed to be 1.20 in the cod liver oil group compared to the placebo group.

In addition, 17,111 participants had one or more negative SARS-CoV-2 test results, the distribution of which was found to be similar in both groups, and 7,798 participants had one or more acute reported a respiratory infection. Analysis of blood samples revealed only a modest increase in 25(OH)D3 levels in the cod liver oil group compared to the placebo group. The mean concentration of 25(OH)D3 increased by 15.0 nmol/L and the omega-3 index increased by 1.9%.

One or more side effects were reported by 11.3% and 10.1% of participants in the placebo and cod liver oil groups, respectively, with mild gastrointestinal symptoms belonging to CTCAE Grade 1 being the most common side effect. Grade 2 side effects were observed more frequently in the placebo group. Finally, 7616 participants in the placebo group and 7220 participants in the cod liver oil group did not know which supplements they were taking or believed they were taking placebo, whereas the placebo group did not know what supplements they were taking or believed they were taking placebo. 1,058 in the cod liver oil group and 1,966 in the cod liver oil group believed to consume cod liver. oil supply.

Therefore, the current study suggests that low-dose vitamin D supplementation with docosahexaenoic acid and eicosapentaenoic acid for 6 months may reduce the risk of SARS-CoV-2 infection, severe COVID-19, and other acute respiratory infections. However, taking this supplement caused only mild side effects.

Limitations

Current research has certain limitations. First, self-reported endpoint data can introduce bias. Second, the duration of the intervention was relatively short, and longer effects of cod liver oil could not be assessed. Third, the effects of vitamin D and omega-3 fatty acids could not be distinguished. Fourth, the effect of vitamin D on SARS-CoV-2 risk could not be assessed at the start of the trial. Finally, the number of participants who entered the trial was lower than expected.