Higher Omega-3 Levels May Protect Against COVID-19 Adverse Outcomes: Study

Research supports the practice of increasing the consumption of oily fish, like salmon, or omega-3 fish oil supplements as a potential risk reduction strategy for COVID-19. Oksana_Slepko/Shutterstock

Higher levels of omega-3 fatty acids may provide some protection against contracting or experiencing adverse outcomes of COVID-19 infection according to a recent study.

The study, published in The American Journal of Clinical Nutrition, compared the risk for three COVID-19 outcomes: testing positive for COVID-19, hospitalization with confirmed COVID-19 infection, and death from COVID-19 as a function of plasma DHA levels.

The research mainly focused on two long-chain omega-3 fatty acids of marine origin: eicosapentaenoic (EPA) and docosahexaenoic acids (DHA).

“This study confirms previous findings that low omega-3 status is associated with increased risk for hospitalization with COVID-19,” the lead author of the study, William S. Harris, professor in the Department of Internal Medicine at the Sanford School of Medicine–University of South Dakota, said in a March 1 statement.

“We extended these findings by also showing reduced risk for testing positive with the infection and by providing evidence that the risk for death may also be reduced,” added Harris, who is also the president of the Fatty Acid Research Institute.

UK Cohort

The data was obtained via UK Biobank (UKBB), a cohort of approximately 500,000 individuals recruited across England, Wales, and Scotland. All data was taken from electronic medical records.

The outcomes and factors examined in the study were available for 110,584 individuals, regarding hospitalization and death.

The study included COVID-19 data between January 2020 and March 2021.

Among the 110,584 subjects included in this study, the mean age at the beginning of the pandemic was about 68 years. The mean plasma DHA level was 2 percent, and the estimated omega-3 index value was 5.6 percent.

Less than 1 percent of the full cohort was hospitalized with COVID-19, and approximately 20 percent of those hospitalized died from it.

About 15 percent of the 26,597 people included in the dataset who were tested for SARS-CoV-2 infection, tested positive at some point between Jan. 1, 2020, and March 23, 2021.

DHA Levels

The study found an inverse relationship between DHA levels and the risks of testing positive and hospitalization.

Subjects were divided into five equal-sized groups according to their omega-3 levels: Subjects in quintile five—with the highest omega-3 index levels—were 21 percent less likely to test positive than those in quintile one.

A significant inverse relationship between COVID-19 hospitalization and plasma DHA levels was found as well. Quintile five subjects were 26 percent less likely to be hospitalized than those in quintile one.

The inverse relationship between death from COVID-19 and plasma DHA levels was observed in quintiles one through four, but it reversed in quintile five. The researchers said the reason for the reversal in quintile five was unclear, but they said it could be attributed to the small number of deaths.

The percent of individuals experiencing COVID-19 outcomes between Jan. 1, 2020, and March 23, 2021, by quintile of the plasma DHA%. The median estimated Omega-3 Index of each quintile is also shown. Percent testing positive for severe acute respiratory syndrome coronavirus 2 (n = 26,597) (A); percent hospitalized with COVID-19 (n = 110,584) (B); and percent dying with COVID-19 (n = 110,584) (C). UKBB/Harris et al.

Omega-3 Index Levels

The researchers translated DHA levels to omega-3 index values and estimated that omega-3 index values across the five quintiles ranged from 3.5 percent in quintile one to eight percent in quintile five.

The values fit well with the Omega-3 Index risk cut points (originally proposed in 2004 for death from cardiovascular disease) of less than 4 percent (high risk) and greater than 8 percent (low risk) and “imply that these target levels apply to COVID-19 outcomes as well,” according to the researchers.

A worldwide pattern linking higher omega-3 fatty acid intakes with lower death rates with COVID-19 was documented by a study published in 2021, according to the researchers in the statement.

The 2021 study is suggestive of the “potential role of omega-3s EPA and DHA in the prevention of fatal COVID-19 disease,” the researchers said.

Other reports from within the UKBB have described an inverse relationship between reported fish oil supplement use and the risk of death from all causes and incident cardiovascular events, primary liver cancer, inflammatory bowel disease, dementia, and COVID-19.

A limitation of the study the researchers identified was that UKBB does not provide a random selection of individuals across the UK. It is also limited to those who agree to participate, potentially introducing some bias.

The researchers did not report any conflicts of interest.

‘Increasing Consumption of Oily Fish’

The researchers said the study confirmed the findings of previous studies that had found that a low omega-3 status was associated with an increased risk of hospitalization with COVID-19.

The study also provided some evidence for a reduction in the risk of death from COVID-19.

“These results support the practice of increasing consumption of oily fish like salmon or omega-3 fish oil supplements as a potential risk reduction strategy when it comes to COVID-19,” said Harris.