Can the Mediterranean Diet Protect You from COVID-19?

Ceria Halim, MD

Credit: LinkedIn

High adherence to the Mediterranean diet—an eating plan known for its immunomodulatory and anti-inflammatory benefits—was shown to be a protective factor against COVID-19, according to a recent study published in Plos One. However, the benefits against COVID-19-related symptoms and their severity were unclear.

“Inflammation has been widely recognized as a critical factor in the development and the degree of severity in COVID-19,” wrote lead investigator Ceria Halim, MD, associated with the Department of Center of Evidence Based Medicine, Faculty of Medicine, Universitas Sumatera Utara, in Indonesia. “After the initial innate immune response, a potent uncontrolled inflammatory response called cytokine storm may follow. Cytokine storm, characterized by excessive inflammation caused by high levels of cytokines, particularly interleukin (IL)-6, IL-1, and tumor necrosis factor (TNF)-α, can lead to advanced disease, multiorgan involvement, and serious consequences.”

The Mediterranean diet consists of plenty of fruits, vegetables, nuts, legumes and olive oil, all of which are well-known antioxidants. This diet plan has been shown to lower the expression of pro-inflammatory molecules, reduce overall systemic inflammatory status, and may benefit patients who are diagnosed with persistent low-grade inflammatory conditions. Prior research has also shown a possible link between diet and viral infections. Therefore, investigators were interested in examining the protective effects of a Mediterranean diet regarding COVID-19 infection.

To assess any links between the Mediterranean diet and COVID-19, investigators conducted a systematic review in August 2023 using data from Pubmed, Proquest and Google Scholar. Eligible studies were written in English, included human participants, and reported the association between the Mediterranean diet and COVID-19 infection risk, COVID-19 symptoms and COVID-19 severity. The risk of bias was determined using the Newcastle Ottawa Scale (NOS).

Of the 325 studies initially identified, six observational studies published between 2020 and 2023 were included, comprised of 55,489 patients. Diet adherence was evaluated using food frequency questionnaires (FFQ), although the scoring system varied across studies. The ratio of monosaturated to saturated fat was an important component in the diet score; however, four studies replaced the monosaturated fat to saturated fat ratio with olive oil intake because the ratio does not correspond to a specific food and olive oil is the main source of monosaturated fat in this particular diet plan.

Four of the six studies reported a significant correlation between an increased adherence to the Mediterranean diet and reduced COVID-19 risk, although one study observed a non-significant association. Although one study observed a significant association between higher adherence to the diet and COVID-19 symptoms, three studies showed a non-significant adherence. One study reported patients who had higher adherence to the Mediterranean diet had a reduced likelihood of developing severe COVID-19, as determined using self-reported hospitalization information. However, two other studies demonstrated inconclusive findings.

Investigators noted using self-administrated FFQs may have introduced recall and estimation biases. Additionally, the small number of studies and lack of a meta-analysis did not allow for precisely measured effects. However, investigators mentioned this study is the first to specifically investigate the link between COVID-19 risk, severity and symptoms and the Mediterranean diet. Further, the study selection and bias assessment process was performed by multiple reviews to minimize any potential bias.

“The results of the present study may shed some light on additional benefits of Mediterranean diet against COVID-19,” investigators concluded. “The findings also suggest that specific food groups in the Mediterranean diet may be more important in reducing COVID-19 odds. More studies should be conducted before definitive conclusions can be drawn.”