Though the world has mostly left the spectre of Covid-19 behind, scientists continue to study the data in order to learn all they can from the experience of this sudden new worldwide infection. This has led to the publishing of a new study that examined the benefits of eating plants for dealing with a threat like Covid-19.
The prospective observational study from January, 2024 (1)
It involved 702 adult volunteers who filled out an online questionnaire regarding their sociodemographics, lifestyle, past medical history, eating patterns and eating habits. They were then placed into three groups.
- 1 – Omnivore – 424 participants who regularly consumed food of animal origin along with plant-sourced food.
- 2 – Vegetarian – 191 participants who were primarily plant-based eaters. This group included vegans (who eat only plant-sourced foods) and lacto-ovo-vegetarians (who eat mostly plant-sourced foods along with some eggs and/or dairy products but no meat, fish or shellfish)
- 3 – Flexitarian (including Semi-Vegetarian) – 87 participants who consumed a mix of animal-sourced food (three times a week or less) and plant-sourced foods.
At the start of the study, participants reported on their physical activity level, their weight and height (from which their body mass index was calculated). Their history of Covid-19 disease was confirmed by medical diagnosis. Factors related to their exposure to Covid-19 were also taken into account including vaccination status and the severity of any Covid-19 disease that they may have experienced.
Results of the study are as follows;
- 330 participants reported a previous diagnosis of Covid-19 with 224 having mild symptoms and 106 with moderate to severe symptoms
- The Omnivore group had a significantly higher incidence of Covid-19 at 51.6% compared to the 39.9% incidence of Covid-19 in the Vegetarian group.
- The Omnivore group had a higher rate of moderate to severe Covid-19 symptoms at 17.7% compared with the Vegetarian group at 11.2%
- Individuals in the Vegetarian group had a lower incidence of COVID-19 than the Omnivore or Flexitarian group even after adjusting for several confounding variables (physical activity, BMI and pre-existing conditions).
- Duration of Covid-19 symptoms did not differ between the three groups.
- Among the three dietary pattern groups, Vegetarians had higher consumption of cereals, fruits, vegetables, nuts, seeds and vegetable oils and a lower consumption of dairy and eggs. Omnivores had higher consumption of meats than the other dietary groups.
Earlier studies on dietary protection from Covid-19
Previous studies hypothesized that dietary habits might play an important role in COVID-19 infection. For instance, populations in Okinawa, Japan and in Sub-Saharan Africa eat predominantly a plant-based diet and their mortality from Covid-19 was low. Both populations also have low incidence of chronic diseases in general, including metabolic syndrome, a risk factor for heart disease, stroke and diabetes. (1,2). On the other hand, the consumption of a diet rich in animal-sourced foods, with high amounts of saturated fats and ultra-processed foods, is known to result in more risk factors for the complications of Covid-19 in adults and elderly people. (1)
In 2021, data from 529,571 participants of the smartphone-based COVID-19 Symptom Study was gathered. Diet quality was assessed using a healthful Plant-Based Diet Score which emphasizes healthy plant foods such as fruits and vegetables. Results showed that eating a high-quality diet was associated with 9% lower risk of contracting Covid-19 and a 41% lower risk of suffering severe Covid-19. This association seems to be particularly evident in individuals living in areas of higher socioeconomic deprivation who, simply by living in a deprived area, suffer increased risks of harms from factors such as disease, smoking, drinking, lack of physical activity and psychosocial stresses. (3,4)
Also from 2021, health-care workers from six countries (France, Germany, Italy, Spain, UK and USA) provided their demographics, dietary information, and Covid-19 outcomes (5) . Among 568 cases of Covid-19, 138 individuals had moderate-to-severe Covid-19 and 430 individuals had very mild to mild Covid-19. After adjustment for confounding factors, participants who reported following plant-based diets had 73% lower risk of moderate-to-severe Covid-19 compared to participants who did not follow a plant-based diet. Those reporting following pescatarian diets had 59% lower risk of moderate-to-severe Covid-19. Those following low carbohydrate, high protein diets had an almost 4-fold increased risk of moderate-to-severe Covid-19 compared with participants following plant-based diets.
In 2022 a cross-sectional study looked at the impact of dietary fiber, vegetables and fruits on the risk of severe Covid-19 (6). The study included 250 Covid-19 patients aged 18 to 65 years who had recovered from the disease. The dietary intake of the participants was assessed using an online 168-item food frequency questionnaire. The National Institutes of Health (NIH) COVID-19 Treatment Guideline was used to determine the patients’ COVID-19 severity. Participants completed a general questionnaire detailing their Covid-19 symptoms including fever, weakness, shivering, muscle pain, shortness of breath, cough, sore throat, nausea and vomiting. Data was also collected on their demographic characteristics, height, weight, physical activity, supplement intake, duration of convalescence, and the use of corticosteroids or antiviral medication during Covid-19 infection. Measurement of C-reactive protein, a marker of inflammation, was taken from hospital records.
Results from this study showed:
- Patients with higher consumption of fruits had 72% lower odds of contracting severe Covid-19.
- Patients with higher consumption of vegetables had 67% lower odds of contracting severe Covid-19.
- Patients with higher consumption of dietary fiber had 75% lower odds of contracting severe Covid-19.
- In addition, all of these patients had shorter periods of hospitalization and convalescence, lower serum C-reactive protein and reduced risk of developing Covid-19 symptoms such as sore throat, nausea and vomiting, shortness of breath, muscle aching, cough, weakness, fever and chills.
To sum up, patients with a higher intake of fruits, vegetables, and dietary fiber had a decreased likelihood of developing a severe form of COVID-19 and its related symptoms. In addition, the need for corticosteroids and antiviral medications, the length of hospitalization, and convalescence, and also the levels of the inflammatory marker, CRP, were significantly lower in patients who consumed more fruits vegetables, and fiber.
Researchers from this study pointed out that diets rich in vegetables, fruits and fiber have undergone a lengthy history of investigations elucidating their many health benefits. Plant-based diets, such as the Mediterranean diet, which are high in these dietary elements, are well known for their anti-inflammatory and antioxidant potential, as well as their benefits for optimal immune activity. Such diets are routinely recommended as a preventive strategy in the development of cardiometabolic diseases, including obesity, cardiovascular disease, type 2 diabetes mellitus, malignancies, asthma, allergies, and respiratory tract infections. On the other hand, it has been demonstrated that the Western diet, which is high in fats and refined carbohydrates and low in fiber and antioxidants, is pro-inflammatory, producing reactive oxygen species and hindering the adaptive immune system which is important for protection against threats such as viral infections. Plant-based diets are also rich in micronutrients and bioactive natural compounds, such as vitamins A, C, D, and/or E, minerals (iron, selenium, and zinc), probiotics, fibers, polyphenols, and omega-3 polyunsaturated fatty acids which enhance the immune system’s response.
Final Message
Our world’s experience with Covid-19 should be put to good use in the future as, inevitably, other dangerous infections rear their ugly heads. The benefits of eating plants on our general health and on our immune systems can be a powerful weapon against future infections. But they’ll do us little good if we wait until another threat is staring us in the face. Now is the time to increase your intake of plant-sourced foods both to optimize your present health and to prepare your body for the inexorable onslaught of the next menacing microrganism .
SOURCES:
1 Acosta-Navarro, J.C., Dias, L.F., de Gouveia, L.A.G., Ferreira, E.P., de Oliveira, M.V.P.F., Marin, F.A., Oliveira, J.V.C., da Silva, A.C., Silva, I.L., Freitas, F.O., Soares, P.R. Vegetarian and plant-based diets associated with lower incidence of COVID-19. BMJ Nutr Prev Health. 2024 Jan 9;7(1):4-13. Doi: 10.1136/bmjnph-2023-000629. PMID: 38966114; PMCID: PMC11221288.
2 https://www.mayoclinic.org/diseases-conditions/metabolic-syndrome/symptoms-causes/syc-20351916
3 Merino, J., Joshi, A.D., Nguyen, L.H., Leeming, E.R., Mazidi, M., Drew, D.A., Gibson, R., Graham, M.S., Lo, C.H., Capdevila, J., Murray, B., Hu, C., Selvachandran, S., Hammers, A, Bhupathiraju, S.N., Sharma, S.V., Sudre, C., Astley, C.M., Chavarro, J.E., Kwon, S., Ma, W., Menni, C., Willett, W.C., Ourselin, S., Steves, C.J., Wolf, J., Franks, P.W., Spector, T.D., Berry, S., Chan, A.T. Diet quality and risk and severity of COVID-19: a prospective cohort study. Gut. 2021 Nov;70(11):2096-2104. Doi: 10.1136/gutjnl-2021-325353. Epub 2021 Sep 6. PMID: 34489306; PMCID: PMC8500931.
4 Foster, Hamish M.E., et al. The effect of socioeconomic deprivation on the association between an extended measurement of unhealthy lifestyle factors and health outcomes: a prospective analysis of the UK Biobank cohort. The Lancet Public Health; 3(12): e576 – e585.
5 Kim, H., Rebholz, C.M., Hegde, S., et al. Plant-based diets, pescatarian diets and COVID-19 severity: a population-based case–control study in six countries BMJ Nutrition, Prevention & Health 2021;4: Doi: 10.1136/bmjnph-2021-000272.
6 Tadbir, Vajargah K., Zargarzadeh, N., Ebrahimzadeh, A., Mousavi, S.M., Mobasheran, P., Mokhtari, P., Rahban, H., Găman, M.A., Akhgarjand, C., Taghizadeh, M., Milajerdi, A. Association of fruits, vegetables, and fiber intake with COVID-19 severity and symptoms in hospitalized patients: A cross-sectional study. Front Nutr. 2022 Sep 29;9:934568. Doi: 10.3389/fnut.2022.934568. PMID: 36245547; PMCID: PMC9557193.