Key Practice Point #1
Recommendation
Limited research suggests that consuming plant-based and Mediterranean dietary patterns may reduce the risk or severity of COVID-19 infection. No evidence was identified examining the effects of these dietary patterns on symptoms related to long COVID.
A low histamine diet is not recommended for managing the symptoms of long COVID due to a lack of evidence and the challenges of eliminating dietary histamine.
Nutritional considerations in individuals with post-COVID-19 syndrome are based on nutritional deficiencies to support recovery. Little clinical research has been conducted on individuals with long COVID and it is derived from indirect evidence in other populations:
- Oral nutritional supplements can support improved energy and nutrient intake in individuals with malnutrition and early satiety.
- Higher protein (15-30 g/meal) may improve sarcopenia.
- Adequate hydration (2.5-3 L/day) is recommended to prevent dehydration.
- Individuals living with obesity may be at greater risk for worse outcomes after acute infections. Weight loss may be beneficial; however, the effects of interventions to modify body weight on symptoms of COVID-19 have not been studied.
Evidence Summary
A 2023 systematic review and meta-analysis identified that "high quality" dietary patterns (including plant-based and Mediterranean diet patterns) were associated with a reduced risk of COVID-19 infection (RR 0.72) and decreased hospitalization (RR 0.38). Subgroup analysis suggested plant-based diets reduced the risk of infection by 50% and Mediterranean diet patterns reduced the risk of infection by 22%. The results are limited by high heterogeneity among studies and that infection rates were assessed during the first wave of the pandemic only.
Grade of Evidence C
A 2022 narrative review examining the role of nutrients on features of long COVID identified that:
- Adequate energy and protein intake was needed to treat sarcopenia; however, individuals living with obesity (not defined) may be at a risk of worse outcomes after acute infection.
Grade of Evidence C - No studies were identified that examined the effects of interventions to modify body weight on symptoms of long COVID.
Grade of Evidence D - Adequate hydration (2.5-3 L/day) was recommended to prevent dehydration.
Grade of Evidence C. - A Mediterranean diet pattern may be beneficial as it contains bioactive compounds with anti-inflammatory and antioxidant effects. The recommendations in the review are limited as they were largely obtained from studies treating diseases with similar outcomes, but not post-COVID-19 syndrome.
No clinical research has examined the effects of dietary patterns on the symptoms related to long COVID.
Grade of Evidence DNo published studies were identified that examined the effects of a low histamine diet on the risk of COVID-19 infection or the symptoms of long COVID.
Grade of Evidence D
Remarks
Post-COVID-19 condition can affect anyone exposed to SARS-CoV-2. It is defined as continuing or the development of symptoms three months after the initial infection that lasts for at least two months. Over 200 different symptoms have been reported; common symptoms include: fatigue, shortness of breath and cognitive dysfunction.
It has been suggested that the increased inflammatory responses observed with long COVID may be due to histamine release by dysfunctional immune cells. In contrast, plant-based and Mediterranean dietary patterns are examples of anti-inflammatory diets that have been associated with reduced inflammatory markers.
See Additional Content:
Evidence
- A systematic review (searched to September 2022) examined the effects of "high quality" dietary patterns on the risk and severity of COVID-19 (1). The review followed PRISMA reporting standards. Of the five included studies (three cohorts and two cross-sectional studies, n= 4,023,663 ), three examined a plant-based diet and two examined a Mediterranean diet. Diet was assessed using self-reported questionnaire or food frequency questionnaires or Mediterranean Diet Scores collected from one to 10 years before the pandemic. The quality of studies (assessed with Newcastle-Ottawa Scale) was moderate to high quality. Pooled analyses of all studies found that a high quality dietary pattern was associated with decreased risk of COVID-19 infection (RR 0.72, 95%CI 0.64 to 0.81, I2=85%) and decreased hospitalization (RR 0.38, 95%CI 0.20 to 0.72, I2=95%). The high heterogeneity was attributed to different study designs, with cross-sectional studies showing an exaggerated effect. Subgroup analysis by the type of diet observed that a plant-based diet was associated with a 50% (95%CI 30 to 65%, I2=97%) reduced risk of COVID-19 infection and that a Mediterranean diet pattern was associated with a 22% (95%CI 12 to 31%, I2=66%) reduced risk of infection. The authors identified the limitations of the review including that dietary patterns were assessed in a range of periods (one to 10 years) before the pandemic and infection rates were assessed from the first wave only and did not include ICU admission and mortality rates (1). Furthermore, the high heterogeneity among the studies could not be explained even in subgroup analysis by study design.
- A 2022 narrative review examined the role of nutrients on features of post-COVID-19 syndrome (2). A search of PubMed included all study types in adults published in English; quality assessment of the studies was not conducted. Nutrition-related issues associated with post-COVID-19 syndrome identified included malnutrition, loss of fat-free mass, low grade inflammation and persistent symptoms including impaired functional status (e.g. fatigue, muscle weakness), dysphagia (associated with intubation), loss of appetite and alterations in taste and smell. The following nutrient and dietary factors were identified to correct nutritional deficiencies and support recovery:
- Energy: Observational studies suggest that individuals may present with early satiety. Based on a consensus statement from ESPEN, oral nutritional supplements can be considered to increase energy intake. In contrast, individuals living with obesity are at risk of worse outcomes after acute infections and weight loss may be beneficial to prevent viral infections and subclinical inflammation. No studies were identified that examined the effects of interventions to modify body weight on symptoms of long COVID.
- Macronutrients: Higher protein intake (15-30 g protein/meal) was suggested to improve sarcopenia and exert a possible anti-inflammatory effect; however, no studies were included examining outcomes in patients with long COVID. Omega-3 fatty acids (1.5-3/g day) and extra virgin olive oil were suggested to improve inflammation; however, no studies were included examining outcomes in patients with COVID-19.
- Mediterranean Diet: A Mediterranean diet was promoted as it is characterized by containing bioactive compounds with anti-inflammatory and antioxidant effects (2). Observational studies (some of which were included in the aforementioned review (1)) were identified highlighting an association between an adherence to a Mediterranean diet and a reduced risk of COVID-19 infection, but no studies were identified that examined the effect of this dietary pattern on symptoms of long COVID (2).
- Hydration: Adequate hydration (2.5-3 L/day fluids) was recommended based on studies to prevent dehydration in older adults.
Based on the range of symptoms, the authors suggested individual assessment of nutritional status and tailoring diet recommendations based on identified nutrient deficiencies (2). The recommendations in the review are limited as they were largely obtained from studies treating diseases with similar outcomes, but not post-COVID-19 syndrome.
- A low histamine diet involves restricting food and drinks considered to be high in histamine for several weeks (3); however, there is a lack of consensus on which foods are high in histamine (4). No published studies were identified that examined the effects of a low histamine diet on the risk of COVID-19 infection or the symptoms of long COVID.
Comments
Post-COVID-19 condition can affect anyone exposed to SARS-CoV-2 (5). It is defined as continuing or the development of symptoms three months after the initial infection that lasts for at least two months. Over 200 different symptoms have been reported; common symptoms include: fatigue, shortness of breath and cognitive dysfunction.
Rationale
Some foods can promote inflammatory markers in the body while other food components may have anti-inflammatory effects (6). Plant-based and Mediterranean dietary patterns are examples of anti-inflammatory diets that have been associated with reduced inflammatory markers and reduced risk of chronic disease outcomes.
It has been suggested that the increased inflammatory responses observed with long COVID may be due to histamine release by dysfunctional immune cells (7).
References
- Rahmati M, Fatemi R, Yon DK, Lee SW, Koyanagi A, Il Shin J, Smith L. The effect of adherence to high-quality dietary pattern on COVID-19 outcomes: A systematic review and meta-analysis. J Med Virol. 2023 Jan;95(1):e28298. doi: 10.1002/jmv.28298. Epub 2022 Nov 18. PMID: 36367218; PMCID: PMC9877891. Abstract available from: https://pubmed.ncbi.nlm.nih.gov/36367218/
- Barrea L, Grant WB, Frias-Toral E, Vetrani C, Verde L, de Alteriis G, Docimo A, Savastano S, Colao A, Muscogiuri G. Dietary Recommendations for Post-COVID-19 Syndrome. Nutrients. 2022 Mar 20;14(6):1305. doi: 10.3390/nu14061305. PMID: 35334962; PMCID: PMC8954128. Abstract available from: https://pubmed.ncbi.nlm.nih.gov/35334962/
- Sánchez-Pérez S, Comas-Basté O, Veciana-Nogués MT, Latorre-Moratalla ML, Vidal-Carou MC. Low-Histamine Diets: Is the Exclusion of Foods Justified by Their Histamine Content? Nutrients. 2021 Apr 21;13(5):1395. doi: 10.3390/nu13051395. PMID: 33919293; PMCID: PMC8143338. Abstract available from: https://pubmed.ncbi.nlm.nih.gov/33919293/
- Comas-Basté O, Sánchez-Pérez S, Veciana-Nogués MT, Latorre-Moratalla M, Vidal-Carou MDC. Histamine Intolerance: The Current State of the Art. Biomolecules. 2020 Aug 14;10(8):1181. doi: 10.3390/biom10081181. PMID: 32824107; PMCID: PMC7463562. Abstract available from: https://pubmed.ncbi.nlm.nih.gov/32824107/
- World Health Organization. Post COVID-19 condition (Long COVID). 2022 Dec 7. Available from: https://www.who.int/europe/news-room/fact-sheets/item/post-covid-19-condition
- Marx W, Veronese N, Kelly JT, Smith L, Hockey M, Collins S, Trakman GL, Hoare E, Teasdale SB, Wade A, Lane M, Aslam H, Davis JA, O'Neil A, Shivappa N, Hebert JR, Blekkenhorst LC, Berk M, Segasby T, Jacka F. The Dietary Inflammatory Index and Human Health: An Umbrella Review of Meta-Analyses of Observational Studies. Adv Nutr. 2021 Oct 1;12(5):1681-1690. doi: 10.1093/advances/nmab037. PMID: 33873204; PMCID: PMC8483957. Abstract available from: https://pubmed.ncbi.nlm.nih.gov/33873204/
- Obara I, Fernandes JPS, Tiligada E. Histamine research advancements in the second year of the COVID-19 pandemic: report of the European Histamine Research Society (EHRS). Inflamm Res. 2022 Aug;71(7-8):995-998. doi: 10.1007/s00011-022-01589-9. Epub 2022 Jun 1. PMID: 35648157; PMCID: PMC9158306. Abstract available from: https://pubmed.ncbi.nlm.nih.gov/35648157/