This Summary of Recommendations and Evidence synthesizes the Key Practice Point(s) for each Practice Question (PQ) in this Knowledge Pathway. It is organized by the Nutrition Care Process and contains statements or recommendations that have been graded using either the
PEN or
GRADE approaches to critical appraisal. For additional information on the evidence and references, see the PQs in this
Knowledge Pathway.
As part of the PEN evidence synthesis process, the research in an area is reviewed, as well as various national recommendations. The most recent national recommendations do not typically supersede other evidence, as these recommendations are country-specific. PEN recommendations are based on evidence. Government agencies' recommendations are based on their assessment of the evidence in light of the populations served, risk and their ability to implement and monitor recommendations. These recommendations may not be based on a rigorously conducted systematic review. Country-specific recommendations, as well as PEN’s synthesis of the best evidence, are presented in the Key Practice Point for the PEN user to use at their discretion.
Content
- Dietary Recommendations for Reducing The Risk or Severity of COVID-19 and Managing Symptoms of Post-COVID-19 Syndrome
- Vitamin D
- Dietary Recommendations for the Treatment of Adults with Postural Orthostatic Tachycardia Syndrome (POTS)
- Diet or Supplements to Improve Symptoms in Individuals With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS)
1. Dietary Recommendations for Reducing The Risk or Severity of COVID-19 and Managing Symptoms of Post-COVID-19 Syndrome
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 CA 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 D
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.
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:
Recommendation
Very limited evidence suggests that vitamin D may reduce disease severity in individuals with moderate to severe COVID-19; however, results are limited by small studies with imprecise results. The safety of vitamin D could not be determined due to lack of reporting. Results from ongoing studies are needed prior to providing a recommendation regarding the effectiveness and safety of vitamin D for treating COVID-19.
Evidence Summary
A 2021 Cochrane review of individuals hospitalized with moderate to severe COVID-19 (two RCTs) reported low certainty of evidence that vitamin D may decrease the need for mechanical ventilation (RR 0.52). The effects of vitamin D on mortality and adverse events could not be determined due to inconsistent and imprecise results.
A 2022 systematic review and meta-analyses of systematic reviews identified ten systematic reviews representing three to 13 primary studies of all designs reported that vitamin D2 or D3 (280,000-400,000 IU) was associated with a decreased odds of mortality (OR 0.48), a decreased odds of ICU admission (OR 0.35) and a decreased requirement for mechanical ventilation (OR 0.54). Adverse events were not reported. The results of the review represent very low certainty of evidence as results from RCTs and nonrandomized studies were combined, there was considerable overlapping of primary studies for each outcome, and the studies were small and heterogeneous.
Grade of Evidence C
Remarks
It is difficult to determine if there is an association between vitamin D deficiency and severe COVID-19 as risk factors for both conditions are similar (e.g. poor health, poor diet or a preexisting health condition such as diabetes, liver and kidney disease).
3. Dietary Recommendations for the Treatment of Adults with Postural Orthostatic Tachycardia Syndrome (POTS) Recommendation
Postural orthostatic tachycardia syndrome (POTS) has been reported as a postinfectious complication of COVID-19. Diet is recommended as a first-line treatment for POTS.
For the management of POTS, fair evidence suggests beneficial effects from:
- Increasing sodium intake to 10-12 g salt/day spread throughout the day as added salt or salt tablets. It is recommended to consult with the medical team regarding sodium goals, especially for those with co-morbidities (e.g. hypertension, renal disease).
Limited evidence suggests the following dietary recommendations can improve or stabilize POTS symptoms:
- Consume 2-3 L water/day (starting fluids early in the morning before rising).
- Avoid alcohol, caffeine and dehydration.
- Consume small, frequent meals and lower glycemic carbohydrates.
- Higher reported rates of the following conditions in individuals with POTS suggest screening and treating for the following: digestive symptoms (including irritable bowel syndrome), celiac disease, eating disorders and nutrient deficiencies (including iron-deficiency anemia).
Evidence Summary
Recommendations are based on empirical evidence reported in guidelines and narrative reviews
Grade of Evidence C, except for the salt recommendation, which was based on a randomized crossover study that found that a high sodium compared to a low sodium diet (6.9 versus 230 mg/day) was helpful in improving POTS but did not completely normalize symptoms
Grade of Evidence B.
4. Diet or Supplements to Improve Symptoms in Individuals With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS)
Recommendation
There is insufficient evidence to support the effectiveness of any diet or nutritional supplement for managing symptoms of ME/CFS.
The 2021 NICE guidelines include general dietary guidance based on managing complications of ME/CFS related to nausea; dysphagia; and difficulties buying, preparing and eating food; and referring individuals to a dietitian who present with malnutrition or a restrictive diet.
A 2017 consensus document for management of ME/CFS in young individuals suggests eliminating caffeine beverages in the late afternoon and evening as caffeine can cause tachycardia and agitation and exacerbate sleep problems. Additional suggestions include consuming regular, small meals and snacks and avoiding large amounts of fluids with meals to address symptoms of anorexia, nausea and bloating.
Evidence Summary
A 2017 systematic review and 2021 follow-up review by the same investigative group examining dietary and nutritional interventions for treating ME/CFS identified 14 interventions described in generally single, small, short-term studies of heterogeneous design. Although some studies reported modest improvements in some ME/CFS symptoms with nutrition supplements (i.e. NADH, ubiquinol-10, polyphenol, probiotics, pollen extract), the authors concluded that study limitations provided insufficient evidence for using nutritional supplements or modified diets to improve symptoms of ME/CFS.
Grade of Evidence D
Remarks
ME/CFS has also been defined as systemic exertion intolerance disease. Symptoms include debilitating fatigue, post-exertion malaise and unrefreshing sleep, combined with orthostatic intolerance or cognitive decline that lasts for six months or more. The etiology of ME/CFS is unknown but has been attributed to infectious illness, stress and environmental toxins. The characteristics of long COVID suggest an overlap of many symptoms with ME/CFS.