Introduction: Long COVID is a term that encompasses a range of signs, symptoms, and sequalae that continue or develop after an acute COVID-19 infection. The lack of early recognition of the condition contributed to delays in identifying factors that may contribute toward its development and prevention. The aim of this study was to scope the available literature to identify potential nutritional interventions to support people with symptoms associated with long COVID. Methods: This study was designed as a systematic scoping review of the literature (registration PROSPERO CRD42022306051). Studies with participants aged 18 years or older, with long COVID and who underwent a nutritional intervention were included in the review. Results: A total of 285 citations were initially identified, with five papers eligible for inclusion: two were pilot studies of nutritional supplements in the community, and three were nutritional interventions as part of inpatient or outpatient multidisciplinary rehabilitation programs. There were two broad categories of interventions: those that focused on compositions of nutrients (including micronutrients such as vitamin and mineral supplements) and those that were incorporated as part of multidisciplinary rehabilitation programs. Nutrients included in more than one study were multiple B group vitamins, vitamin C, vitamin D, and acetyl-l-carnitine. Discussion: Two studies trialed nutritional supplements for long COVID in community samples. Although these initial reports were positive, they are based on poorly designed studies and therefore cannot provide conclusive evidence. Nutritional rehabilitation was an important aspect of recovery from severe inflammation, malnutrition, and sarcopenia in hospital rehabilitation programs. Current gaps in the literature include a potential role for anti-inflammatory nutrients such as the omega 3 fatty acids, which are currently undergoing clinical trials, glutathione-boosting treatments such as N-acetylcysteine, alpha-lipoic acid, or liposomal glutathione in long COVID, and a possible adjunctive role for anti-inflammatory dietary interventions. This review provides preliminary evidence that nutritional interventions may be an important part of a rehabilitation program for people with severe long COVID symptomatology, including severe inflammation, malnutrition, and sarcopenia. For those in the general population with long COVID symptoms, the role of specific nutrients has not yet been studied well enough to recommend any particular nutrient or dietary intervention as a treatment or adjunctive treatment. Clinical trials of single nutrients are currently being conducted, and future systematic reviews could focus on single nutrient or dietary interventions to identify their nuanced mechanisms of action. Further clinical studies incorporating complex nutritional interventions are also warranted to strengthen the evidence base for using nutrition as a useful adjunctive treatment for people living with long COVID.
Keywords: chronic fatigue; dietary rehabilitation; long COVID; nutritional intervention; nutritional supplementation; post-acute SARS-CoV-2; sarcopenia.