The Role of Nutrition in COVID-19 Susceptibility and Severity of Disease: A Systematic Review.

BACKGROUND: Many nutrients have powerful immunomodulatory actions with the potential to alter susceptibility to coronavirus disease 2019 (COVID-19) infection, progression to symptoms, likelihood of severe disease, and survival. OBJECTIVE: The aim was to review the latest evidence on how malnutrition across all its forms (under- and overnutrition and micronutrient status) may influence both susceptibility to, and progression of, COVID-19. METHODS: We synthesized information on 13 nutrition-related components and their potential interactions with COVID-19: overweight, obesity, and diabetes; protein-energy malnutrition; anemia; vitamins A, C, D, and E; PUFAs; iron; selenium; zinc; antioxidants; and nutritional support. For each section we provide: 1) a landscape review of pertinent material; 2) a systematic search of the literature in PubMed and EMBASE databases, including a wide range of preprint servers; and 3) a screen of 6 clinical trial registries. All original research was considered, without restriction to study design, and included if it covered: 1) severe acute respiratory syndrome coronavirus (CoV) 2 (SARS-CoV-2), Middle East respiratory syndrome CoV (MERS-CoV), or SARS-CoV viruses and 2) disease susceptibility or 3) disease progression, and 4) the nutritional component of interest. Searches took place between 16 May and 11 August 2020. RESULTS: Across the 13 searches, 2732 articles from PubMed and EMBASE, 4164 articles from the preprint servers, and 433 trials were returned. In the final narrative synthesis, we include 22 published articles, 38 preprint articles, and 79 trials. CONCLUSIONS: Currently there is limited evidence that high-dose supplements of micronutrients will either prevent severe disease or speed up recovery. However, results of clinical trials are eagerly awaited. Given the known impacts of all forms of malnutrition on the immune system, public health strategies to reduce micronutrient deficiencies and undernutrition remain of critical importance. Furthermore, there is strong evidence that prevention of obesity and type 2 diabetes will reduce the risk of serious COVID-19 outcomes. This review is registered at PROSPERO as CRD42020186194.

Climate change mitigation through dietary change: a systematic review of empirical and modelling studies on the environmental footprints and health effects of 'sustainable diets'.

The adoption of healthy diets with low environmental impact has been widely promoted as an important climate change mitigation strategy. Typically, these diets are high in plant-sourced and low in animal-sourced and processed foods. Despite the fact that their environmental impacts vary, they are often referred to as 'sustainable diets'. Here we systematically review the available published evidence on the effect of 'sustainable diets' on environmental footprints and human health. Eight databases (OvidSP-Medline, OvidSP-Embase, EBSCO-GreenFILE, Web of Science Core Collection, Scopus, OvidSP-CAB-Abstracts, OvidSP-AGRIS, and OvidSP-Global Health) were searched to identify literature (published 1999-2019) reporting health effects and environmental footprints of 'sustainable diets'. Available evidence was mapped and pooled analysis was conducted by unique combinations of diet pattern, health and environmental outcome. Eighteen studies (412 measurements) met our inclusion criteria, distinguishing twelve non-mutually exclusive sustainable diet patterns, six environmental outcomes, and seven health outcomes. In 87% of measurements (n = 151) positive health outcomes were reported from 'sustainable diets' (average relative health improvement: 4.09% [95% CI -0.10-8.29]) when comparing 'sustainable diets' to current/baseline consumption patterns. Greenhouse gas emissions associated with 'sustainable diets' were on average 25.8%[95%CI -27.0 to -14.6] lower than current/baseline consumption patterns, with vegan diets reporting the largest reduction in GHG-emissions (-70.3% [95% CI: -90.2 to -50.4]), however, water use was frequently reported to be higher than current/baseline diets. Multiple benefits for both health and the environment were reported in the majority (n = 315[76%]) of measurements. We identified consistent evidence of both positive health effects and reduced environmental footprints accruing from 'sustainable diets'. The notable exception of increased water use associated with 'sustainable diets' identifies that co-benefits are not universal and some trade-offs are likely. When carefully designed, evidence-based, and adapted to contextual factors, dietary change could play a pivotal role in climate change mitigation, sustainable food systems, and future population health.

Climate change mitigation in food systems: the environmental and health impacts of shifting towards sustainable diets, a systematic review protocol.

Food systems contribute greatly to global climate change due to their substantial contributions to greenhouse gas emissions, water use, and resource allocation. In addition, current food systems fail to deliver healthy and sustainable foods for all, with obesity as well as undernourishment remaining a pertinent global issue. Mounting pressures such as population growth and urbanisation urge rapid and transformational adaptations in food systems to sustainably feed a growing population. Sustainable diets have been promoted as a potential climate change mitigation strategy, and are characterized by high plant based foods and reduced animal-sourced and processed foods. While the evidence base on the potential health and environmental impacts of shifts towards sustainable diets has been growing rapidly over the past decade, there has been no recent synthesis of the evidence surrounding the health and climate mitigation benefits of sustainable consumption patterns. This systematic review will synthesize the evidence of both empirical and modelling studies assessing the direct health outcomes (such as all-cause mortality and body mass index) as well as environmental impacts (greenhouse gas emissions, land use, water use etc.) of shifts towards sustainable diets. Eight literature databases will be searched to identify studies published between 1999-2019 that report both health and environmental outcomes of sustainable diets. Evidence will be mapped and subsequently analysed based on the comparability of results and reported outcomes.