Plant-based diets, pescatarian diets and COVID-19 severity: a population-based case–control study in six countries
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  • Published on:
    A strange definition of a low carbohydrate diet

    The food consumption of the subjects declaring themselves to be on a "Low carbohydrate, high protein" diet is hidden in the supplementary materials Table 2, so readers may not notice that there is no significant difference between the consumption of potato, bread, fruit, fruit juice, SSBs etc between this group and those declaring a different diet. P >0.5

    Only academic researchers could contemplate a low carb diet with bread, potato, fruit and fruit juice at this same level as the other dietary choice. Nobody eating a low carbohydrate diet would recognise this pattern.

    Conflict of Interest:
    None declared.
  • Published on:
    Diet and COVID-19 clinical manifestation – Methodological Inquiry and Prospects of Gut Microbiome
    • Ki Kwan Hui, Preclinical Medical Student Faculty of Medicine, The Chinese University of Hong Kong

    Dear Editor,
    I read with interest the potential influence of plant-based and/or pescatarian diets on the clinical manifestation of COVID-19 by Kim and his colleagues [1], which has gained media traction over the weeks.
    The conclusion of this study is unsurprising. However, when reviewing tables with scrutiny, one would see that nearly none of the values reached statistical significance. First, the incidence of COVID-19 lacks association with any diet, but the trend of protective effect has strengthened when solely analysing the 298 test-positive (either PCR/antibody) individuals. Second, the authors demonstrated that plant-based diets, and plant-based or pescatarian diets might reduce COVID-19 severity (in Figure 1 of article). However, their statistical significances are lost when only comparing severity among 298 test-positive individuals (in Supplemental Table 5), partly because COVID-19 PCR/antibody test results are confounding the relationship between diets and COVID-19 severity: COVID-19 test results (positive/negative) are “marginally” associated with plant-based diets (exposure) (in Supplemental Table 5), and are associated with COVID-19 severity (outcome) (n = 483, using information from Table 1, we can compute an χ² ~ 15.74, p < 0.001 with degree of freedom = 1). Although authors decided to classify “symptomatic” individuals with negative test results as “cases”, since negative antibody test does not rule out COVID-19, infection status can unquesti...

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    Conflict of Interest:
    None declared.
  • Published on:
    A misleading and potentially dangerous paper

    This paper is based on an on-line survey of 2,884 healthcare workers from 6 countries. All data were filled in on-line. All data were self-reported. Participants were asked to choose which of 11 diets (including ‘other’ or ‘none of the above’) they had followed over the year before the COVID-19 outbreak. All diets were self-reported.

    The main diets examined in the study were i) ‘whole food, plant-based’ diets ii) ‘whole food, plant-based or pescatarian’ combined and iii) ‘low carbohydrate’ or ‘high protein’ diets combined. These three diet groups comprised just 27% of participants. Most people and most diets were not examined in this study (other than to be grouped as “people not following the diet in question”). Paleo and keto diets were not included in the low carb or high protein group. The ‘whole food, plant-based’ diet was remarkably like, but apparently better than, the ‘Mediterranean’ diet.

    There was no vegan diet in this study. The vegetarian diet was combined with the ‘whole food, plant-based’ diet, and thus not even a vegetarian diet was studied separately. Both the ‘plant-based’ diets and non-plant-based diets included eggs, dairy, poultry, red and processed meats, fish and seafood. The ‘plant-based’, ‘plant-based or pescatarian’ and the ‘low carb, high protein’ groups all had higher self-reported intake of legumes and nuts than people not following these diets.

    The headline claims were i) that participants who reported following ‘plant-base...

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    Conflict of Interest:
    I write and publish content in the field of diet and health.
  • Published on:
    Plant-Based Panacea? Not Really.

    Response to: Plant-based diets, pescatarian diets and COVID-19 severity: a population-based case–control study in six countries(1; 2)

    In their paper “Plant-based diets, pescatarian diets and COVID-19 severity: a population-based case–control study in six countries”, Kim H, Rebholz CM, Hegde S, et al argue that dietary habits may play an important role in Covid-19 infection, duration, and severity of the illness. In support, they show a data analysis of what nutrition those in their dataset ate and used statistical analysis to show that there is a significant causal effect of what the sick have eaten to the outcome of their disease.
    There are a few important point to be noted:
    1) Using a statistical model that specifically requires certain rules to be met before conclusion is invalidated if the conclusion is used without meeting those rules. I am referring to the Bradford Hill Criteria(3), which was completely ignored.
    2) The use and consideration of the P value for this type of data analysis(4) is questionable.
    3) While there are many studies showing association of Covid-19 disease outcome and the metabolic health of the individual(5; 6; 7), there have not been clinical-trial-based studies showing that a plant-based nutrition improves metabolic health.
    4) The use of food surveys for data collection from memory, which are riddled with errors(8), is questionable.
    The Bradford Hill Criteria specifically requires that the statistics u...

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    Conflict of Interest:
    None declared.