Plant-based diets, pescatarian diets and COVID-19 severity: a population-based case–control study in six countries

Hyunju Kim; Casey M Rebholz; Sheila Hegde; Christine LaFiura; Madhunika Raghavan; John F Lloyd; Susan Cheng; Sara B Seidelmann

doi:10.1136/bmjnph-2021-000272

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Plant-based diets, pescatarian diets and COVID-19 severity: a population-based case–control study in six countries

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A misleading and potentially dangerous paper
Zoe Harcombe
Published on: 3 November 2023
A strange definition of a low carbohydrate diet
Philip D Thompson
Published on: 30 August 2021
Diet and COVID-19 clinical manifestation – Methodological Inquiry and Prospects of Gut Microbiome
Ki Kwan Hui
Published on: 30 August 2021
A misleading and potentially dangerous paper
Zoe Harcombe
Published on: 30 June 2021
Plant-Based Panacea? Not Really.
Angela A Stanton
Published on: 30 June 2021

Published on: 3 November 2023
A misleading and potentially dangerous paper
- Zoe Harcombe, Researcher, writer, speaker Independent
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...
Show More

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-based’ diets and ‘plant-based or pescatarian’ diets had 73% and 59% lower odds of moderate-to-severe COVID-19, respectively, compared with participants who did not follow these diets. And ii) compared with participants who reported following ‘plant-based’ diets, those who reported following ‘low carbohydrate, high protein’ diets had almost four times the odds of moderate-to-severe COVID-19.

Regarding headline claim (i), the paper claimed that there were 568 cases of COVID-19 and this was the number used in the associations claimed. But the paper also reported that there were 298 positive COVID-19 tests (so 270 of the self-reported cases were not supported by a positive test). When just the positive test cases were examined (supplemental material), there was no association between self-reported diet and self-reported COVID-19 severity. This means that the main claim was invalid when positive test cases of COVID-19 (not self-reported cases) were used.

Regarding headline claim (ii), the ‘four times as likely’ claim was based on just four cases of self-reported COVID-19 in the ‘plant-based’ group. Such a tiny (self-reported) denominator is an unreliable basis upon which to make such a strong “four-fold” claim.

Virtually all the findings were non-findings (i.e., not statistically significant). The supplemental material showed that there were no associations between self-reported diet and self-reported cases of COVID-19. There were no associations between self-reported diet and the self-reported duration of cases of COVID-19. There were no associations between self-reported diet and the duration of positive test cases of COVID-19. There were no associations between self-reported diet and the severity of positive test cases of COVID-19.

This paper is misleading and potentially dangerous. Assertions such as those made in this paper should not be made during a public health crisis when they fail to withstand scrutiny.
Show Less

Conflict of Interest:
I write and publish content in the field of diet and health.
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Published on: 30 August 2021
A strange definition of a low carbohydrate diet
- Philip D Thompson, Armchair Cynic None
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.
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Published on: 30 August 2021
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...
Show More

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 unquestionably be affected by overreporting, thereby altering the accuracy of analysis. Apart from sick building syndrome in hospitals that somewhat resembles respiratory tract infection [2], the nocebo effects of symptom perception among frontline staff that stems from health anxiety [3,4] can lead to overreporting of infection status/symptomaticity based on one single question. Intriguingly, poor sleep quality that might also influence health anxiety and self-reported infection status is discussed in another article using the same dataset [5].
Another issue would pertain to dietary pattern analysis. Authors have analysed differences in individual food item consumption among participants who self-report following certain dietary pattern, and only the dietary pattern is used in subsequent analysis. I am uncertain whether reliance on the self-reported dietary pattern (plant-based diet vs. non-plant-based diet), as opposed to the posteriori-derived dietary pattern by e.g., k-means clustering method [6,7], or a priori dietary indices e.g., Medi-lite adherence score approach [8], would yield contrasting results. Dietary pattern analysis harnesses the synergy between different nutrients. However, post-hoc individual food and/or nutrient analysis can disentangle their correlation with different disease endpoints. For instance, recent studies show that dietary fiber intake per se is associated with reduced asthma incidence and symptoms [9,10], whose effect could have been diluted by or combined with other components of diet, as indicated by the very weak or null association between high fruit, high vegetable diet and asthma prevalence in systematic reviews [11,12]. Recent food analysis has shed light on the impact of coffee and vegetable consumption and reduced COVID-19 incidence [13]. It would be beneficial if one could utilize the dataset of this article for result replication.
This “black box” epidemiologic study [14] that correlates lifestyle exposure (diet) to outcome (COVID-19 severity, incidence and duration) warrants investigation on gut microbiota to consolidate its biological plausibility, which is indeed one of the Hill’s criteria. Yeoh and his colleagues [15] has discovered that loss of certain immunomodulatory bacterial species (e.g. Faecalibacterium prausnitzii) in stool sample is correlated with both COVID-19 severity and elevated level of inflammatory biomarkers. Through the lens of microbiota, it becomes reasonable to investigate impact of fermented food (e.g., yoghurt that belongs to
“dairy” in Food Frequency Questionnaire [1]) and supplement use (prebiotics, probiotics or synbiotics) that might modulate gut microbiota. Notably, fermentation of dietary fibres produces short-chain fatty acids (SCFAs) e.g. butyrate that sustains gut barrier integrity, and possesses immunomodulatory effects [16], such as activating regulatory T cell that reduces cytotoxic T cell activation and cytokine production [17]. Primate model reveals lowered SCFA production under SARS-CoV-2 infection [18], which possibly explains for the phenomena of “leaky gut” and gut microbial translocation, leading to bacteraemia and systemic inflammatory response [19,20]. It would be fascinating to see if certain diet/supplement could prophylactically prevent or lessen the severity of COVID-19 infection via manipulating gut microbiome composition.

Reference:
1. Kim H, Rebholz CM, Hegde S, LaFiura C, Raghavan M, Lloyd JF, Cheng S, Seidelmann SB. Plant-based diets, pescatarian diets and COVID-19 severity: a population-based case–control study in six countries. BMJ Nutrition, Prevention & Health. 2021 May 18:bmjnph-2021.
2. Babaoglu UT, Milletli Sezgin F, Yag F. Sick building symptoms among hospital workers associated with indoor air quality and personal factors. Indoor and Built Environment. 2020 Jun;29(5):645-55.
3. Shayganfard M, Mahdavi F, Haghighi M, Sadeghi-Bahmani D, Brand S. Sources of health anxiety for hospital staff working during the covid-19 pandemic. International Journal of Environmental Research and Public Health. 2021 Jan;18(6):3094.
4. Daniali H, Flaten MA. Experiencing COVID-19 symptoms without the disease: The role of nocebo in reporting of symptoms. Scandinavian Journal of Public Health. 2021 May 27:14034948211018385.
5. Kim H, Hegde S, LaFiura C, Raghavan M, Luong E, Cheng S, Rebholz CM, Seidelmann SB. COVID-19 illness in relation to sleep and burnout. BMJ Nutrition, Prevention & Health. 2021 Mar.
6. Hu FB. Dietary pattern analysis: a new direction in nutritional epidemiology. Current Opinion in Lipidology. 2002 Feb 1;13(1):3-9.
7. Zhao J, Li Z, Gao Q, Zhao H, Chen S, Huang L, Wang W, Wang T. A review of statistical methods for dietary pattern analysis. Nutrition Journal. 2021 Dec;20(1):1-8.
8. Ponzo V, Pellegrini M, D’Eusebio C, Bioletto F, Goitre I, Buscemi S, Frea S, Ghigo E, Bo S. Mediterranean Diet and SARS-COV-2 Infection: Is There Any Association? A Proof-of-Concept Study. Nutrients. 2021 May;13(5):1721.
9. Andrianasolo RM, Hercberg S, Kesse-Guyot E, Druesne-Pecollo N, Touvier M, Galan P, Varraso R. Association between dietary fibre intake and asthma (symptoms and control): results from the French national e-cohort NutriNet-Santé. British Journal of Nutrition. 2019 Nov;122(9):1040-51.
10. Saeed MA, Gribben KC, Alam M, Lyden ER, Hanson CK, LeVan TD. Association of dietary fiber on asthma, respiratory symptoms, and inflammation in the adult national health and nutrition examination survey population. Annals of the American Thoracic Society. 2020 Sep;17(9):1062-8.
11. Lv N, Xiao L, Ma J. Dietary pattern and asthma: a systematic review and meta-analysis. Journal of Asthma and Allergy. 2014;7:105.
12. Hosseini B, Berthon BS, Wark P, Wood LG. Effects of fruit and vegetable consumption on risk of asthma, wheezing and immune responses: a systematic review and meta-analysis. Nutrients. 2017 Apr;9(4):341.
13. Vu TH, Rydland KJ, Achenbach CJ, Van Horn L, Cornelis MC. Dietary Behaviors and Incident COVID-19 in the UK Biobank. Nutrients. 2021 Jun;13(6):2114.
14. Hu FB, Metabolic Profiling of Diabetes: From Black-Box Epidemiology to Systems Epidemiology, Clinical Chemistry, Volume 57, Issue 9, 1 September 2011, Pages 1224–1226, https://doi.org/10.1373/clinchem.2011.167056
15. Yeoh YK, Zuo T, Lui GC, Zhang F, Liu Q, Li AY, Chung AC, Cheung CP, Tso EY, Fung KS, Chan V. Gut microbiota composition reflects disease severity and dysfunctional immune responses in patients with COVID-19. Gut. 2021 Apr 1;70(4):698-706.
16. Machado MG, Sencio V, Trottein F. Short-chain fatty acids as a potential treatment for infections: a closer look at the lungs. Infection and Immunity. 2021 Jun 7:IAI-00188.
17. Chen J, Hall S, Vitetta L. Altered gut microbial metabolites could mediate the effects of risk factors in Covid‐19. Reviews in Medical Virology. 2021 Jan 13:e2211.
18. Sokol H, Contreras V, Maisonnasse P, Desmons A, Delache B, Sencio V, Machelart A, Brisebarre A, Humbert L, Deryuter L, Gauliard E. SARS-CoV-2 infection in nonhuman primates alters the composition and functional activity of the gut microbiota. Gut Microbes. 2021 Jan 1;13(1):1-9.
19. Giron LB, Dweep H, Yin X, Wang H, Damra M, Goldman AR, Gorman N, Palmer CS, Tang HY, Shaikh MW, Forsyth CB. Plasma Markers of Disrupted Gut Permeability in Severe COVID-19 Patients. Frontiers in Immunology. 2021 Jun 9;12:1996.
20. Prasad R, Patton MJ, Floyd JL, Vieira CP, Fortmann SD, DuPont M, Harbour A, See JR, Wright J, Lamendella R, Stevens BR. Plasma microbiome in COVID-19 subjects: an indicator of gut barrier defects and dysbiosis. bioRxiv.
Show Less

Conflict of Interest:
None declared.
- Back to top
Published on: 30 June 2021
A misleading and potentially dangerous paper
- Zoe Harcombe, Researcher, writer, speaker Independent
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...
Show More

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-based’ diets and ‘plant-based or pescatarian’ diets had 73% and 59% lower odds of moderate-to-severe COVID-19, respectively, compared with participants who did not follow these diets. And ii) compared with participants who reported following ‘plant-based’ diets, those who reported following ‘low carbohydrate, high protein’ diets had almost four times the odds of moderate-to-severe COVID-19.

Regarding headline claim (i), the paper claimed that there were 568 cases of COVID-19 and this was the number used in the associations claimed. But the paper also reported that there were 298 positive COVID-19 tests (so 270 of the self-reported cases were not supported by a positive test). When just the positive test cases were examined (supplemental material), there was no association between self-reported diet and self-reported COVID-19 severity. This means that the main claim was invalid when positive test cases of COVID-19 (not self-reported cases) were used.

Regarding headline claim (ii), the ‘four times as likely’ claim was based on just four cases of self-reported COVID-19 in the ‘plant-based’ group. Such a tiny (self-reported) denominator is an unreliable basis upon which to make such a strong “four-fold” claim.

Virtually all the findings were non-findings (i.e., not statistically significant). The supplemental material showed that there were no associations between self-reported diet and self-reported cases of COVID-19. There were no associations between self-reported diet and the self-reported duration of cases of COVID-19. There were no associations between self-reported diet and the duration of positive test cases of COVID-19.
There were no associations between self-reported diet and the severity of positive test cases of COVID-19.

This paper is misleading and potentially dangerous. Assertions such as those made in this paper should not be made during a public health crisis when they fail to withstand scrutiny.
Show Less

Conflict of Interest:
I write and publish content in the field of diet and health.
- Back to top
Published on: 30 June 2021
Plant-Based Panacea? Not Really.
- Angela A Stanton, scientist Independent, Retired
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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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 used need to reach a risk ratio (OR in the article) of greater than 2 in order to consider the particular item for further study to evaluate its significance. “Hill stressed the importance of repetitive findings because a single study, no matter how statistically sound, cannot be relied upon to prove causation due to ever-present threats to internal validity”(9). In the paper by Kim H, Rebholz CM, Hegde S, et al, the largest OR reached only 1.49, so right away, their further analysis is not based on well-understood statistical principles because an OR of <2 suggests lack of causality and no association whatsoever.
The use of P values is a bit more arguable but given that this data analysis is a dataset collected based on memories of subjects about what they usually eat, the use of P values is not appropriate. Even if we accept the use of the P values, in order for it to be of significance, the statistical definition is that it must be <0.05. In their findings, none of the three models of the low carbohydrate high fat dieters had met this P value requirement, and so this too clearly shows no causality and no association.
There are many research papers speculating about the importance of metabolic health in being able to successfully fight and overcome Covid-19. Studies on the virus itself explain the endothelial nature of the disease(6) and that high levels of blood glucose(10) (as in hyperglycemia, type 2 diabetes mellitus, obesity) was found to be an independent driver of the severity of the disease outcome.
In conclusion, the paper by Kim H, Rebholz CM, Hegde S, et al has not shown any association between eating a plant-based diet and the seriousness of Covid-19 outcome. They have misused statistics and misrepresented the findings.
Previous studies found that there is a causal relationship between hyperglycemia and metabolic disease, and that these were causal risk factors for worsening the Covid-19 severity; Kim H, Rebholz CM, Hegde S, et al assumed that a plant-based diet is beneficial for these. Yet, while a plant-based diet has not been shown in clinical trials to be beneficial for reversing metabolic disease, the low carbohydrate high fat diet that has shown in clinical trials that it can reverse type 2 diabetes(11; 12). Further, research shows that hyperglycemia and obesity are the preexisting condition of metabolic disease that are of possible causal to the severity of Covid-19 disease outcome(13).
To prove that a plant-based diet may have a better outcome, Kim H, Rebholz CM, Hegde S, et al should prove first that a plant-based diet can prevent or reverse hyperglycemia and metabolic disease. Then run a clinical trial to ascertain if for those eating a plant-based diet the Covid-19 severity outcome is reduced.
1. Kim H, Rebholz CM, Hegde S et al. (2021) Plant-based diets, pescatarian diets and COVID-19 severity: a population-based case–control study in six countries. BMJ Nutrition, Prevention;, Health, bmjnph-2021-000272.
2. Bhanpuri NH, Hallberg SJ, Williams PT et al. (2018) Cardiovascular disease risk factor responses to a type 2 diabetes care model including nutritional ketosis induced by sustained carbohydrate restriction at 1 year: an open label, non-randomized, controlled study. Cardiovascular Diabetology 17, 56.
3. Hill AB (1965) THE ENVIRONMENT AND DISEASE: ASSOCIATION OR CAUSATION? Proceedings of the Royal Society of Medicine 58, 295-300.
4. Colquhoun D (2019) The False Positive Risk: A Proposal Concerning What to Do About p-Values. The American Statistician 73, 192-201.
5. Dennis JM (2021) Type 2 diabetes ‘disproportionately’ affects COVID-19 mortality risk in middle-aged adults. Endocrine today. https://www.healio.com/news/endocrinology/20210209/type-2-diabetes-dispr....
6. Costa FF, Rosário WR, Ribeiro Farias AC et al. (2020) Metabolic syndrome and COVID-19: An update on the associated comorbidities and proposed therapies. Diabetes Metab Syndr 14, 809-814.
7. Pugliese G, Vitale M, Resi V et al. (2020) Is diabetes mellitus a risk factor for COronaVIrus Disease 19 (COVID-19)? Acta Diabetol 57, 1275-1285.
8. Archer E, Marlow ML, Lavie CJ (2018) Controversy and debate: Memory-Based Methods Paper 1: the fatal flaws of food frequency questionnaires and other memory-based dietary assessment methods. Journal of Clinical Epidemiology 104, 113-124.
9. Fedak KM, Bernal A, Capshaw ZA et al. (2015) Applying the Bradford Hill criteria in the 21st century: how data integration has changed causal inference in molecular epidemiology. Emerging themes in epidemiology 12, 14-14.
10. Ceriello A (2020) Hyperglycemia and the worse prognosis of COVID-19. Why a fast blood glucose control should be mandatory. Diabetes research and clinical practice 163, 108186-108186.
11. Hallberg SJ, McKenzie AL, Williams PT et al. (2018) Effectiveness and safety of a novel care model for the management of type 2 diabetes at 1 year: an open-label, non-randomized, controlled study. Diabetes Ther 9.
12. Athinarayanan SJ, Adams RN, Hallberg SJ et al. (2019) Long-Term Effects of a Novel Continuous Remote Care Intervention Including Nutritional Ketosis for the Management of Type 2 Diabetes: A 2-Year Non-randomized Clinical Trial. Front Endocrinol (Lausanne) 10, 348.
13. Coppelli A, Giannarelli R, Aragona M et al. (2020) Hyperglycemia at Hospital Admission Is Associated With Severity of the Prognosis in Patients Hospitalized for COVID-19: The Pisa COVID-19 Study. Diabetes Care 43, 2345-2348.
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Conflict of Interest:
None declared.
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