December 1, 2020

expert reaction to preprint from the ZOE COVID Symptom Study app looking at vitamin supplements and likelihood of reporting a positive COVID-19 test

A preprint, an unpublished non-peer reviewed study, posted on medRxiv uses data from the ZOE COVID Symptom Study app to look at dietary supplements and likelihood of testing positive for COVID-19.

Dr David Richardson, Founder and Director of DPR Nutrition Limited (a company that provides specialist consultancy on food science and nutrition), & Visiting Professor of Food Bioscience, University of Reading, said:

“A key limitation of the observational study  is that the research does not include the nutritional status of the participants at baseline. Those people who have suboptimal status, say for vitamin D and omega 3 fish oils (DHA and EPA) will show a benefit  with supplementation, whereas with vitamin C and zinc , people are more  likely to  already have a satisfactory status.

“We do not know the socio economic status of the participants but they are probably not at the lower end.

“The results are very encouraging but only a fully controlled study with people of known nutritional status at the start would unravel the benefits of the micronutrients on  the immune system and ultimately on the severity and duration of COVID 19.

“Overall , a very encouraging at the role of micronutrients on health and wellbeing.”

Prof Jon Rhodes, Emeritus Professor of Medicine, University of Liverpool, said:

“The statistically significant but fairly small possible impact of vitamin D supplementation on risk of contracting COVID-19 is interesting and is in keeping with other studies on vitamin D status and COVID-19 infection, as reviewed in our RS Open Science paper¹.  Experimental and clinical studies suggest that vitamin D deficiency may though be associated more with severity of COVID-19 illness rather than on risk of infection.  Regarding the other supplements looked at in this study, (a) the multivitamins will likely include vitamin D, (b) 95% confidence interval for odds ratios for different supplements mostly overlap with each other so no strong conclusions can be drawn from relative size of odds ratios for different supplements.  We note that the USA data in this study showed an association between reported vitamin D supplementation and reporting a positive COVID-19 test in both men and women.  A sex difference (as shown in the UK data) is plausible though as there is good evidence (not about COVID, but from 2010) that immune cells in women are more responsive to vitamin D than immune cells from men, an effect that can be reversed in the laboratory by addition of oestrogen. Ref: https://www.jimmunol.org/content/early/2010/09/20/jimmunol.1000588.”

1 https://royalsocietypublishing.org/doi/10.1098/rsos.201912 

Prof Seif Shaheen, Professor of Respiratory Epidemiology, Queen Mary University of London, said:

“In this non-peer reviewed observational study, use of a variety of dietary supplements is reported to be associated with a lower risk of SARS-CoV-2 positivity in women, but not in men.  A major concern is that these findings may be confounded by socioeconomic status, given that individuals of higher status are more likely to take supplements, and are also less likely to become infected with SARS-CoV-2.  The authors only adjusted for a crude, area-based, measure of deprivation, rather than individually based measures of socioeconomic background such as educational attainment; thus residual confounding by socioeconomic status is highly likely.  Evidence in this study for a causal, protective effect of supplements is very weak.”

Prof Guy Poppy, Director of Transforming the UK food system for healthy people and a healthy environment (https://www.foodsecurity.ac.uk/research/foodsystems-spf/) and Professor Of Ecology, University Of Southampton, said:

“Whilst this is another interesting finding from the Zoe Covid-Symptom app, one should be cautious about how much one can really infer from this dataset, as recognised by the study authors.

“What is becoming very clear is the importance of food system and diet on many diseases including Covid and the increasing recognition of a need for us to try to transform the UK food system to ensure people have access to and consume a healthy diet, which in turn will improve planetary health.  Supplements, as shown in this study, might have a role to play but the real attention should be on ensuring people consumer a diet which is varied and rich in fruit and vegetables, which will supply the micronutrients required for health and will help ensure your immune system is best placed to help fight infections like Covid and other microbes which constantly challenge us humans.”

Prof Naveed Sattar, Professor of Metabolic Medicine, University of Glasgow, said:

“These are interesting results BUT due to the way the study has been conducted, these data absolutely cannot tell us that taking such supplements ‘protects’ against infection from COVID-19.  It may be that by being more health conscious, some women are less likely to become infected, so that it’s the behaviours that explain these results not the supplements.  The lack of any association in men also suggests the results may be confounded in ways not measured since there is no biological reason to think some supplements should work in women but not men.  So, lets await the results of randomised trials.

“In the meantime, as taking supplements can sometimes provide people with false reassurance, people should be advised that to lessen infection risk, continue to do the things proven to work, especially social distancing until the pandemic passes.  Also, keeping active and watching ones weight has more evidence to suggest it may protect against more severe COVID-19, and other chronic diseases.  Supplements have no such evidence.”

Preprint (not a paper): ‘Dietary supplements during the COVID-19 pandemic: insights from 1.4M users of the COVID Symptom Study app – a longitudinal app-based community survey’ by  Panayiotis Louca et al. was posted online on 30 November 2020.  This work is not peer-reviewed.

https://www.medrxiv.org/content/10.1101/2020.11.27.20239087v1

Declared interests

Prof Jon Rhodes: “I chair the Trustees for the medical charity Guts UK.”

Prof Seif Shaheen: “I am also studying this area, but have no other conflicts of interest.”

Prof Guy Poppy: “Former CSA at the Food Standards Agency and current Director of Transforming the UK food system for healthy people and a healthy planet alongside my substantive post as a professor at the University of Southampton.”

Prof Naveed Sattar: “No COI.”

None others received.