MD, PhD, MAE, FMedSci, FRSB, FRCP, FRCPEd.

I came across this article via a German secondary report about it entitled “Scientists discover what else protects from severe symptoms” (Forscher finden heraus, was noch vor schweren Symptomen schützt). The article rightly stressed that vaccination is paramount and then explains that, once you have caught COVID, nutrition can prevent serious symptoms.

Even though I rarely discuss standard nutritional issues on my blog (nutrition belongs to mainstream not so-called alternative medicine [SCAM], in my view), this subject did attract my attention. Here are the essentials of the original scientific paper:

Australian scientists studied the association between habitual frequency of food intake of certain food groups during the COVID-19 pandemic and manifestations of COVID-19 symptoms in adult outpatients with suspected SARS-CoV-2 infection. They included 236 patients who attended an outpatient clinic for suspected COVID-19 evaluation. Severity of symptoms, habitual food intake frequency, demographics and Bristol chart scores were obtained before diagnostic confirmation with real-time reverse transcriptase PCR using nasopharyngeal swab.

The results of the COVID-19 diagnostic tests were positive for 103 patients (44%) and negative for 133 patients (56%). In the SARS-CoV-2-positive group, symptom severity scores had significant negative correlations with the habitual intake frequency of specific food groups. Multivariate binary logistic regression analysis adjusted for age, sex, and occupation confirmed that SARS-CoV-2-positive patients showed a significant negative association between having higher symptom severity and the habitual intake frequency of legumes and grains, bread, and cereals.

The authors concluded that an increase in habitual frequency of intake of ‘legumes’, and ‘grains, bread and cereals’ food groups decreased overall symptom severity in patients with COVID-19. This study provides a framework for designing a protective diet during the COVID-19 pandemic and also establishes a hypothesis of using a diet-based intervention in the management of SARS-CoV-2 infection, which may be explored in future studies.

So, the authors seem to think that they found a causal relationship: A CHANGE IN DIET DECREASES SYMPTOMS. In different sections of the article, they seem to confirm this notion, and they state that they tested the hypothesis of the effect of diet on SARS-CoV-2 infection symptom severity.

Yey, the investigation was merely a correlative study that cannot establish cause and effect. There are many other variables that might be linked to dietary habits which could be the true cause of the observed phenomenon (or contributors to it).

What’s the harm? If the article makes people adopt a healthier diet, all is pukka!

Perhaps, in this case, that might be true (even though one could argue that this paper might support anti-vax notions arguing that vaccination is not important if it is possible to prevent severe symptoms through dietary changes). But the confusion of correlation with causality is both frequent and potentially harmful. And it is unquestionably poor science!

I feel that we need to be concerned about the fact that even reputable journals let such things pass – not least because the above example shows what the popular press subsequently can make of such misleading messages.

 

22 Responses to A change in diet protects us from severe COVID symptoms – REALLY?

  • Severity of symptoms, habitual food intake frequency, demographics and Bristol chart scores were obtained

    In case anybody is wondering what Bristol chart scores are, I thought I should explain that it refers to a standard scale for describing the firmness of stools.

    https://en.wikipedia.org/wiki/Bristol_stool_scale

  • EE: Yey, the investigation was merely a correlative study that cannot establish cause and effect. There are many other variables that might be linked to dietary habits which could be the true cause of the observed phenomenon (or contributors to it).

    This was mentioned in the study as a limitation.

    “This cross-sectional investigation shows a correlation between food intake patterns and symptom severity, while it does not necessarily determine causality. Some confounders have been addressed, including age, sex and occupation. Nevertheless, other variables that could influence the outcomes of this work remain to be studied…”

    • SO WHAT!
      The point is that, if they make statements like the one in the abstract, journalists will pick them up and mislead the public.

      • Oh my, they used words like:

        Correlation, association, framework, hypothesis

        • OH, DEAR!
          see what the journalist made of it
          [or, if you prefer, continue to refuse to see my point]

          • Regarding the journalist: the magazin is a magazine from a German telecom company (it was formerly, before licences for telecom licences were sold, the offical German telecom company).
            Thus, it is a free magazine which is a mix of magazine and advertisement. Sometimes they have hints on interesting contents. However, it is always better to find the original source of the information. It’s not a magazin with any scientific pretension.

          • that is true. AND IT IS ALWAYS BETTER TO HAVE ORIGINAL PAPERS THAT DO NOT DRAW MISLEADING CONCLUSIONS.

          • @Holger

            Vast majority of people do not have the background knowledge to understand the original source of information i.e., scientific studies. Therefore, it is very important that the journalist accurately report on the outcome of the study. In the case of the German article, it appears the author did not read past the Australian study’s abstract. If they had done their due diligence they would have realized that the study itself is poorly done and does not establish a causal relationship between diet and severity of covid symptoms. There is always the danger of anti-vaxxers using such poorly done studies to further their agenda. So, the reporters would need to do a better job at weeding out poorly done studies before they shout out of their megaphones.

          • So the thought here is: Authors, publish your scientific paper so journalists can understand it thus they will not be able to misinterpret what it says?

          • are you a bit dim?
            the message is: authors do not draw misleading conclusions!!!

          • So the thought here is: Authors, publish your scientific paper so journalists can understand it thus they will not be able to misinterpret what it says?

            No DC, what all this really means is that reporters who can’t read past the abstracts should quit their jobs, researchers who cannot differentiate between causation vs correlation should reconsider their career objectives and readers who don’t have basic reading comprehension skills may want to stay away from reading and commenting, so they don’t make a fool of themselves.

          • Do you the difference between “may” and “can”?

            “ As a result, it may be concluded that an increase in habitual frequency of intake of such food groups may decrease the severity of symptoms in those infected with SARS-CoV-2. “

  • Dear Edzard,
    you wrote: “Perhaps, in this case, that might be true (even though one could argue that this paper might support anti-vax notions arguing that vaccination is not important if it is possible to prevent severe symptoms through dietary changes). But the confusion of correlation with causality is both frequent and potentially harmful. And it is unquestionably poor science!”

    Is it poor science? My opinion is: Yes and no.
    Yes, as it includes no hypothesis or strategy that tests a direct causal relation.
    No, as it has as finding statistically significant correlations between performance of the immune system and nutrational provision.

    Of course, this relation could have a causal relation to another factor which was not measured and which is correlated with nutrition. This could be a life-style effect having its foundation in things like: people who drink a lot of milk and eat a lot of beans also drink a lot of tea which acts as Covid19 killer (just an example how a co-correspondance could work!).

    On the other hand, we can expect that a living system which is well provided with all nutritional factors an immune system needs to perform well, will do better in fighting a health threat.

    All those recommendations of how much nutritional elements you should eat each day refer to the need of a healthy person to stay alive. However, if your body runs into trouble, it needs more of certain parts of food (proteins, amino acids, anti-oxidants etc.) and if your store is filled well, your immune system is enabled to do a very good job. This link is not proven by the study. Nevertheless, it looks like the most appropriate explaination for the observed effect.

    Thus, it may not be very good science but it could be a very helpful science, which should be welcome in times of a pandemic situation.

    We should keep in mind that the authors of the study do not give an alternative to vaccination but try to give some hints on how vaccination could be supported for a better efficiancy.

    • it has as finding statistically significant correlations between performance of the immune system and nutrational provision.

      Where do they say that? My understanding is that they found a correlation between severity of illness and certain aspects of nutrition. Nowhere does Edzard mention any measurements of immune function.

      • The grade of illness is a very good measurement for the grade of function of the immune system, if you compare different people with different immune system facing the same threat.
        What else than the immune system will end a threat based on a virus infection? Thus, if you have different durations and grades of acutal signs of the illness, these factors are the best measurements for the performance of the immune system you can get.

  • According to Zelenko (“…I have not lost a patient in the last seven months, thank God…”), it is a zinc ionophore problem:
    https://www.eastonspectator.com/2021/10/17/dr-vladimir-zelenko-proved-everyone-wrong-about-hydroxychloroquine/

    Evidently a nutritional deficiency will cause a problem by definition hence the discoveries of vitamin C, B12, D3 etc, so it is not implausible that diet could protect against covid 19, it is to be expected, not just for covid 19 but heart disease etc, from for example, obesity, lack of exercise and so on.

    Zelenko (and others) make the case specifically for zinc (and those supporting zinc: selenium, vitamin C etc).

  • The study is not by Australian scientists. While the corresponding author is Australian, all the others are in Mexico. The Australian author Professor Kourosh Kalantar-Zadeh describes his expertise as:
    “Sensors, nanotechnology, liquid metals, materials science, electronics, gastroenterology, and medical devices”
    So he seems an odd participant in a poor quality nutritional study.

    They assessed symptoms only at time of presentation to a Mexican outpatient clinic for COVID-19 testing, not the full course of the disease, so the study assesses the relationship between nutrition and decision to present to the clinic, not how severe the disease became. The conclusion in the abstract seems quite unjustifiable.

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