I am sure that most of us have wondered how we might be able to boost our immune defence in order to minimise the risk of catching the corona-virus. Many have asked, what role does nutrition play? There is, of course, a substantial amount of research on this topic, but are there any clinical trials at all? And if such studies have been published, how rigorous are they?
Here is a brand-new paper that might answer these questions.
In this review, the authors aimed to evaluate evidence from clinical trials that studied nutrition-based interventions for viral diseases (with special emphasis on respiratory infections). Studies were considered eligible if they were controlled trials in humans, measuring immunological parameters, on viral and respiratory infections. Clinical trials on vitamins, minerals, nutraceuticals and probiotics were included.
A total 43 studies met the inclusion criteria:
- vitamins: 13;
- minerals: 8;
- nutraceuticals: 18
- probiotics: 4
Among vitamins, A and D showed a potential benefit, especially in deficient populations. Among trace elements, selenium and zinc have also shown favourable immune-modulatory effects in viral respiratory infections. Several nutraceuticals and probiotics may also have some role in enhancing immune functions. Micronutrients may be beneficial in nutritionally depleted elderly population.
There were 15 studies with a high score for methodological quality. Here is what their results showed:
- No significant difference in incidence of winter-time upper respiratory tract infection in children with high versus low dose vitamin D.
- Significantly less acute respiratory infections in elderly individuals with vitamin D versus placebo.
- Higher TGFbeta plasma level in response to influenza vaccination but no improved antibody response in elderly, vitamin D-deficient individuals with vitamin D versus placebo.
- No effect on lower respiratory tract infections; however, a protective effect was noted on upper respiratory tract infections in elderly individuals with vitamin E versus placebo.
- Neither daily multivitamin + mineral supplementation at physiological dose nor 200 mg of vitamin E showed a favourable effect on incidence and severity of acute respiratory tract infections in well-nourished, non- institutionalized elderly individuals.
- Better improvement in the clinical status, respiratory rate and oxygen saturation in children suffering from pneumonia with zinc sulphate versus placebo.
- Selenium-yeast increased Tctx-antibody-dependent cellular cytotoxicity cell counts in blood before flu vaccination + dose-dependent increase in T cell proliferation, IL-8 and IL-10 secretion after in vivo flu challenge in healthy volunteers.
- Frequency and duration of acute respiratory infections during the first two months was unaffected in healthy elderly with ginseng versus placebo.
- Broccoli sprout homogenate favourably affected immunological variables in healthy volunteers.
- The incidence of illness was not reduced, however significantly fewer symptoms were reported and the proliferation index of gd-T cells in culture was almost five times higher after 10 weeks of cranberry polyphenol supplements versus placebo.
- Higher antibody titres against all 3 strains contained in the seasonal influenza virus vaccine than the placebo in healthy elderly individuals with a sea-weed extract versus placebo.
- Non-inferiority was demonstrated for Echinacea compared to oseltamivir in early treatment of clinically diagnosed and virologically confirmed influenza virus infections.
- Significant reduction of cold duration and severity in air travellers with elderberry supplement versus placebo.
- Increased NK cell activity with probiotics versus placebo in tube-fed elderly patients.
- Titres against the influenza B strain increased significantly more with probiotics compared to placebo in healthy elderly individuals.
The authors concluded that nutrition principles based on these data could be useful in possible prevention and management of COVID-19.
Given the current concern of millions of people, this is a most useful review, in my view. The paper also has a table recommending the following nutrients from food or as dietary supplements as possibly effective:
- Vitamin A
- Vitamin D
- Broccoli sprouts
I am not sure that the evidence is sufficiently strong for such explicit advice, but I am quite certain that the recommendations are nevertheless more suitable than Trump’s little ramblings on disinfectant.