An panel of doctors and professors, in cooperation with the Swiss Society of Nutrition, have reviewed the scientific evidence on the role of micronutrients in supporting a well-functioning immune system for optimal health, with special focus on viral infections.
The Panel includes: Prof Mette Berger, of University Lausanne; Prof Heike Bischoff-Ferrari, of University Hospital and University of Zürich; Prof. Michael Zimmermann, from ETHZ, a public research university in Zürich; Dr. Isabelle Herter, from ETHZ and Swiss Society for Nutrition SSN; Dr. Jörg Spieldenner, from the Swiss innovation agency Innosuisse; Prof. Manfred Eggersdorfer, from University Groningen.
Their recently published white paper notes that the global pandemic has made nutrition and immune support of particular relevance and the Swiss population are at risk for suboptimal, inadequate or even deficient status for a number of nutrients that support our immune response, especially vitamin D, omega-3 fatty acids and selenium.
The paper states: "The role of nutrition, optimal micronutrient status and a well-functioning immune system as a modifiable factor to reduce risk of virus infections and its severity is highlighted in several recent scientific publications. These publications address the role of good nutritional status for a well-functioning immune system and report a deficient or low status in some micronutrients, especially vitamin D, among COVID-19 patients...
"The crisis requires prompt action to secure adequate nutrient status and replenish nutrient stores fast, which can only be achieved by complementing a well-balanced diet."
The Panel agreed it was important to stress the recommendation to follow a well-balanced diet however the white paper notes: "To change nutritional habits on a population level is a difficult and long lasting endeavor and does not correspond to the urgency of a pandemic. Furthermore an optimal nutritional status is often not achieved without a complement."
Therefore the Panel recommends a complement of supplements that should be added to the diet and fill the nutrient gap for the general population, especially for the adults age 65 and older.
This complement has the following nutrients composition:
The paper states that Vitamin C deficiency increases the susceptibility to infections such as pneumonia and plasma levels decrease during an acute infection such as pneumonia, therefore supplementation with 200 mg/day is recommended.
Vitamin D deficiency or inadequacy is associated with a reduced regulation of innate and adaptive immune system as well as increased levels of inflammation. Vitamin D stimulates the antimicrobial defence and inhibits pathogens entry into tissues, it stimulates pathogen inhibition and elimination and regulates cytokines (IL-2, IL-6, IL-8, IL-12, IL-17, TNF-alpha, IFN-gamma, NFkBA).
The white paper states: "A recent meta-analysis by Martineau and colleagues reported that daily or weekly supplementation with vitamin D reduced the incidence of acute respiratory tract infections.14 Since the coronavirus pandemic more than 1500 scientific papers have been published which address potential roles of vitamin D for the immune system in the context of SARS-CoV-2 infections.
"Currently more than 30 human studies with vitamin D are initiated to evaluate the benefit in the context of the coronavirus pandemic (www.clinicaltrials.gov).
"Vitamin D supplementation, irrespective of dosing and schedule, reduced the probability for respiratory tract infections by 12% in a meta-analysis of 25 randomized controlled trials (RCT) with 11321 participants, by 36% in 11 RCTs with 5660 patients and 42% in 5 RCTs, respectively."
The panel recommends a daily intake of 2000 IU (50 µg) per person per day which is higher than the daily recommended intake in Switzerland (DRI = 800 IU).
The experts say this dose has demonstrated to reduce risk for respiratory tract infections (Martineau 2019) and is well within the safety range as the Upper Limit (UL) for vitamin D (4000 IU/day).
Selenium influences the immune response largely through its action in selenoproteins that function as cellular antioxidants. Low selenium status levels are common in European countries, including Switzerland. Deficiency appears to enhance virulence or progression of some viral infections as evidenced by the relationship between Keshan disease, coxsackievirus B3 and influenza A, all of those are exacerbated by low selenium status.
Selenium also has an important role in the modulation of the inflammatory response and cytokine production. Supplementation of selenium improves the immune system response to viruses in deficient individuals. COVID-19 patients with low selenium status have been shown to have higher mortality.
The panel recommends supplementation with 50 -100 µg per person and day as the Swiss population is low in selenium, as are other European populations.
DHA and EPA
Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) with adequate intakes show a role in the mitigation of adverse effects of inflammation. One of the most important discoveries relating to clinical nutrition is that both DHA and EPA are substrates for the synthesis of highly active lipid mediators important in regulating inflammatory processes and responses, including resolvins, protectins and maresins.
As a result, they support the resolution of inflammation and consequently support healing, which seems to be hampered in case of nutritional deficiencies of DHA and EPA.
The panel recommendation is 500 mg DHA and EPA per person and day to reduce inflammation risks.
Zinc is essential as approximately 10% of all human gene encoded proteins contain zinc. Zinc affects both the innate and the adaptive immune systems as it regulates intracellular signaling pathways.60 Inadequate zinc status and/or deficiency is known to reduce the effectiveness of various immune cells, resulting in thymic atrophy, lymphopenia, and impaired adaptive immunity.
It is also crucial in antiviral defense, by inhibiting the entry of viruses into the host cell through stabilization of the cell membrane, and interfering with their replication ability.
In institutionalized elderly, a low status (≥70 mg/dL vs. <70 mg/ dL) is associated with lower incidence of and faster recovery from pneumonia, and fewer antibiotic days.
Zinc deficiency further favours an inflammatory response and oxidative stress, contributing to the negative effects of inflammaging. Prevalence of zinc inadequate/deficient status is close to 30% in older people living in care homes, compared to around 5% in their community-dwelling.
The risk increases with hospitalization and multiple comorbidities. Several studies reported beneficial effects of zinc complements on immunity and infections in elderly people. Given the potentially severe immunological impact of zinc deficiency, additional 10 mg/d of zinc are advised.