Since the onset of the COVID-19 pandemic, people have turned to our journals collection for studies that link nutrition to the prevention and treatment of viral infection. As a result, there has been a renewed interest in many ASN journal articles; some were published recently, others published years ago.
All four ASN journals have published relevant studies. Part One of this blog post presents articles published in Advances in Nutrition, ASN’s international review journal. Part Two explores articles published in The American Journal of Clinical Nutrition, The Journal of Nutrition, and Current Developments in Nutrition. None of these articles directly addresses the COVID-19 virus; however, they may provide important clues as to how nutrition science can support global efforts to prevent and manage COVID-19 infection.
As nutrition researchers, practitioners, and public policy advocates, we all play a role in keeping people healthy during these difficult times. We hope these articles will support your important work.
“The Role of Zinc in Antiviral Immunity,” April 2019
In this review, Scott A. Read et al. summarize the basic science and clinical evidence examining zinc both as a direct antiviral and as a stimulant of antiviral immunity. Zinc is an essential trace element crucial for growth, development, and the maintenance of immune function. Zinc deficiency is common, affecting up to a quarter of the population in developing countries, but also affecting certain populations in the developed world as a result of lifestyle, age, and disease-related factors. “Consequently, zinc status is a critical factor that can influence antiviral immunity, particularly as zinc-deficient populations are often most at risk of acquiring viral infections.”
“Zinc treatment applied at a therapeutic dose and in the right form has the potential to drastically improve the clearance of both chronic and acute viral infections.”
Evidence accumulated over the past 50 years demonstrates the antiviral activity of zinc against a variety of viruses. According to the authors, “zinc treatment applied at a therapeutic dose and in the right form has the potential to drastically improve the clearance of both chronic and acute viral infections, as well as their accompanying pathologies and symptoms.” The authors, however, caution that “there remains much to be learned regarding the antiviral mechanisms and clinical benefit of zinc supplementation as a preventative and therapeutic treatment for viral infections.”
Given that COVID-19 has disproportionally affected older adults, it is important to keep in mind that “aged individuals are also significantly more susceptible to zinc deficiency, increasing their
likelihood of acquiring life-threatening viral infections.” Studies, however, suggest that zinc supplementation may lower the incidence of viral infection among older populations.
Vaughan S. Somerville et al. conducted a systematic review to assess the efficacy of dietary flavonoids on upper respiratory tract infections and immune function. Following an exhaustive search of the scientific literature, the authors identified 14 studies that met their criteria.
Flavonoids are a diverse group of phytonutrients that are responsible for the vivid colors in fruits and vegetables. They are powerful antioxidants with anti-inflammatory and immune system benefits. Diets rich in flavonoid-containing foods have been associated with a lower incidence of cancer, neurodegenerative and cardiovascular disease.
“The findings demonstrate that flavonoids decrease upper respiratory tract infection incidence compared with control with no increase in adverse effects.”
Findings from this review “demonstrate that flavonoids decrease upper respiratory tract infection incidence compared with control with no increase in adverse effects.” In fact, overall, flavonoid supplementation, which ranged from 0.2 to 1.2 grams per day, decreased upper respiratory tract infection incidence by 33% compared with control groups. On the other hand, the authors did not find conclusive evidence that flavonoids decrease the duration or severity of upper respiratory tract infection. For example, there was no strong evidence that flavonoid supplementation reduces the number of upper respiratory tract infection sick days.
The authors did find that while flavonoids may help lower the incidence of upper respiratory tract infection, most people don’t get enough from their average daily intake. Fortunately, boosting intake of flavonoids can be achieved “through simple practices such as consuming green tea, a glass of Shiraz, blueberries, or some dark chocolate.”
Viral and bacterial infections are associated with deficiencies in macronutrients and micronutrients, including the essential trace element selenium. Selenium is a mineral found in the soil. It is known for its antioxidant properties and role in supporting healthy metabolism. Selenium has also been studied for the treatment of several conditions, including asthma, arthritis and infertility, with inconclusive results.
Currently, the recommended selenium intake for adults ranges between 25 and 100 micrograms per day. Selenium intake varies greatly around the world, in part dependent on the selenium content of local soil and, consequently, the accumulation of selenium in farm crops and animals. In particular, many regions in sub-Saharan Africa are selenium deficient.
“Dietary multi-micronutrient supplements containing selenium up to 200 micrograms have potential as safe, inexpensive, and widely available adjuvant therapy in viral infections.”
Working with data from epidemiologic studies and intervention trials, Holger Steinbrenner et al. looked at the role of selenium supplementation in the treatment of a broad range of viral and bacterial infections, including HIV, influenza A, and Ebola virus. According to the authors’ findings, “dietary multi-micronutrient supplements containing selenium up to 200 micrograms per day have potential as safe, inexpensive, and widely available adjuvant therapy in viral infections.” Among the health benefits conferred by selenium supplementation were weight gain, slower disease progression, and accelerated antiviral immune response.
The authors called for more research to better understand how selenium might be best used to treat viral and bacterial infection, including a better understanding of interactions between selenium and other micronutrients to improve protocols for multi-micronutrient supplementation.
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