Immunonutrition may improve COVID-19 patients' recovery

By Dr. Ananya Mandal, MDNov 26 2020

Researchers duo Emma Derbyshire and Joanne Delange from the Nutritional Insight, Surrey, United Kingdom, explore the role of immunonutrition – nutrition that boosts or influences the immune system for those over 65 years of age in COVID-19. Their study titled, “COVID-19: is there a role for immunonutrition, particularly in the over 65s?,” was released in the latest issue of the BMJ Nutrition, Prevention and Health.

Study: COVID-19: is there a role for immunonutrition, particularly in the over 65s? Image Credit: Ekaterina Markelova / Shutterstock

Background

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), since its emergence in late December 2019 in the city of Wuhan, Hubei Province, China, has infected over 60 million people worldwide, with over 1.43 million succumbing to severe COVID-19 disease. The World Health Organisation (WHO) declared a pandemic on the 11^th of March this year, and since then, the pandemic remains one of the most significant public health problems in recent human memory.

Public health strategies to prevent the spread of this highly infective virus include social distancing, prevention of gatherings, wearing masks, and hand hygiene. The focus has not been on the immune system and foods that could help boost the immune system, write the researchers.

This review attempted to gather the present evidence in favor of immune-nutrition or nutrition and diet that helps boost the immune system, especially among the elderly who are more susceptible to the SARS CoV-2 infection and its complications.

The researchers call immunonutrition a form of prevention of disease or “prehabilitation,” which could help the “body to cope with potentially lethal viruses such as coronavirus.”

Prehabilitation

The researchers explain that the definition of prehabilitation in scientific literature says these are “interventions that can help improve patient’s health in advanced of being exposed to a physiological stressor, so they are then better able to cope with that stress.”

Nutrition and disease

The researchers say that there is ample evidence that poor nutrition, protein-energy malnutrition as well as deficiencies of micronutrients such as vitamins and minerals are part of “related lifestyle factors” which can contribute to a suboptimally functioning immune system.

Certain components of the diet, including fruit, vitamin C, antioxidants, vitamins, minerals, and probiotics, are termed as immunonutrition that could help boost immunity and have a possible role in “resisting respiratory viruses and diseases,” write the researchers.

SARS CoV-2 and immune system

The COVID-19 pandemic raging around the world is caused by the SARS-CoV-2, which is part of the coronavirus family. At present, there are no safe and effective treatments against this virus nor vaccines to prevent infection. SARS-CoV-2, in some vulnerable individuals, especially the elderly, may lead to atypical viral pneumonia. Some may even need oxygen or artificial ventilation and ICU care. Elderly with other health problems such as heart disease, obesity, diabetes, etc., may have a greater risk of developing complications such as acute respiratory distress syndrome (ARDS), leading to multiple organ failure and even deaths.

The immune system has four components - T cells, B cells, the complement system, and phagocytes. There are two arms of the immune system – innate and adaptive immunity. These protect the body against infections. A healthy diet and nutrition boost the immune system.

The team writes that Professor Philip Calder, an expert on immune nutrition, says in his paper, “Feeding the Immune System,” that the immune system functions by acting as a barrier against incoming infections.

Age and immune system

With age, the immune function declines. This is called ‘immunosenescence.’ Both innate and acquired immune systems decline with age. The reasons for this decline include:

• Reducing functions of the T cells due to involution of the thymus gland and also reduced production of new naïve T cells
• “Inflammaging” or inflammation associated with aging processes
• Poor nutritional status associated with age. There is typically micronutrient deficiencies seen in the elderly
• Menopause and andropause can also contribute to nutritional deficiencies

Immunonutrition and COVID-19

Some of the main findings from the scientific literature search by the researchers were:

• A healthy immune system requires vitamins A, D, C, E, B₆, B₁₂, folate, copper, iron, zinc, and selenium. There is an interplay of these nutrients in a healthy immune system
• Immunonutrients of considerable importance are vitamin C, D, and zinc.
• Vitamin C helps in the development of the epithelial barrier functions of the respiratory system that prevents invasion by pathogens. It can help prevent pneumonia.
• Vitamin D is a powerful immunoregulator. B and T lymphocytes, macrophages, and monocytes are some of the immune cells that have vitamin D receptors on their surface. Vitamin D has a protective role in respiratory infections
• Authors write, “Zinc is regarded as a ‘gatekeeper’ of immune function.”

Recommendations

The researchers wrote, “The general public and indeed the aging population should be encouraged to follow guidance from Public Health England and continue taking supplements containing 10 μg of vitamin D daily...”. They recommend foods rich in vitamin C (broccoli (60 mg/100 g), blackcurrants (130 mg/100 g), fortified breakfast cereals (up to 134 mg/100 g) and oranges (37–52 mg/100 g). They recommend foods rich in natural zinc such as “canned crab (5.7 mg/100 g), canned shrimps (3.7 mg/100 g), canned adzuki beans (≈2.3 mg/100 g) and boiled eggs (1.3 mg/100 g)”. The recommendations are for vitamin D supplementation with an upper limit of 50 µg/day and an upper limit of daily zinc at 25 mg/day.

Future directions

There is a dearth of studies that examine the effects of immune nutrients on “vulnerable groups such as those aged >65, with underlying health conditions, such as asthma, chronic obstructive pulmonary disease, diabetes, and heart disease, or who are immunosuppressed”.

The research duo feels that public health strategies should also focus on immunonutrition as a form of prehabilitation to prevent the spread of the infection, boost recoveries and reduce the burden on the healthcare systems due to an increase in hospital admissions.