As the pandemic stretches on, our online feed is overflowing with “quick fixes” to boost our immunity. Sadly, the sources for such solutions are often unclear and may thus be misleading. The “Clinical Dietician” world has also responded but with nutritional guidelines based on scientific research and unprecedented worldwide cooperation. These guidelines could thus help improve our understanding of how to build immunity better for the long term.

Nutrition does boost immunity but what I have to tell my patients is that the link is complicated. It is impacted by the multi-functional interactions of our cells, organs, tissues and molecular build in dealing with our environmental pathogens. Stress, obesity, age, genetics and time of the day can also affect it. Balanced eating, regular physical exercises and quality sleep often go hand in hand to reinforce immunity.

For vulnerable groups, such reinforcements are now crucial, especially amongst those aged 65 and above, with underlying health conditions, such as asthma, chronic obstructive pulmonary disease (COPD), diabetes, heart disease, chronic kidney and liver disease or who are immunosuppressed. Based on existing research, specific vitamins and minerals in our food intake can target such vulnerabilities individually or synergistically which I refer to in more detail below. 

Insufficient dietary intake of micronutrients such as vitamins and minerals can compromise immune functions and increase the overall risk of infection. The micronutrients which are pivotal for strengthening the immune system are vitamins A, C, D, E, B2 (riboflavin), B6 (pyridoxine), B12 (cobalamin) and B9 (folic acid) and minerals iron, selenium, zinc, magnesium and copper- these are found in a variety of foods as shown below and should be part of a healthy balanced diet. Individuals should not take extra supplements without consulting a doctor or dietitian.


VitaminPurposeFood SourcesContext 
AInsufficient amount in our diet increases susceptibility to a range of infections.Preformed – Animal foods such as liver and fat portions of dairy foods(milk, cheese, butter), egg yolk and fish. Provitamin A and β-Carotene– Dark yellow, red, green and orange pigment in plants such as carrots, spinach, pumpkin, tomatoes, broccoli. Should be taken with 3g of fat (e.g. oil, ghee, butter) to be absorbed properly.Cooking helps release the vitamin from plants making them available for absorption.
B2/ riboflavinFirst-line host immune response against invading pathogens; helps iron absorption.Milk and cheese.70% B2 will be lost by exposure to sunlight.
B6/ pyridoxineHelps in the production of antibodies and immune cells.Whole grains (brown flour and rice, oats), pulses (chickpeas, lentils dry beans) and legumes (green beans and peas, soybeans), bananas, potatoes and meat (poultry). 
B9/ folic acidMaintain the balance of the immune system and increase resistance to infections.Dark green leafy vegetables (spinach, cabbage, cauliflower, broccoli), citrus fruits (oranges), tomatoes, cantaloupe and legumes (green beans and peas, soybeans). Some cereals and bread are fortified with folic acid.Folate absorption depends on its source with only 50% being absorbed from plant sources. Older people are unable to absorb enough due to low gastric acid therefore intake should be more
B12/  cobalaminModulates immunity against viruses and bacteria.Only in animal food – meat, poultry, fish, milk, eggs and cheese.Individuals who are vegan or have low gastric acid levels (older population) are unable to meet daily requirements.
C/ ascorbic acidReduces risk, severity and duration of upper and lower respiratory tract infections.Requirements increase during infections.Citrus fruits (oranges and lemons), sweet potatoes, guava, strawberries, mangoes, papaya, capsicum, broccoli.Can be easily destroyed by heat, light and action of oxygen in the air. Cook for a limited amount of time.
DReduces risk of respiratory tract viral infections, therefore, improving immune functions.‘The sunshine vitamin’, as its source is the sunlight. Only a few other natural sources such as fish liver oils and egg yolks (only small amounts). Sources can be oily fish like trout and freshwater river carps.Staying indoors in a lockdown can deprive us of the daily requirements of sunlight. It is recommended to take a supplement of 10 mcg = 400 IU (International Units). The recommended daily amount of vitamin D is 400 IU for children up to age 12 months, 600 IU for ages 1 to 70 years, and 800 IU for people over 70.
EPotent antioxidant modulating host immune functions.Vegetable oils (canola, sunflower, safflower) and lower amounts in olive oil and corn oil. Also nuts (peanuts, hazelnuts and almonds), green vegetables (spinach and broccoli), sunflower seeds. Some breakfast cereals, spreads and fruit juices are fortified with vitamin E.Benefits the elderly, may reduce the risk of upper respiratory tract infections.


Mineral typePurposeFood SourcesContext
IronProduces immune cells that attack foreign bacteria in the body. Non-Heme Iron: spinach and legumes  Heme Iron: fish, poultry, eggs  Heme iron improves the absorption of non-heme iron, so its deficiency in diets should be monitored. Also, an acidic environment increases iron absorption (iron taken with vitamin C) while severe infection depresses it.
ZincEven a marginal zinc deficiency can impact immunity as it leads to increased diarrhoea and respiratory morbidity.Sources can be seafood (shellfish-lobster, crab and oysters), meat, lamb, leafy and root vegetables, pumpkin seeds, eggs and milk.Zinc is better absorbed from animal protein than plant protein. Zinc supplements can interfere with iron and copper absorption and vice versa. Older individuals with optimum zinc status have greater resistance to infections and less need for antibiotics. Excessive zinc intake, especially from supplements, can lead to a suppressed immune system.
SeleniumAn integral part of antioxidants that protects the cell and lipid membrane from oxidative damage. Selenium influences the innate and acute immune systems. Selenium partners with vitamin E.Meat and meat products, fish, poultry, eggs and Brazil nuts.Lacto-ova vegetarians and vegans may be at risk of deficiency.
MagnesiumSome functions of the immune system are dependent on magnesium.Almonds, cashew nuts, green vegetables and spinach, pulses (beans, red, green, yellow and brown lentils, peas), whole grain cereals (wheat, corn, barley, oats, rye and millet).Deficiency associated with cardiac arrhythmias and cardiac arrest.
CopperEssential for optimal innate immune function.Liver, seafood, nuts and seeds.a deficiency increases susceptibility to bacterial infection.
Probiotics (live microflora) and prebiotics‘Desirable’ bacteria benefiting the gastrointestinal tract by promoting the proliferation of good bacteria and limiting the development of harmful bacteria preventing the colonisation of pathogens. Prebiotics – Bananas, onions and garlic. Dietary sources of probiotics can be cultured milk and yogurt, cheese, pickled cabbage and tempeh.Probiotics may be effective in treating infectious diarrhoea. Individuals with compromised immune function should not use probiotics without medical supervision. Accurate information regarding the dosage and requirements and safety of particular supplements are still uncertain.

Dietary considerations for COVID-19 positive patients at home

  1. Optimization of nutritional status: Energy and protein need individually adjusted according to body weight, age, disease status, energy expenditure, and tolerance to reduce the risk of complications.
  2. High calorie and high protein diets are important for patients with COVID-19 to protect against the breakdown of muscles. Try eating 6 times a day every 2-3 hours. Protein intake of at least 75-100 grams from sources that include meat, fish, poultry, eggs, milk, and yoghurt.
  3. Hydration: 2-3 liters of fluids per day (2-4 ounces every 15 minutes). Fever is associated with excess loss of fluid which may lead to dehydration. Caution should be used for individuals who have fluid restrictions.
  4. Proper nutrition adjusted on an individual basis can help reduce carbon dioxide levels and improve breathing (high fat and low carbohydrate diet).
  5. Supplementation with vitamins and minerals: vitamins A, B, C, and D, also omega-3 polyunsaturated fatty acids, as well as selenium, zinc, and iron should be considered in the assessment of micronutrients in COVID-19 patients.
  6. Physical activity: For people in quarantine, every day > 30 min or every second day > 1h exercise is recommended to maintain fitness, mental health, muscle mass, and thus energy expenditure and body composition.
  7. Oral nutritional supplements or enteral feeding should be considered for people whose nutritional needs cannot be met orally.

This article was published in The Daily Star authored by Tazreen Yusuf Mallick, Praava Health’s Nutritionist. She also worked in the NHS, United Kingdom as a registered clinical dietician.

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