Immunity Boosing Foods and COVID-19

I had promised to share some of the chapters from my book on COVID-19. I am sharing one chapter today.

The links to the eBook COVID-19 are in the following links given below.



Since immunity boosting foods has been mentioned so often in connection with COVID-19, I thought it would be useful to bring in a section on this topic. Based on my experience, I thought it would be a simple process of opening up online literature and just copy and paste the relevant information. It wasn’t easy as I imagined.

A cardiologist based from the US has looked at immunity boosting foods in a critical manner. A number of questions that he had raised, forced me to go deeper into this topic. Here are some of his questions.

Can you boost your immune system to fight COVID-19? This is the question on everyone’s mind as we face a worldwide crisis. There are online claims that we can “boost” our immune system with just about everything from Vitamin C or Vitamin D to a number of immunity-boosting foods. But how do we know which of these recommendations, if any, really work? He indicated that the immune system is an intricate and delicate system with many different components. Helping one section might impair another and may not contribute to fighting viruses. How do we know if something that helps with another virus will help with this new corona virus?

To understand immunity boosting foods, I have classified them into four broad categories. The first category is vitamins and minerals given as supplements or through foods rich in these. The second category is the regular fruits and vegetables used in day to day cooking and diet, considered to have immune promoting properties. I am handling both the first and second categories together, relating the immunity boosting foods with the foods that are rich in these vitamins and minerals.

The third category is the variety of condiments and spices used, and claimed to have immunity boosting properties. Finally, in the fourth category are traditional herbs and other substances considered to be immunity boosting.  While the first category is the most scientifically studied, there is not enough scientific studies to conclude on the immunity boosting properties of the other three categories.

Vitamins, Minerals and Supplements

Taking vitamins, minerals, or other supplements could help protect from COVID-19. Here’s what we do know about certain supplements that reportedly have immune-boosting properties. Consuming foods rich in these would also be helpful.

Vitamin C has been used to help prevent the common cold. It may improve the function of certain white blood cells that fight infection. Vitamin C is known to strengthen the body’s T cells and phagocytes, which are the two main components of the immune system. There’s no harm in taking up to 2,000 mg per day (the upper limit set by the National Academy of Medicine).

Taking a Vitamin D supplement seemed to have a mild protective effect against respiratory tract infections in most people, especially those who were very deficient in Vitamin D. It is probably wise to take a Vitamin D supplement, especially if there is increased risk for COVID-19. Additionally, try to get some sunlight for about fifteen minutes daily if possible.

Vitamin E the next is a great source of strength to fight infections. Nuts such as almonds and walnuts as well as certain seeds like sunflower seeds, flax seeds, pumpkin seeds and melon seeds are excellent sources of protein and vitamin E with anti-inflammatory properties. Vitamin A, B6, C, D and E can help increase the strength of the immune system. Vitamin C is the biggest booster of all.

Zinc is a mineral involved in the white blood cell response to infection. It has been identified that supplementing with zinc reduced the duration of the common cold. It is not sure whether it can have a similar effect on COVID-19. Taking supplementary zinc (< 40 mg) may be a good strategy for older people and others at increased risk. Selenium is another important trace mineral that is useful for increasing immunity. This naturally leads me to the second group.

Fruits and vegetables

Citrus fruits are an excellent source of vitamin C, a nutrient that strengthens the immune system. Some of the popular citrus fruits are: orange, lemon, lime, grapefruit or pomelo, sweet lime or mosambi (citrus limetta), mandarin, tangerine, galgal (citron) or naarthenkai in Tamil. Other fruits include mangoes, strawberries, blue berries and apples.

Broccoli is packed with vitamins A, C and E. Tomatoes have valuable nutrients. Vegetables such as the red or the green bell peppers contain large amounts of vitamin C. Bell peppers are also a great source of beta carotene. Gooseberry or amla is considered another good immunity boosting food. Cashews, pumpkin seeds, chickpeas contribute to providing zinc. Consuming a wide variety of seasonal vegetables would contribute to boosting immunity.

Leafy vegetables such as spinach or palak or pasalai (Tamil), and kale or parattai keerai (Tamil) are a great source of daily vitamin intake. Spinach is rich in high amounts of carotenoids, vitamin C, vitamin K, folic acid, iron, and calcium. Kale is rich in Vitamin A, Vitamin K, Vitamin C, Vitamin B6, Manganese, Calcium, Copper, Potassium, Magnesium, vitamin B1, B2, B3, iron and phosphorus. 

Condiments and spices

Turmeric a spice commonly used in Indian and Asian cuisine belongs to the third category. It contains a bright-yellow compound known as curcumin, which emerging research suggests might enhance immune function, although not sure that it helps fight viral infections.

Garlic, another popular and widely used pungent herb with a characteristic aroma, is widely believed to have antibacterial and antiviral effects, including helping to fight the common cold. In one study, people who took a garlic supplement had fewer colds and recovered more quickly from colds than people who didn’t take garlic.

Ginger is another common food stuff used that is believed to have immunity building properties. Many test-tube and animal studies suggest that ginger can enhance immune response. Specific compounds in ginger, such as gingerols, shaogals and zingerone, have been found to inhibit viral replication and prevent viruses from entering host cells.

Traditional herbs and other food stuffs

It is the fourth category that is apparently not well studied scientifically. However anecdotal experiences and some of the studies carried out point to their usefulness in boosting immunity. I have listed two scientific studies from this category in the bibliography section to add weight to their possible role in increasing immunity.

The first one is drum stick leaves. Moringa have seven times more vitamin C than oranges and fifteen times more potassium than bananas.  It is also packed with antioxidants, substances that can protect cells from damage and may boost your immune system. They can be consumed as a leafy vegetable, or boiled and juice extracted, or shade dried and powdered and then consumed as a powder or extracted as juice. Personally, I have witnessed HIV/AIDS patients using this as an immunity boosting food, just before the arrival of Anti-Retroviral Treatment for the disease. Their CD4 count as a marker of immunity remained high.

Based on the above, I can add other similar herbal products. First is aloe vera. The next is Rosella, used as a juice extract.  Black pepper is known for its potent antioxidant and anti-inflammatory properties through its active compound, piperine. Star anise, black cumin (jeera), tulsi leaves or royal basil are used in traditional home remedies. Fenugreek seeds are packed with antiviral properties and have the ability to kill viruses that cause sniffles and sore throats. Onion is a rich source of organo sulfur compounds like quercetin and allicin which are associated with inhibition of viral infection.

Egg yolks and mushrooms are a good source of Vitamin D with eggs additionally having selenium. Milk contains nutrients like probiotics, vitamin D and immunoglobulins that boost the immune system and in turn reduce the risk of allergies. Honey, especially ‘Manuka’ honey, has strong antiviral properties against the varicella-zoster virus, the respiratory syncytial virus, and also has anti-influenza activity. It is also known to soothe a sore throat, suppress cough and can boost the cold-fighting action of black peppercorn. While I do not know the basis, drinking hot water is supposed to improve immunity.

Personal experience

I just want to add a few from my experience. My mother always gave me a special blend of hot drink prepared with dried ginger and coriander seeds, whenever I had cough. It was effective.

Earlier, my grandmother used to make a preparation using ginger fresh or dried, long pepper or tippili (Tamil language), betel leaves and the bark of neem tree. I have forgotten the other ingredients that went into it. It was not the tastiest concoction. We grandchildren, just closed our eyes and gulped it in one go once a month. Today, I presume that the action of these is by boosting the immunity. I can tell of other herbal practices to overcome childhood constipation or even abdominal colic among children. I would however, like to present my own experience with a chronic cough.

In my sixty fifth year, while visiting the US, suddenly I had a bout of cough. I knew it was not infection. There was a tendency to blame the allergens of the season. I put up with it for the two months that I was there, without visiting a doctor. When I returned to India, I still had the cough. I went to my physician. Walking along with me he could hear a loud wheeze. Without even putting a stethoscope on my chest, he said that I had asthma. I knew it was not asthma.

Later, I visited one of my relatives who was being trained in herbal medicines. We had just arrived that morning in their home and as we sat down for breakfast, I started coughing. He told me he had the correct medicine for my cough.

Immediately after breakfast, he took out a bottle of a dark greenish powder, took one spoonful mixed with honey and then asked me take it. He told me to take it three times a day for three days. By the time we left the next evening, I had taken it for two days and I began to feel better. Actually, I had to take to take it for about a week and the cough vanished and I had no indication of asthma at all.

He called this ‘five medicines,’ the literal translation of the Tamil name ‘anjumarunthu.’ They are dried ginger, black pepper, long pepper or tippili, akkara, and chitharathai all locally available herbal medical substances. He gave me the proportions to be used for preparing them and I always had them locally prepared and in my fridge.

Research on immunity boosting foods

Having said that there are not enough studies to either prove or disprove the effectiveness of these substances in boosting the immunity levels, I would like to take it to the next level. This is an excellent area for research by some of the younger professionals. If teams consisting of pharmacologists, virologists, physicians of different specialties and some from Siddha or Ayurvedha come together and carry out research on the immunity boosting potential of these foods, it would be a great contribution to the future of medicine.

 Just to take the first step, I have listed some of the indicators that could be measured to test the effectiveness of these foods. Probably the two that stand out are levels of infection-fighting proteins (immunoglobulin) in the blood and measure the levels of blood cells and immune system cells. May be other indicators could be added by experts in this area as they start working together.

I am a firm believer in herbal medicines and practice them regularly. In our home we take moringa juice once or twice each week. I frequently consume one fresh tender betel leaf from a plant that grows in our home garden. I take a herbal candy for my cough. I wish someone would come forward and carry out the research that is needed and prove one way or the other the effectiveness of these herbal medicines in increasing the immunity for treating or controlling the commonly prevalent diseases as well as COVID-19.

The links to the eBook COVID-19 are in the following links given below.



Rajaratnam Abel

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Published by rajaratnamabel

Having completed my undergraduate medical education from Christian Medical College, Vellore, India. Then I had the privilege of completing my Master of Public Health from the Johns Hopkins University, Baltimore, USA. I could also complete my PhD in Chennai, India. Based on my extensive work in nutrition backed by a number of scientific publication, I also received the Fellowship of the International College of Nutrition (FICN). I retired from active service in 2005. Since then God enabled me to be a Consultant Public Health Physician, at the SUHAM Trust of the DHAN Foundation in Madurai. I am involved in providing community based health care support to a large number Self Help Groups in 14 Indian states.

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