In these days of COVID-19 Pandemic, people are focussing on various means towards building a stronger immune system. Besides cooking at home, eating healthy, social distancing and practising regular hand hygiene medical experts are also strongly recommending vitamin supplements to shield the body against virus infections.

The common symptoms associated with COVID-19 are cold and flu, where vitamins like C, D, E and mineral zinc are known to be beneficial in boosting the immune system and fighting these warning signs. However, it is imperative to understand that these supplements need to be popped in the right amounts and as per the daily dosage recommendations. 
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In this article, we bring you how each and every vitamin supplement functions and the possible side-effects, in case of an overdose. 

How Immune System Functions?

The immune system comprises of a complex collection of cells, processes and chemicals that are working regularly to defend the body against attacking harmful pathogen, microbes, including viruses, toxins and bacteria. Hence it is extremely critical to maintain the immune system healthy at all times to prevent infections and keep diseases at bay.

Leading a disciplined lifestyle by eating wholesome foods, staying well hydrated, getting a sound sleep and regular exercise are the most significant ways to boost the immune system. Furthermore, evidence has revealed that augmenting with vitamins, minerals, herbs and other natural food sources can also help in enhancing the immune response and possibly shield against illness.

Read this article to an overview of how different supplements help in triggering the immunity and what happens if we are overdosing.

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Vitamin C

Vitamin C is a water-soluble vitamin also termed as Ascorbic acid which is required by the body to perform several metabolic activities. It is one of the most effective nutrients for treating common cold, cough and protecting against infection. Vitamin C plays a significant role in the functioning of immune cells and stimulates the body’s ability to fight against infection. It is also needed for cellular death, which facilitates to keep the immune system healthy by removing out old and worn-out cells and restores with new ones.

This vitamin is valued as a powerful antioxidant which safeguards the cells from oxidative stress and scavenges free radicals. Oxidative stress has a negative impact on the immune system and elevates the risk of diseases. Supplementing with vitamin C is known to lessen the risk of respiratory infections such as common cold and viral infections. Also Read: Vitamin C – Functions, Food Sources, Deficiencies and Toxicity

Food Sources

As vitamin C is a water-soluble nutrient it is dissolved in water and not stored in the body, hence it must be supplemented through diet. There is a whole range of natural food sources that are overpowered with vitamin C to fulfil the demands which include orange, lemon, amla, kiwi, guava, mango, melons, berries, cabbage, potato, tomato, cauliflower, spinach, thyme and winter squash to name a few.

Recommended Dietary Allowance

The recommended intake of vitamin C for normal adults is 40 mg/day.

Is Vitamin C Overdosing Possible?

Complimentary daily dose range from 250-1000mg/day and maximum limit is 2000 mg a day. However, it is observed that excess dietary supplement with vitamin C is unlikely to be harmful, but mega doses which exceed the limit may lead to diarrhoea, nausea, vomiting, heartburn, abdominal pain and headache.

Vitamin D

Vitamin D, the sunshine vitamin is a fat-soluble nutrient which the body produces when exposed to sunlight. It plays a significant role in maintaining the optimal level of calcium and phosphorus, which promotes bone growth and development and musculoskeletal balance. It is also actively involved in cell growth, repair, immune function and supports wound healing. Adequate vitamin D in the diet can also protect from respiratory infections. Studies have shown that supplementing with vitamin D can remarkably lower the chance of respiratory tract infections. Also Read: Vitamin D – Functions, Food Sources, Deficiencies and Toxicity

Food Sources

Although sunlight is the best source of vitamin D, it is also plentiful in natural food sources such as fortified cereals, soy milk, almond milk, dairy products, orange juice, mushroom, fish, cod-liver oil and eggs.

Recommended Dietary Allowance

The recommended dietary intake of vitamin D for normal adults is 400- 600 I.U and for adult above 70, the RDA is 800 IU/day. 

Is Vitamin D Overdosing Possible?

The safe upper limit of vitamin D supplement is 1000-2000 I U / day. However, an overdose of vitamin D toxicity leads to hypercalcemia in the blood, which causes nausea, vomiting and frequent urge to urinate. It also leads to hypercalciuria, when the body tries to eliminate excess calcium via the kidneys.

Vitamin B6

Vitamin B6 is one among the nine water-soluble nutrients which play a vital in several bodily process and metabolic functions. It is essential for the normal functioning of the brain and for keeping the immune system and nervous system healthy. It also works as a potent antioxidant and helps to scavenge the free radicals from the body, thus preventing oxidative damage. Vitamin B6 is important for facilitating biochemical reactions in the immune system and deficiency of this vitamin result in reduced production of white blood cells, antibodies, T cells and other immune factors needed to combat infections and ward off germs.

Food Sources

Vitamin B6 is a water-soluble nutrient which gets excreted from the body, hence should be supplemented through diet. Mother Nature has bestowed us the natural food sources abundant in vitamin B6 such as sweet potato, spinach, green peas, plantain, banana, papaya, beans and lentils, whole grain cereals, nuts, egg, fish and meat.

Recommended Dietary Allowance

The recommended dietary allowance of vitamin B6 is 1.3- 1.7 mg/d for normal adults. 

Is Vitamin B6 Overdosing Possible?

The tolerable upper limit of vitamin B6 supplement is 100 mg/day for adults. Overdosing with vitamin B6 supplements may result in nerve damage, loss of control and balance, poor appetite, abdominal pain, diarrhoea, nausea and vomiting, headache and heartburn. Hence it is pivotal to seek the advice from your physician before taking a vitamin B6 supplement.


Zinc is an essential trace mineral needed by the body to perform several bodily processes like maintaining the defence mechanism and lowering inflammation. It is a vital element commonly added to supplement and lozenges which are known to bolster the immune response. It plays a crucial role in immune cell development, communication and inflammatory response. Deficiency of this mineral significantly affects the body’s immune response resulting in an increased risk of infection like pneumonia and other diseases. Several pieces of evidence have disclosed that zinc supplements may prevent respiratory tract infections like the common cold and also stimulate the immunity power for those who are already unwell.

Food Sources

Zinc cannot be synthesized in the body, hence it should be obtained as part of the diet. Some of the food sources that contain copious amounts of this trace mineral include legumes, almonds, pumpkin seeds, milk and milk products, quinoa, mushroom, peas, dark chocolate, eggs and spinach to mention a few.

Recommended Dietary Allowance

The recommended dietary allowance of zinc for normal adults is 10-12 mg/day. 

Is Zinc Overdosing Possible?

The upper limit of zinc supplement should not exceed above 40mg/d. Zinc supplements are a safe and effective way to enhance optimal health if taken under proper medical guidance. However, overdosing of zinc supplements leads to adverse side effects including nausea, vomiting, diarrhoea, and stomach pain and may also hinder the absorption of copper.

Vitamin E

Vitamin E is one of essential fat-soluble nutrient that is extremely valuable in the normal functioning of the body. It plays a crucial role in treating several ailments and triggers the immune system against invading pathogens and microbes. It is also a potent antioxidant which shields the body from oxidative stress and free radical damage. Several studies have shown that vitamin E is effective in treating respiratory ailments, asthma and allergies.

Food Sources

Mother Nature has bestowed upon us a myriad of food sources extremely abundant in vitamin E that suffices our daily needs which includes green leafy vegetable, almonds, hazelnut, peanuts, fortified cereals, sunflower oil, wheat germ oil, soybean oil and fish.

Recommended Dietary Allowance

The recommended daily intake of vitamin E is 8-10 mg/d of vitamin E.

Is Vitamin E Overdosing Possible?

The upper limit of vitamin E supplement should not exceed above 400 IU/ and consuming a high dose of vitamin E supplements may result in nausea, vomiting, bleeding, blurred vision, tiredness and abdominal cramps.


A healthy diet with a rich array of natural produces plentiful in fruits and vegetables will provide you with needed amounts of vitamins and minerals. It is always best to seek the advice of your doctor or health care provider before taking any supplements and also to know about the exact dose of supplement needed.