Using nutrition in the battle against viruses

Every day, there are billions of influenza-causing viruses and other microbes all around us. According to the United States Centers for Disease Control and Prevention (CDC), it is estimated that influenza has resulted in between 12,000 – 61,000 deaths every year since 2010. Yet, despite this sobering statistic, our body is actually created in astonishing ways that enable it to fight off colds and flu. In addition, specific nutrients in our diet, taken in the right amount, are also capable of supporting and activating our body’s immune response to fend off invading bacteria or viruses.


Our immune system is a complex and pervasive system with a key aim of fighting against infections and illnesses in our bodies. It comprises of different types of cells carrying out their specific functions with their own unique ways of communicating among immune cells and other cells. This is done through signaling, identifying pathogens with their special detecting mechanisms and getting rid of the pathogens. Depending on the cell types, immune cells can either station at specific strategic sites or move around the body to carry out their functions.

Our immune system can be grouped into 2 main functions.

INNATE IMMUNITY: These “inborn” or “built-in” immune responses form the first line of defense. They include barriers created by our bodily structures and secretions; gathering of immune cells to sites of infection by means of inflammation; destroying pathogens by consuming them, tagging them so that they can be easily identified for eradication, lysing them; and activation of adaptive immunity.

ADAPTIVE IMMUNITY: The slower yet highly-specific immune responses of this system form the second line of defense. This system creates precise immunological memories upon the first encounters with pathogens so that subsequent attacks by the same pathogens will not be successful in causing illnesses. Hence, it is also known as the “acquired” immune system.

Upon infection with an influenza virus, both innate and adaptive immune responses are involved in controlling infection. Good nutrition with adequate amounts of necessary nutrients is important in improving our innate immunity.


The reality is that an appropriate diet can work wonders in maintaining our immunity at its peak. There is a variety of receptors on our immune cells that can be activated by different nutrients. So, besides having a well-balanced diet with adequate protein, vegetables and fruits, we can specifically zero in on the following nutrients to stimulate immune cells and help them to battle against viral respiratory infections.


70 – 80% of our immune cells are found in the gut. The intricate interactions between our gut flora and the surrounding immune cells in supporting the development and signaling of immune cells also help to sustain our bodies’ immunity. In other words, healthy population and balance of gut microbiome is linked to a healthy gut and strong immunity. Studies have shown that probiotics may reduce flu-like symptoms and also reduce the duration of these symptoms.

With this in mind, we can load our intestinal flora by including various probiotic foods daily, such as yogurt, kefir, kimchi, miso and natto, among others. Look for strains from the lactobacillus and bifidobacteria groups. In sufficient amounts, they can withstand our stomach acid to reach the intestine where we want them to be. Alternatively, consider probiotic supplements that have enteric coating capsules – a layer that protects the probiotics from the stomach acid, or acidic-resistant probiotic strains. Equally important is the consumption of adequate fibre, especially soluble fibre, so that the little armies in our gut will not be starved to death. Hence, do include foods containing β-glucans in your diet.

β-glucans are a group of soluble fibre. Different β-glucans have different structural properties, which may influence their functions and activities in the body upon consumption. Foods that contain relatively higher amounts of β-glucans include certain types of mushrooms (like reishi, shiitake, maitake and white button mushrooms), sea vegetables, microalgae (especially a unique microalgae called Euglena gracilis), cereals (oats and barley) and some fruits.

β-glucans contribute to gut health by serving as prebiotics – food for the probiotics – in the gut, enhancing the healthy growth of probiotics. The good gut bacteria feeds on β-glucans and other soluble fibre by means of fermentation and releases immune-modulating short-chain fatty acids (SCFA).

What is even more interesting about β-glucans is that they can penetrate the gut barrier and sit on specific receptors on the immune cells in the inner surface of the intestine. Subsequently, the immune cells will be kindled and their communication and growth will be augmented, boosting the innate immunity.



Vitamin D, the sunshine vitamin, is an active hormone made by the skin when exposed to strong sunlight. This vitamin does more than just prevent the softening of bones. Our immune cells possess receptors that can be activated by vitamin D for optimal functioning. When vitamin D reaches a blood level of 30 ng/mL, it will transform into an “immune cell motivator” by occupying the vitamin D receptors on the immune cells, increasing their communications, growth and differentiation, and modulating inflammatory responses.

Since vitamin D deficiency is widespread nowadays and in view of the current climate with regards to viruses, it is advisable to test your blood vitamin D level and replenish accordingly and regularly.


Vitamin C participates in both the innate and adaptive immunity systems. Immune cells have active vitamin C transporter molecules embedded in their membranes that actively pump the vitamin into the cells during times of inflammation or infection. The content of vitamin C in the immune cells is directly proportional to their antimicrobial and antiviral activities.

A number of studies have demonstrated the immune-boosting benefits of vitamin C, particularly among older people, when it is taken at high doses of around 1000mg per day. In fact, vitamin C produces beneficial effects on virtually all aspects of the immune system; from energising immune cells, enhancing their growth to raising levels of some antibodies. It is little wonder that many studies recommend a regular and sufficient vitamin C intake.

Curb the double whammy of a suboptimal consumption of vitamin C and depletion of your body’s vitamin C during times of infection by having a diet rich in fruits and vegetables, and

supplement your diet with 1000mg of vitamin C daily to optimally support your immunity during the flu season.


Zinc fortifies our body’s natural immune defenses. It can be found in lean meat, poultry, seafood, soya products, wholegrains, nuts and seeds.

Zinc is made into lozenges so that it can be slowly released, helping to support immunity and fight colds and flu. Among the different forms of zinc lozenges, zinc acetate which releases zinc as ionic zinc has the unique ability to ward off colds and reduce the overall symptoms of cold, particularly in the initial phase when the cold symptoms are kicking in. This ionic form of zinc perches on cell receptors. The reaction may prevent cold-causing viruses from entering cells and establishing a common cold infection. However, zinc lozenges are not meant for daily use; just a few of these lozenges are required when extra support is needed in the beginning of cold and flu symptoms. On usual days, take a well-balanced diet with adequate zinc food sources.



Garlic, a member of the allium family, is rich in immune-boosting phytochemicals known as allicin. Allicin, together with other sulphur-containing compounds in garlic, has been proven to have potent and direct antiviral and antimicrobial properties. Aged garlic also have other exceptional immune-boosting compounds. To get the most out of garlic, it is best to consume them fresh right after cutting or mincing. Chopping or mincing will release the allicin and the natural enzymes in fresh garlic enhance the absorption of allicin in the body.


The high concentrations of anthocyanins and other flavonoids in berries provide both antioxidant and immune support to kill viruses. In addition, some berries are rich in vitamin C. Among all the berries, the phytochemicals in elderberries are especially active in killing flu-causing viruses.


Besides maintaining optimal immunity with good nutrition, do also remember to keep calm, manage your stress levels, and have good and adequate rest. Stay hydrated by drinking plenty of water and maintain good personal hygiene by washing hands often with soap and water for at least 20 seconds.

Last but not least, be socially responsible. Amidst the current chaotic influenza season, we should be safe in the knowledge that our bodies are equipped, aided by the right nutrients at the optimal dose, to fight the good fight against virus infections. Our immune cells are able but they can also have more support in combating these viruses. Build up your defense today by eating the right food!

Caleb Mok, Dietician

Caleb Mok is a dietitian who seeks to inspire people to live a disease-free, fulfilling and quality life by making healthy diet delicious and healthy lifestyle fun and achievable. Having trained in a heart institute and an acute hospital, his interest is focused on preventive and rehabilitative nutrition. He is actively advocating healthy lifestyle through article publications, public talks and seminars, individual counselling sessions, recipe development, cooking demonstrations, food photography and others.