You need nutrients to build a strong immune system. Obviously then, insufficient nutrients weaken the body.
'If one does not eat enough, certain parts of our system cannot function normally,' said Dr Loh Keh Chuan, an endocrinologist at Mount Elizabeth Hospital. 'For example, the immune cells may not work as effectively as they should.'
Long-term inadequate nutrient intake can therefore undermine the body's defence system in the long run, said MsAnn Selina Chang, a nutritionist at The Nutrition Place.
However, not all kinds of food are immune-boosting. vitamins like A, C and E, and minerals like zinc and selenium are key, she said.
Vitamin A helps to maintain mucusol surfaces - found in the digestive and respiratory tract - which act as a physical barrier to germs. Food with vitamin A is usually deep yellow or orange coloured. These include vegetables like capsicums and fruits like pumpkins.
Citrus fruits and berries should go into your shopping cart too, as these fruits contain vitamin C, which enhances immune cell activity.
Vitamin E - an antioxidant that quells unstable molecules called free radicals - is present in nuts and seeds. High amounts of this vitamin are found in immune cells to aid in fighting germs, said Ms Chang.
'White blood cells often use free radicals to destroy pathogens,' she said. 'High concentrations of antioxidants like vitamin E allow white blood cells to use the destructive power of free radicals without being harmed.'
The mineral zinc is often found in wholegrain foods and helps in white blood cell growth, while selenium works in tandem with vitamin C and E to boost immune response and DNA repair, MsChang added.
Generally, young children need more nutrient-dense foods as they are still growing. Because the elderly tend to eat less due to teeth and digestion problems, their food should also be packed with as many nutrients as possible, said Ms Chang.
People with chronic conditions and pregnant mothers also have to take extra care of their diets to keep their immune system in shape.
High blood sugar levels in diabetics can affect the immune system's ability to fight infections, said Dr Loh. As for pregnant mothers, they need more folic acid and iron to keep both themselves and their babies healthy.
That's not all. One also needs a balanced lifestyle that is as stress-free as possible.
'When one does not exercise regularly and sleep well, the body becomes stressed and this affects the cell repair process that is key to a strong immune system,' said Dr Loh.
