How to Boost Your Immune Function with the Right Food

What you eat plays a bigger role in supporting your immune system than you think.


Words Jackie Green

It has been documented that people who do moderate exercise for about one hour a day suffer fewer infections and illnesses than their sedentary friends. However, large volumes of medium to high intensity exercise can reduce immune function and increase the chances of infections.

Not only does illness make us feel rotten, but it interrupts training and interferes with fitness and competition goals.

Stress hormones such as cortisol and adrenaline rise during exercise, which suppress the function of white blood cells. White blood cells have a crucial role removing viruses and bacteria from our systems so any interference will increase our susceptibility to picking up an infection.

Upper respiratory tract infections with coughs, sore throat, runny nose, headache and watery eyes are the most common illnesses suffered by athletes. Marathoners and ultra-runners are most vulnerable to picking up an infection in the first 72 hours after a tough endurance event.

You can build stronger resistance to illnesses by eating the right vitamins and nutrients regularly, and it’s not a difficult thing to do. Here are the essentials that you need to ensure you are stocked up on.

Vitamin  D

Despite our position near the equator and a sunny climate, a surprising number of Singaporeans are deficient in Vitamin D. Runners may feel that they are safely outside this bracket, but if you are out in the evenings or wear sunscreen, there is still a chance that insufficient Vitamin D is formed. Of course, it is crucial to protect your skin from the sun’s harmful rays but if you are in direct sunlight without sunscreen for less than 10 minutes every day, get your Vitamin D levels checked as food only makes a small contribution to vitamin D levels.

Food sources of Vitamin D: oily fish such as salmon and trout, egg yolk and mushrooms. In fact, you can increase the amount of vitamin D in mushrooms by placing them in the sun.

Pro and pre biotics

The microbiome (gut bacteria) has been linked with good digestion, body weight, mental health and immune function.

A probiotic is a food or supplement containing live bacteria. For generations, communities who eat fermented foods have known them to be beneficial for good health. Try kimchi, kombucha, saurkraut, kefir and yoghurt. For people wanting to take a probiotic supplement, a daily dose of Lactobacillus and/or Bifidobacterium is likely to have the most benefit.

A prebiotic is a food or supplement containing fibre. Fibre in vegetables, fruit, nuts, seeds, beans, lentils, and wholegrains are food for good gut bacteria, and given a plentiful supply and varying types of fibre, the microbiome thrives.


Fat and protein eaten during exercise seem not to have an impact on markers of immune function. However, consuming carbohydrates during exercise lasting 90 minutes or more reduces the rise in stress hormones caused by intense and prolonged exercise.

30g of carbohydrate per hour during a run should limit the immune depressing effects of prolonged exercise.

Vitamin C

A diet rich in vitamin C promotes good immune function. There is evidence that Vitamin C supplements may reduce the duration of a cold, however, there is no consensus on the adequate dose.

Food sources: peppers, tomatoes, dark green leafy vegetables such as spinach and kale, oranges, kiwi fruit and berries.


At least 75mg zinc per day taken immediately after symptoms of a cold occur have been shown to reduce its duration, probably  by inhibiting the replication of the rhinovirus, which is the most common cause of colds. Zinc also supports a strong immune system and aids the healing of cuts.

Food sources of zinc: red meat, liver, shell fish and pumpkin seeds.


Low iron levels reduce immune function. Unless you have a known iron deficiency, reach for iron rich foods rather than supplements.

Food sources of iron: red meat, eggs, beans and lentils, tofu, almonds and dried apricots

Recovery Nutrition

Refuel and rehydrate after exercise. Water and a nutritious meal will be sufficient for most recreational runners, whist those training multiple times a day will need to pay closer attention to recovery in the hour post exercise

Knowledge is king in preventing illness  

1. Sleep: 7-8 hours a night

2. Hygiene: just before an event, when training volume and intensity are at a peak, your immune system may be depressed. It will be especially important to take practical measures to limit exposure to viruses and bacteria. Keep away from people with coughs and colds, be meticulous  hand washing, take care eating and drinking unfamiliar foods and drinks, scrub water bottles and use disposable straws rather than drinking from cans.

3. Good Nutrition: pay attention to Vitamins D and C, iron, carbohydrate, digestive health and recovery nutrition


RUN Singapore aims to be a complete resource for Singaporean runners and marathoners of all ages and abilities. With its continuing efforts, the website seeks to uncover the latest news, information and expert advice to motivate runners to run efficiently, train intelligently and lead a balance life. If you have enjoyed a good read with RUN Singapore magazine, be enticed further as we unleash more running content to feed your running needs.


Comment (0)

RUN Singapore is the first flagship title created by Bold Ink Magazines in 2012. Positioned as the only running magazine in Singapore, the publication has since built its strong reputation within the running/sports industry. With almost 80% of all leading sports brands advertising with the magazine and a fast growing subscriber base, the publication is set to be the leading running magazine in the region.


Bold Ink Magazines Pte Ltd
8 Kaki Bukit Avenue 1
#01-01/02 Singapore 417941