Woman in yellow jumper sneezing. Covers mouth and nose with a tissue.

Ah-choo! Cold and flu season is well and truly upon us. Spend it fighting fit instead of fighting off a lurgy with these expert tips to strengthen your immune system.


In addition to helping the body absorb and retain calcium and phosphorus, vitamin D helps the body facilitate normal immune system function. It is sometimes called the sunshine vitamin as it is produced in your skin in response to sunlight, as well as being found in certain foods.

“People with low vitamin D levels are more susceptible to getting sick,” says Kate Save, clinical dietitian, exercise physiologist, diabetes educator and CEO and co-founder of Be Fit Food. “The best source of vitamin D is UVB radiation from the sun and optimal exposure to the sun varies depending on where you live and the time of year.”

It is common for vitamin D levels to drop in winter when people have less exposure to sunlight. According to the Cancer Council, when the UV Index is three or above (such as in summer), just a few minutes outdoors most days is all most people require to achieve the required levels of vitamin D.

In late autumn and winter, when the UV Index drops below three in some parts of Australia, they recommend spending time outdoors in the middle of the day with some skin uncovered. Download the SunSmart app or visit the Australian Bureau of Meteorology website, to check the UV Index in your area.

“It’s understandably tricky for many to get the recommended daily intake of sun while in isolation therefore load up where you can on foods that have good sources of vitamin D,” says Save. “These include, mushrooms, oily fish (salmon, tuna, mackerel), and dairy that is fortified with vitamin D.”


The gut plays a crucial role in immunity. “The gut microbiota acts as our first line of defence against harmful bacteria we have ingested, helping to prevent absorption or colonisation of pathogens,” says Accredited Practising Dietitian Kate Gudorf. “Sometimes our gut bacteria need a helping hand, so choose foods which are high in probiotics to boost the number of healthy bacteria in your gut.”

Gudorf recommends regularly eating yoghurt and fermented foods, such as kefir, tempeh and miso to help increase good gut bacteria, which in turn assists immunity.


In the 1970s Nobel laureate Linus Pauling declared that vitamin C could be used to prevent and treat the common cold. The claim has been debated ever since with further studies producing mixed results.

“The data shows that vitamin C is only marginally beneficial when it comes to the common cold,” says Dr Bruce Bistrian, chief of clinical nutrition at Harvard-affiliated Beth Israel Deaconess Medical Center.

While vitamin C supplements may not reduce your likelihood of catching a cold, they may reduce its severity and duration. One study found that consuming at least 200mg of vitamin C a day seemed to reduce the duration of cold symptoms by an average of 8 percent in adults and 14 percent in children, roughly one less day of illness.

Dr Bistrian recommends getting your vitamin C from food rather than supplements. “It’s better to get your vitamin C from food, because you also get other nutrients,” he says. “Eat the recommended five servings of fruits and vegetables per day for general health and you’ll get enough vitamin C.”

To really experience any benefits from vitamin C, you’ll need to consume it each and every day, not just during cold and flu season. While you probably know that citrus fruits are a great source of vitamin C, Save notes that there are plenty of vegetables you can feast on too. “Vegetables that are high in vitamin C include red capsicum, broccoli, cauliflower and spinach,” she says.


Sleep and the immune system are inextricably linked. Immune responses, like those caused by a cold, can affect your sleep. At the same time, getting the recommended eight hours of sleep every night is known to help immune function.

“You probably know that the immune system is like a defence mechanism of the body,” says Certified Sleep Science Coach Alex Savy, founder of SleepingOcean.com. “When we don’t get enough sleep, the defence weakens, and the immune system may lose some of its “protective” abilities.”

To improve the quality of your slumber Savy encourages readers to reserve evenings for relaxation. “To sleep well, you need to learn how to manage your stress effectively,” he says. “The first step would be giving yourself some time to wind down in the evening. It’s better to dedicate around an hour to a relaxing activity of your choice before sleep, mute the notifications, and ideally, stop using your devices. It’s also important to build your daily schedule accordingly so that you have enough time to yourself in the evenings.”