With the cold and flu season in full swing, many people are looking for ways to stay healthy and avoid getting sick.
While there's no magic food that can "boost" the immune system overnight, maintaining a strong and resilient immune system relies on consistent healthy lifestyle choice, says Swinburne Dietetics Lecturer Dr Nina Imad.
"The immune system is your body's frontline defence against infection and illness. Keeping it strong involves consistent healthy habits, including getting enough sleep, staying physically active, managing stress, supporting gut health and eating a variety of nutrient-rich foods-what we call eating the rainbow. Fruits and vegetables are packed with essential vitamins, minerals, and antioxidants, which help your immune system function normally."
Do oranges really work?
Oranges and other Vitamin C-rich foods like berries, kiwi, capsicum, broccoli and dark leafy greens, do play an important role, says Dr Imad.
"While taking Vitamin C won't prevent you from catching a cold, research shows that having adequate Vitamin C daily can reduce the duration and severity of cold symptoms. However, starting Vitamin C only after you get sick doesn't seem to have the same benefit.
"Including a variety of fruits and vegetables is key to ensuring adequate intake. Most of these are in season during autumn and winter, and if not, frozen varieties are just as nutritious, often snap-frozen at peak ripeness, preserving their nutrient content."
What about garlic and echinacea tablets?
Garlic and echinacea have been popularised as natural cold remedies and are sprouting across chemist aisles.
Dr Imad explains that some studies suggest that garlic may help stimulate immune function, and that echinacea may offer antioxidant and antibacterial properties.
"However, the scientific evidence is weak and inconsistent," she says. "These supplements are unlikely to prevent infections and should be viewed as complementary and not replace evidence-based approaches such as a balanced diet and healthy lifestyle."
Does zinc help?
Dr Imad says that zinc is an important nutrient for normal development and function of cells and antibodies.
"Some evidence suggests that taking zinc at the first sign of cold symptoms may help shorten the duration of a cold. Zinc with Vitamin C work well together as a supportive combo. Good food sources of zinc include meat, shellfish, legumes, dairy, nuts, and seeds."
What about Vitamin D?
Vitamin D plays a crucial role in supporting immune function," says Dr Imad.
"Many Australians are deficient-especially in winter when sunlight exposure is reduced. You can top up your Vitamin D levels through moderate sun exposure and foods like eggs, mushrooms, fortified milk, liver, and oily fish such as salmon."
Supplements: helpful or hype?
"Dietary supplements can support immune health when there is a deficiency or when intake is inadequate," says Dr Imad. "However, they should not replace a balanced diet. It's important to consult a healthcare professional before starting supplements, especially long-term."
Gut and immunity
A healthy gut microbiome plays a vital role in supporting immune function, thanks to the gut-brain-immune connection, shares Dr Imad.
"Eating fermented and probiotic-rich foods can help maintain a diverse gut microbiota. Including probiotics such as yoghurt, kimchi, and sauerkraut can help populate the gut with beneficial microbes, which in turn help regulate immune responses."
The bottom line
Dr Imad says that, unfortunately, you can't "boost" your immune system with any one food or supplement.
"But you can support your immune system by ensuring you are having a well-balanced, varied diet rich in colourful fruits and vegetables, getting enough sleep, staying physically active and supporting your gut health with probiotic foods like yoghurt, kimchi, and sauerkraut."
