Want to know which foods pack most immune-boosting punch per bite? Read the credentials of our superfood line-up — foods so high in certain nutrients they win the nutritionist's version of the Oscars.
Kellie Bilinski, spokesperson of the Dietician's Association of Australia, says Brazil nuts have a higher level of selenium than any other food source. So why is selenium so good? A trace mineral, selenium forms selenoproteins in the bloodstream, which fight free radicals and prevent cellular damage — all of which compromise the immune system.
Aside from being the best source of selenium, Brazil nuts are high in monounsaturated fats, vitamin B, thiamin and manganese.
"A lot of research has gone into Omega 3 oils, because they show the most nutritional promise," says Bilinski. "Basically you're looking for anything that boosts your white blood cells and antibodies, to fight infections, such as colds and flu, and prevent inflammatory processes such as cancer."
Fatty fish, says Bilinski, is one of the best natural sources of omega 3 fats. Opt for tuna, mackerel, sardines, salmon and rainbow trout.
If you're not a fish fan, flaxseed oil is extremely high in omega 3 oils too.
If you simply can't bear either of those options, try taking a reflux-free fish oil supplement every day.
While fortified bread, eggs and milks also have trace amounts of omega 3 oils, nothing is as high as fatty fish or flaxseed oil, according to Bilinski.
Beta carotene is a super-nutrient known to be good for the immune system because it helps fight antioxidants and keeps the blood healthy. Pumpkin, sweet potato, carrots and even spinach (despite it being green, not orange) are all high in beta carotene.
Many studies show a diet high in beta carotene makes us much more resilient to signs of ageing.
Vitamin D is another nutrient which boosts the immune system and fights off colds and flu.
During the winter months, when sunlight isn't as plentiful, it's more important than ever to ensure we're getting a bit of extra vitamin D from our food. Mushrooms are one of the best natural sources.
Specially fortified 'vitamin D' mushrooms were launched in Australia late last year, and Bilinski says they are so high in vitamin D that just three a day will give you your daily requirement.
Mushrooms are also high in B group vitamins (essential for thyroid function and the body's response to stress), as well as essential minerals which act as antioxidants including magnesium, selenium and zinc.
Speaking of zinc, which is essential for preventing and lessening infections, oysters are the best natural source of this super mineral. Other sources include beef, chicken, pumpkin seeds and sesame seeds.
Aside from being essential for cellular function and a healthy infection-fighting immune system, zinc has been proven to fight colds and even reduce the severity and length of an infection.