Take a few tips from the top and read on for secrets of people who don't get sick...
James Davis, an ex-special forces soldier, once had a job which could see him flying overseas and hitting the ground (literally) running, sometimes going without sleep or food for days on end depending on the situation.
Davis says he'd simply talk his body into adapting, promising himself rewards such as food and sleep as soon as each mission was over.
He'd eat a high protein diet while travelling to stay alert while
crossing time zones, and load up on sleep, water and food when it was available.
When each mission was over and he was back on safe ground, he'd plan a high carbohydrate meal such as pasta or rice and vegies followed by a 12 to 14 hour sleep. No jetlag, no post-flight snuffle, straight back into his life — "no colds allowed".
Sleep it off
Numerous studies have proven the effects of sleep on the immune system. But there's another reason sleep is so important: when you're tired, you're more likely to head for sugary snacks and caffeinated beverages, both of which can lower immunity. So skip the caffeine, turn the phone off and get some shut eye. It's the simplest health trick, with the most widely proven health benefits.
Stress has been linked to lowered immunity in dozens of studies, and this is thought to be because cortisol (the hormone released when we're under stress) can have a detrimental effect when chronically released over time.
Other studies show that laughter and music both boost the immune system and reduce the stress response in the body
So grab a comedy DVD or turn up the radio, and reap the rewards.
If you've got the flu, you don't need antibiotics
Dr Parnis says antibiotics are unnecessary unless you have a bacterial infection like pneumonia on top of your cold or flu virus. "Anything you get from the pharmacy will ease the symptoms, but the main prerogative is to rest. Rest and fluids are the best thing you can do for a cold or influenza."
Catch it early
A study by the Australian National University has found that vitamin C loading can reduce the severity of colds.
Sue Heintze, who once won training competitions and now runs a successful personal training business as well as caring for a toddler, says she doesn't get sick with a few simple steps.
"If I do feel like I'm coming down with something, I don't push through it. I go to bed and rest. I also take load with powdered vitamin C, about 6g over the course of the day. I swear I've beaten most colds in a day when I've done this. You don't get any medals for turning up to work or the gym and sharing your germs with everyone else plus you'll stay sick for longer if you don't let your body rest and recuperate.