It's the season of sniffles again. If you haven't already been laid low with a cold this winter, chances are high: colds are the most common illness in humans.
We can each expect to experience between two and five colds a year; there are more than 200 different respiratory viruses that cause cold symptoms. Flu, a far more serious beast, landed 180 people a week in hospital at its peak last winter.
It's no wonder, then, that there's a huge natural health industry based on cold and flu prevention. The editor's desk at Healthy Food Guide is groaning with immunity-boosting supplements, all vaguely promising protection from circulating lurgies.
But does any of it really work? And can you kill a bug with diet?
Researching the evidence on colds and flu proves interesting, revealing several triumphs of marketing over substance.
The things we all think prevent or cure colds seem to have very little evidence behind them. Vitamin C, for example, according to the evidence, does not prevent colds in most people.
The exception is people under extreme physical stress, for example marathon runners or skiers, in whom the risk of colds is halved with regular supplements. Once you have a cold, there's a little evidence that vitamin C slightly reduces its duration.
Echinacea and garlic occupy a lot of shelf space in the colds and flu section, yet there's weak or insufficient evidence that either prevents or shortens the duration of a cold.
One that does seem to have a bit to it is zinc. Take it early in a cold and you'll reduce your suffering by a day or so. There's emerging evidence around probiotics for prevention, the gut being a key part of our immune systems. And there's preliminary evidence that vitamin D may lower the risk of colds in some people, but experts say more research is needed.
So if supplements are marginal, what can we do to stop ourselves getting a cold?
Apart from the obvious and important hygiene things (thorough hand washing, not hanging out with sick people etc), there are some ways you can eat to potentially lower your risk of cold or flu.
Having a healthy immune system to start with is a good way to boost your chances of being well all winter. Fruits and vegetables, of course, are top of the list of immune-boosting foods. Plenty of gut-friendly fibre and omega-3 from oily fish will boost your gut's population of good bugs to help fight off potential bad invaders.
If the worst happens and you get a cold, there's no magic cure. Hydration and comfort is what you want from food. That might be why the good old chicken soup is so popular. While there's just one 20-year-old study suggesting chicken soup may have anti-inflammatory effects, there's no doubt it's comforting when you're sick. You'll get fluids, warmth and nose-clearing steam; add lots of veges and you'll get good nutrition too. Much better than popping a pill.
• Niki Bezzant is editor-at-large for Healthy Food Guide www.healthyfood.co.nz