When your immune system needs a boost

Some people survive flu season without a single sniffle, Fox News reports. And yet plenty others seem to catch cold after cold; sidelined with a perpetually stuffed-up nose and hacking cough that lasts all winter. So what's different between these two groups? Research shows your cold and flu vulnerability may come down to a few important and unexpected habits, like how much sugar you eat.

Eating too much sugar doesn't just pack on pounds. A study published in the American Journal of Clinical Nutrition found that eating 100 g of sugar (think three cans of soda) significantly hampered the ability of white blood cells to kill bacteria.

Your body needs plenty of water to flush out toxins—and yes, coffee and tea are acceptable sources. How much fluid you should drink daily varies from person to person. You're drinking the right amount if your urine is pale yellow.

Excess weight is unhealthy for your heart, brain, and other organs. But it's also bad for your immune system. In fact, those who become the most seriously ill with swine flu tend to share the same characteristic: a body mass index over 40, meaning they are morbidly obese. Excess weight can cause hormonal imbalances and inflammation that impairs the immune system's ability to fight infection.

Surprisingly, the cleanliness of your drinking water can play a role in whether or not you get sick. When researchers from Dartmouth Medical School inoculated two groups of mice with the H1N1 virus, the group that had spent 5 weeks drinking arsenic-tainted water developed suppressed immune systems, and many died. The mice that didn't drink the water got the flu but recovered completely.

As uncomfortable as it may be, a runny nose is actually a good defense against colds and the flu. Mucus traps viruses and clears them from the body. If your nasal passages are too dry, irrigate them with a squeeze bottle or neti pot of saline solution. A humidifier can also help. If dryness is chronic, see your doctor to determine the underlying cause.

It's no coincidence that you tend to catch a cold after a big work deadline. According to a report by the American Psychological Association, long-term stress weakens the responses of your immune system. In addition, "if you become stressed while you have the flu, your symptoms can get worse," says Philip Tierno, director of clinical microbiology and immunology at New York University and author of The Secret Life of Germs: What They Are, Why We Need Them, and How We Can Protect Ourselves Against Them.

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