The personal entertain­ment monitor on this 15-hour Cathay Pacific flight from Toronto to Hong Kong is telling me it’s 3:25 p.m. in our destination, but my body clock is complaining it’s really 3:25 a.m.

I’m torn between getting some mid-flight shut-eye or staying awake and tricking the body into a new time zone. Either way, changing time zones and travel in general means stress on the system, upping the vulnerability to lurking germs.

Flu season colliding head on with holiday travel begs the question: How does one stay healthy when flying, especially on longer flights?

Dr. Nayana Suchak, a family doctor at Mount Sinai Hospital, says that “when we change time zones that usually means sleep deficit resulting in a compromised immune system.”

A weakened immune system, of course, means greater chance of catching a cold, flu or worse. “(Keeping) the immune system strong is your first and most powerful defense,” says Suchak.

In preparation for a flight, she recommends adapting to local time as early as possible; but if you’re exhausted during or following the flight, you can still take the time to nap. Sleep boosts the immune system.

But it also needs hydration to work at maximum capacity, notes Suchak, so she recommends minimizing your alcohol intake before and during a flight because of alcohol’s dehydrating effect. Instead, opt for water and plenty of it.

Minutes after taking off for Hong Kong, a flight attendant passes out individual bottles of water to passengers. For those booked on airlines that don’t offer this service, it’s a good idea to carry your own. Just remember bottled water won’t get through security, so you’ll need to purchase it once you get beyond the check point.

While many turn to popping Vitamin C prior to a flight, Suchak says that while the practice won’t hurt, there’s no great evidence that it will help either.

She says it’s better to stick with a healthy diet that includes lots of fruits and vegetables. Along with proper diet and drinking plenty of water, regular exercise and good sleep habits are also important for the immune system, particularly at stressful times such as before and after a trip.

“A lot of patients come to see me within 48 hours of returning from a flight because the stress of travel does take its toll,” she says.

A travel-sized bottle of hand sanitizer is a good item to keep in your purse or briefcase, but according to the doctor, good old-fashioned hot water and soap will also do the trick. Wash hands often, she says, and keep them away from the face. Especially avoid rubbing the eyes and putting your fingers in your mouth — those are both good ways to spread germs.

Some airlines are also going the hand-sanitizer route. Cathay Pacific hands out individually packaged anti-bacterial towels to passengers, and also offers anti-bacterial soaps in onboard washrooms.

Of course, the thought of sitting next to a coughing, sneezing fellow passenger isn’t awfully appealing, nor is the thought of that very same air recirculating within a confined space. One can’t do too much such seatmates, other than offering the offender a box of tissues and hoping they get the message, but with regard to cabin air, sophisticated filtrations systems are pretty much the norm today.

Cathay Pacific spokes­person Jennifer Pearson, says the airline’s High Efficiency Particulate Arresters(HEPA) system “filters 99.999 per cent of dust particles and airborne contaminates.”

– Anne Dimon is a freelance spa and wellness travel writer and editor of