Anyone who is taking an overseas airline flight of seven to 10 hours this summer, as I am, faces two potential health issues, one of them mostly just annoying and another that's potentially life-threatening.

The annoyance is jet lag, the condition that affects virtually all long-distance travelers when the body's circadian rhythm, or natural waking-and-sleeping cycles, is disrupted. The more serious threat is deep-vein thrombosis, or the formation of blood clots in veins that can be caused by long periods of inactivity.

Regarding jet lag, when you arrive in Europe after hours jammed into a coach seat alongside 300 fellow sufferers, the clock may say its 8 a.m. but your body thinks its 2 a.m., and time to go to bed. For most people, it can take at least several days to adjust to a new time zone so that they're waking and sleeping at normal hours.

While you may not be able to really "cure" jet lag, there are a number of ways to combat its symptoms of insomnia, irritability, and disorientation.

One way that I tried on a trip to Europe more than 15 years ago is the "anti-jet-lag diet," developed in the 1980s by the U.S. Department of Energy's Argonne National Laboratory. More information about it is available online at www.AntiJetLagDiet.com.

Studies published in medical journals have found that travelers who follow the diet are seven times less likely to experience jet lag when traveling west, and 16 times less likely when traveling east, according to Argonne officials.

The diet requires you to start it four days before leaving on a long flight, alternating between days of eating large meals full of carbohydrates and smaller, lighter meals low in carbs. You can have caffeine only between 3 and 5 p.m. on each of the days, followed by drinking two or three cups of coffee with caffeine just before boarding your flight.

You also cannot eat or consume alcohol on the flight, and must try to sleep the entire trip, something that can be tough if you've just had a lot of coffee. After arriving, you need to spend all the time you can outside, absorbing sunlight, and resist the temptation to sleep before your normal bedtime.

Unfortunately for me, I'm a morning coffee drinker and the caffeine withdrawal gave me a nasty headache each day I followed the diet. But I had followed the meal plan, got a little sleep on the flight over, and then stayed up the first day until evening. It worked well enough that by the next day, my body had adjusted to my new time zone.

There are other remedies for jet lag, mostly homeopathic medicines designed to adjust chemicals in the body that help you cope. I'm trying one called JLg [Jet Lag] by Liddell Laboratories that I bought at a health-food store. I will let you know after my upcoming trip how it worked.

You can find basic jet-lag prevention advice on the www.webmd.com Web site's page on sleep disorders, and on other Internet sites. Here's what they say:

Several days before departure, try to adjust your sleeping habits to the new time zone. As soon as you board the flight, reset your watch to the new time zone. Eat a light meal, and drink water and a limited amount of alcohol in flight. Sleep or nap as much as possible.

Upon arrival, walk around in daylight for several hours; this is very important because it helps replenish your vitamin D. Take no more than a two-hour nap and avoid excessive amounts of caffeine, alcohol, and tobacco. Try to go to bed at a normal hour the first night.

If you have experience overcoming jet lag, tell me what has worked best for you. And tell me if you were unable to overcome jet lag.

I also found good information on the WebMD Web site on deep-vein thrombosis or DVT. It occurs when blood clots form, usually in a calf or thigh muscle, after a long airplane flight.

The WebMD entry says a "blood clot . . . can partly or completely block blood flow and damage valves in blood vessels. It can also break free and travel through your blood to major organs, such as your lungs, which can be fatal."

The site also suggests that to help prevent DVT while traveling, avoid wearing tight socks and crossing your legs for long periods. Drink plenty of fluids and avoid dehydrating ones, including alcohol and coffee.

Here's the key part: During long flights, get up and move around as much as possible. If you can't get up and move around, curl or press your toes down often. You may also want to consider buying compression stockings at a medical-supply store and wearing them during the flight.

I'm counting on you to also suggest resources for travelers on preventing DVT.

Contact Tom Belden at 215-854-2454 or tbelden@phillynews.com.