Jet lag can put the brakes on the most exciting vacations. Almost everyone who has ever flown across time zones knows what it feels like. The experience ranks somewhere between eating day-old cooked oatmeal and nursing a hangover.
These food and drink metaphors aren't just a coincidence. Jet lag, it turns out, affects more than our sleep; it affects our internal organs as well. Given what is known about the importance of intestinal bacteria (called the microbiome) and their connection to immune function and well-being, it's clear that any discussion of jet lag, and how to deal with it, needs to consider "gut lag" as well.
Beyond sleepiness at the wrong time, jet lag affects our internal organs: The liver, pancreas, heart and gastrointestinal tract have their own daily rhythms.
While these schedules are regulated in part by a master pacemaker in a tiny region of the brain, called the suprachiasmatic nucleus, time change may affect different organs differently.
The most obvious signs of this is "gut lag" - feeling hungry (or having no appetite) at the wrong times, experiencing constipation or having an urge to use the bathroom at unexpected times.
There is even evidence that gut lag can affect the intestinal microbiome (those bacteria colonizing our gut) and make us more susceptible to traveler's diarrhea. That's in part because disrupting the daily rhythms of our 100 trillion intestinal microbes can impair their immune function.
As with jet lag, there are some things you can do to manage gut lag.
Experts recommend eating as little as possible while en route, to avoid the possibility of indigestion from unusual eating schedules. This can be hard for sleep-deprived souls: It's well known that eating is often a way of compensating for lack of sleep. (Sleep-deprived people tend to gain weight.)
For some, eating a meal before starting your travel can prevent hunger before you arrive.
Bowel habits will adjust more quickly if you immediately shift to eating during scheduled mealtimes in the new time zone. Exercise also can help regulate bowel function, with the added bonus that it can make you feel less sleepy. Whatever you do, drink a lot of water or other fluids: People often get dehydrated in flight, which can add to constipation, a well-known feature of gut lag. If it persists beyond a few days, gentle laxatives may be helpful.
One final caveat about advice regarding jet lag and gut lag. Despite the amazing influence of the cycle of dark and light, we're all slightly different. Some people are naturally early birds; others are naturally late risers.
In addition, our tissues have multiple clocks with varying effects, and some of our internal parts take longer than others to adapt to time shifts. Given this complex interrelationship involving our brain, our other organs and the rhythms of light and dark, there's no one-size-fits-all advice for travelers. It may take several trips across time zones and experimentation with light exposure, sleep patterns, melatonin and diet before you've figured out what works best for you.