 If you're crossing three more time zones and you plan on staying at your destination long enough to make it worthwhile, you can adjust your body clock to the new time with behavioral methods or pharmacological methods. The behavioral method is light exposure and light avoidance at specific times of the day based on which direction you're going and how many time zones you cross. You may want to take a snapshot of this table for future reference. The pharmacological intervention is melatonin, the so-called darkness hormone. It's secreted by a little gland in the center of your head as soon as it gets dark and shuts off when the sun comes up in the morning, thereby helping to set your circadian rhythm. There's been a lot of research done on treating jet lag, but most of it has come from like lab rats instead of people. But most of the handful of human trials that have been done have found taking melatonin close to the target bedtime at the destination to try to sink your body to the new time can effectively decrease jet lag symptoms after long flights. Now, unlike most or really all other drugs, the timing of the dose is critical and determines the effect. Given that the wrong time, it can make your jet lag even worse. For example, if you were to take melatonin at bedtime when traveling west. Dose-wise, taking between 0.5 and 5 milligrams seems to be similarly effective in terms of helping with jet lag symptoms, but the higher dose does seem to have more of a sleeping pill type effect, which appears to plateau at about 5 milligrams. But those are massive doses. Even just taking a 3 milligram dose produces levels in the bloodstream 50 times higher than normal nightly levels. Yeah, works, but we don't know how safe that is. After all, melatonin in the early days used to be known as the anti-gonad hormone, with human equivalent doses of just a milligram or two, reducing the size of sex organs and impairing fertility in laboratory animals. Now, obviously rats aren't people, but considering the pronounced effects of melatonin on reproductive physiology in other mammals, to assume that it would not have some sexual effects in humans would almost seem naive. In fact, they speculate maybe melatonin one day play a role as some sort of contraceptive agent. Wouldn't we know about these effects though? Well, how? Melatonin is available over the counter as a dietary supplement, so there's no post-marketing surveillance, like there is with prescription drugs. And then there's the purity problem. Supplements are so poorly regulated, that you never really know what's actually in them. For these reasons, melatonin supplements cannot be recommended. Is the purity issue just theoretical though? You don't know until you put it to the test. And indeed, due to the poor quality control of over-the-counter melatonin, what they say is often not what you get. Melatonin is not only one of the most popular supplements among adults, but children too, which makes it even more egregious that actual melatonin content varied up to nearly 500%, compared to what it actually said on the label, based on an analysis of 31 different brands, and most had just a fraction of what they said. And the most variable sample was a chewable tablet, which is what kids might take. It said it had 1.5 milligrams, but actually had 9, which could result in like 100 times higher than natural levels. In short, there was no guarantee of the strength or purity of over-the-counter melatonin, leading these researchers to suggest it should be regulated as a drug so that by law, at least it would have what it says on the bottle. Okay, but that strength, what about purity? Four of six melatonin products from health food stores, two-thirds, contained unidentified impurities, with no exclusive patent, no pharmaceutical company wants to pay for the necessary toxicological studies. I mean, this stuff is just sold so dirt cheap. They recommend buying it from some large, reputable pharmacy chain and just hoping for the best, but this study suggests it's not worth the risk. Contaminants present in tryptophan supplements were reported to be responsible for a 1980s outbreak of a disease that affected more than 1,000 people and resulted in dozens of deaths. Given the structural similarities of tryptophan and melatonin, maybe when you're trying to synthesize melatonin, those same toxic contaminants could be created. And indeed, here's the contaminant blamed on the tryptophan epidemic, and here's what they found in melatonin supplements. That's a little too close for comfort, suggesting melatonin supplements may just be another accident, another epidemic waiting to happen.