Welcome to the Nutrition Facts Podcast. I'm your host, Dr. Michael Greger. I'm thrilled that you've decided to join me today because the more I learn about the latest in nutrition research, the more convinced I am that this information can make a real difference in all our lives.

And I like nothing better than sharing it with you.

On today's show, I could induce sleepiness by speaking in a monotone or I could tell you about the fascinating sleep inducing properties of melatonin.

The body normally produces melatonin every evening to let us know when to sleep and wake, but sometimes we need little help regulating those important functions.

In our first story, over the counter melatonin supplements may not contain what they say they do and the contaminants could be dangerous.

If you're crossing three more time zones and you plan on staying in 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.

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 at 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 kind of a sleeping pill type effect, which appears to plateau at about 5 milligrams.

But I mean 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 and laboratory animals.

Now obviously rats aren't people, but considering the pronounced effects of melatonin on reproductive physiology and other mammals, to assume that it would not have some sexual effects in humans would almost seem naive.

In fact they speculate maybe melatonin and quen 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 counters, 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, they never really know what's actually in them. For these reasons melatonin supplements cannot be recommended.

It's the purity issue just theoretical though, you don't know until you bought 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 gregious 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 1.5mg but actually had 9 which could result in like 100 times higher than natural levels.

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