Most vitamins are not approved by the FDA for a very good reason...the monetary damage to drug companies would be substanial,that is vitamins do help.

I have used melatonin for a number of years for jet lag. It does work, but my side affect is vivid dreams.
I effectively used melatonin last week for my 1 week 24,000 mile run.Don't use it every day.

Another sleep aid that I use is EX - Stress,made by Nature's Way vitamin. Very effective without any downsides.

One more comment about vitamins,Vitamin E has been extensively tested to show a 50 -80% decrease in heart attacks if taken everyday,for several years. So, don't put a whole lot of trust in the FDA, until you study the proof.