Had a long discussion with an international flight attendant about this recently. His conclusions, from having discussed it with many users, were:

1. It works.

2. Everybody responds to it differently, so you need to find your own dosage. General recommendations from any source may be WAY off. The only way to do it is to experiment with dosage and see what works for you.

3. A given person's response (hence correct dosage) changes over time, whether from aging or exposure.

4. The wrong dosage may make it harder to adjust to a new time zone, not easier.

For what it's worth.