Melatonin メラトニン

In Japan

• In Japan, it is an "ingredient used exclusively as a drug" and cannot be used in foods (supplements).
• A working group at MHLW (2023) decided to keep treating it as a drug. Its reasons included that it is used in Japan as a prescription drug, that health harm related to supplements has been reported overseas, and that animal studies showed effects on the liver and thyroid.
• Advertising or selling melatonin supplements in Japan is not permitted under the Pharmaceuticals and Medical Devices Act. This page has no purchase links.

In the EU: the register of health claims

EU-authorised claim

• In the EU it is treated as a food, and two claims are authorised: "helps reduce the time taken to fall asleep" (1 mg before bedtime) and "helps alleviate subjective feelings of jet lag" (0.5 mg or more).

In the EU, only health claims whose evidence has been assessed by the European Food Safety Authority (EFSA) and authorised by the European Commission may be used on food. “Not authorised” means the evidence for that claim was not established under EU standards — not that the ingredient is dangerous.

What the US NIH says

• It may help with jet lag and with sleep disorders in which sleep timing is shifted later, but there is not enough evidence to recommend it for chronic insomnia (clinical practice guideline of a US medical society).
• It appears safe for most people in the short term, but long-term safety information is lacking. A study of 31 products sold in the US found that for most, the amount on the label did not match the contents.

Sources: MHLW eJIM "Melatonin", NCCIH