In order for us to know what melatonin will do in humans when given for a lifetime, we would need to follow hundreds or thousands of people. Multiple groups would be needed to try different dosages. Such a comprehensive study is not under way at this time. Even if it were, the results would not be available until well into the 21st Century. What shall we do in the meantime?
Different scientists familiar with these studies may recommend different courses of action. One scientist may caution, "Let's wait a few more years." Another may advocate, "If we wait, we'll have to wait decades. I'm 65 now and I'm having trouble sleeping at night. Melatonin provides me with great sleep. In addition it could extend my life span." Who will eventually be proved right? No one can be sure at this time.
There are additional studies that support the role of melatonin and the pineal gland in life extension. It has been known for decades that when rodents have their pineal glands removed, they die sooner (Malm, 1959). When the pineal glands of 4 month old mice were transplanted into 18-month-old mice, the older mice lived longer and aging symptoms were postponed (Lesnikov, 1994). When young mice receive the pineal gland from older mice, they die sooner.
The pineal gland releases substances other than just melatonin that play a role in longevity. One such example is epithalamin, which, together with other pineal gland extracts, has produced life extension in mice (Anisimov, 1994).
How Can Melatonin Extend Life Span?
The pineal gland communicates with every cell of the body through its primary hormone, melatonin. Most hormones need a receptor on the cell membrane before they can enter the cell. Not so for melatonin. As the pineal gland releases melatonin, it quickly goes into the local bloodstream and then into general circulation. From there, melatonin finds its way to every body fluid and tissue. Melatonin has the unusual capacity to easily permeate tissues and enter practically every cell of the body. When melatonin enters the cells, it goes into every compartment, including the nucleus. Researchers speculate that the amount of melatonin reaching the DNA of each cell informs that cell as to which proteins to make. The November 1994 Journal of Biological Chemistry reported that researchers Becker-Andre and colleagues found a specific receptor for melatonin right in the nucleus of cells. They conclude, "A nuclear signaling pathway for melatonin may contribute to some of the diverse and profound effects of this hormone."
One theory proposes that during infancy and childhood there is a high level of melatonin reaching every cell. This high level lets the cells know that the organism is young. Proteins necessary for growth and repair are manufactured. The amount of melatonin released each night is lessened in adults and reduced even more in old age. Therefore, as we advance in years, less melatonin reaches the DNA in our cells. Some researchers (Kloeden, 1993) think the pineal gland functions as a centralized clock to coordinate genes switching on and off.
This decline of melatonin levels may inform all cells of the body's age— i.e., it's time to call it quits, call a lawyer, write a living will, and put the first down payment on a cemetery plot (or cryonics arrangements for futurists). Melatonin supplementation could trick the DNA into thinking, "Maybe I miscalculated. I must be younger than I thought."