In brief, melatonin seems to improve the functioning of the immune system, at least in mice, by restoring the thymus gland, increasing interferon production, enhancing antibody production, and enhancing anti-tumor factors (Caroleo, 1994). With time we are likely to find that melatonin also influences countless other components of the immune system. Whether these benefits will be found in humans is still not established.

To Take it (Regularly), or Not to Take: That is the Question
I know a number of individuals, including pineal gland researchers, who have started taking melatonin nightly at doses ranging from 0.1 mg to 10 mg. They do not necessarily take melatonin for sleep, but for its potential health and longevity benefits. Some organizations involved in seeking ways for life extension are recommending that their members use melatonin regularly.

Before we embrace melatonin as the latest age-reversing miracle and swallow megadoses every night, let's consider these points:

1) There are countless differences between rodents and humans. For one, mice are nocturnal animals— they are active and alert during the night, even though they produce melatonin at night. (For another, they rarely complain of nightmares or depression.)

2) We have little clue on how to extrapolate the life-prolongation doses of melatonin in mice to what would be the right dose in humans. Assuming melatonin does extend human lifespan, is our optimal dose 100mg? 10 mg? 1mg? 0.1mg? or even less? Is it best to take it nightly, every other night, once a week? Would there be a different result with the time-release pills than with the sublinguals?

3) Are there dosage differences between men and women? What are the best doses for different age groups?

4) Could long-term melatonin supplementation have a negative impact on our hormonal system? Could it interfere with our pancreas releasing insulin? our thyroid gland making thyroxine? our adrenal glands making cortisol? etc., etc.? Or, could it help our organs stay young?

5) Since melatonin stimulates the immune system, including lymphocytes, could long-term supplementation lead to uncontrolled multiplication of these cells leading to lymphomas?

6) Are there other substances besides melatonin produced by the pineal gland— such as epithalamin and peptides— that influence longevity? Would melatonin supplementation interfere with their production? Or maybe help?

These are some of our present uncertainties. Anyone who states that they are certain melatonin will increase life span in humans is making a claim that cannot be supported by the currently available scientific data. At this point the continuous use of melatonin for longevity purposes is a gamble. Having said this, and knowing that melatonin levels decline with aging, I feel it is possible that in the future, if we find melatonin supplements can actually make us healthier, physicians may use low doses as a replacement hormone just as we now replace estrogen in postmenopausal women. We could call this MRT (melatonin replacement therapy).

We don't know for certain the long-term effects of continuous melatonin use in humans— positive or negative. Then again, we don't know for certain the long-term (10-50 year) effects, or ideal dosages, of many common medicines or supplements, including aspirin and vitamins. However, we do know how melatonin has been used in the short term to help people, as we'll see in Chapter 6. But first, let's look at some practical matters involving dosage and timing.