The melatonin pulse regulates many neuroendocrine functions. The ability to think clearly, remember key facts, and make sound decisions can be profoundly hampered by these upsets in the biological clock. Jet-lag is characterized by fatigue, early awakening or insomnia, headache, fuzzy thinking, irritability, constipation, and reduced immunity. The symptoms are generally worse when flying in an easterly direction, and it may take as long as one day for each time zone crossed in order to fully recover. Older people have an even tougher time adjusting to these changes than younger people.
Circadian disturbances can easily result from conditions other than jet travel.
Eight subjects took 5 mg of melatonin, while nine subjects took a placebo. Many melatonin fans without any noticeable symptoms of circadian disturbance are now using melatonin to enhance their circadian rhythms. They report that it helps them get to sleep and helps them sleep more soundly. That's when your pineal gland naturally releases melatonin. See the Precautions section in this chapter.