Aging, your pineal gland, and melatonin.
The pineal gland is largest in children, and shrinks after puberty. It is common for the pineal gland to become calcified in adults. This may help to explain the reasoning that children/younger people are better suited for dreaming.
http://en.wikipedia.org/wiki/Pineal_gland
The pineal gland is found in your brain and produces melatonin, a hormone that regulates circadian rhythms(basically regulates your sleep pattern and other functions in our 24 hour days). As many of you probably already know, melatonin is a highly praised supplement for dreaming. I take it and I'm sure many other users here do also. People claim it makes your dreams more vivid/easy to remember, and I'm led to agree. I think it can even lengthen your REM time, especially at large doses (50mg+). As an added bonus, it's a very powerful antioxidant and is #1 on The Life Extension Foundation's list of life extending drugs; and LEF supported it way before the medical field generally agreed on its benefits. It can fight cancer by preventing carcinogens from altering DNA.
http://en.wikipedia.org/wiki/Melatonin
http://www.esculape.com/bricabrac/to...siondrugs.html
Some people believe the pineal gland has mystical powers or possibly even contains our soul. It may also be what some cultures/religions regard as the "third eye", and awakening your third eye is regarded as the pinnacle of spirituality/enlightenment.
http://en.wikipedia.org/wiki/Third_eye
In the Upanishads, a human being is likened to a city with ten gates. Nine gates (eyes, nostrils, ears, mouth, urethra, anus) lead outside to the sensory world. The third eye is the tenth gate and leads to inner realms housing myriad spaces of consciousness.
So in summary(strictly my opinion): eat melatonin if you want to live forever and help keep your pineal gland and dreams alive as well. You should probably not take it until you're 18-21+ though, at least I think that's what's recommended.