Many studies have been conducted on the effects of fluoride on the human body and some notable adverse effects have been noted: it changes bone structure and strength, impairs the immune system and it was linked to some cancers. Another alarming consequence of fluoridation is its effects on brain functions:

“In 1995, neurotoxicologist and former Director of toxicology at Forsyth Dental Center in Boston, Dr. Phyllis Mullenix published research showing that fluoride built up in the brains of animals when exposed to moderate levels. Damage to the brain occured and the behavior patterns of the animals was adversely effected. Offspring of pregnant animals receiving relatively low doses of fluoride showed permanent effects to the brain which were seen as hyperactivity (ADD-like symptoms). Young animals and adult animals given fluoride experienced the opposite effect — hypoactivity or sluggishness. The toxic effects of fluoride on the central nervous system was subsequently confirmed by previously-classified government research. Two new epidemiological studieswhich tend to confirm fluoride’s neurotoxic effects on the brain have shown that children exposed to higher levels of fluoride had lower IQs.”
- Source

A lesser known, but extremely important side effect of fluoride is the calcification of the pineal gland.

Up until the 1990s, no research had ever been conducted to determine the impact of fluoride on the pineal gland – a small gland located between the two hemispheres of the brain that regulates the production of the hormone melatonin. Melatonin is a hormone that helps regulate the onset of puberty and helps protect the body from cell damage caused by free radicals.

It is now known – thanks to the meticulous research of Dr. Jennifer Luke from the University of Surrey in England – that the pineal gland is the primary target of fluoride accumulation within the body.

The soft tissue of the adult pineal gland contains more fluoride than any other soft tissue in the body – a level of fluoride (~300 ppm) capable of inhibiting enzymes.

The pineal gland also contains hard tissue (hyroxyapatite crystals), and this hard tissue accumulates more fluoride (up to 21,000 ppm) than any other hard tissue in the body (e.g. teeth and bone).

- Source 

Other than regulating vital hormones, the pineal gland is known to serve an esoteric function. It is known by mystic groups as the “third eye” and has been considered by many cultures to be part of the brain responsible for spiritual enlightenment and the “link to the divine”. Is enlightenment out of bounds for the modern man?

“In the human brain there is a tiny gland called the pineal body, which is the sacred eye of the ancients, and corresponds to the third eye of the Cyclops. Little is known concerning the function of the pineal body, which Descartes suggested (more wisely than he knew) might be the abode of the spirit of man.”
– Manly P. Hall, The Secret Teachings of All Ages