Monday, January 7, 2013

Effects of the Fluoride on the Central Nervous System


L. Valdez-Jiménez, C. Soria Fregozo, M.L. Miranda Beltrán, O. Gutiérrez Coronado and M.I. Pérez Vega

This is an English Translation from Spanish of the orginal published paper.

Abstract
Introduction: Fluoride (F) is a toxic and reactive element, and exposure to it passes almost unnoticed, with the consumption of tea, fish, meat, fruits, etcetera and articles of common use such as: toothpaste additives; dental gels, non-stick pans and razor blades as Teflon. It has also been used with the intention of reducing the dental caries.

Development: Fluoride can accumulate in the body, and it has been shown that continuous exposure to it causes damaging effects on body tissues, particularly the nervous system directly without any previous physical malformations.

Background: Several clinical and experimental studies have reported that the F induces changes in cerebral morphology and biochemistry that affect the neurological development of individuals as well as cognitive processes, such as learning and memory. F can be toxic by ingesting one part per million (ppm), and the effects they are not immediate, as they can take 20 years or more to become evident.

Conclusion: The prolonged ingestion of F may cause significant damage to health and particularly to the nervous system. Therefore, it is important to be aware of this serious problem and avoid the use of toothpaste and items that contain F, particularly in children as they are more susceptible to the toxic effects of F.


Introduction:
Fluorine (F) is a toxic and reactive element; exposure to the F in humans goes almost unnoticed through the use of compounds with F as an additive in toothpastes (1,000 to 1,500 ppm), mouth rinses (230-900 ppm fluoride), dietary supplements and polymeric surfaces of fluoride in non-stick pans and the use of compounds that contain it as: composite industrial fertilizers, glass, oil refineries, others, and fluorinated hydrocarbons. Thus, a significant proportion of F in the body, comes from exposure to it and the consumption of foods with high F natural input, such as tea, fish of sea, meat, eggs, fruits, and cereal. However, the main source of intake of this element is ordinary drinking water.[1]

The water which has the largest concentration of fluoride corresponds to water resources located in mountainous areas or in areas with geological deposits of marine origin, as in Southeast Asia and Northwest Africa. Studies in the last 15 years show that a significant proportion of individuals in populations exposed to fluoridation through drinking water have poorer health and different degrees of fluorosis.[2]

In Mexico, 5 million people (approximately 6% of the population) are affected by fluoride due to consumption of underground water,[3] which in many cases is of hydrothermal origin, which are characterized by having potentially toxic chemicals, including the F, and up to 6.8 ppm concentrations have been detected. It is worth mentioning that the World Health Organization (who) recommends a concentration of 0.7 ppm for drinking water.[4]

The objective of this review is to publicize information on the toxic potential of F and its effects on the nervous system, with special emphasis on populations exposed to the consumption of this mineral whose concentration is outside the official standard.

Development

The main road to incorporation of F to the human body is the GI; 90% of the ingested F is absorbed in the stomach. In adults, about 10% of the absorbed F settles in the bones, while in the children is set up to 50%. (F) maximum plasma concentration is observed 30 to 60 min after have been swallowed.[5]

In the newborn, nearly 90% of the absorbed F is retained in the bone system. This affinity decreases with age and is stabilized. In the children, about 50% of the absorbed F is set to the skeleton to complete the development phase and the remaining 50% is excreted through the kidney.[6]

The F is able to cross the blood-brain barrier,[7] which can produce biochemical and functional changes in nervous during pregnancy, as the F accumulates in the brain tissue before birth[8]; it has been reported that exposure to F during embryonic development is linked with learning disorders[9]. In this regard, other research mentions that there is an association between the consumption of high levels of F and a decrease in intelligence in children.[10]

Studies to evaluate the F on neurodevelopmental toxicity during pregnancy have shown that there are significant differences in neurological behaviour of subjects of endemically F-rich areas in comparison with the control group when it assesses the reaction of visual and auditory orientation[11].  On the other hand, it has been observed that the level of neurotransmitters such as norepinephrine, 5-hydroxytryptamine and their receptors is reduced in the brains of fetuses aborted in areas that have cases of endemic fluorosis, while the level of epinephrine is greater compared to the levels detected in those subject areas which do not have this problem, by which these results suggest that F accumulation in brain tissue can disrupt the synthesis of certain neurotransmitters and receptors in nerve cells, and can be reached to produce a neural dysplasia or other damage[12].  Also, it has been reported that F has an effect specific on the synthesis of proteins in the brain, leading to degenerative changes in neurons loss in varying degrees of grey matter and changes in the Purkinje cells in the cerebellar cortex[13]; in addition, causes swelling of mitochondria, endoplasmic reticulum granular chromatin grouping, damage in the nuclear membrane and decrease in the number of synapses, synaptic vesicles, as well as damage at the synaptic membrane, mitochondria and microtubules.  These changes indicate that F may slow growth and cell division in the brain, and the fewest number of mitochondria, microtubules and vesicles in the synaptic terminal could decrease the effectiveness between the neural connections and produce an abnormal synaptic function and influence on cognitive development during postnatal life[14]; also, these changes could explain some of the neurological alterations in patients with skeletal fluorosis, such as numbness of the arms and legs, muscle spasms and pain, seizure, tremors and spastic paraplegia.[15]  On the other hand, exposure to F production increased radicals in the brain through activation of different metabolic pathways which have been linked to Alzheimer's disease.  At experimental level, it has been observed that F has an inhibitory effect on free fatty acids, both of male rats and female rats brain fatty acids[16], as well as significant changes in the morphology of the hippocampus, amygdala, the cortex and cerebellum.[17],[18]

In this regard, studies with animals have provided information on the direct toxic effects of fluoride on the brain tissue, such as: reduction in the number of receptors for acetylcholine (ACh), decrease in the lipid content, damage to the hippocampus and Purkinje cells, increase in plaque formation b-amyloid (classic brain abnormalities in patients with Alzheimer's disease), exacerbation of injuries induced by deficiency of iodine and fluoride accumulation in the pineal gland.[19],[20]

On the other hand, it has been reported, in studies with experimental models, the offspring of rats that they provided a dose of 5, 15 or 50 ppm F in the drinking water during pregnancy and lactation are significantly elevated levels of the enzyme acetylcholinesterase at the 80 days of postnatal age.  The high activity of acetylcholinesterase may lower levels of ACh, and given that this enzyme degrades the neurotransmitter ACh, brain development is affected significantly.[21],[22]  The ACh is involved in the regulation of various functions, such as the transition from sleep to wakefulness and related to the learning and memory processes, among others.

On the other hand, at the cerebral level there are precise mechanisms regulating their synthesis and release; it is important that changes in the concentration of any neurotransmitter during development can have permanent neurological effects that occur in adult life.[23]

It is reported that in mice treated with fluoridated water, the process of learning and memory is altered. It was found that the ability to learn decreases in subjects who drink water with high concentrations of F in comparison with those who drink water with a lower concentration[24].

Some research involving subjects who are chronically exposed to F due to industrial pollution reported that individuals have difficulty concentrating, alteration in some aspects of his memory, fatigue and malaise[25]. On the other hand, studies in China with human populations showed the concentration of ppm 3-11 fluoride in drinking water affects the function of the nervous system without causing prior physical malformations.  Evaluations of IQ  in children in communities where exposure to F is high (4-12 ppm) detected an IQ  significantly lower compared to those living in communities that were close to 0.91 ppm concentrations[26].

In another research conducted on children between 6 and 8 years, a low level of visual-spacial organization was observed, which affects their ability to read and write;  also, a concentration of F in urine of 4.3 mgf/creatinine was recorded.  In this regard has been reported that the levels of this chemical element are also high in the urine of people who consume water with high concentrations of F, suggesting that there is relationship between the consumption of F in the drinking water, F excreted through the urine concentration and IQ[27].

Some researchers suggest that adequate intake of iodine could treat or counteract the toxic effect of F on the brain and the IQ.  On the other hand, in research on animals a partial recovery of all parameters studied has been observed when the exposure to F is removed.  However, this recovery on the toxic effects is complete when you administer ascorbic acid, calcium or vitamin E either alone or in combination, while combined recovery is more effective[28].  However, more studies in this regard are required.

Conclusion

F is a chemical element found in high concentrations in the Earth's crust.  In many of the countries where the main source of drinking water is of hydrothermal origin, the concentration of F surpasses the level allowed by the corresponding official standard.  So far the reported work poses interesting disputes about the role that F performs in health.  However, there are data to prove that F has toxic effects on the central nervous system, which depends on the dose administered, the age and exposure at the same time.  We recommend considering the geographical location of a given population and the quality of the water consumed to take preventive measures for use in localities where fluoride concentration is greater than 0.7 mg /l, avoiding the consumption of drinking water, fluoridated salt and the use of toothpastes and substances containing F.

Conflicts of Interest

The authors declare not to have any conflict of interest.

Acknowledgements

This work was conducted during the period of doctoral studies in science and technology at the University of Guadalajara of the Centro Universitario Lakes (CULAGOS). During the period 2008-2010  of the first author.


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