Evidence continues to come in demonstrating that fluoride may increase oxidative stress. This past week, Medline posted two new studies (1,2), which compliment 3 earlier studies this year (3-5) suggesting that this is in fact the case. Many more studies published over the past 15 years have reported similar findings (6-20), although some have not (21, 22).

As noted recently in a review by Dr. NJ Chinoy of India: “a comparatively smaller number of publications exist which do not subscribe to oxidative stress in fluorosis as opposed to the many that do… Strong evidence for oxidative stress by fluoride has been reported in a number of tissues (brain, liver, kidney, testis, cell lines, etc) of animals and humans” (22).

While more research needs to be done to resolve the various means by which fluoride can exacerbate oxidative stress, it is clear that this issue needs to be taken seriously. Oxidative stress is implicated in a wide range of human disease, from cancer, to diabetes, to brain disorders.

On the positive side, however, the link between fluoride & oxidative stress may help aid efforts to mitigate and reverse the symptoms among people suffering from fluoride toxicity. Some evidence is already available suggesting that this is the case. In 2002, Dr. AK Susheela, a consultant to UNICEF, and one of the world’s leading authorities on skeletal fluorosis, published a study (23) which showed that the use of anti-oxidants (in conjunction with substantial reductions in fluoride intake) could help bring about substantial improvement in humans chronically poisoned by fluoride. (An anti-oxidant, as suggested by the name, is a substance which can help counter and reduce oxidative stress.)

It’s been known for many years (24) that deficiencies of vitamin C (a powerful anti-oxidant) can be associated with more severe signs of fluoride toxicity in both animals and humans. As noted in a 1977 review on fluoride by the Canadian government:

“In a study of fluoride supplementation in monkeys, Reddy and Srikanti (1971) showed that a diet low in vitamin C enhanced the onset of skeletal fluorosis… Earlier, Gabovich and Maistruk (1963) had shown that vitamin C supplementation reduced the toxic effects of fluoride in industrial workers and in Guinea pigs. Marier and Rose (1971) discussed Russian studies in which fluorosis was found to be most severe in children who had a vitamin C deficiency. Marier and Rose also discussed Australian work, which showed that vitamin C supplementation alleviated fluorosis in Guinea pigs. It appears possible that chronic exposure to fluoride increases the metabolic requirement for vitamin C…” (24).

Finally, a quick reference to tea may be in order here. As many readers know, the tea plant is one of the rare plants that, even in the absence of acid rain (a factor which increases the accumulation of fluoride in many plants ), accumulates significant levels of fluoride present in soil. The resulting elevated fluoride content of brewed tea has been implicated as a contributing cause of endemic skeletal fluorosis in China and elsewhere (25).

However, teas are also known to have high levels of anti-oxidants as well. Thus, it may turn out that the high, yet varying, levels of anti-oxidants in teas may mitigate (at least partially) the effects of the fluoride. Of course, this isn’t the same as saying that fluoride in tea will have no effect, just that it might have less effect than would otherwise be the case. It should also be noted, meanwhile, that some commercial iced teas – which can have very high levels of fluoride (26) – may have depleted levels of anti-oxidants.

————————

References:

1) Shanthakumari D, et al. (2004). Effect of fluoride intoxication on lipid peroxidation and antioxidant status in experimental rats.Toxicology 204: 219-28.

2) Wang AG, et al. (2004). Effects of fluoride on lipid peroxidation, DNA damage and apoptosis in human embryo hepatocytes.Biomedical and Environmental Sciences 17: 217-22.

3) Inkielewicz I, Krechniak J. (2004). Fluoride effects on glutathione peroxidase and lipid peroxidation in rats. Fluoride 37: 7-12.

4) Shan KR, et al. (2004). Decreased nicotinic receptors in PC12 cells and rat brains influenced by fluoride toxicity-a mechanism relating to a damage at the level in post-transcription of the receptor genes. Toxicology 200: 169-77.

5) Shen X, Zhang Z, Xu X. (2004). [Influence of combined iodine and fluoride on phospholipid and fatty acid composition in brain cells of rats]. Wei Sheng Yan Jiu. 33(2):158-61.

6) Guo X, et al. (2003). Oxidative stress from fluoride induced hepatotoxicity in rats. Fluoride 36: 25-29.

7) Shivarajashankara YM, et al. (2003). Lipid peroxidation and antioxidant systems in the blood of young rats subjected to chronic fluoride toxicity. Indian Journal of Experimental Biology 41: 857-60.

8 ) Wang A, et al. (2003). Effects of selenium and fluoride on apoptosis and lipid perioxidation in human hepatocytes. Fluoride 36: 45-46.

9) Yur F, et al. (2003). Changes in erthrocyte parameters of fluorotic sheep. Fluoride 36: 152-156.

10) Ghosh D, et al. (2002). Testicular toxicity in sodium fluoride treated rats: association with oxidative stress. Reproductive Toxicolology 16(4):385.

11) Shivashankara AR, et al. (2002). Lipid peroxidation and antioxidant defense systems in liver of rats in chronic fluoride toxicity.Bulletin of Environmental Contamination and Toxicology 68: 612-6.

12) Shivarajashankara YM , et al. (2002). Brain lipid peroxidation and antioxidant systems of young rats in chronic fluoride intoxication. Fluoride 35: 197-203.

13) Shivashankara YM, et al. (2001). Oxidative stress in children with endemic skeletal fluorosis. Fluoride 34: 103-107.

14) Shivashankara YM, et al. (2001). Effect of fluoride intoxication on lipid peroxidation and antioxidant systems in rats. Fluoride 34: 108-113.

15) Guan ZZ, et al. (2000). Changed cellular membrane lipid composition and lipid peroxidation of kidney in rats with chronic fluorosis. Archives of Toxicology 74: 602-8.

16) Shao Q, et al. (2000). [Influence of free radical inducer on the level of oxidative stress in brain of rats with fluorosis]. Zhonghua Yu Fang Yi Xue Za Zhi 34(6):330-2.

17) Wang YN, et al. (2000). Effect of long term fluoride exposure on lipid composition in rat liver. Toxicology 146: 161-9.

18) Guan ZZ, et al (1998). Influence of chronic fluorosis on membrane lipids in rat brain. Neurotoxicology and Teratology 20: 537-542.

19) Wang Y, et al. (1997). [Changes of coenzyme Q content in brain tissues of rats with fluorosis]. Zhonghua Yu Fang Yi Xue Za Zhi. 31: 330-3.

20) Guan ZZ, et al. (1989). An experimental study of blood biochemical diagnostic indices for chornic fluorosis. Fluoride 22: 112-128.

21) Reddy GB, et al. (2003). Antioxidant defense system and lipid peroxidation in patients with skeletal fluorosis and in fluoride-intoxicated rabbits. Toxicological Sciences 72: 363-8.

22) Reddy GB, Chinoy NJ. (2004). Fluoride toxicity and oxidative stress. Fluoride 37:43-46.

23) Susheela AK, Bhatnagar M. (2002). Reversal of fluoride induced cell injury through elimination of fluoride and consumption of diet rich in essential nutrients and antioxidants. Molecular and Cellular Biochemistry 234-235(1-2):335-40.

24) Marier J, Rose D. (1977). Environmental Fluoride. National Research Council of Canada. Associate Committe on Scientific Criteria for Environmental Quality. NRCC No. 16081.

25) Wang LF, Huang JZ. (1995). Outline of control practice of endemic fluorosis in China. Social Science & Medicine 41: 1191-5.

26) Behrendt A, Oberste V, Wetzel WE. (2002). Fluoride concentration and pH of iced tea products. Caries Research 36: 405-410.