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Dr. David Derry Answers Reader Questions
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Index of Q&As with Dr. David Derry



Topic: Green Tea and Fluoride

A Reader Writes:

"I have been reading that green tea contains toxic levels of fluoride. Do you agree with this?"

David Derry Responds:

Dear Patient

Although, we do have fluoride in our bodies there is no normal physiological function for it. In higher amounts it is toxic. Iodine is the most important element in our bodies by far. But what is important is fluoride is in the same chemical family as iodine and can replace iodine in the body if the iodine is deficient. But ideally one never wants to do that as fluoride is a toxin and should not be used to replace normal iodine functions. Our main source of iodine in the Western societies is iodized table salt. When we cut back our intake of salt we are in fact depriving ourselves of the much needed daily intake of iodine. This has lead to a significant decrease in the iodine intake of Western societies,(1-4)and iodine deficiency is starting to show up in children as well as adults.(5)

Some countries are fluoridating their water supply for the theoretical benefits of fluoride helping to prevent cavities. What is happening is the ingested fluoride takes the place of iodine that should be there in the teeth, especially growing teeth. Iodine and thyroid for example have complete control of tooth growth along with some help from growth hormone. (6-8) It is only because our iodine intake has been decreasing over the years that fluoride has been mistakenly added to our water with the idea of helping children's teeth. It would have made more scientific sense to have added more iodine. Monitoring of the results of fluoridation and iodine intake have not been consistent. As one would expect there are lots of publications now about the problems with too much fluoride.

Fluoride has also been used against osteoporosis with beneficial results. This again is just replacing what iodine should be doing. The minor problems of osteopenia (minor loss of calcium) seen in some patients put on thyroid is related to the fact that the same patients are low in iodine. The low iodine causes the hypothyroidism and also the inappropriate short term bone response. If iodine is given with the thyroid hormone this abnormal response can be avoided. So persons taking adequate daily iodine will unlikely to ever develop osteoporosis.

The thyroid gland uses iodine to make thyroid hormone. We know the thyroid gland appeared in evolution at the same time as back bones (vertebrates). Radioactive iodine injected into patients shows a full outline of the bones on a total body scan. This means one of the places iodine goes to immediately is bones. Thyroid hormone makes bones grow, mature and remodel, when necessary. Together thyroid hormone, iodine and growth hormone maintain a healthy bone structure. As vertebrates (animals with backbones) are the only animals with thyroid glands it makes sense that iodine and thyroid control bone structure and function.(6-8)

So even though fluoridation might work in children it does not work in adults. Therefore adults using fluorinated tooth paste will unlikely see any benefit and may end up with signs of excess fluoride such as browning of the teeth. It does not make sense to substitute a toxin for the natural iodine that should be there. It would have been simpler and more effective if the iodine intake of children was raised. This would provide the needed iodine and make stronger thyroid glands.

Green tea is supposed to help prevent stomach cancer in China. But in fact the way to prevent stomach cancer is to take more iodine. (9) Thus the benefits of the Green tea may be related to the fluoride in the tea substituting for iodine. Iodine therapy would be more effective.

I want to thank Edna Kyrie of London, England and her website on thyroid history for many references on fluoride.

1. Lee,K., Bradley,R., Dwyer,J., S. L. Lee,S.L.. Too much or too little: The implication of current Iodine intake in the United States. Nutrition Reviews 57:177-181, 1999.

2. Hollowell,J.G., Staehling,N.W., Hannon,W.H. et al. Iodine nutrition in the United States. Trends and public health implications: Iodine excretion data from national health and nutrition examination surveys I and III (1971-1974 and 1988-1994). J Clin Endocrinol Metab 83:3401-3408, 21998.

3. Thomson,C.D., Colls,A.J., Conaglen,J.V., Macormack,M., Stiles,M., Mann.J.. Iodine status of New Zealand residents as assessed by urinary iodide excretion and thyroid hormones. British Journal of Nutrition 78 (6):901-912, 1997.

4. Glinoer,D. Feto-maternal repercussions of iodine deficiency during pregnancy. An update. Annales d Endocrinologie. 64 (1):37-44, 2003.

5. Kamala Guttikonda, Cheryl A Travers, Peter R Lewis and Steven Boyages Iodine deficiency in urban primary school children: a cross-sectional analysis MJA 2003; 179 (7): 346-348

6. Baume, L.J.. Hormonal control of tooth eruption; effect of thyroidectomy on upper rat incisor and response to growth hormone, thyroxin or combination of both. J Dent Res 33:89-90, 1954.

7. Muhler,J.C.. Experimental dental caries; effect of feeding desiccated thyroid and thiouracil on dental caries in rats. Science 119:687-689, 1954.

8. Muhler,J.C.. The relationship between fluorine and the activity of the thyroid gland on the incidence of dental caries in the rat. J Dent Res 36:382-385, 1957.

9. Derry DM. Breast cancer and iodine Trafford Publishing. Victoria Canada 2001



About Dr. Derry:

Dr. Derry is no longer practicing medicine.

These answers are personal opinions. Please discuss any ideas you get with your physician.

Born in 1937, I am at the cutting edge of the war baby boom. With one exception the baby boomers tend to do what I do in large numbers about ten years later. The exception was that after finishing my internship at the Toronto General Hospital in 1963, as I had planned, I started a PhD in biochemistry at the Montreal Neurological Institute at McGill University in Montreal. After completing my PhD, I was hired by the Department of Pharmacology at the University of Toronto to teach and do research. Within a short time I became a Medical Research Council Scholar, which meant the Medical Research Council of Canada paid my salary to do research. Domestic rearrangements suddenly placed five children between the ages of 5 and 9 under my care. I abandoned my research career and took all five children, a new wife and dog out west to Victoria British Columbia.

My aim in 30 years of General Practice (an honor and a privilege) was to learn carefully and persistently how to listen to the patient. This is the one area of medical research that has gone almost totally un-examined. Sir William Osler, who I feel was the greatest physician of all time, said: if you listen to the patient they will usually give you the diagnosis and if you listen even more carefully they will likely indicate the best treatment for them. Gradually with the help of multiple self-development courses over the years I learned to listen by just getting my ego out of the way. From my patients I learned everything. Because of the arrival of effective treatments with potential side-effects, in 1945 the out-dated Hippocratic oath of “do no harm” was replaced with a new principle of ethical patient care namely “Consider first the well-being of the patient.” Combining extensive medical-literature reading with what I learned daily from patients clarified which approaches and treatments assured the “well-being of the patient.”

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