Excerpt from:

Ramseyer WF, et al. (1957). Effect of Sodium Fluoride Administration on Body Changes in Old Rats. J Gerontol. 12: 14-19.

"The purpose of the present study was to determine the effects of feeding of low levels of sodium fluoride from conception until later life on the animal body in old age. Albino rats were used in this research because their normal span of life is less than two years. Furthermore, the albino rat is considered to have a high tolerance against fluoride toxicity. Therefore, one might expect other species to be affected more adversely than this one.

...The importance of knowledge about the lifetime ingestion of fluorides and their effect upon the diseases of old age is obvious. Hundreds of investigations deal with short-time ingestion of different levels of fluoride, but as far as we have been able to ascertain the literature contains no reports of studies made on a large number of animals and human subjects throughout the whole life span.


The experiments were designed to evaluate 4 levels of sodium fluoride, 0, 1, 5, and 10 PPM fluorine, administered in the drinking water, which had been distilled. A total of 456 albino rats were included in the investigation.


No gross lesions were found in the kidneys. Microscopic examinations were made on the kidneys from 6 animals which had not received fluoride in the drinking water, on 3 receiving 1 PPM, on 1 receiving 5 PPM, and on 6 receiving 10 PPM.

Interstitial nephritis was observed in all the animals examined histologically, and the severity increased in proportion to the level of the sodium fluoride in the drinking water. Renal tubule hypertrophy and hyperplasia were found in those animals receiving sodium fluoride in the water but not in the 6 rats which had not been given sodium fluoride supplementation. The hypertrophic and hyperplastic changes consisted of large numbers of newly formed hyperchromatic tubule cells, which in places were more than one layer deep. The nuclei were much larger than those of normal cells; there were a few mitotic figures. This histologic picture is usually considered to represent tissue regeneration following a loss of degenerate or necrotic cells. However, inasmuch as no necrosis was observed in these kidneys, a possible stimulation of the tubule cells to proliferate, directly or indirectly by the fluoride, must be considered.


The effects of feeding low levels of sodium fluoride from conception until old age were determined in a total of 456 albino rats. Four levels of sodium fluoride (0, 1, 5, and 10 PPM fluorine) were given to 4 groups of animals in their drinking water. In one study half of the rats were killed at 150 days of age and half at 520 days. In the second experiment all rats were killed at 150 days.

...Hypertrophy and hyperplasia of the kidney tubules were found in rats receiving fluoride but were not observed in the unsupplemented animals."

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