10.8 NUTRITIONAL FACTORS AFFECTING FLUORIDE TOXICITY
There is a growing interest in the interaction of nutrition with F toxicity as
several nutrients have been shown to alleviate injuries caused by exposure to F.
The nutrients studied so far include proteins and Ca, and vitamins C (ascorbic
acid), D, and E. Glutathione (GSH), which is not a nutrient but a well-known
antioxidant, has also been studied. The adverse effects of F are often mitigated
by administration of one or more of these nutrients.
A large number of studies have indicated a relationship between vitamin C
and F-exposure in animals. In one of these studies, growing chicks (Gallus
domesticus) were fed a diet supplemented with 150 ppm of F as NaF.
32 At the
end of 4 weeks, no differences in body weight were observed; however F-treated
chicks showed a marked decrease in ascorbic acid levels in the heart, spleen,
brain, gizzard, and pancreas, while the levels were increased in the lungs and
kidneys. In a separate study, growing cockerels were given a diet supplemented
with 150, 300, or 500 ppm F for 4 or 8 weeks, and then subjected to analysis of
tissue levels of ascorbic acid and dehydroascorbic acid (DHA, the oxidized
form of ascorbic acid). Results showed marked decline of ascorbic acid in
adrenal glands and kidneys in the F-treated cockerels. Furthermore, the levels
of DHA in the kidneys of the F-exposed cockerels increased more than 100%
compared with the control levels.
33
In laboratory mice, both protein and vitamin C were shown to lower F
accumulation in bone. For example, mice fed a low-protein diet (containing
4% protein) supplemented with 150 ppm NaF deposited five times more F in
the tibia than did control mice fed a regular diet (containing 27% protein) and
exposed to the same level of NaF. Furthermore, supplemental vitamin C
greatly lowered F deposition in the bone.
34 (It should be noted that mice also
produce vitamin C.)
Fluoride treatment has been shown to induce embryotoxicity in pregnant
rats.
35 Oral administration of NaF (40 mg/kg body weight) to pregnant rats
from day 6 of gestation to day 19 caused decreased body weight, feed
consumption, absolute uterine weight, and number of implantations, compared
with the control. A higher incidence of skeletal and visceral abnormalities
(subcutaneous hemorrhage) was observed in the fetuses of the F-treated
pregnant rats. Oral administration of vitamin C (50 mg/kg body weight) with
NaF significantly reduced the severity and incidence of F-induced embryotoxicity in the rats.
35
Exposure of male mice to NaF (10 mg/kg body weight) for 30 days showed
a marked decrease in cauda epididymal sperm count, motility, and viability,
resulting in significant reduction in fertility rate.
36 Withdrawal of NaF
treatment for 30 days produced incomplete recovery. However, when vitamin
E or vitamin D was supplemented during the withdrawal period, the toxic
effect of NaF was significantly alleviated, as the treated mice restored their
reproductive functions and fertility. Additionally, it was found that a combined
administration of vitamins D and E was generally more effective than either
vitamin D or E administered alone.
36
Environmental Fluoride
167
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Ref: 4365 MING-HO YU Chap-010 Page: 167 149-170
There is a growing interest in the interaction of nutrition with F toxicity as
several nutrients have been shown to alleviate injuries caused by exposure to F.
The nutrients studied so far include proteins and Ca, and vitamins C (ascorbic
acid), D, and E. Glutathione (GSH), which is not a nutrient but a well-known
antioxidant, has also been studied. The adverse effects of F are often mitigated
by administration of one or more of these nutrients.
A large number of studies have indicated a relationship between vitamin C
and F-exposure in animals. In one of these studies, growing chicks (Gallus
domesticus) were fed a diet supplemented with 150 ppm of F as NaF.
32 At the
end of 4 weeks, no differences in body weight were observed; however F-treated
chicks showed a marked decrease in ascorbic acid levels in the heart, spleen,
brain, gizzard, and pancreas, while the levels were increased in the lungs and
kidneys. In a separate study, growing cockerels were given a diet supplemented
with 150, 300, or 500 ppm F for 4 or 8 weeks, and then subjected to analysis of
tissue levels of ascorbic acid and dehydroascorbic acid (DHA, the oxidized
form of ascorbic acid). Results showed marked decline of ascorbic acid in
adrenal glands and kidneys in the F-treated cockerels. Furthermore, the levels
of DHA in the kidneys of the F-exposed cockerels increased more than 100%
compared with the control levels.
33
In laboratory mice, both protein and vitamin C were shown to lower F
accumulation in bone. For example, mice fed a low-protein diet (containing
4% protein) supplemented with 150 ppm NaF deposited five times more F in
the tibia than did control mice fed a regular diet (containing 27% protein) and
exposed to the same level of NaF. Furthermore, supplemental vitamin C
greatly lowered F deposition in the bone.
34 (It should be noted that mice also
produce vitamin C.)
Fluoride treatment has been shown to induce embryotoxicity in pregnant
rats.
35 Oral administration of NaF (40 mg/kg body weight) to pregnant rats
from day 6 of gestation to day 19 caused decreased body weight, feed
consumption, absolute uterine weight, and number of implantations, compared
with the control. A higher incidence of skeletal and visceral abnormalities
(subcutaneous hemorrhage) was observed in the fetuses of the F-treated
pregnant rats. Oral administration of vitamin C (50 mg/kg body weight) with
NaF significantly reduced the severity and incidence of F-induced embryotoxicity in the rats.
35
Exposure of male mice to NaF (10 mg/kg body weight) for 30 days showed
a marked decrease in cauda epididymal sperm count, motility, and viability,
resulting in significant reduction in fertility rate.
36 Withdrawal of NaF
treatment for 30 days produced incomplete recovery. However, when vitamin
E or vitamin D was supplemented during the withdrawal period, the toxic
effect of NaF was significantly alleviated, as the treated mice restored their
reproductive functions and fertility. Additionally, it was found that a combined
administration of vitamins D and E was generally more effective than either
vitamin D or E administered alone.
36
Environmental Fluoride
167
[16:52 26/8/04 P:/CRC PRESS/4365 MING-HO.751 (1670)/4365-010.3d]
Ref: 4365 MING-HO YU Chap-010 Page: 167 149-170