© 2025 American Dental Association l 49
Fluoridation Facts
25. When fluoride is ingested, where does it go?
Answer
Much of the ingested fluoride is excreted. Of the fluoride retained, almost all is found in calcified
(hard) tissues, such as bones and teeth.
Fact
After ingestion of fluoride, such as drinking a glass of fluoridated water, the majority of the fluoride
is absorbed from the stomach and small intestine into the bloodstream. This causes a short-term
increase in fluoride levels in the blood. Fluoride is distributed through the body by plasma (a component
of blood) to hard and soft tissues. Following ingestion, the fluoride plasma levels increase quickly
and reach a peak concentration within 20–60 minutes. The concentration declines rapidly, usually
approximating the baseline levels within three to 6 hours, due to the uptake of fluoride by calcified
tissues and excretion in urine. In adults, approximately 50% of the fluoride absorbed each day
becomes associated with calcified tissues within 24 hours, while the remainder is excreted in the urine.
Approximately 99% of the fluoride present in the body is in calcified tissues (mainly bone).221
Ingested or systemic fluoride becomes incorporated into developing tooth structures. Fluoride
ingested regularly during the time when teeth are developing is deposited throughout the tooth
structure and contributes to long-lasting protection against tooth decay.78,79,82,83,222
Additional information on this topic can be found in the Benefits Section, Question 2.
An individual’s age and stage of skeletal development will affect the rate of fluoride retention.
The amount of fluoride taken up by bone and retained in the body is negatively associated with age.
A greater percentage of fluoride is absorbed in young bones than in the bones of older adults.221
However, once fluoride is absorbed into bones, some of it can be released back into plasma when
fluoride levels in plasma fall to maintain a near steady state. This absorption and release cycle
continues throughout the life span.221
26. Will drinking water that is fluoridated at the recommended level
adversely affect bone health?
Answer
No. According to the best available science, drinking water that has been fluoridated at the
recommended level does not have an adverse effect on bone health.
Fact
Several systematic reviews have concluded that fluoride at the level used in community water
fluoridation has no adverse effect on bone health. A systematic review published in 2000 concluded
that there was no clear association between water fluoridation and hip fracture.223 Twenty-nine studies
that looked at the association between bone fracture/bone development and water fluoridation
were included in the review. The evidence regarding other types of bone fractures was similar.223
A systematic review published in 201734 concurred with the earlier review, concluding that fluoridated
water at recommended levels is not associated with bone fracture.34
The following studies, listed in reverse chronological order, add to the body of evidence indicating
that there is no association between consumption of optimally fluoridated water and bone fracture.
Fluoridation Facts
25. When fluoride is ingested, where does it go?
Answer
Much of the ingested fluoride is excreted. Of the fluoride retained, almost all is found in calcified
(hard) tissues, such as bones and teeth.
Fact
After ingestion of fluoride, such as drinking a glass of fluoridated water, the majority of the fluoride
is absorbed from the stomach and small intestine into the bloodstream. This causes a short-term
increase in fluoride levels in the blood. Fluoride is distributed through the body by plasma (a component
of blood) to hard and soft tissues. Following ingestion, the fluoride plasma levels increase quickly
and reach a peak concentration within 20–60 minutes. The concentration declines rapidly, usually
approximating the baseline levels within three to 6 hours, due to the uptake of fluoride by calcified
tissues and excretion in urine. In adults, approximately 50% of the fluoride absorbed each day
becomes associated with calcified tissues within 24 hours, while the remainder is excreted in the urine.
Approximately 99% of the fluoride present in the body is in calcified tissues (mainly bone).221
Ingested or systemic fluoride becomes incorporated into developing tooth structures. Fluoride
ingested regularly during the time when teeth are developing is deposited throughout the tooth
structure and contributes to long-lasting protection against tooth decay.78,79,82,83,222
Additional information on this topic can be found in the Benefits Section, Question 2.
An individual’s age and stage of skeletal development will affect the rate of fluoride retention.
The amount of fluoride taken up by bone and retained in the body is negatively associated with age.
A greater percentage of fluoride is absorbed in young bones than in the bones of older adults.221
However, once fluoride is absorbed into bones, some of it can be released back into plasma when
fluoride levels in plasma fall to maintain a near steady state. This absorption and release cycle
continues throughout the life span.221
26. Will drinking water that is fluoridated at the recommended level
adversely affect bone health?
Answer
No. According to the best available science, drinking water that has been fluoridated at the
recommended level does not have an adverse effect on bone health.
Fact
Several systematic reviews have concluded that fluoride at the level used in community water
fluoridation has no adverse effect on bone health. A systematic review published in 2000 concluded
that there was no clear association between water fluoridation and hip fracture.223 Twenty-nine studies
that looked at the association between bone fracture/bone development and water fluoridation
were included in the review. The evidence regarding other types of bone fractures was similar.223
A systematic review published in 201734 concurred with the earlier review, concluding that fluoridated
water at recommended levels is not associated with bone fracture.34
The following studies, listed in reverse chronological order, add to the body of evidence indicating
that there is no association between consumption of optimally fluoridated water and bone fracture.
