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Section 2: Safety
Iowa Fluoride Study/Iowa Bone Development Study
The Iowa Fluoride Study/Iowa Bone Development Study followed a cohort in Iowa from birth to
age 23, with frequent assessment of fluoride exposures with parents completing detailed fluoride
questionnaires linked to water fluoride assay results and multiple bone densitometry assessments
during bone development. The combined fluoride intakes were estimated from a number of sources,
including water, other beverages, selected foods, dietary fluoride supplements, and fluoride toothpaste.
Six publications looked at the associations of fluoride intakes over defined periods and cumulatively from
birth with bone densitometry outcomes at ages 11–23, including dual-energy x-ray absorptiometry
(DXA), peripheral quantitative computed tomography (pQCT), and multi-detector computed tomography
(MDCT).224-229 The studies consistently found weak and almost all non-significant relationships between
the fluoride intakes and bone densitometry outcomes in adjusted regression analyses. This includes
DXA bone mineral content and density outcomes of the hip, lumbar spine, and whole body at age 15,226
multiple pQCT radial and distal tibial measures at ages 11225 and 17,227 and MDCT distal tibial measures
at ages 19228 and 23.229 The authors concluded that fluoride exposures at typical levels for most US
adolescents in fluoridated areas do not have significant effects on bone mineral measures.224,225,227
Additional analyses found that fluoride intakes were not associated with estimated strength measures
from finite element analyses (FEA) at age 23.230
Swedish Study
In one of the largest studies of its kind with nearly half a million subjects, Swedish researchers looked
at residents’ chronic consumption of various levels of fluoride and the risk of hip fracture.231 All
individuals born in Sweden between January 1, 1900, and December 31, 1919, alive and living in their
municipality of birth at the time of the start of follow-up, were eligible for the study. Information on
the study population was linked to the Swedish health registers. Estimated individual drinking water
fluoride exposure was stratified into four categories: very low, 0.3 mg/L low, 0.3 to 0.69 mg/L
medium, 0.7 to 1.49 mg/L and high, ≥ 1.5 mg/L. The 2013 published study found no association
between chronic fluoride exposure and the occurrence of hip fracture. The authors concluded that,
“The risk estimates did not change in analyses restricted to only low-trauma osteoporotic hip fractures.
Chronic fluoride exposure from drinking water does not seem to have any important effects on the
risk of hip fracture, in the investigated exposure range.”231
Bone Mineral Density Study
A study published in 2005 evaluated the bone mineral density levels and rates of bone fracture of
1,300 ambulatory women aged 20–92 years living in three separate communities with diverse mineral
content.232 The sizes and demographics of the three communities were similar. One part of the study
looked at whether fluoride was associated with adverse bone-related outcomes. The study measured
fluoride serum levels, fluoride exposure, and bone metabolism as related to fluoride exposure and
fluoride’s interaction with other important bone factors, including age, menopause status, and
medications. The high-fluoride community was found to have significantly higher serum fluoride
levels (2.11 µmol/L) compared to the control and high-calcium communities. Serum fluoride was not
significantly associated with bone mineral density, except for higher distal radius bone mineral density
in the high-fluoride community. No relationship was found between serum fluoride levels and the risk
of osteoporotic fractures over 4 years. The study concluded that long-term exposure to fluoride was
not associated with adverse effects on bone health.232
Section 2: Safety
Iowa Fluoride Study/Iowa Bone Development Study
The Iowa Fluoride Study/Iowa Bone Development Study followed a cohort in Iowa from birth to
age 23, with frequent assessment of fluoride exposures with parents completing detailed fluoride
questionnaires linked to water fluoride assay results and multiple bone densitometry assessments
during bone development. The combined fluoride intakes were estimated from a number of sources,
including water, other beverages, selected foods, dietary fluoride supplements, and fluoride toothpaste.
Six publications looked at the associations of fluoride intakes over defined periods and cumulatively from
birth with bone densitometry outcomes at ages 11–23, including dual-energy x-ray absorptiometry
(DXA), peripheral quantitative computed tomography (pQCT), and multi-detector computed tomography
(MDCT).224-229 The studies consistently found weak and almost all non-significant relationships between
the fluoride intakes and bone densitometry outcomes in adjusted regression analyses. This includes
DXA bone mineral content and density outcomes of the hip, lumbar spine, and whole body at age 15,226
multiple pQCT radial and distal tibial measures at ages 11225 and 17,227 and MDCT distal tibial measures
at ages 19228 and 23.229 The authors concluded that fluoride exposures at typical levels for most US
adolescents in fluoridated areas do not have significant effects on bone mineral measures.224,225,227
Additional analyses found that fluoride intakes were not associated with estimated strength measures
from finite element analyses (FEA) at age 23.230
Swedish Study
In one of the largest studies of its kind with nearly half a million subjects, Swedish researchers looked
at residents’ chronic consumption of various levels of fluoride and the risk of hip fracture.231 All
individuals born in Sweden between January 1, 1900, and December 31, 1919, alive and living in their
municipality of birth at the time of the start of follow-up, were eligible for the study. Information on
the study population was linked to the Swedish health registers. Estimated individual drinking water
fluoride exposure was stratified into four categories: very low, 0.3 mg/L low, 0.3 to 0.69 mg/L
medium, 0.7 to 1.49 mg/L and high, ≥ 1.5 mg/L. The 2013 published study found no association
between chronic fluoride exposure and the occurrence of hip fracture. The authors concluded that,
“The risk estimates did not change in analyses restricted to only low-trauma osteoporotic hip fractures.
Chronic fluoride exposure from drinking water does not seem to have any important effects on the
risk of hip fracture, in the investigated exposure range.”231
Bone Mineral Density Study
A study published in 2005 evaluated the bone mineral density levels and rates of bone fracture of
1,300 ambulatory women aged 20–92 years living in three separate communities with diverse mineral
content.232 The sizes and demographics of the three communities were similar. One part of the study
looked at whether fluoride was associated with adverse bone-related outcomes. The study measured
fluoride serum levels, fluoride exposure, and bone metabolism as related to fluoride exposure and
fluoride’s interaction with other important bone factors, including age, menopause status, and
medications. The high-fluoride community was found to have significantly higher serum fluoride
levels (2.11 µmol/L) compared to the control and high-calcium communities. Serum fluoride was not
significantly associated with bone mineral density, except for higher distal radius bone mineral density
in the high-fluoride community. No relationship was found between serum fluoride levels and the risk
of osteoporotic fractures over 4 years. The study concluded that long-term exposure to fluoride was
not associated with adverse effects on bone health.232
