Patterns of Fluoride Intake from 6 to 17 Years of Age: The Iowa Fluoride Study

Abstract

Objectives:

This paper reports on estimated daily fluoride intake from water, other beverages and selected foods, dentifrice, and dietary fluoride supplements by both individual sources, and all sources combined, among 787 children participating in the Iowa Fluoride Study (IFS) from 6 to 17 years of age.

Methods:

Total daily fluoride intake (mg F) and fluoride intake per kilogram bodyweight (mg F/ kg bw) were estimated using responses to questionnaires sent every 3–6 months. Dietary assessments included frequencies and amounts of beverage intake for the previous week from water, milk, ready-to-drink beverages, beverages made by adding water to concentrate or powder, and selected foods with substantial water content. Descriptive statistics and bivariate and multivariable analyses with linear mixed models were used to assess associations with each of mg F and mg F/ kg bw.

Results:

Mean combined dietary fluoride (mg F) from all sources examined in the study increased slightly with age, whereas the fluoride intake per kg bw decreased with age. Age, sex, and socioeconomic status were significantly associated with fluoride intake (mg F and mg F/ kg bw). Each year increase in age was associated with a 0.02-mg increase in fluoride consumption, on average, after adjusting for the effects of covariates.

Conclusions:

Daily mean fluoride intakes from single and combined sources were relatively stable, while the intake of fluoride per kg bw decreased from 6 to 17 years of age. Fluoridated water was the major source of ingested fluoride, contributing over 50% of total daily intake at all ages.

Introduction:

Fluoride is among the most widely used caries prevention agents globally. There has been a significant increase in the number of sources of fluoride over the past few decades (1). Prior to the discovery of the caries prevention benefits of fluoride, the major source of fluoride intake was naturally fluoridated water. An undesirable side effect of the ingestion of higher levels of fluoride during tooth development is dental fluorosis. Individual teeth develop at different times, so the risk of development of dental fluorosis in permanent teeth ranges from birth to about 8 years of age (2). The maxillary central incisors, the most esthetically prominent teeth in the mouth, are susceptible to dental fluorosis during the first 4 years of life (3). The late-erupting teeth, the canines, premolars and second molars, are at risk for development of dental fluorosis up to the age of 8 years (2). The caries preventive effects of fluoride are both pre- and post-eruptive although topical and post-eruptive effect is considered to play a predominant role in caries prevention (4). Burt (5) suggested that the optimum intake range for fluoride to avoid substantial fluorosis was 0.05– 0.07 mgF/kg-bw. Warren et al. (6) found that many children whose fluoride intake was at or below 0.05 mgF/kg-bw up to the age of 48 months had no caries experience and no fluorosis at age 9. Those with lower intake were more likely to have higher caries rates and those with fluorosis tended to have higher fluoride intakes.

Additionally, fluoride binds to hard tissues, so it could also impact bone health, which is especially important to consider among these age groups where bone development occurs at relatively higher rates (6). Analyses from the Iowa Bone Development Study, investigating fluoride’s impact on developing bone tissue, suggest that the effects of fluoride on bone mineral content and density could differ between girls and boys (6, 7). Oweis et al. (7) identified positive associations between cortical BMC and fluoride intake among 14- to 17-year-old males, and among females aged 0–8.5 years. Along with the caries prevention benefits, the effect of fluoride on bone makes it important to study the sources and amounts of fluoride consumed in the adolescent age group even though there is modest risk of developing esthetically significant dental fluorosis.

One of the few studies reporting on fluoride intake in adolescent children, Oweis et al.(8), reported that the mean daily fluoride intake ranged from 0.7 to 0.8 mg F/day for females and from 0.7 to 0.9 mg F/day for males from birth to age 17 years. Most previous studies of fluoride intake have been cross-sectional studies of dental fluorosis or focused on intakes from one or two sources among younger individuals (9–12). These previous studies have found that, among individuals living in both fluoridated and non-fluoridated areas, fluoride intake occurs from numerous sources, such as foods and beverages prepared with fluoridated water, dietary fluoride supplements, and swallowing of fluoride-containing oral hygiene products such as dentifrice. Some research suggests that daily fluoride ingestion is related to fluid consumption patterns and that children’s fluid consumption patterns are highly variable. Sohn et al. (10) found that fluid consumption among children varied significantly by age, sex, race/ethnicity, and socioeconomic status. Soft drink consumption has increased sharply in the United States and Canada in recent years in both fluoridated and non-fluoridated areas (9). Hence, soft drinks and other beverages prepared with fluoridated water are important sources of fluoride intake and important to analyze(13).

This paper reports the findings on combined estimated fluoride daily fluoride intake and daily fluoride intake per kg bw from individual sources, including water, beverages and selected foods, dentifrice, and dietary fluoride supplements, and all sources combined, among participants of the Iowa Fluoride Study from 6 to 17 years of age.

Methods:

The data for this analysis were collected from participants in the Iowa Fluoride Study (IFS), which is a longitudinal study of a birth cohort that began in the early 1990s. The IFS was approved by the Institutional Review Board of the University of Iowa, Iowa City, IA. Parents of 1,882 children were recruited from postpartum wards of eight hospitals across the state of Iowa during 1992 to 1995. Informed consent was obtained from the parents while they were in the hospital. Demographic information, including ages of the parents, mothers’ education, family income, and number of children in the household, was obtained from the parents

The methods and procedures of Iowa Fluoride Study have been described in detail in previous publications (11, 12). We provide a brief description here. The families were sent questionnaires on a regular basis, mostly at 3- and 4-month intervals from birth to age 48 months, with questionnaires subsequently sent at six-month intervals. Fluoride intake was estimated based on parents’ responses to the fluoride questions and use of publicly available information on fluoride levels of community water systems and assay of participants’ individual well or filtered water. The questionnaires collected detailed information on items concerning children’s daily fluoride exposures and ingestion during the preceding weeks from various sources, including water, beverages, selected food products with substantial water added, dietary fluoride supplements and fluoride toothpaste. Dietary assessments included frequencies and amounts of beverage intake in the previous week from water, milk, juice & juice drinks, drinks made from powder from powder, liquid or frozen concentrate, other beverages (soda pop, sports drinks, coffee, or tea) and selected foods with substantial water content (instant cereals, pasta, rice, concentrated soup, Jello®). Note that until the questionnaire at age 8.5 years, juices and juice-drinks were combined, whereas thereafter they were separated more specifically, and more detailed product-specific information was obtained. Documented levels of fluoride in home, childcare and school water sources, individual water fluoride assays and assays of purchased samples of bottled water and other beverages were used, in conjunction with the amounts consumed, to estimate total dietary fluoride ingestion (11, 12).

Amounts of fluoride ingested from dentifrice were estimated by combining frequency of tooth brushing, fluoride concentration in the reported brand of toothpaste, amount of dentifrice used, and estimated percentage of dentifrice that was swallowed. The quantity of toothpaste used was estimated by having parents selecting pictures of toothbrushes with different amounts of toothpaste. Parents also provided the estimates on the amounts of toothpaste swallowed. Amounts of fluoride ingested from supplements were estimated from the frequency of use and dosage level of each supplement used (11, 12).

A total of 787 participants were included in these analyses, based on the criteria of having at least one questionnaire returned providing fluoride intake information and having water fluoride information available for each of the years from ages 6 to 17. Descriptive statistics were computed for each time period for combined fluoride intake from all sources (water, beverages, selected foods, supplements and dentifrice), as well from the individual sources. Bivariate analyses were performed to examine the relationships between combined F intake from all sources and the variables of interest (sex, socioeconomic status, and income level in the year 2007, first child, race, and bodyweight). The bivariate analyses used linear mixed models to account for changes over time and within-subject correlation via a random intercept for subject and a linear effect of age. We performed multivariable analysis with the covariates that were significant in the bivariate analysis, along with age, to allow for interpretation of the effects of age and time. P-values <0.05 were considered statistically significant.

Results:

As shown in Table 1, about half of the participants were female (50.8%). The study subjects were from relatively high socioeconomic status families. Approximately, 14% had a family income of less than $40,000 and 50 percent had family income $80,000 or higher in 2007. For perspective, the Federal Poverty Level for a family of four in 2007 was annual income of $20,650 or less. Fifty-one percent of the mothers and forty-one percent of fathers, respectively, had a four-year college degree or higher levels of education. A three-category composite SES variable (Low, Middle, High) combining maternal education level and household income was created to include both dimensions. As can be seen in Table 1, only one-fourth of the children were from low SES families.

Table 1:

Sociodemographic characteristics of the study population

Sex:
Male	379 (49.2%)
Female	391 (50.8%)
Income:
Less than $20k	17 (2.7%)
$20k – $39,999	71 (11.2%)
$40k – $59,999	116 (18.3%)
$60k – $79,999	119 (18.8%)
$80k or more	310 (49.0%)
Mothers Education:
Some High School	5 (0.8%)
High School/GED	62 (9.6%)
Some College	107 (16.6%)
Two Year College Degree, Technical/Beauty School	140 (21.7%)
Four Year College Degree	200 (31.0%)
Postgraduate/Professional Degree	128 (19.8%)
Not Present	3 (0.5%)
Father’s Education:
Some High School	7 (1.1%)
High School/GED	129 (20.1%)
Some College	87 (13.5%)
Two Year College Degree, Technical/Beauty School	97 (15.1%)
Four Year College Degree	143 (22.2%)
Postgraduate/Professional Degree	120 (18.7%)
Not Present	60 (9.33%)
Socioeconomic Status in 2007:
Low	182 (24.6%)
Middle	279 (37.8%)
High	278 (37.6%)
Total (N)	770

Table 2 presents summary information, including the mean, median, 75th and 90th percentile values, for estimates of combined total daily fluoride intake and fluoride intake per kg bw from all sources (selected foods, beverages including water, dentifrice, and supplements). The estimated combined mean fluoride intake in milligrams (mg) increased slightly from 0.72 mg/day at age 6 to 0.86 mg/day at age 17. The mean fluoride intake per kg bw decreased from 0.03 mg F/ kg bw to 0.01 mg F/ kg bw. Larger changes in both mg F and mg F/ kg bw were noted in the higher intake percentile groups. The intake (in mg F) among children in the 95^th percentile increased from 1.53 to 2.29 mg F and the intake in mg F kg bw decreased from 0.07 mg F/ kg bw to 0.03 mg F/ kg bw. Detailed information on the distribution of home water fluoride levels by age are seen in the Appendix Table 1. Categories of combined intake in mg F/ kg bw by age are shown in Table 2 in the Appendix.

Table 2.

a: Summary statistics of total fluoride intake (mg F)

Age	Number of Participants	Mean	Standard Deviation	Minimum	Median	75th Percentile	90th Percentile	95th Percentile	Maximum
6	669	0.72	0.42	0.09	0.63	0.92	1.31	1.53	3.09
7	614	0.71	0.42	0.07	0.62	0.89	1.22	1.49	3.39
8	608	0.75	0.46	0.07	0.65	0.96	1.30	1.58	3.21
9	617	0.68	0.41	0.08	0.59	0.88	1.19	1.42	2.92
10	604	0.72	0.45	0.05	0.60	0.93	1.23	1.55	4.21
11	617	0.73	0.42	0.06	0.63	0.94	1.29	1.58	2.62
12	555	0.80	0.61	0.05	0.67	0.99	1.39	1.74	9.99
13	581	0.82	0.52	0.00	0.68	1.01	1.53	1.89	3.71
14	536	0.86	0.59	0.09	0.71	1.05	1.63	2.06	4.45
15	550	0.87	0.60	0.07	0.72	1.12	1.62	2.08	3.94
16	485	0.85	0.57	0.05	0.71	1.11	1.67	1.82	4.15
17	366	0.86	0.64	0.08	0.67	1.12	1.69	2.29	3.76
Table 2b: Summary statistics of total fluoride per kg bodyweight (mg F/ kg bw)
6	660	0.03	0.02	0	0.03	0.04	0.06	0.07	0.14
7	604	0.03	0.02	0	0.02	0.03	0.05	0.06	0.10
8	604	0.03	0.02	0	0.02	0.03	0.04	0.05	0.16
9	607	0.02	0.01	0	0.02	0.03	0.04	0.04	0.12
10	588	0.02	0.01	0	0.02	0.02	0.03	0.04	0.09
11	607	0.02	0.01	0	0.02	0.02	0.03	0.04	0.10
12	551	0.02	0.01	0	0.01	0.02	0.03	0.03	0.26
13	574	0.02	0.01	0	0.01	0.02	0.03	0.03	0.07
14	528	0.01	0.01	0	0.01	0.02	0.03	0.03	0.07
15	544	0.01	0.01	0	0.01	0.02	0.03	0.03	0.07
16	482	0.01	0.01	0	0.01	0.02	0.02	0.03	0.05
17	366	0.01	0.01	0	0.01	0.02	0.02	0.03	0.06

Figures 1 and 2 present the combined total daily fluoride intake and mg F/ kg bw values, respectively, from water alone, and other beverages and selected foods. The plots show five key summary measures- the minimum, first quartile, median, third quartile, and maximum intake values, with the boxes representing the interquartile range (IQR). The whiskers extend no further than 1.5 times the IQR from the edges of the box, and the points represent individual values outside of that range. Since no one had intake amounts at the bottom of the graph lower than 1.5*IQR, the whiskers only go upwards and not down. The plots show a slight increase in the mg F intake and decline in the mg F/ kg bw values with greater age from 6–17 years old.

Figure 1.

Box and Whisker plots showing total (mg F) fluoride intake by age

Figure 2.

Box and Whisker plots showing fluoride intake in in mg F/ kg bw by age

Figure 3 presents the estimated mean fluoride intakes in mg F from each of the individual sources and the mean combined intake from all sources. Water was the predominant source of fluoride intake in every age group, contributing a mean of approximately 50–60 percent of total daily fluoride ingestion. Other beverages and selected foods were the second largest source of fluoride, accounting for a mean of approximately 25–30 percent of total daily intake. Dentifrice contributed moderately to daily fluoride intake (mean of about 10–20 percent) and supplements contributed very little (0–2 percent). The mean percentages of total fluoride ingested from water and from other beverages and selected foods showed positive trends with age, and the mean percentage of total fluoride ingested from dentifrice decreased from 6 to 17 years of age. Estimated mean fluoride intake from dietary supplements was consistently low (<0.02), because less than 5 percent of children during each time period used supplements.

Figure 3.

Mean percentages of total daily fluoride intake (mg F) by source from age 6–17 yearss

The individual fluoride intake values in mg F and mg F/ kg bw for all participants over the entire study period are shown in the Appendix in Figures 1 and 2, respectively. The points are the observations, with connecting lines to depict the trends. Although it is difficult to discern the individual level trends with so many participants’ data included, they provide information about the overall patterns of fluoride intake. Substantial variation within individuals is demonstrated, with great fluctuations in intake for those in the higher intake percentiles. The solid black line depicts the general increasing trend in combined fluoride intake amounts (mg) with an increase in age (Appendix Figure 1). Detailed summaries of mean daily fluoride intake in mg F from water by itself and from dentifrice are reported in Appendix Figures 3 and 4, respectively.

In our bivariate analysis (results not shown), we found that higher socioeconomic status (in year 2007) was again a significant predictor, although sex was only marginally significant in this model. Being male was associated with a 0.001-mg per kg increase in fluoride consumption and being in a higher socioeconomic status (mid- or high-level) was associated with lower fluoride consumption (0.003 mg/kg less, on average for each of mid/high vs. low). Participants’ race and being a first child were not significantly associated with mean fluoride intake (mg F) values in the bivariate analysis and were excluded from the multivariable models. The results from the multivariable analysis are shown in Table 3. Each of age, sex, and SES remained statistically significant in the multivariable analysis. Each year of age was associated with a 0.002-mg decrease in fluoride consumption per kg bodyweight, on average, after adjusting for the effects of covariates.

Table 3:

Results from multivariable analysis of factors associated with fluoride intake total

Variable Name	Estimate	Standard Error	p-value
Total fluoride intake (mg F)
Age	0.02	0.002	<0.001
Sex (Male)	0.10	0.026	<0.001
Socioeconomic Status in 2007 (Middle)	−0.08	0.033	0.01
Socioeconomic Status in 2007 (High)	−0.11	0.033	<0.001
Total fluoride per kg bodyweight (mg F/ kg bw)
Age	−0.002	0.00004	0.117
Sex (Male)	0.001	0.0007	0.045
Socioeconomic Status in 2007 (Middle)	−0.003	0.0009	0.001
Socioeconomic Status in 2007 (High)	−0.003	0.0009	<0.001

Discussion:

This study used data from the Iowa Fluoride Study to examine, simultaneously and longitudinally, the estimated daily fluoride intakes from various dietary and non-dietary sources among children aged 6 to17 years. There is very sparse published literature that has examined period-wise fluoride intake from multiple sources in a longitudinal study for children in this older age group, making comparisons to other studies difficult.

The varieties of foods and the portion sizes consumed by children undergo considerable changes from ages 6 to 17 years as the children grow older. A report from the EPA (13) found an increase in the amount of fluoride consumed from all sources between ages 6 and 19 years among children living in fluoridated and non-fluoridated areas. In fluoridated areas, the increase was from a mean of 0.68 mg/day among children 6–11 years old to 1.11 mg/day among those who were 12–19 years old, respectively. In non-fluoridated communities, the mean intake increased from 0.56 mg/day among children 6–11 years old to 0.84 mg/ day among children 12–19 years old, respectively.

In this study, we found that the estimated combined mean and the median daily fluoride intakes from selected foods and beverages, dentifrice and supplements were generally stable from ages 6 to 17 years and increased only slightly with age. Previous studies on fluoride intake in the IFS cohort at younger ages reported clearer increases in the amounts of total fluoride intake from birth to 36 months, and from age 36 to 72 months (11, 12). Among the older children in the IFS cohort, Oweis et al.(8) reported that the mean daily fluoride intake stayed relatively stable from age 0 to 17 years, ranging from 0.7 mg F/ day to 0.9 mg F/ day among males and from 0.7 mg F/ day to 0.8 mg F/ day among females, respectively.

The importance of the fluoride intake in mg F/kg bw is less clear in the 6–17 years age group given that the teeth/ regions of teeth that are susceptible to fluorosis at this age are not esthetically prominent (2, 14). Nonetheless, we examined the association of fluoride intake per unit body weight with increasing age and, as expected, found the amount of fluoride intake per kg-bodyweight decreased over the study period due to growth in the body weight over the course of the study. The mean daily fluoride intake values per kg bw (0.01–0.03 mg F/ kg bw) in this study are generally lower than the threshold for any adverse oral or general health effects. The IOM’s Dietary Reference guide for fluoride intake suggests an adequate daily fluoride intake value of (AI) 0.05 mg/kg/day (15). The risk of esthetically significant dental fluorosis is higher among children with developing teeth if their mean daily fluoride intakes are more than 0.10 mg/kg (16). Hence, a small portion of children who had higher levels of fluoride intake extended periods in this study may have elevated risk for development of dental fluorosis in the late-erupting teeth.

Consistent with the findings of previous reports from the IFS and the other studies of fluoride intake, we found substantial individual level variation in the mean and median daily fluoride intake amounts at each age. This variation arises from the substantial number and complexity of intakes from those sources. The variation demonstrates the complexity in categorizing individuals into a ‘high’ or ‘low’ intake category for extended periods, as relatively few participants were consistently in the same intake category.

Individual level variations in fluoride intake levels were greater at the higher intake levels for both the mg F and mg F/ kg bw, albeit to a lesser extent in the latter measure (Appendix graphs Figures 1 and 2). The estimated mean daily fluoride intake increased from 0.72 to 0.86 mg/day (a net increase of 0.14 mg/day) from the age 6 to 17 years, while the 95^th percentile intake amounts increased from 1.53 to 2.29 mg/day (a net increase of 0.76 mg/day) over the same ages. The patterns we found are generally similar to the patterns of intake among 36- to 72-month-old children reported in previous analyses from the Iowa Fluoride Study (11, 12).

Approximately 62%–69% of participants in this IFS study sample had optimal home water fluoride levels. At every age, the home water fluoride levels of children in the higher intake percentile groups were higher than those in the lower percentile groups. Additionally, the home water fluoride levels declined slightly among participants in the lower percentile groups as the cohort grew older. This difference in water fluoride levels, coupled with greater water intakes in the higher percentile groups, led to the overall increases in intake amounts among children in the higher percentile groups compared to lower ones and the means and medians. We conducted additional analyses (data not shown) to better understand possible reasons for the greater increases in fluoride intake values among children in the 90th or 95th percentiles groups as compared to children in the lower intake percentiles.

Fluoridated water was the major source of ingested fluoride and accounted for 50% of fluoride intake at age 6 years age and approximately 55% at age 17 years. These levels are similar to what was reported by Singer et al. (17) who conducted a “market basket” food survey from 1975 to 1982. Previous studies of the IFS cohort have reported that fluoride from water by itself accounted for a mean of about 20 percent of total fluoride intake for ages 36 to 48 months and about 30 percent at 72 months, while the percentage of fluoride from other beverages was steady at about 35 percent from 36 to 72 months (11, 12). A report from the Environmental Protection Agency (EPA) noted that the mean fluoride intake from water alone increased from about 0.39 to 0.66 mg/day from ages 7–10 to 15–19 years, respectively (13). In the current study, the mean fluoride intake from water alone increased from 0.4 mg/day to 0.5 mg/day between the ages of 6 and 17 years.

Drewnowski et al. (18) assessed water and beverage consumption among US children ages 4 to 13 years and reported a significant difference in the consumption of plain water among 4- to 8- year-old children compared to 9- to 13-year-old children, with the older children consuming significantly larger volumes of water than the younger children. Using dietary data from the National Health and Nutrition Examination Survey 2005–2006 to analyze total daily water intake among children 2–19 years of age, Kant and Graubard (19) also found that mean intakes of total water increased with age.

Swallowing of fluoride-containing products such as toothpastes and mouthwashes is an important contributor to the etiology of dental fluorosis. Levy (20) reported that only 5% of children spit after brushing, almost half of them did not rinse after brushing and 27% swallowed almost all of the water used for rinsing. Franzman et al. (21) reported that a majority of children under the age of 3 years swallowed more than 75% of the dentifrice. The swallowing control develops as children grow older and hence the amount of toothpaste ingested among children in this group is low when compared to reports on younger children. We found that mean fluoride ingestion from dentifrice decreased with age (from approximately, 0.2 mg/ day (10% of daily intake) at age 2 years to less than 0.1 mg/day (10% of daily intake) by age 17 years, even though tooth brushing frequency and amount of dentifrice used per brushing increased. Barnhart et al.(22) reported that the mean amount of toothpaste swallowed per brushing was 0.30 mg among children aged 2 to 4 years, 0.13 mg among those 5 to 7, and 0.07 mg among those 11 to 13 years. Strittholt et al. (23), based on a randomized control trial modelled after the Barnhart et al. study, reported similar findings. They found that mean amounts ingested were: 0.205g among children 2–4 years old, 0.125g among those 5–7 years old and 0.135g among children aged 8–12 years (23). Martınez-Mier et al. (24) reported that ingested toothpaste was the biggest source of fluoride intake among children (15–36-month-old) in two cities in Mexico, accounting for 64–72% of total daily fluoride intake.

Dietary fluoride supplements were a minor source of ingested fluoride, as supplement use from 6 to 17 years of age was minimal. In a previous study of the Iowa Fluoride Study cohort, Hamasha et al. (25) reported that, at age 92 months, only 3.5% of the study participants were using dietary fluoride supplements. Hamasha et al. (25) also found that, among participants who used dietary fluoride supplements, the estimated daily average fluoride ingested from supplements increased from 0.06 mg (birth-12 months) to 0.07 mg (12–60 months) to 0.18 mg (60–96 months). In comparison, Wagener et al.(26), who analyzed data from the National Health Interview Survey from 1983–1989, reported that 15% of older kids took dietary fluoride supplements.

The data used for this study were collected between the years 1998 and 2013 and they predate the official downward adjustment of community water fluoride concentrations by the U.S. Department of Health and Human Services in 2015 (29). Hence, the results were not affected substantially by the downward adjustment of water fluoride concentrations. As found in the current and previous studies, drinking water is the most important source of fluoride among children of all ages. The downward adjustment of fluoride levels will certainly lead to a decrease in the amount of total fluoride ingested. This underscores the need for studies to understand the relative contributions with new fluoride levels.

Some of the limitations of this study are that the data used in the analyses were self-reported and obtained from non-validated questionnaires. Also, the questionnaires collected information on consumption of beverages (water and non-water) and selected foods for the previous week and may not accurately represent subjects’ yearly consumption patterns. The Iowa Fluoride Study’s sample is not a representative sample of the United States and is disproportionately white/non-Hispanic, as is the state of Iowa. While people of racial/ ethnic minority populations were oversampled in the original recruitment for the IFS sample, higher rates of attrition (data shown in Appendix Table 3) led to smaller proportions of participants from racial/ ethnic minority groups and low SES families. Lastly, parental education and family income of these subjects is higher, on average, than that of the general Iowa and U.S. populations.

Conclusion:

Overall, the mean and median daily fluoride intake from all sources we examined at every age were within the currently recommended adequate daily fluoride intake range of 1–3 mg F/day. There was substantial individual level variation in the daily fluoride intake values from individual sources and combined. Mean daily fluoride intakes from single and combined sources were relatively stable from 6 to 17 years of age, while F intake per kg body weight decreased with age. Fluoridated water was the most important source of fluoride. Mean and median fluoride intake levels generally were consistent with previous studies. Fluoride intake from dentifrice and dietary supplements declined substantially as the children grew older.