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Fluoride intake and urinary fluoride excretion in 4- and 8-year-old children living in urban and rural areas of Southwest Nigeria

Lookup NU author(s): Olushola Ibiyemi, Dr Vida Zohoori, Professor Ruth Valentine, Emerita Professor Anne Maguire



This is the authors' accepted manuscript of an article that has been published in its final definitive form by Wiley-Blackwell, 2018.

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Objectives: To estimate and compare total daily fluoride intake (TDFI), daily urinary fluoride excretion (DUFE), daily fluoride retention (DFR), fractional urinary fluoride excretion (FUFE) and fractional fluoride retention (FFR) in 4- and 8 year-old Nigerians and explore associations between these outcomes to improve understanding of fluoride metabolism. Methods: Using a cross-sectional observational study, 72 four year-olds and 72 eight year-olds were recruited from nursery and primary schools (respectively) in lower and higher water F areas of urban and rural localities in Oyo State, south-west Nigeria. TDFI from diet and toothpaste ingestion was assessed using a validated Food Frequency Questionnaire and visual scale of toothpaste used during toothbrushing. DUFE was measured by collecting a 24-hour urine sample, FUFE estimated as the ratio between DUFE and TDFI, DFR estimated as TDFI-TDFE (where TDFE = DUFE + estimated faecal F excretion (i.e.TDFI x10%), and FFR was estimated as [(TDFI-DFR)/TDFI] x 100. Data were analysed using ANOVA with post-hoc tests and Students t tests and strengths of associations between key variables measured. Results: Mean (SD) TDFI, DUFE, DFR, FUFE and FFR were 0.137 (0.169) mg/kg bw/d, 0.032 (0.027) mg/kg bw/d, 0.091 (0.147) mg/kg bw/d, 44% (44%) and 46% (44%), respectively for 4-year-olds. Corresponding values for 8-year-olds (n=63) were 0.106 (0.130) mg/kg bw/d, 0.022 (0.017) mg/kg bw/d, 0.073 (0.107) mg/kg bw/d, 36% (30%) and 54% (30%), respectively. Dietary contribution to TDFI was 79% and 75% (respectively), for 4- and 8-year-olds. Mean (SD) TDFI from toothpaste ingestion was 0.021 (0.013) mg/kg bw/d in 4-year-olds, 0.014 (0.010) mg/kg bw/d in 8-year-olds (p=0.002) but with no differences between areas. Differences in dietary F intake determined the main differences in F exposure between areas. The positive correlation between TDFI and DUFE was weak for 4 year-olds (r = +0.29) and strong for 8 year olds (r = +0.64). A strong positive correlation was observed between TDFI and DFR for both age groups: (r) = +0.98 for 4-year-olds and (r) = +0.99 for 8-year-olds. Conclusion: Fluoride intake in these 4- and 8 year-old Nigerians was much higher than the “optimal range” of 0.05-0.07 mg/kg bw/d in rural, higher F water areas, with diet as the main contributor. F retention was similar in both age groups, with almost half of TDFI retained in the body. In terms of risk versus benefit for fluorosis and dental caries, this finding should be considered when mitigating against excessive fluoride exposure and planning F-based prevention.

Publication metadata

Author(s): Ibiyemi O, Zohoori FV, Valentine RA, Maguire A

Publication type: Article

Publication status: Published

Journal: Community Dentistry and Oral Epidemiology

Year: 2018

Volume: 46

Issue: 5

Pages: 482-491

Online publication date: 03/07/2018

Acceptance date: 30/05/2018

Date deposited: 20/06/2018

ISSN (print): 0301-5661

ISSN (electronic): 1600-0528

Publisher: Wiley-Blackwell


DOI: 10.1111/cdoe.12396


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Funder referenceFunder name
Centre for Oral Health Research, Newcastle University
Commonwealth Scholarship Commission