The fluoride intake from diet, water and toothpaste of New Zealand adolescents

Abstract

Background: Fluoride plays an essential role in the prevention of dental caries, the most common chronic disease for New Zealanders of all ages. Despite public controversy, community water fluoridation (CWF) is considered one of the top 10 greatest public health achievements of the past century. Currently, only 48% of New Zealanders have access to fluoridated water, with limited data on fluoride intakes in the New Zealand (NZ) population available. Objective: To assess the fluoride intake of NZ adolescent males and females from water, diet and toothpaste and to evaluate the necessity and contribution of fluoridated water to daily fluoride intake. Design: For this cross-sectional, multi-centred study, 266 females and 135 males aged 15-18 years were recruited from 13 high schools across NZ, located in areas with and without CWF. Participants completed online self-administered questionnaires to provide information about demographics and toothbrushing habits. Anthropometric measurements (weight and height) and interviewer-assisted 24-hour recalls were carried out during an in-school visit. A follow-up 24-hour recall was conducted virtually the following week to assess usual dietary intake. Dietary data were entered and analysed in FoodWorks Professional Software; the multiple source method was used to adjust data for usual intake. An extended version of the 2018 NZ Food Composition Tables was used, with missing fluoride values imputed from the NZ Total Diet Study and a recent UK database, all of which included different fluoride contents for food affected by CWF. Community water fluoride concentration of each school district was acquired through direct contact with regional councils or online reports. Only participants who had provided data on usual diet and toothbrushing habits were included in the calculations for fluoride intake. Results: The water fluoride concentration was 0.56-0.75mg/L in areas with CWF (F areas) and 0.03-0.11mg/L in areas without CWF (NF areas). Of the total enrolled participants, 50% of males and 41% of females attended schools in areas with CWF. There were 223 female and 80 male participants included in the final analysis. Only 32 females (14%) and 2 males (3%), all residing in F areas, met the Adequate Intake (AI) for fluoride of 3mg/day. The mean difference (95% CI) in fluoride intake was 1.81 (1.60, 2.01)mg/day for females and 1.13 (0.92, 1.35)mg/day males in F versus NF areas. In F areas, females had a significantly higher total fluoride intake than males, with mean difference of 0.74 mg/day; this was largely associated with the higher water intake of females versus males in F area with mean difference (95% CI) of 1.05 (0.70,1.39)L/day. Tap water contributed 60-79% of total daily fluoride intake in F areas and 16-18% of the total daily fluoride intake in NF areas. No participant consumed more than the Upper Limit (UL) for fluoride of 10 mg/day for fluoride. Diet and toothpaste provided, on average, less than 1.00mg/day of fluoride to total fluoride intake. Conclusion: This is the first study to measure fluoride intakes in NZ adolescents using a robust method of dietary assessment that accounted for CWF. The key finding of this study was the importance of CWF and the consumption of tap water, which together, were essential to ensure NZ adolescents meet the AI, set to reduce their risk of dental caries.