Micronutrients: Flouride

Micronutrients: Flouride
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An essential mineral for healthy teeth, fluoride is stored in the body as calcium fluoride. For more than 70 years, fluoride has been added to drinking water in the United States to promote dental health, an achievement the Centers for Disease Control and Prevention considers one of the 10 great public health achievements of the 20th century. Seventy-five percent of the U.S. population receives fluoridated water.

The American Dental Association recommends water fluoridation as a safe, effective means of protecting against cavities and reducing tooth decay by 20 percent to 40 percent. Despite numerous studies showing safety and efficacy, water fluoridation sparks a heated debate.

Roles in health
Fluoride protects teeth by strengthening the enamel, making it more resistant to acid and demineralization and thereby preventing cavities. Fluoride also helps remineralize enamel, reverse early signs of tooth decay and can prevent growth of harmful oral bacteria.

A 2015 Cochrane review questioned the impact of fluoride on cavities in adults, yet two government reviews concluded water fluoridation is effective in decreasing the prevalence and severity of cavities among adults and children. The CDC estimates fluoridated water reduces tooth decay by 25 percent among children and adults.

Current recommendations
Because insufficient data was available to set a Recommended Dietary Allowance, an Adequate Intake of fluoride was established in 1997.

AgeAI mg/dayUL
0-6 months0.010.7
7-12 months0.50.9
1-3 years0.71.3
4-8 years1.02.2
9-13 years2.010.0
14-18 years3.010.0
Females 19+3.010.0
Males 19+4.010.0

In 2015, the U.S. Department of Health and Human Services revised the optimal fluoride level to 0.7 ppm for dental health. Concerns about dental fluorosis, a condition in which excess fluoride causes white lines or specks on children’s teeth, spurred this change from the 1962 recommendation of 0.7 to 1.2 ppm. In areas with naturally higher fluoride levels, communities must ensure the maximum level is below 4 ppm, a level considered hazardous.

Signs of deficiency
The only known sign of fluoride deficiency is an increased risk of cavities.

Potential adverse effects
Dental fluorosis can occur in children 8 and younger while teeth are still forming under the gums. Most cases of fluorosis are mild, affecting the appearance but not health of teeth. The National Research Council estimates the prevalence of severe dental fluorosis at near zero when fluoride concentrations are under 2 ppm. The incidence of fluorosis has increased primarily due to reconstituted infant formula made with fluoridated water and children swallowing toothpaste.

Parents of infants exclusively fed prepared formulas are advised to use fluoride-free water to minimize the risk of mild fluorosis. Children younger than 6 should not use fluoridated mouthwash and should be discouraged from swallowing toothpaste.

Skeletal fluorosis, also rare in the United States, involves the bones and joints. Early signs include nausea and vomiting, joint pain and stiffness that can advance over time to affect bone structure and increase risk of fractures. Risk for skeletal fluorosis occurs when consumption is above 6 ppm.

A 2017 study suggested high levels of fluoride in utero could impact cognition and IQ, yet a 2015 study refutes that water fluoridation is neurotoxic and lowers IQ. The Evidence Analysis Library’s Fluoride Systematic Review rated the association as having “limited evidence.”

Numerous studies have reviewed the potential association between water fluoride levels and cancer; most have not found a strong link.

Sources of fluoride
Fluoride is found naturally in soil, water and food; it also is commonly added to toothpaste, mouthwash, dental gels, fillings, dental floss and water supplies. In the U.S., the largest source of fluoride is fluoridated water. Amounts vary between communities, bottled waters and well water. Fluoride in most foods is low, less than 0.5 ppm. Tea and foods that are fortified or mixed with water can have higher levels. Prescription supplements are available for children living in areas where water is not fluoridated.

Bottom line
Numerous studies support the safety of low-dose fluoridated water for dental health. If desired, fluoride consumption can be lowered by drinking bottled water, using a fluoride filter for tap water and choosing fluoride-free toothpaste. Anyone concerned about excess fluoride consumption should consult a dentist.

References

2018 Fluoridation Facts. ADA website. Accessed February 8, 2019.
5 Reasons Why Fluoride in Water is Good for Communities. American Dental Association website. Accessed February 8, 2019.
America’s Health Rankings 2018 Annual Report. United Health Foundation website. Accessed February 8, 2019.
Bashash M, Thomas D, Hu H, et al. Prenatal Fluoride Exposure and Cognitive Outcomes in Children at 4 and 6-12 Years of Age in Mexico. Environ Health Perspect. 2017;125(9): 097017.
Choi AL, Sun G, Zhang Y, Grandjean P. Developmental Fluoride Neurotoxicity: A Systematic Review and Meta-Analysis. Environ Health Perspect. 2012;120(10):1362–1368.
Chuck E. Science says fluoride in water is good for kids. So why are these towns banning it? NBC news website. Published October 17, 2018. Accessed February 8, 2019.
Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. NASEM website. Accessed February 8, 2019.
Fluoridation FAQs. American Dental Association website. Accessed February 8, 2019.
Fluoride (FL) Systematic Review. Academy of Nutrition and Dietetics Evidence Analysis Library. Published 2010. Accessed February 8, 2019.
Fluoride in Drinking Water. Washington, D.C.: The National Academic Press. 2006.
Fluorosis. American Dental Association website. Accessed February 8, 2019.
Iheozor‐Ejiofor Z, Worthington HV, Walsh T, et al. Water fluoridation for the prevention of dental caries (Review). Cochrane Database of Syst Rev. 2015;6.
Inadequate or Excess Fluoride: A Major Public Health Concern. WHO website. Accessed February 8, 2019.
Levy SM, Broffitt B, Marshall TA, Eichenberger-Gilmore JM, Warren JJ. Associations between fluorosis of permanent incisors and fluoride intake from infant formula, other dietary sources and dentifrice during early childhood. J Am Dent Assoc. 2010;141(10):1190-1201.
Over 70 Years of Community Water Fluoridation. CDC website. Updated May 4, 2016. Accessed February 8, 2019.
Promoting Oral Health through Water Fluoridation. FDI World Dental Federation website. Updated September 2014. Accessed February 8, 2019.
USDA National Fluoride Database of Selected Beverages and Foods, Release 2. USDA website. Accessed February 8, 2019.
U.S. Public Health Service Recommendation for Fluoride Concentration in Drinking Water for the Prevention of Dental Caries. Public Health Rep. 2015;130(4):318-331.
Water Fluoridation and Cancer Risk. ACS website. Updated July 24, 2015. Accessed February 8, 2019.
Water Fluoridation. CDC website. Updated August 5, 2016. Accessed February 8, 2019.
Water Fluoridation. Healthy Children website. Updated April 20, 2012. Accessed February 8, 2019.

Kathleen Zelman
Kathleen Zelman, MPH, RDN, is the nutrition director of WebMD.