What do systematic reviews say?

Higher drinking-water fluoride exposure vs Null / lowest drinking-water fluoride exposure (reference)

Non-linear positive dose-response: little change in overall fracture risk below ~1.5 mg/L drinking-water fluoride, with risk increasing above that threshold (RR 1.06, 1.19, 1.35 at 2.0, 3.0, 4.0 mg/L vs null); ungraded (4 studies).

• The association of fluoride exposure with bone density and fracture risk: a dose-response meta-analysis. 2025 All outcomes

  Long-term / lifetime fluoride exposure · General population; 37 observational studies (1944-2024), predominantly North America (USA, Canada) and Northern Europe (Finland, Sweden), plus UK, Poland, Italy, Germany, China, Taiwan, South Korea, Ethiopia; exposure mainly community drinking-water fluoride · Drinking-water fluoride 1.2 mg/L vs null
  RR 1.00 [0.80, 1.24]
  4 studies
  GRADE not reported
• The association of fluoride exposure with bone density and fracture risk: a dose-response meta-analysis. 2025 All outcomes

  Long-term / lifetime fluoride exposure · General population; 37 observational studies (1944-2024), predominantly North America (USA, Canada) and Northern Europe (Finland, Sweden), plus UK, Poland, Italy, Germany, China, Taiwan, South Korea, Ethiopia; exposure mainly community drinking-water fluoride · Drinking-water fluoride 4.0 mg/L vs null
  RR 1.35 [0.94, 1.95]
  4 studies
  GRADE not reported
• The association of fluoride exposure with bone density and fracture risk: a dose-response meta-analysis. 2025 All outcomes

  Long-term / lifetime fluoride exposure · General population; 37 observational studies (1944-2024), predominantly North America (USA, Canada) and Northern Europe (Finland, Sweden), plus UK, Poland, Italy, Germany, China, Taiwan, South Korea, Ethiopia; exposure mainly community drinking-water fluoride · Drinking-water fluoride 3.0 mg/L vs null
  RR 1.19 [0.87, 1.64]
  4 studies
  GRADE not reported