Dr. Lars C. Stene, of the Norwegian Institute of Public Health in Oslo, and colleagues first detected a significant association between diabetes and the use of well water, as opposed to water from waterworks, after questioning subjects in Vest-Agder county. In a survey of 85 individuals diagnosed with diabetes before age 15 and 1071 control subjects, the odds ratio for the association was 2.3.

The researchers then analyzed tap water samples from the homes of 64 patients and 250 control subjects. The odds ratio for type 1 diabetes was 5.56 for tap water with pH between 6.2 and 6.9 compared with water of pH 7.7 or above after adjusting for potential confounders such as zinc concentration, maternal education, water source, area of residence, gender and birth year. The association for the trend was highly significant at p = 0.002.

Higher concentrations of zinc were associated with a decreased risk of diabetes after adjusting for pH and the other confounders. Compared with zinc concentrations below 15 g/L, the adjusted odds ratio was 0.38 for concentrations between 45 and 74.9 g/L, while for higher concentrations, the odds ratio was 0.28.

These findings were independent of individual carrier state for the protective HLA-SQB1*0602 allele, the authors note.

"The mechanisms by which water acidity or mineral content may be involved in etiology of type 1 diabetes remain unknown, but the mechanisms are most likely indirect and may involve an influence on survival of microorganisms in the water," the investigators maintain. For example, enteroviruses or rotaviruses "that may be relevant in the etiology of type 1 diabetes" survive optimally at pH levels of about 6.2-6.9.

Diabetes Care 2002;25:1534-1538.