Magnesium remineralization of desalinated drinking water and residents' health outcomes: a prospective cohort baseline study

Background Desalination substantially reduces magnesium concentrations in drinking water, potentially increasing the risk of magnesium deficiency-related chronic diseases. Israel, where desalinated water now comprises more than 70% of the household supply, provides a unique natural setting for evaluating these effects. This study characterizes the baseline health and magnesium-exposure status of residents of Kibbutz Ma'agan Michael — a community relying almost exclusively on desalinated water for approximately two decades — prior to the planned addition of magnesium to the community water supply. Methods A prospective cohort study was conducted. A structured, self-administered questionnaire was distributed to 1,600 adult residents in April–May 2025, capturing sociodemographic characteristics, health history, dietary habits, and magnesium supplement use. For baseline analyses, participants were classified as "magnesium-exposed" (supplement users) or "unexposed" (tap-water-only drinkers without supplementation). Descriptive statistics, chi-square and Fisher exact tests, and multivariable logistic regression were performed using SPSS. Follow-up data collection is planned at one and two years after initiation of water remineralization (April 2026). Results A total of 443 residents completed the questionnaire (response rate 46%). Most were female (56%), with a mean age of 51.5 ± 15.9 years and a high educational level (66% academic). Approximately 37% reported magnesium supplementation. Supplement users were significantly older (mean 56.2 vs 48.8 years; p < 0.001), more likely to be female (p < 0.001), less likely to consume alcohol (p < 0.01), and had a higher prevalence of at least one chronic disease (43.2% vs 29.5%; p < 0.01). No significant differences were observed in the individual prevalence of cardiovascular disease or diabetes mellitus. Multivariable logistic regression identified female sex (OR 1.87; 95% CI 1.24–2.82), absence of alcohol consumption (OR 1.56; 95% CI 1.03–2.36), and presence of chronic disease (OR 1.62; 95% CI 1.07–2.45) as independent predictors of supplementation. Conclusions This baseline assessment establishes a well-characterized cohort for longitudinal evaluation of magnesium remineralization in a desalination-dependent community. The pattern of supplementation use — concentrated among older women and those with existing chronic conditions — suggests that magnesium intake from water may be particularly relevant for vulnerable subgroups. Planned follow-up measurements will assess temporal changes in morbidity and health behaviors following water remineralization, contributing evidence to inform regulatory policy for desalinated water systems globally.