Background: Desalination of seawater and brackish water (mixed seawater and freshwater) provides an increasing portion of the Israeli drinking water supply. However, desalinated water contains little calcium (Ca) and magnesium (Mg), and consumers may be at risk for deficiencies of these essential minerals.

Objectives: To assess intakes of Mg and Ca from water, other beverages, and food in communities with different water supplies, and assess the proportion of individuals with intakes below the estimated average requirement (EAR).

Methods: Telephone interviews were conducted using a food frequency questionnaire to assess Mg and Ca intakes by adults in four communities. The proportion of individuals with Mg and Ca intakes below the EAR were evaluated based on current intakes and on potential intakes assuming that desalinated water had been introduced countrywide.

Results: The proportion of individuals with Mg intake below the EAR was higher in Kibbutz Maagan Michael (30.6%), an agricultural settlement supplied with desalinated water, than in Hadera (16.7%), a city supplied by the National Water Carrier (NWC) (P < 0.01). The proportion of individuals with Ca intake below the EAR was higher in Maagan Michael (15.3%) than in the communities supplied with water from the NWC or mixed water (27.7%–33.8%), P < 0.02.

Conclusions: Returning Mg and Ca to desalinated water may be beneficial for raising intakes in Israeli communities supplied with desalinated water. Individuals with intake of Mg and/or Ca below the EAR may be at risk for cardiac abnormalities and other medical conditions.