What are the potential health risks of drinking demineralized water for more than 5 years?
Executive summary
Drinking demineralized (demi, distilled, deionized or RO-treated) water exclusively for years can lower intake of beneficial minerals and has been associated in reviews and WHO reports with altered mineral and water metabolism and suboptimal nutrient intake, with specific concerns for calcium and magnesium losses and effects in vulnerable groups such as infants and pregnant people [1] [2] [3]. Evidence comes from animal experiments, human volunteer studies, systematic reviews and WHO technical assessments that warn demineralized water “without further enrichment” is not fully appropriate for long‑term consumption, while other sources argue short‑term drinking is unlikely to harm healthy adults if diet supplies minerals [1] [2] [4] [5].
1. Mineral deficiency and poorer nutrient intake — a plausible long‑term pathway
Demineralized water lacks dissolved calcium and magnesium and therefore removes one regular dietary source of these elements; systematic reviews and WHO‑linked chapters conclude long‑term consumption “may lead to a lower quality of the intake of certain nutrients” and that regular use might not be corrected automatically by diet alone [4] [6] [2]. WHO working groups and technical reports recommended minimum levels for drinking water (for example, at least ~30 mg/L calcium, and total dissolved solids around 100–250 mg/L as guidance) because very low mineral waters were linked in experiments to changes in physiological functions [1] [2].
2. Metabolic and electrolyte effects observed in studies and reports
Experimental animal work and some human volunteer observations have reported effects on water and mineral metabolism when animals or people consume very low‑mineral or desalinated waters, including changes in thyroidal function in rats given very low calcium water and reports of disturbed mineral balance and increased diuresis in human studies summarized by WHO [1] [2]. A WHO‑linked chapter cites clinical concerns such as early symptoms of low electrolytes—tiredness, weakness, headache, and in severe cases brain edema or convulsions—and notes metabolic acidosis has been reported in infants when formula or drinks were prepared with distilled or low‑mineral waters [6] [2].
3. Special risks for vulnerable populations — infants, pregnant people, people with restricted diets
Infants, people on low‑mineral diets, and those with higher mineral needs are singled out in WHO and academic reviews because small losses of calcium or magnesium can have outsized effects; documented infant cases of metabolic acidosis tied to very low‑mineral water used for formula preparation underline the practical risk when dietary compensations are absent [6] [2]. WHO guidance therefore treats demineralized water without remineralization as inappropriate for unrestricted public supply absent measures to restore minerals [1] [3].
4. Indirect harms — cooking, leaching and taste that affect intake
Reports note cooking with demineralized water can leach minerals from food, sometimes substantially reducing magnesium and calcium content of prepared food, and the bland taste of very low‑mineral water can reduce voluntary water intake and thus hydration in some people, creating an indirect pathway to health effects [3] [7]. WHO analysis also flagged the tendency of demineralized water to be more aggressive toward plumbing and possibly increase the leaching of metals if distribution or storage materials are unsuitable, although the degree of risk depends on local systems and was discussed as a secondary concern in reviews [1] [2].
5. How strong is the evidence and the counterarguments?
The literature is mixed: WHO and multiple reviews present mechanistic, animal and human‑study evidence sufficient to recommend remineralization for long‑term drinking water, while other sources and practical observations—such as routine use of distilled or RO water by some populations (and arguments that dietary intake supplies most minerals)—emphasize that short‑term or occasional consumption is unlikely to harm healthy adults [1] [2] [4] [5]. Public health guidance errs conservative: where demineralized water is used long‑term for populations, remineralization or dietary mitigation is advised [1] [2].
6. Practical takeaways and open questions
For individuals, the immediate risk of serious harm from drinking demineralized water for a few months is low if dietary mineral intake is adequate, but long‑term exclusive consumption raises plausible risks for lower mineral intake and metabolic effects—especially for infants and other vulnerable groups—prompting WHO‑based recommendations to ensure minimum mineral levels or remineralize treated water [4] [1] [2]. Key uncertainties remain around the magnitude of risk in well‑nourished adults over many years and the real‑world impact of modestly low mineral waters versus fully demineralized waters; the cited reviews and WHO chapter are the primary sources documenting observed effects and policy recommendations [1] [6] [2].