What are the health effects of drinking very soft (low‑mineral) water long term?
Executive summary
Drinking very soft or very low‑mineral water over long periods has been associated in multiple human epidemiologic studies and animal experiments with lower bone mineral content and possible adverse effects on bone development, and some observational signals tie low‑mineral water to cardiovascular risks; however, causality and mechanisms remain incompletely established and study populations vary [1] [2] [3] [4]. The balance of current literature suggests caution—especially for infants, children and other vulnerable groups—while acknowledging that many questions about dose, context (dietary mineral intake) and long‑term clinical outcomes remain unresolved [5] [6].
1. What “very soft” or low‑mineral water means and how common it is
Very soft water refers to drinking water that has been demineralized by processes such as reverse osmosis (RO) or desalination and therefore contains very low concentrations of calcium, magnesium and other trace elements; commercial bottled waters span a spectrum from natural mineral waters to purified low‑mineral waters and purified/RO types are increasingly common in many markets [1] [7] [8].
2. Strongest signal: bone health — consistent associations with reduced mineral density
Multiple human studies and animal experiments report associations between long‑term consumption of very low–mineral water and reduced bone mineral content, increased markers of bone resorption, developmental delays in bone modelling in children, and weakened biomechanical bone properties in female rats across generations, leading reviewers to flag osteopenia/osteoporosis and dental caries as plausible concerns [2] [3] [8] [1].
3. Cardiovascular and metabolic hints, but not settled
Epidemiologic reviews and some recent studies suggest an inverse relationship between water hardness (higher magnesium/calcium) and cardiovascular disease mortality, and small studies in children indicate drinking very low‑mineral water may disturb homocysteine and lipid metabolism and increase oxidative stress—potential pathways to cardiovascular risk—yet researchers acknowledge these findings are limited and require replication before firm clinical conclusions [6] [9] [4].
4. Mechanisms proposed and animal model findings
Proposed mechanisms include reduced dietary intake of essential minerals (notably Ca and Mg) when water contributes appreciable amounts to total intake, altered hormone regulation of calcium (cholecalciferol/vitamin D pathways), and metabolic shifts detected in liver metabolomics in animals exposed to purified water; animal data show metabolic and bone‑quality changes but do not prove identical effects in humans at typical consumption levels [4] [3] [2].
5. Who is most at risk and what the evidence cannot yet answer
Children, pregnant people, elderly women (post‑menopausal bone loss) and populations with low dietary intake of Ca/Mg are the groups most plausibly vulnerable according to cohort and experimental work, but evidence is often observational, retrospective, or from animal models so causality, the threshold of mineral deficit that matters, and interactions with total diet are not firmly established in humans [2] [8] [5].
6. Caveats, potential benefits, and industry/communication agendas
Some research and reviews emphasize benefits of mineral‑rich waters (e.g., calcium supply, magnesium and lower CHD risk in some European cohorts), and commercial stakeholders in bottled and filtration industries may frame messages around convenience or purity; conversely, alarmist claims that demineralized water is uniformly dangerous overreach beyond the evidence, while industry messaging emphasizing mineral water as a panacea can also be biased [6] [7] [10]. Public‑health guidance historically has noted the plausibility of modest cardiovascular benefits from harder water but calls for balanced policy on remineralization and dietary context [5] [6].
7. Practical takeaways and research gaps
Pragmatically, individuals relying heavily on RO/desalinated/very soft bottled water should consider total dietary mineral intake—especially calcium and magnesium—and vulnerable groups (children, pregnant people, elderly) may warrant monitoring or alternative sources of minerals; at a population level, more long‑term human trials and clearer dose–response data are urgently needed to determine causality, thresholds, and whether simple remineralization of drinking water or dietary counseling solves the observed associations [1] [5] [2].