{"url":"https://whatshealthyandwhy.com/reverse-osmosis-water/is-reverse-osmosis-water-too-pure","path":"/reverse-osmosis-water/is-reverse-osmosis-water-too-pure","alternates":{"json":"https://whatshealthyandwhy.com/api/articles/reverse-osmosis-water/is-reverse-osmosis-water-too-pure.json","markdown":"https://whatshealthyandwhy.com/reverse-osmosis-water/is-reverse-osmosis-water-too-pure.md"},"topic":{"slug":"reverse-osmosis-water","name":"Reverse Osmosis Water","url":"https://whatshealthyandwhy.com/reverse-osmosis-water"},"slug":"is-reverse-osmosis-water-too-pure","order":1,"title":"Is Reverse-Osmosis Water Too Pure?","question":"Is reverse-osmosis or distilled water too pure to drink?","answer":"Unlikely to be a problem for healthy adults who eat a varied diet: food supplies most minerals, though evidence on long-term low-mineral water is thin.","description":"RO and distilled water are low in minerals, but food supplies most of them. What the evidence says, who should pay attention, and the wastewater trade-off.","confidence":3,"confidenceNote":"Germany's risk agency saw no discernible harm on balanced diets and WHO lacks data for mineral minimums; few observational studies link low-mineral water to heart disease or children's bone mineral.","evidenceSummary":{"rctCount":0,"observationalCount":3,"metaAnalysisCount":1,"totalParticipants":"185,000+","replicated":false,"newestStudyYear":2026},"category":{"categoryTitle":"What's Harming You","categorySlug":"harming-you","subcategoryName":"Water & Hydration","subcategorySlug":"water","url":"https://whatshealthyandwhy.com/explore/harming-you/water"},"actions":["Cover calcium and magnesium through food, since food, not water, supplies most of them [2][1]; see [magnesium](/magnesium/why-magnesium-matters) and [calcium](/calcium/bone-muscle-and-cardiovascular-health).","Adding minerals back with a remineralizing stage or mineral drops is a reasonable preference but optional; we found no trial comparing remineralized with plain RO water [2].","Choose an RO unit certified to NSF/ANSI 58 for your contaminants, and consider a WaterSense model: at most 2.3 gallons to drain per gallon treated versus 5+ typically [5][10]."],"cautions":["If pregnant, breastfeeding, vegan, dairy-free, fasting long or on a very limited diet, check your total calcium and magnesium intake when RO or distilled water is your main drink [2].","During endurance exercise lasting more than about 1.5 hours, very low-mineral water alone is not recommended for fluid replacement because it lacks sodium and carbohydrate [2].","Children with low calcium and magnesium intake may be most affected: Chinese schoolchildren drinking low-mineral water for four years had lower bone mineral content, though intakes were also low [12][2]."],"simpleText":"Reverse osmosis (RO) and distillation remove nearly everything dissolved in water, including calcium and magnesium, so some people worry the water is “too pure.” But food, not water, supplies most of these minerals [1], and Germany's federal risk-assessment institute found no adverse effects from very low-mineral water for people on a balanced diet [2]. Long-term evidence is thin, so diet matters more than the water.","mediumText":"How it works\n\nWhat RO takes out. An RO system pushes water through a membrane that holds back dissolved solids. The CDC lists RO as removing parasites, bacteria and viruses and some chemicals, including lead, copper and chromium, and says it may reduce arsenic, fluoride and nitrate [3]. A review of point-of-use treatment found that carbon, ion exchange and RO are all used against PFAS (long-lasting industrial “forever chemicals”), but real-world performance, especially for short-chain PFAS, is poorly characterized [4]. Look for NSF/ANSI 58, the RO standard, and for the specific contaminants listed on the label [5]; see choosing a filter.\n\nWhere minerals come from. A 1981 study noted that only 10–20% of daily calcium and magnesium intake comes from drinking water [1]. The BfR estimated that bottled mineral water supplies about 30 mg of magnesium a day to the median German consumer, 7–8% of total intake [2]. Tap water varies: in half of 21 North American supplies, 2 liters a day gave 8–16% of the calcium and 6–31% of the magnesium reference intake [6]. RO removes that contribution, and food has to cover it. Cooking in soft water also lowered the calcium in potatoes and vegetables, while hard water raised it [1].\n\nWhat the agencies concluded. WHO's 2005 monograph, Nutrients in drinking-water, examined the long-term effects of demineralized water [7]. In 2020 Germany's Federal Institute for Risk Assessment (BfR) re-reviewed the evidence. It called the 2005 chapter's statements outdated, since they rested on older, mostly Russian-language studies, and noted that later WHO guidance found too little data to propose minimum or maximum mineral levels. Its conclusion: with a balanced diet and normal drinking amounts, no adverse effects are discernible. It advised extra attention to calcium and magnesium for people with very unbalanced diets, vegans and others avoiding dairy, and pregnant or breastfeeding women who rely mainly on very low-mineral water [2].\n\nObservational signals. Pooled studies link higher magnesium in drinking water to lower cardiovascular mortality [8], but a large Dutch cohort found no overall link [9], and regional differences in diet and lifestyle could explain the pooled finding.\n\nThe waste trade-off. A typical point-of-use RO unit sends five gallons or more of reject water down the drain per gallon treated; WaterSense-labeled models must send 2.3 gallons or less [10].","deepText":"The evidence in detail\n\nPooled case-control data. Catling and colleagues' systematic review included 14 studies (9 case-control, 5 cohort). Pooling seven case-control studies, higher magnesium in drinking water went with lower cardiovascular mortality (odds ratio 0.75, 95% CI 0.68–0.82). Evidence for calcium was unclear, and the cohort studies found no association between water hardness and cardiovascular or stroke mortality [8]. People in different areas differ in diet, income and smoking, and exposure is typically assigned by place of residence.\n\nA large null cohort. Leurs and colleagues linked tap-water hardness, calcium and magnesium in every Dutch postal code to mortality in a cohort of 120,852 people aged 55–69 followed for 10 years (a case-cohort analysis of 1,944 ischemic heart disease deaths, 779 stroke deaths and 4,114 subcohort members). Hard versus soft water showed no relation to ischemic heart disease mortality (hazard ratio 1.03, 95% CI 0.85–1.28 in men; 0.93, 0.71–1.21 in women) or stroke. Only in men in the lowest fifth of dietary magnesium intake did higher tap-water magnesium go with less stroke death (HR 0.75 per mg/L, 95% CI 0.61–0.91), and women showed the opposite pattern [9].\n\nA natural experiment. After Israel began supplying desalinated seawater, which is nearly free of magnesium, Koren and colleagues examined serum magnesium in 66,764 people. In communities that switched in 2013, mean serum magnesium slipped from 2.065 to 2.057 mg/dL, and the share at or below 1.6 mg/dL rose from 1.62% to 2.01%, a 24% relative increase; communities that did not switch showed no such change [11]. The average shift is tiny, and whether the rise in low values matters clinically is unknown.\n\nChildren. Huang and colleagues compared 10–13-year-olds who had drunk very low-mineral water (conductivity 40 µS/cm; 431 children) or normal-mineral water (345 µS/cm; 229 children) at school for four years, in a retrospective cohort. The very-low-mineral group had a smaller height gain (16.6 versus 22.3 cm), lower bone mineral content (1.92 versus 2.14 kg) and a higher bone-resorption marker [12]. The BfR noted that total daily calcium and magnesium intakes in both groups were well below recommendations (about 36–41% of the calcium and 82–86% of the magnesium recommended), so the study may reflect poor diets as much as water [2].\n\nThe agency review. The BfR weighed animal studies (rating a long-term rabbit study as low in scientific relevance for design reasons), human intervention studies (judged inadequate as a basis for risk assessment) and epidemiology. It concluded that the WHO position stands: the evidence on magnesium or hardness and cardiovascular mortality is debated and does not prove causality [2].\n\nNull and conflicting results. The pooled association [8] and the small magnesium shifts after desalination [11] point one way, while the large Dutch cohort [9] and the BfR review [2] point the other. A causal reading remains unproven, and we found no trial testing RO water against mineral water on health outcomes.\n\nBottom line (confidence 3 of 5). For healthy adults eating a varied diet, RO or distilled water is probably fine to drink; the minerals lost are small compared with what food provides. The people to think about are those with poor or restricted diets, pregnant or breastfeeding women, children with low mineral intakes, and endurance athletes drinking only very low-mineral water. Remineralizing is a reasonable preference, not a proven necessity.","deepTruncated":false,"references":[{"id":"1","title":"Changes in the mineral composition of food as a result of cooking in \"hard\" and \"soft\" waters","authors":"Haring BS, Van Delft W","year":1981,"journal":"Arch Environ Health","pmid":"7469489","url":"https://pubmed.ncbi.nlm.nih.gov/7469489/"},{"id":"2","title":"Health risk assessment of mineral water with very low mineral content","authors":"German Federal Institute for Risk Assessment (BfR)","year":2020,"journal":"BfR Opinion No 041/2020","url":"https://www.bfr.bund.de/cm/349/health-risk-assessment-of-mineral-water-with-very-low-mineral-content.pdf"},{"id":"3","title":"About Home Water Treatment Systems","authors":"Centers for Disease Control and Prevention","year":2024,"journal":"CDC","url":"https://www.cdc.gov/drinking-water/about/about-home-water-treatment-systems.html"},{"id":"4","title":"Removal of perfluoroalkyl and polyfluoroalkyl substances from tap water by means of point-of-use treatment: A review","authors":"MacKeown H, Magi E, Di Carro M, et al.","year":2024,"journal":"Sci Total Environ","pmid":"39393709","url":"https://pubmed.ncbi.nlm.nih.gov/39393709/"},{"id":"5","title":"NSF Certified Drinking Water Treatment Units: listing search","authors":"NSF International","year":2026,"journal":"NSF International","url":"https://info.nsf.org/Certified/dwtu/"},{"id":"6","title":"Comparison of the mineral content of tap water and bottled waters","authors":"Azoulay A, Garzon P, Eisenberg MJ","year":2001,"journal":"J Gen Intern Med","pmid":"11318912","url":"https://pubmed.ncbi.nlm.nih.gov/11318912/"},{"id":"7","title":"Nutrients in drinking-water","authors":"World Health Organization","year":2005,"journal":"World Health Organization","url":"https://www.who.int/publications/i/item/9241593989"},{"id":"8","title":"A systematic review of analytical observational studies investigating the association between cardiovascular disease and drinking water hardness","authors":"Catling LA, Abubakar I, Lake IR, et al.","year":2008,"journal":"J Water Health","pmid":"18401109","url":"https://pubmed.ncbi.nlm.nih.gov/18401109/"},{"id":"9","title":"Relationship between tap water hardness, magnesium, and calcium concentration and mortality due to ischemic heart disease or stroke in The Netherlands","authors":"Leurs LJ, Schouten LJ, Mons MN, et al.","year":2010,"journal":"Environ Health Perspect","pmid":"20064792","url":"https://pubmed.ncbi.nlm.nih.gov/20064792/"},{"id":"10","title":"Point-of-Use Reverse Osmosis Systems","authors":"US Environmental Protection Agency WaterSense","year":2026,"journal":"EPA WaterSense","url":"https://www.epa.gov/watersense/point-use-reverse-osmosis-systems"},{"id":"11","title":"Seawater desalination and serum magnesium concentrations in Israel","authors":"Koren G, Shlezinger M, Katz R, et al.","year":2017,"journal":"J Water Health","pmid":"28362310","url":"https://pubmed.ncbi.nlm.nih.gov/28362310/"},{"id":"12","title":"Consumption of Very Low Mineral Water Is Associated with Lower Bone Mineral Content in Children","authors":"Huang Y, Ma X, Tan Y, et al.","year":2019,"journal":"J Nutr","pmid":"31373351","url":"https://pubmed.ncbi.nlm.nih.gov/31373351/"}],"wordCount":993,"source":{"path":"src/content/topics/reverse-osmosis-water/is-reverse-osmosis-water-too-pure.md"},"citeAs":"“Is reverse-osmosis or distilled water too pure to drink?.” What's Healthy and Why. https://whatshealthyandwhy.com/reverse-osmosis-water/is-reverse-osmosis-water-too-pure","notice":"General information backed by peer-reviewed research, not medical advice."}