Know Your Water
What The Science Actually Says
Most of what you've been told about drinking water came from a salesperson. Here's what published research says instead, about minerals, TDS, and what happens when a purifier strips them all out.
Findings
The World Health Organization published a detailed review of what happens when drinking water is stripped of its minerals. These are among its most striking findings.
More urine output
In human volunteer studies, water below 100 mg/L TDS increased diuresis by almost a fifth on average along with greater elimination of sodium, potassium, calcium and magnesium from the body.
WHO / Kozisek 2005Adults studied
A large Russian cohort study found the lowest morbidity where water carried 30–90 mg/L calcium, 17–35 mg/L magnesium and TDS around 400 mg/L, which the author called physiologically optimum.
Lutai 1992Reactions need magnesium
Magnesium acts as a cofactor and activator in more than 300 enzymatic reactions including glycolysis, ATP metabolism, protein synthesis, and muscle contraction.
WHO / Kozisek 2005Lower haemoglobin
In a six-month animal study, mean haemoglobin content of red blood cells was 19% lower in subjects given non-supplemented demineralised water compared with tap water.
Kondratyuk 1989TDS
TDS measures the minerals dissolved in your water, calcium, magnesium, bicarbonates and more. Indian standards cap the upper limit, but research is equally clear that going too low carries its own risks.
Upper acceptable limit per Bureau of Indian Standards (IS 10500). Optimum ranges as recommended in the WHO review of demineralised drinking water. Your own tap water's TDS can be checked with an inexpensive TDS meter.
Myths
"Lower TDS means purer, healthier water."
The WHO review recommends a minimum TDS of 100 mg/L, with an optimum around 250–500 mg/L for bicarbonate waters. Adverse effects on water-salt balance were observed not only in fully demineralised water but also between 50 and 75 mg/L.
WHO 1980 · Kozisek 2005"You get all your minerals from food anyway."
The review notes that minerals in water are usually present as free ions, making them more readily absorbed than the bound forms in food. It concludes that diets deficient in calcium and magnesium may not fully compensate for their absence in drinking water.
WHO 1980 · Kozisek 2005"Adding minerals back after RO solves it."
The review concludes that possibly none of the commonly used re-mineralisation methods can be considered optimum, since the resulting water does not contain all of its beneficial components current methods mainly aim to reduce corrosiveness, not to restore health value.
WHO / Kozisek 2005"A storage tank keeps water safe."
The Czech National Institute of Public Health found that pressure tanks in reverse osmosis units are prone to bacterial regrowth — partly because treatment removes residual disinfectant, and partly because the internal rubber bag surface favours bacterial growth.
Czech NIPH, cited in WHO reviewCooking
This is the finding almost nobody mentions. When food is cooked in soft, low-mineral water, essential elements leach out of the vegetables, cereals and meat themselves. Reported losses, per the WHO review
Reported loss ranges for food cooked in soft water versus hard water, as summarised in the WHO review (citing Haring & Van Delft 1981; Oh et al. 1986; Durlach 1988). Losses vary with food type and cooking time.
Context
The Rig Veda already knew
The WHO review opens by noting that awareness of minerals in drinking water goes back thousands of years. The Rig Veda described good water as Sivam: having nutritive value, requisite minerals and trace elements. Purity and emptiness were never the same idea.
Symptoms within weeks, not decades
The review describes Czech and Slovak households that installed reverse osmosis systems at their taps between 2000 and 2002. Within weeks to months, complaints suggestive of magnesium and calcium deficiency were reported, cardiovascular symptoms, tiredness, weakness and muscle cramps.
Empty water is hungry water
Demineralised water is described as unstable and aggressive toward materials it touches, dissolving metals more readily from pipes, tanks and fittings. Calcium and magnesium also have documented antitoxic activity, helping limit absorption of metals like lead and cadmium.
- Kozisek, F. (2005). Health Risks from Drinking Demineralised Water. In: Nutrients in Drinking Water, World Health Organization, Geneva, pp. 148–163. — Read the paper
- World Health Organization (1980). Guidelines on health aspects of water desalination, ETS/80.4. Geneva. — Read the paper
- Lutai, G.F. (1992). Chemical composition of drinking water and the health of population. Gigiena i Sanitariya, 1: 13–15. — Read the paper
- Kondratyuk, V.A. (1989). On the health significance of microelements in low-mineral water. Gigiena i Sanitariya, 2: 81–82. — Read the paper
- Haring, B.S.A. & Van Delft, W. (1981). Changes in the mineral composition of food as a result of cooking in hard and soft waters. Archives of Environmental Health, 36: 33–35. — Read the paper
- Bureau of Indian Standards. IS 10500: Drinking Water — Specification. Acceptable TDS limit 500 mg/L; pH range 6.5–8.5. — Read the paper
This page summarises published research for general information. It is not medical advice. FIN Mini is a water purifier, not a medical device, and makes no claim to treat or prevent any condition. Consult a qualified professional for health guidance.
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