What does the 2005 WHO report actually say about demineralised water?

The 2005 WHO monograph chapter highlighted three legitimate concerns regarding 100% demineralized water: lack of minerals in populations with already deficient diets, substantial loss of minerals from food during cooking (up to 60%), and technical pipe corrosion. The WHO did not declare pure water toxic, and official guidelines set no mandatory minimum health threshold for TDS. Modern remineralization solves these issues completely.

Why is remineralization recommended for Cyprus reverse osmosis systems?

Passing pure RO permeate through certified food-grade calcite and dolomite restores 50–100 mg/L of natural calcium and magnesium, neutralizes weak carbonic acidity to pH 7.2–7.8, prevents culinary extraction losses, and delivers optimal drinking palatability.

Peer-Reviewed Fact Check Chemistry & Engineering Cyprus Potable Standards

Is Reverse Osmosis Water Safe to Drink? Science vs. The "Dead Water" Myth

Q: Does reverse osmosis water acidify the human body?

No. While pure RO water absorbs ambient atmospheric carbon dioxide, dropping its unbuffered pH to 6.0–6.5, it has virtually zero buffer capacity. It is instantly neutralized by gastric juice and saliva without affecting systemic arterial pH (7.35–7.45), which is maintained by the pulmonary and bicarbonate buffering systems.

Authored by: Filter.cy Technical Department • Medical & Chemical Validation

Updated: September 2026

Engineering & Standards Compliance Notice: This documentation analyzes water filtration physics, chemical equilibria, and human gastrointestinal kinetics based on peer-reviewed literature. It contains no medicinal or therapeutic treatment promises. Domestic filtration systems serve exclusively to remove physical, chemical, and biological impurities in accordance with EU Directive 2020/2184.

Consumers researching drinking water filtration in Cyprus frequently encounter polarized claims. On one side, alarmist publications label reverse osmosis (RO) permeate as "dead, acidic water" that "extracts minerals from bones". On the other side, commercial marketing claims that "minerals in water are toxic rocks the human body cannot use".
Both assertions are scientifically inaccurate.
To evaluate the true safety profile of reverse osmosis water, we examine human gastrointestinal physiology, the official positions of the World Health Organization (WHO), European Union drinking water directives, and published clinical trials on mineral absorption.

1. Nutritional Contribution: Food vs. Drinking Water

A primary question in water biochemistry: How much does drinking water actually contribute to our daily mineral intake?

Solid Food Sources >90% Total Intake

Dense, Highly Concentrated

100g Halloumi / Greek Feta: ~490 mg Calcium
1 Glass Whole Cow's Milk: ~300 mg Calcium
1 Cup Cooked Spinach: ~150 mg Magnesium
Handful of Almonds (30g): ~80 mg Magnesium

Drinking Water Sources <10% Total Intake

Trace Delivery Vehicle

1 Litre Cyprus Tap Water: ~30–45 mg Calcium
Daily Adult Calcium Target: 950–1,000 mg (EFSA)
Practical Reality: Requires drinking 25 to 35 Litres daily to hit the PRI through tap water alone.

Daily Calcium Pathway Distribution (EFSA PRI Benchmark) ~7% Water / 93% Food

Solid Nutritive Diet (90–95%) Potable Tap Water (5–10%)

The Bioavailability Reality: Calcium and magnesium in water are bioavailable (fractional absorption rate of 25–40%, identical to dairy [Heaney, 2006]). However, water is fundamentally a solvent for hydration ($\text{H}_2\text{O}$), not an adequate nutritional delivery vehicle to correct deficiencies.

2. Does Pure Water "Leach" Minerals from Your Bones?

The internet myth claiming that hypotonic water creates an osmotic vacuum pulling minerals out of bones and teeth collapses when evaluated against basic human gastrointestinal and endocrine kinetics.

Immediate Gastric Equalization (Stomach)

Pure water instantly enters a fluid environment containing hydrochloric acid ($\text{HCl}$) and electrolytes ($\text{Na}^+, \text{K}^+, \text{Cl}^-$) with a baseline osmolality of 140–300 mOsm/kg. The osmotic gradient of RO water is buffered within seconds before it ever reaches the absorptive intestinal walls [Guyton & Hall, 2021].

Isotonic Intestinal Uptake (Enterocytes)

By the time water enters the duodenum, it is an isotonic chyme. Water molecules traverse enterocytes via transcellular aquaporin channels driven by active sodium electrochemical gradients [Kiela & Ghishan, 2016].

Renal-Endocrine Homeostasis (Kidneys)

Blood serum calcium is maintained strictly at 2.15–2.55 mmol/L. Parathyroid hormone (PTH), Calcitriol ($\text{1,25(OH)}_2\text{D}_3$), and Aldosterone instruct kidneys to either conserve or excrete ions. Your skeleton does not dissolve to compensate for drinking low-TDS water [Costanzo, 2018].

3. The 2005 WHO Assessment: What the Science Stated

Opponents of reverse osmosis frequently cite Chapter 12 of the 2005 WHO monograph (*Dr. František Kožíšek*). A rigorous review of the publication highlights three core points:

The Three Core Concerns Raised by Kožíšek (WHO 2005):

1. Malnutrition Risk Applied to impoverished populations where food intake is already deficient in basic Ca/Mg.

2. Cooking Extraction Boiling food in 0-TDS water leaches up to 60% of micronutrients into discarded cooking broth.

3. Pipe Corrosion Unbuffered water is aggressive to municipal metal pipelines, causing toxic secondary leaching.

Official Regulatory Position: WHO GDWQ (4th Edition, 2022)

"The epidemiological evidence was considered insufficient to provide a basis for deriving a health-based guideline value for calcium or magnesium, or for total dissolved solids (TDS)."

4. Acid-Base Equilibrium: Does RO Permeate Acidify the Body?

When pure permeate is exposed to atmospheric carbon dioxide ($\text{CO}_2$), it forms trace carbonic acid ($\text{H}_2\text{CO}_3 \rightleftharpoons \text{H}^+ + \text{HCO}_3^-$), lowering measured pH to ~6.0–6.5.

Why this does not cause clinical acidosis: Pure water contains zero buffering capacity. The human stomach operates at an aggressive pH of 1.5 to 2.0, which instantly overwhelms the trace acidity of the water. Systemic blood pH remains securely locked between 7.35 and 7.45 via renal bicarbonate buffering and respiratory expiration [Guyton & Hall, 2021].

5. Local Water Conditions in Cyprus: The Physical Filtration Shield

In Cyprus, municipal tap water is produced mainly through industrial Seawater Reverse Osmosis (SWRO) plants (Vasilikos, Dhekelia, Limassol). It is already reverse osmosis water. The primary threat to health is secondary contamination in distribution and domestic storage:

Rooftop Tanks (Ntepozito) Baking in 40°C heat, overhead cisterns cultivate bacterial biofilms, algae, sediment, and microplastics from deteriorating tank linings.

Aging Branch Pipelines Municipal cast-iron and older domestic piping introduce heavy metals (copper, lead solder) and loose pipe scale into kitchen taps.

Agricultural Aquifer Nitrates Rural and suburban wells blended into supplies contain elevated nitrates ($\text{NO}_3^-$) from synthetic agricultural fertilizers.

Absolute Physical Barrier

Filtration Selectivity by Pore Dimension

Sediment Pre-Filter (Sand, Rust, Scale) 5.0 – 20.0 µm

Activated Carbon Block (Chlorine, THMs, VOCs) 0.5 – 5.0 µm

Bacteria, Biofilms & Microplastics 0.2 – 2.0 µm

Semi-Permeable RO Membrane (Heavy Metals, Nitrates, PFAS) ~0.0001 µm (0.1 nm)

6. The Engineering Solution: Balanced Post-Remineralization

To eliminate the taste limitations and culinary extraction risks identified in the 2005 WHO monograph without reintroducing toxic contaminants, modern domestic inline RO systems with active remineralization utilize multi-stage post-filtration cells:

Stage 1

Tap Inflow

TDS ~450 ppm

→

Stage 2

0.0001 µm RO

Permeate <20 ppm

→

Stage 3 (Active)

Calcite & Dolomite

Ca²⁺, Mg²⁺ Enriched

→

Balanced Output

Alpine Taste

TDS 50–100 ppm | pH 7.4

Taste Optimization (Palatability)

Purified permeate washes over food-grade calcite (CaCO₃) and dolomite (CaMg(CO₃)₂), restoring 50–100 mg/L of natural mineral ions. This delivers a crisp mouthfeel matching top European spring waters without scaling kettles or coffee machines.

Culinary & Pipeline Protection

By naturally introducing bicarbonate buffer ions, water pH is maintained in the optimal alkaline range of 7.2 to 7.8. This stabilizes the water, completely preventing the culinary leaching of nutrients during boiling.

Summary Comparison: Potable Water Types

Metric / Parameter	Cyprus Tap (Roof Tank)	Pure Permeate	Remineralized RO	Plastic Bottled
Total Dissolved Solids (TDS)	350 – 700+ ppm	5 – 20 ppm	50 – 100 ppm	150 – 400 ppm
Microbiological Shield	Biofilm risk in summer	Physically blocked	Physically blocked	Controlled at bottling
Chemicals, PFAS & Heavy Metals	Pipe-age dependent	Excluded (>98%)	Excluded (>98%)	Source dependent
Cooking Mineral Leaching	Preserved	Leaches food minerals	Balanced retention	Preserved
Taste Profile & pH	Hard / Chlorinated	Flat / Slightly acidic	Crisp (pH 7.2–7.8)	Neutral
Microplastic Ingestion Risk	High (UV tank wear)	Excluded by membrane	Excluded by membrane	High (PET degradation)

Actionable Checklist

Cyprus Domestic Water Optimization Protocol

Follow this 3-step engineering procedure to secure clean drinking water from municipal supplies without risking secondary storage contamination:

Step 1: Quantify Supply Parameters

Measure baseline TDS, incoming line pressure (bar), and inspect your rooftop cistern (ntepozito) for sediment sedimentation and biological biofilms.

Step 2: Install Tankless Direct-Flow RO

Avoid pressurized rubber-bladder storage tanks where warm water can stagnate. Utilize certified direct-flow inline RO systems delivering purified water on demand.

Step 3: Integrate Calcite/Dolomite Post-Mineralization

Ensure the system includes a food-grade remineralizing cartridge to restore 50–100 mg/L TDS and buffer the pH between 7.2 and 7.8.

Frequently Asked Technical Questions

Does reverse osmosis water leach minerals from bones and teeth? ↓

No. Ingested water mixes immediately with hydrochloric acid (pH 1.5–2.0) and gastric electrolytes in the stomach, reaching osmotic equilibrium within minutes before entering the duodenum. Systemic blood calcium and magnesium are regulated strictly via parathyroid hormone, calcitonin, and renal tubular absorption, not bone demineralization.

Is reverse osmosis water acidic? ↓

Without buffering ions, pure RO permeate absorbs ambient atmospheric carbon dioxide, dropping its unbuffered pH to 6.0–6.5. Because it has virtually zero buffer capacity, it is instantly neutralized by gastric juice and saliva without affecting systemic arterial pH (7.35–7.45), which is maintained by pulmonary and bicarbonate buffering systems.

Why does the WHO recommend remineralizing pure water? ↓

The WHO 2005 monograph pointed out that 100% demineralized water leaches up to 60% of micronutrients from food during cooking, has a flat taste, and aggressively corrodes metallic distribution pipes. Modern systems integrate calcite and dolomite stages to supply 50–100 ppm TDS, preventing these extraction losses.

Can reverse osmosis water be used for baby formula? ↓

Yes. Pediatric guidelines favor low-mineral, contaminant-free water when reconstituting infant formula. Commercial formula powder is already precisely fortified with calcium and magnesium; preparing it with hard tap water increases the renal solute load on developing infant kidneys.

Scientific References & Primary Sources:

World Health Organization (2005). Nutrients in Drinking Water. Geneva: WHO Guidelines. (Includes Chapter 12: Health risks from drinking demineralised water by F. Kožíšek).
World Health Organization (2022). Guidelines for Drinking-water Quality: Fourth Edition. Geneva: WHO Press.
European Food Safety Authority (EFSA) NDA Panel (2015). Scientific Opinion on Dietary Reference Values for Calcium and Magnesium. EFSA Journal, 13(5):4101.
Heaney, R. P. (2006). Absorbability and utility of calcium in mineral waters. American Journal of Clinical Nutrition, 84(2), 371–374.
Guyton, A. C., & Hall, J. E. (2021). Textbook of Medical Physiology (14th ed.). Elsevier. Chapters 25 & 31.
European Parliament & Council (2020). Directive (EU) 2020/2184 on the quality of water intended for human consumption.

Not sure which water filter is right for you?

Take our quick quiz to discover the perfect solution tailored to your lifestyle and needs

Start now!

Conclusion

Scientific evidence overwhelmingly supports the safety and benefits of drinking RO water. The idea that RO water is harmful due to a lack of minerals is a myth not supported by research. The human body obtains minerals from food, not drinking water, and concerns about pH levels are scientifically unfounded.
By removing harmful contaminants and offering customizable options (such as remineralization), RO systems provide one of the safest, most effective methods of water purification available today. In regions with hard or contaminated water, RO filtration remains an optimal solution for ensuring clean, safe drinking water for households and businesses alike.