Why shouldn't you drink RO water? The hidden health risks.

January 1, 2026 •

3 min read

The World Health Organization has warned that consuming demineralized water, like that produced by a basic Reverse Osmosis (RO) system, can have adverse effects on human health. While highly effective at removing contaminants, this process also strips water of essential minerals, raising concerns for long-term consumption.

Quick Summary

Drinking untreated reverse osmosis (RO) water can lead to mineral deficiencies and potential health issues because the filtration process removes essential minerals. Modern systems offer remineralization to mitigate these risks.

Key Points

Mineral Depletion: Basic RO filtration removes essential minerals like calcium and magnesium, which are vital for bone health and other bodily functions.
WHO Warnings: The World Health Organization has published reports cautioning against the long-term consumption of demineralized water.
Health Impacts: Potential long-term health risks include mineral deficiencies, electrolyte imbalance, and a compromised metabolic system.
Increased Acidity: RO water can become slightly acidic due to the removal of mineral buffers, which may be a concern for some individuals.
Water Waste: Traditional RO systems produce a significant amount of wastewater, which is an environmental concern.
Remineralization is Key: Modern RO systems often include remineralization stages to add healthy minerals back into the water.
Dietary Compensation: Relying solely on diet to compensate for minerals lost in water may not be enough, especially for those with borderline deficiencies.

The Problem with Purity: Essential Mineral Loss

While reverse osmosis (RO) systems are praised for their ability to remove a wide spectrum of harmful contaminants, from heavy metals to bacteria, this efficiency comes with a significant drawback: the removal of beneficial minerals. The semi-permeable membrane at the core of the RO process is so fine that it filters out naturally occurring, essential minerals like calcium and magnesium, along with the unwanted impurities. This leaves the water highly pure, but also demineralized, and potentially detrimental to long-term health.

The World Health Organization's Warning

The World Health Organization (WHO) has extensively documented the potential health risks associated with drinking demineralized water. They've found that consuming water low in mineral content for extended periods can impact the body's mineral and water metabolism. The WHO noted that reduced mineral intake from water might not be fully offset by diet and could lead to increased mineral loss from the body.

How Demineralized Water Affects Your Health

Consuming demineralized water over time can lead to several health issues due to the lack of vital minerals.

Mineral Depletion and Deficiency: The absence of minerals like calcium and magnesium in RO water can lead to a deficiency. These minerals are vital for bone health and numerous bodily functions.
Electrolyte Imbalance: Essential electrolytes like potassium, sodium, calcium, and magnesium are critical for bodily functions. Drinking demineralized water can dilute these electrolytes, possibly causing fatigue or cramps.
Increased Acidity: Natural water's mineral content often helps maintain a balanced pH. RO filtration removes these minerals, which can result in slightly acidic water (pH potentially as low as 5.0). While not always harmful, it could affect individuals with sensitive digestive systems.
Cooking Concerns: Using RO water for cooking can cause minerals to leach from food, potentially reducing the nutritional value of meals.

RO Water vs. Mineralized Water: A Comparison


Feature	Untreated RO Water	Natural Mineralized Water
Mineral Content	Very low to non-existent (especially Ca and Mg).	Contains naturally occurring, essential minerals.
pH Level	Slightly acidic (potentially pH 5.0-6.5).	Generally neutral or slightly alkaline, buffered by minerals.
Taste	Often described as flat, insipid, or lacking flavor.	Can have a crisp, more pleasant taste due to mineral content.
Hydration & Electrolytes	Can dilute electrolytes in the body, requiring dietary compensation.	Helps maintain hydration and electrolyte balance naturally.
Effect on Cooking	Leaches minerals out of food during cooking.	Minimal mineral loss from food; can even enhance mineral content.
Contaminant Removal	Highly effective against most contaminants, including heavy metals, pesticides, and bacteria.	Varies significantly depending on the source; may require additional filtration.

The Environmental Toll of Reverse Osmosis Systems

Besides health considerations, traditional RO systems can negatively impact the environment due to significant water wastage. Some systems may waste several gallons of water for each gallon of purified water produced. While newer systems are more efficient, this remains a concern for water conservation.

Smart Solutions: Remineralization and Alternatives

Achieving clean and healthy water is possible. Modern RO systems frequently include a remineralization stage that adds a balanced amount of essential minerals back into the water after filtration. This provides both contaminant removal and beneficial mineral content.

Conclusion: Making an Informed Choice about Your Water

Reverse osmosis effectively removes harmful pollutants, but the resulting demineralized water poses potential health risks due to the loss of essential minerals. The solution lies in choosing a system that combines effective filtration with remineralization. Understanding both the benefits of purification and the drawbacks of mineral depletion allows for an informed decision that supports both water purity and long-term health. For more scientific information, refer to the {Link: WHO Health Risks from Demineralised Water https://aguaenmexico.com/wp-content/uploads/2021/02/WHO-HEALTH-RISKS-FROM-DRINKING-DEMINERALISED-WATER.pdf} report.

Frequently Asked Questions

While RO water is free of harmful contaminants, drinking it exclusively over a long period can be unhealthy because it also removes essential minerals like calcium and magnesium, potentially leading to deficiencies.

Demineralized RO water can cause a leaching effect, where minerals are pulled from your body during hydration to compensate for the water's lack of mineral content. This can disturb your electrolyte and metabolic balance.

The removal of mineral buffers can leave RO water slightly acidic (lower pH). While a slight acidity is not dangerous for most, some people may experience digestive discomfort, and the WHO has noted it as a consideration.

While diet is the primary source of minerals, research suggests that the minerals obtained from water can be more readily absorbed by the body. Relying solely on food might not be enough for everyone, particularly those with existing dietary deficiencies.

A remineralization cartridge is a filter stage in an RO system that adds essential minerals back into the water after purification. It is highly recommended to counteract the mineral loss and ensure the water is healthy for long-term consumption.

Yes, many people find un-remineralized RO water to have a 'flat' or insipid taste because the minerals that contribute to flavor have been removed. Remineralization can restore a more natural taste.

Standard RO systems are not very environmentally friendly due to the significant amount of water they waste during the filtration process. However, some newer, high-efficiency systems are designed to reduce this wastage.