Is Reverse Osmosis Water Bad For You?

Despite the widespread use of reverse osmosis filtration systems in homes and municipal water treatment plants, some internet sources claim that drinking reverse osmosis water over long periods can harm your health.

Why do some people make this claim, and is it true?

The short answer:

No, reverse osmosis water isn’t bad for you. There’s no accepted evidence that supports this internet rumor.

Reverse osmosis water is demineralized, which means it doesn’t contain the small amounts of minerals sometimes found in natural water. If you eat a regular diet, however, this is unlikely to make any real difference to your dietary intake.

Why do some people say that reverse osmosis water is bad for you?

The basis for the idea that reverse osmosis water is harmful to health is unclear. Some googling suggests that the claim stems from a handful of articles published on Indian websites between 2010 and 2014.

These articles point to the fact that RO filtering is so powerful, it removes practically all dissolved substances, including naturally occurring minerals, from the water supply.

Because reverse osmosis water is “demineralized” it has a pH level that’s more acidic than regular water, and it also lacks minerals such as calcium and magnesium that are often found in unfiltered water supplies.

There are three claims associated with these facts about reverse osmosis water:

  • That drinking demineralized water causes malnutrition
  • That drinking slightly acidic water increases the risk of cancer and organ disease
  • That drinking very pure water causes a “leaching” of nutrients or salts from the body’s cells

Sounds scary, hey?

Is there any evidence for these claims?

Not really. Articles claiming that reverse osmosis water is bad for you often cite this paper from the Medical Journal Armed Forces India, which argues that the use of “demineralized water over a long duration needs to be debated and discussed.”

Unfortunately, the paper contains no data to support this argument, instead making reference to mostly unrelated papers about the potential effects of mineral deficiencies in malnourished populations.

Claims about the dangers of slightly acidic water or highly pure water are even more unfounded and hard to pin down.

There is some minorly related science behind the idea that cancerous mutations are more likely to occur in acidic environments. Likewise, it’s true that the body’s fluid balance and overall health can be seriously affected when you don’t consume enough mineral salts.

However, neither of these things are directly related to the consumption of reverse osmosis water.

The differences in acidity and mineral content between unfiltered water and reverse osmosis water are very small, so the idea that switching from regular to RO water could cause these dramatic health effects is… highly improbable.

So what’s the truth?

The truth is that even the most mineral-rich unfiltered water isn’t a significant source of beneficial salts or minerals. We get our recommended mineral intake from the foods we eat, not the water we drink.

So, while drinking reverse osmosis water will slightly lower your mineral intake in comparison to drinking mineral water, there is no significant difference or health effect.

Getting enough minerals from your diet, whether you’re drinking regular water or reverse osmosis water, is as simple as eating a balanced diet.

Acidic water

There is also no recognized recommendation against drinking slightly acidic water. Normal water has a pH of around 7, whereas RO water has a pH of around 6.5. So, the difference in acidity is much smaller than sources against RO water tend to admit.

It’s worth pointing out that considerably more acidic foods and drinks such as lemons, soda, tea, and coffee are all widely consumed without concern.


Some reverse osmosis systems even contain a remineralization stage to reintroduce beneficial minerals into the water supply after filtering.

Once the water has passed through the RO membrane, these systems reintroduce calcium and magnesium salts, so that you can access RO-filtered mineral water.

The bigger picture

As often occurs with internet rumors about health concerns, the conversation about the risks of reverse osmosis water tends to miss the bigger picture – which is that reverse osmosis is a powerful filtration method designed for use when water is unsafe for drinking.

Reverse osmosis systems successfully remove many known harmful pollutants such as lead, arsenic, bacteria, and industrial chemicals.

It sounds obvious, but consuming any of these contaminants poses a far greater health risk than drinking water that’s very slightly acidic or low in mineral content.

So, if your water supply may contain any of the common contaminants removed by reverse osmosis, it’s definitely healthier to use an RO system than not.