Is filtered water healthier than tap water and bottled water? What are the benefits of filtered water vs bottled water? We decided to compare the three and find a scientific answer to the questions. The study is based on Europe for the purpose of simplification but will also be valid in many other regions of the world. For US information change language.

This article is an extensive piece of research. If you don’t care about all the details then fee free to skip to the conclusion at the end. Also read our shorter article about bottled water vs tap water.

Nutrients in water

Before looking at the individual sources of drinking water it’s important to understand what the potential nutrition contribution of drinking water is. Many people consume mineral waters because of the perception that they may be more healthful. But are they?

In 2005 WHO held a conference with experts from around the world to investigate. At the conference, information was shared from over 80 epidemiology studies of varying quality over the last 50 years. The studies addressed the issue of hard water consumption, mineral impact on health and possibly reduced incidence of ischemic cardiovascular diseases in populations.

Water supplies for tap and bottled water are highly variable in their mineral contents and, while some contribute appreciable amounts of certain minerals either due to natural conditions (e.g., Ca, Mg, Se, F, Zn), intentional additions (F), or leaching from piping (Cu), most provide lesser amounts of nutritionally – essential minerals.

With all of these considerations in mind, the nutrients sometimes found in drinking water at potentially significant levels of particular interest are:

  • Calcium–important in bone health and possibly cardiovascular health
  • Magnesium–important in bone and cardiovascular health
  • Fluoride–effective in preventing dental caries
  • Sodium–an important extracellular electrolyte, lost under conditions of excess sweat
  • Copper–important antioxidant function, iron utilization and cardiovascular health
  • Selenium–important in general antioxidant function and in the immune system
  • Potassium is important for a variety of biochemical effects but it is usually not found in natural drinking waters at significant levels.

The meeting concluded that on balance they indicated that

  1. the hard water beneficial hypothesis was probably valid, i.e. hard water which has more minerals reduces cardiovascular diseases 
  2. that magnesium was the more likely positive contributor to the benefits.

Source: WHO Water Saniation Health Conference 2015 

Read more about the “Health benefits of mineral water”.

Bottled Water

For the past 30 years the bottled water and in particular the mineral water industry has lead us to believe that their water is the healthiest option. But is there any real evidence or proof of this?

European legislation (2009/54/EC Directive) natural mineral waters are “originated from an aquifer or underground reservoir, spring from one or more natural or bore sources and have specific hygienic features and, eventually, healthy properties”

Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5318167/

What are the benefits of mineral water?

There are many studies specifically focused on showing the positive health benefits of certain minerals in bottled water. This includes calcium, magnesium, bicarbonate, chloride, iron, sulphate or combinations thereof.

For example “Effects of a bicarbonate-alkaline mineral water on gastric functions and functional dyspepsia: a preclinical and clinical study by Bertoni M et al in 2002;46(6):525–531.”

However, these studies confirmed that minerals are healthy and not necessarily that mineral water is healthier than other water. As per above tap water or food with these minerals will provide the same health benefits. 

  • Chloride – salt and vegetables
  • Bicarbonate – bread
  • Magnesium – black beans, spinach, banana
  • Calcium – dairy, broccoli, almonds, kale
  • Potassium – banana, potato, broccoli, zucchini
  • Sulphate – eggs, garlic, broccoli, kale
  • Iron – spinach, broccoli, dried fruits, nuts

Source: https://www.healthline.com/nutrition

For regions where people lack a varied diet of vegetables and fruits the mineral content of drinking water could however make a difference as per the conclusion from the 2005 WHO Conference.

What are the negative aspects of bottled water?

Many studies have also focused attention on the safety of bottled mineral water, in particular on the migration of chemicals from plastic containers to water but also microplastics and microbial contaminants.

Plasticizers and EDs

Plasticizers (additives used to impart flexibility and handling properties to several kinds of plastics and endocrine disruptors (EDs – chemicals that interfere with function of the endocrine system) are the main compounds involved in adverse effects on human health.

One concern about bottled mineral water is related to the release of chemicals from the bottles to the water. Among these are the plasticizers, like the Di(2-ethylhexyl)phthalate (DEHP) – widely used as plasticizer and is also present in PET bottles.

Source: Migration of phthalates from plastic products to model solutions. Coll Antropol. 2003;27 (Suppl 1):23–30. 

The EDs represent another important issue for bottled water. Some in vitro studies investigated the exposure to chemicals with estrogen-like activity in bottled mineral water. Pinto et al. analyzed 30 samples of nine Italian mineral waters, stored in PET bottles, and the results show that 90% of samples elicited an estrogenic activity lower than 10% of the activity induced by the reference model. On the contrary, analysis on German mineral water, stored in PET, glass and TetraPak bottles, demonstrate a significantly elevated estrogenic activity in 12 of 20 brands (Ref). In an updated study, bioanalytical techniques and in vivo experiments with molluskan model are used to determine the estrogenicity of bottled water. The estrogenic activity of bottled water form PET containers is approximately twice compared to products from glass bottles (Ref).

Furthermore 29 glass and plastic bottles sold to consumers in Southern Spain were tested by the University of Granada. All of the water samples analyzed showed hormonal activity Endocrine-disrupting chemicals (EDCs).

Estrogens at pollutant levels have been linked with breast cancer in women and prostate cancer in men. Estrogens also perturb fish physiology and can affect reproductive development in both domestic and wild animals.

Sources:

Screening of estrogen-like activity of mineral water stored in PET bottles. Pinto B, Reali D. Int J Hyg Environ Health. 2009 Mar;212(2):228–32. 

Endocrine disruptors in bottled mineral water: total estrogenic burden and migration from plastic bottles. Wagner M, Oehlmann J. Environ Sci Pollut Res Int. 2009 May;16(3):278–86. 

Endocrine disruptors in bottled mineral water: estrogenic activity in the E-Screen. 61. Wagner M, Oehlmann J. J Steroid Biochem Mol Biol. 2011 Oct;127(1–2):128–35. 

Screening of hormone-like activities in bottled waters available in Southern Spain using receptor-specific bioassays. 2015. 

Environmental impact of estrogens on human, animal and plant life: A critical review, 2016. 

Microplastics in bottled water

In addition to the plasticizers and EDs, microplastics were found in 92% of all bottled water in Europe according to testing of 250 bottles from 11 brands by OrbMedia in 2018. The bottles contained an average of 314.6 plastic particles per liter. In one bottle 10,000 plastic particles per 1 liter. For microplastic debris around 100 microns in size, about the diameter of a human hair, bottled water samples contained nearly twice as many pieces of microplastic per liter (10.4) than the tap water samples (4.45).

Source: OrbMedia, 15 March 2018, Microplastics in Bottled Water report. 

Research details: SYNTHETIC POLYMER CONTAMINATION IN BOTTLED WATER Sherri A. Mason, Victoria Welch, Joseph Neratko, State University of New York at Fredonia, Department of Geology & Environmental Sciences  14 March 2018.

Microbial contaminants

Bottled and tap water may contain microbial contaminants. People with sensitive immune systems and/or that are weakened by conditions such as AIDS, chemotherapy or transplant medications are more vulnerable to microbial contaminants in drinking water such as Cryptosporidium. To avoid waterborne cryptosporidiosis it’s recommended to either bring the drinking water to a boil for a full minute or use a point of use water filter.

Source: EPA Bottled Water Health Series 2005

Verdict: Generally mineral water is safe to drink, containing minerals with proven health benefits. On the other hand most bottles contain microplastics and/or estrogenic residue which could pose a health risk.

Tap Water

40 years ago few people questioned the quality of public tap water. We were warned to drink tap water in some places during short visits as sensitive tummies might take time to adopt to the local bacteria culture but that was it. Since then a growing interest in health, new research about water contaminants (e.g. nitrates, lead, disinfectant bi-products and microplastics) have changed everything.

People are right to be concerned and increased awareness for a fluid that we consume 2-3 liters of everyday is great. What is not good is that too many people have given up healthy tap water for bottled water due to these concerns.

In reality, water regulation and treatment technologies have vastly improved during this period and tap water quality is very likely better today. Examples of recent improvements include stringent regulation, filtering and monitoring of nitrates in germany.

How healthy is tap water?

Assuming a daily intake of water to be 2-3 liters, the water would provide >1% of recommended intake for only four minerals; copper, 10%; calcium, 6%; magnesium, 5%; and sodium, 3%. With the maximum concentration would supply about 20% of Ca, 23% of Mg, 10% of Zn, and 33% of Na.

Source: USDA

Tap water can be a clinically significant source of magnesium, another mineral essential to the human body. Magnesium supports blood cell turnover and the immune system.

According to the “Journal of General Internal Medicine” a study published by researchers at McGill University in March 2001 affirmed that drinking 2 liters of tap water in some cities can fulfill between 6 percent and 18 percent of your recommended daily allowance of calcium.

We also compared well known mineral water brands to tap water in Barcelona and concluded that the tap water in Barcelona has higher mineral content than almost all mineral water. This is generally true for cities with hard water.

Most water providers offer frequently updated water quality reports online including minerals, contaminants and other substances. In Europe a good starting point can be EU water directives per country. Also check out the “Can I drink the tap water in…” for more insights.

What are the risks of tap water?

Drinking water is delivered via 7 million kilometers of pipes across Europe. Many of those pipes were laid in the early to mid‐ 20th century with a lifespan of 75‐100 years. We would need to double our sectors annual investment of €45 billion in order to modernise our infrastructure and protect health, the environment and, at least to some extent, reduce costs.

Sources:

Euractiv 2 May 2018

Blufield Research 16 Sep 2016

What’s the risk with lead in tap water?

In 2009 it was estimated that 25% of domestic households in the EU have a lead pipe, either as a connection to the water main, or as part of the internal plumbing, or both, potentially putting 120 million people at risk from lead in drinking water within the EU.

In 2016, the American Academy of Pediatrics issued, Prevention of Childhood Lead Toxicity, outlining the scope of child lead exposure, its health impacts, and management guidance. The report asserts that there is no safe level of lead in blood.

Sources:

Is lead still a problem in Europe? Dec 2009

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4824718/

Chlorination issues

Published reports have revealed increased risk of colorectal cancers in people exposed to chlorinated drinking water or chemical derivatives of chlorination. There is also inconclusive evidence from observational studies that disinfection by-products (DBPs) in drinking water are associated with colorectal cancer.

Source: https://academic.oup.com/ije/article/39/3/733/628142

This meta-analysis of the best available epidemiological evidence indicates that long term consumption of chlorinated drinking water is associated with bladder cancer, particularly in men.

Source: https://www.ncbi.nlm.nih.gov/m/pubmed/12594192/

A 2012 Committee Opinion on Lead Screening During Pregnancy and Lactation by the American College of Obstetricians and Gynecologists outlines the available evidence related to lead exposure and maternal-fetal health. While the opinion does not recommend routine blood-lead testing for all pregnant women, it recommends steps for pregnant and lactating women whose blood levels exceed certain thresholds.

This review showed that various meta-analyses and pooled analyses have found statistically significant excess risk for some indicator of exposure to chlorinated water or trihalomethanes and bladder and colorectal cancer, small for gestational age, stillbirth, all congenital anomalies combined and ventricular septal defects, but no statistical significant excess risk for many other congenital anomalies. The excess risk was generally small, but robust, with little sensitivity to the results of individual studies or evidence of publication bias.

Source: https://pubs.acs.org/doi/abs/10.1021/bk-2010-1048.ch024

Pharmaceuticals

Over the past 10 years there have been frequent alerts about pharmaceuticals and in particular birth control pills. Although the risk of birth control pills in particular has been debunked there are other pharmaceutical residues to be concerned about. Livestock production appears to account for more than 90% of the estrogen found in the environment and in the water supply including some bottled water. The remaining 10% appear to come from industrial chemicals commonly used in manufacturing (like BPA) and synthetic estrogens in fertilizer spread over crops.

On the other hand recent studies have concluded that esterogen from tap water most like poses a small risk compared to other sources such as milk with 150x.

Sources:

Birth Control Hormones In Water: Separating Myth From Fact

MDPI: Pharmaceuticals in the Built and Natural Water Environment of the United States

An Assessment of Potential Exposure and Risk from Estrogens in Drinking Water

Microplastics

Research by OrbMedia recently found that 83% of water samples collected across five continents tested positive for the presence of microplastics (Europe 74%). We don’t know the health risk of this yet but it’s likely to be negative.

Source: OrbMedia September 2017

Verdict: Public tap water is generally safe to drink. Some tap water also has the same amount of minerals as the most mineral rich bottled water. However, just like with mineral water there are risks due to well known contaminants such as lead, chlorine bi-products and new ones like microplastics and pharmaceuticals.

Filtered tap water

Home water filters are nothing new but recent advancements have made the filtering process better, the filters easier to install and use, reduced cost and vastly improved sustainability. This means that having a water filter installed at home is now feasible for any household in Europe. So is filtered water healthier and what are the benefits of filtered water?

The choice of water filter will impact the quality of the water a lot. In some cases the filtered water might be worse than tap water due to bacteria growth on the filter or removal of all minerals. Choose a filter that suits your needs in terms of installation, contaminant removal, volume filtered and cost. Always make sure that it’s a credible brand and that the filters have been independently tested in accordance to international standards such as NSF.

The most common water filters today are activated carbon filters with or without ion-exchange including pitchers/carafes, faucet filters, gravity filters, reverse osmosis, refrigerator filters, UV-light and distillation. Generally the best value for money and sufficient filtration for Europe is a faucet filter with a carbon block (also referred to as PAC Filter or Charcoal Filter). Read more in our water filter comparison

Is filtered water healthier?

As outlined in this document both tap water and bottled water is facing major challenges with contamination and aging infrastructure. Some of these problems such as microplastics will take decades to solve. Therefore point of use filters that removes or vastly reduces such contaminants can reduce the risk of contamination and thus improve the health of individual households.

A recent study also concluded that “activated carbon based tap water filters could provide an important short-term public health benefit through removal of halogenated DBPs, but regular filter cartridge exchange is critical to maintain a good filter efficacy”.

Source:

Point-of-use water filters can effectively remove disinfection by-products and toxicity from chlorinated and chloraminated tap water, Environmental Science: Water Research & Technology, Issue 5 2016

Negative aspects of filterer water

Some filters such as reverse osmosis remove all good and bad content of the water. This means that there are no minerals left after the filter process. With a varied diet this probably does not matter.

Another challenge is when the filters unintentionally make the tap water worse over time.

A recent study of PoU (Point of Use) reverse osmosis water filters revealed widespread bacterial
contamination in the treatment devices. Other studies have come to similar conclusions. The use of reverse osmosis filters is only advisable if the devices are constantly and carefully maintained.

Sources:

Quality of Drinking Water Treated at Point of Use in Residential Healthcare Facilities for the Elderly. 2015. 

Assessment of the extent of bacterial growth in reverse osmosis system for improving drinking water quality. 2010. 

This also applies to activated carbon filters that trap, but do not kill bacteria. Because the filter cannot kill bacteria, it may actually becomes a breeding ground for the microorganisms if not changed regularly. An old, unchanged PoU filter can be dangerous because its use may add bacteria, which had been killed in the tap by chlorine, back into water. As long as the filters are changed as per instructions this risk is minimal.

Similar tests by a laboratory in Germany concluded that 24 out 34 filters tested increased the amount of bacteria. 4 out of 6 had higher bacteria count after 7 weeks than the tap water.

Sources:

University of Berkeley on December 6, 2000

Microbiological contamination of drinking water in a commercial household water filter system. 1996.

Verdict: A fit for purpose quality water filter will vastly reduce the risk of contaminants in tap water and therefore probably be healthier than tap and bottled water. The wrong water filter or a poorly maintained one could however increase risk.

Conclusion – bottled, filtered or tap water?

All three types of water including bottled mineral water, tap water and filtered water are generally safe to drink in Europe. Therefore the choice is really about eliminating risk and thus improving long term health prospects. Fully eliminating risk is impossible, and because gauging risk is so difficult, safety is really a matter of managing risk to a reasonable degree, not trying to eliminate them altogether. Safe and risk-free are different things. 

Here’s our attempt to rate each type

Bottled Mineral
Water
Tap Water Filtered Water
Minerals Low to High

Depends on bottle

Low to High

Depends on location

Zero to High

Depends on the type of filter

Contaminants Medium risk Medium risk Very low risk

In conclusion, filtered water is healthier. A quality water filter independently tested for the type of tap water in your household will reduce risk and thus likely have long term health benefits.

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