The healthfulness of bottled water is complex, as the “healthiest” choice depends on individual priorities, from mineral intake to contaminant avoidance. The variety of products, sources, and processing methods makes the choice difficult for the average consumer. Understanding the labels requires looking beyond marketing claims to the water’s actual composition and its container. By examining water types, health metrics like mineral content and pH, and packaging risks, one can make an informed decision.
Decoding Water Types and Treatment
Bottled water falls into three primary categories distinguished by their source and treatment. Purified water, often sourced from municipal tap water, is subjected to intense filtration processes like reverse osmosis, deionization, or distillation. These methods effectively strip the water of contaminants, but also remove nearly all naturally occurring minerals, resulting in a product that is close to pure H₂O.
Spring water must be collected from an underground formation where water flows naturally to the surface or through a borehole. It typically undergoes only minimal processing, such as light filtration, to ensure safety while preserving its natural mineral profile. The exact mineral content of spring water can vary significantly depending on the geology of the source.
Mineral water is sourced from an underground, protected source, but it carries a specific requirement regarding its dissolved solids content. To earn the “mineral water” designation, it must contain a minimum of 250 parts per million (ppm) of Total Dissolved Solids (TDS). This naturally occurring mineral content must remain constant from the source, giving each brand a consistent and unique taste profile.
Key Health Metrics: Minerals and pH
The concentration of dissolved substances in water, known as Total Dissolved Solids (TDS), is a direct measure of its mineral content and a significant health metric. TDS includes beneficial minerals like calcium, magnesium, and potassium, which are readily absorbed by the body. Water classified as “hard” has high concentrations of calcium and magnesium, which studies have associated with a lower risk of cardiovascular issues.
Magnesium in drinking water has been shown to have a protective effect against cerebrovascular disease and supports functions like muscle function and energy production. Water can contribute a measurable amount to the daily recommended intake of magnesium, which is beneficial for individuals who may be deficient. The World Health Organization suggests that moderate TDS levels, often between 300 to 500 mg/L, provide a superior taste and balanced nutrient profile compared to very low TDS water.
Another measurable factor is pH, which indicates how acidic or alkaline the water is on a scale of 0 to 14. Water neutrality is generally accepted to be a pH of 7, with higher numbers being alkaline and lower being acidic. While some brands promote highly alkaline water, most health organizations state that the body’s internal mechanisms efficiently regulate pH regardless of the water consumed. For the average person, water near a neutral pH is perfectly sufficient, and the presence of beneficial minerals is a much more important consideration.
Contaminant Exposure and Bottle Material
The material used for bottling introduces a different set of health concerns, especially regarding chemical leaching and microplastics. Most single-use plastic bottles are made from polyethylene terephthalate (PET), which can leach various chemicals into the water despite being generally stable. Exposure to high temperatures, sunlight, or repeated reuse significantly increases the leaching of compounds like antimony and certain hormone-disrupting chemicals.
Microplastics and nanoplastics are consistently found in bottled water at concentrations higher than in tap water. Recent studies indicate that a single liter of bottled water may contain hundreds of thousands of plastic particles, with a large portion of these being nanoplastics. The primary sources of these particles are the bottle material itself and the friction created by the cap’s opening and closing.
Some older or larger plastic containers, particularly those labeled with the recycling code #7, may still contain Bisphenol A (BPA), a known endocrine disruptor linked to various health issues. Glass and stainless steel containers show no detectable leaching of BPA and are the preferred options for minimizing chemical exposure. Purified water, if sourced from a municipal supply, still carries the risk of environmental contaminants like PFAS or heavy metals if the filtration process is inadequate, although the goal of purification is to remove these entirely.