What makes drinking water truly good?

Mineralization is the amount of minerals and salts dissolved in a liter of water, measured in milligrams per liter (mg/L); on a water report, it’s listed as total dissolved solids (TDS). Water brings calcium, magnesium, potassium and other elements with it — and the World Health Organization notes that drinking water can contribute calcium and magnesium to the diet.

Water that’s too “empty” — distilled or reverse-osmosis water, far below 100 mg/L — is clean but carries almost no calcium or magnesium. If it’s your everyday water, your food has to supply those minerals on its own.

The other extreme is heavily mineralized water, above 1,000 mg/L — traditionally taken in courses rather than as everyday drinking water. For comparison, EPA’s non-enforceable guideline for total dissolved solids in tap water is 500 mg/L, set for taste and deposits rather than health.

For everyday drinking, Prof. Pokotylo’s benchmark is the middle ground: 100–⁠500 mg/L. That’s enough minerals, without an overload of salts — water that works for the whole family every day, gently and without you noticing.

pH is a scale of acidity from 0 to 14: anything below 7 is acidic, above 7 is alkaline. For reference, lemon juice is around pH 2, coffee around 5 and pure water 7 — while blood stays at about 7.35–⁠7.45, slightly alkaline. The scale is logarithmic, so each whole number is a tenfold change.

That range is tightly controlled: the body keeps its internal pH steady on its own, with built-in buffering systems, whatever you eat or drink. Many everyday foods and drinks, from coffee to soda, are acidic, and that’s normal.

So alkaline water isn’t a way to “alkalize” your body. Mayo Clinic’s view is that for most people it isn’t better than plain water — and where naturally alkaline spring waters are praised, researchers credit their minerals, such as calcium and magnesium, rather than the pH.

What a mildly alkaline pH does offer is a softer taste that’s pleasant to drink every day. Higher isn’t automatically better, though: Mayo Clinic flags safety concerns especially above pH 9.8.

Put simply, ORP — oxidation-reduction potential — is the “charge” of water. It’s measured in millivolts (mV) and can be positive or negative. A negative reading means the water tends to give up electrons (it reduces); a positive one means it tends to take them (it oxidizes).

Prof. Pokotylo writes that the body’s internal fluids — blood, lymph and the fluid inside and around cells — have a negative redox potential of roughly −70 to −200 mV, depending on the tissue. Biochemistry research points the same way: biological fluids are generally reducing.

Almost all the water we drink every day — from the tap, from a bottle or through an ordinary filter — reads positive, about +100 to +400 mV. Part of the reason is what keeps tap water safe: chlorine-based disinfectants are oxidizers. In Prof. Pokotylo’s view, water with a negative ORP is closer to the body’s own environment, so the body spends less energy bringing it into line.

Water reads negative when it holds dissolved molecular hydrogen, a reducing agent: the more H₂, the more negative the ORP. But ORP also shifts with pH, so it shows that hydrogen is present — not how much. For an actual concentration, measure H₂ directly.

The parameter that sets hydrogen water apart is dissolved molecular hydrogen (H₂). Hydrogen is a gas — “the smallest and most common molecule in the universe,” as Prof. Pokotylo puts it. In hydrogen water it’s dissolved much the way carbon dioxide is in sparkling water, only without bubbles, taste or smell. The gas slowly escapes, so hydrogen water is best drunk fresh.

Why does it matter? The body produces free radicals all the time, and some of them do useful work. Trouble starts when the most reactive ones, such as the hydroxyl radical, pile up and damage fats, proteins and DNA — the imbalance known as oxidative stress. Intense exercise, polluted air and age can all add to the load.

Molecular hydrogen is studied as a selective antioxidant: in lab work, it reacted with the most aggressive radicals and left alone the ones the body needs. That selectivity is exactly what makes researchers so interested in it.

The field began in 2007, when a team led by Prof. Shigeo Ohta reported in Nature Medicine that, in cultured cells, H₂ selectively reduced the hydroxyl radical. The research has grown fast since then, but it’s still young — much of it in animals, with small human trials — so we describe hydrogen water by what research suggests, never as a treatment.