The increasing popularity of specialized waters, such as alkaline water and hydrogen water, has led to confusion about whether they are the same product. Despite both being marketed as enhanced forms of water, they are fundamentally different in their chemical composition and production methods. This article clarifies the distinction between these two beverages by examining their unique properties.
The Chemistry of Alkaline Water
Alkaline water is defined by its potential of hydrogen (\(\text{pH}\)) level, which measures the concentration of hydrogen ions (\(\text{H}^+\)) in a solution. Pure water has a neutral \(\text{pH}\) of 7, while alkaline water possesses a \(\text{pH}\) greater than 7, typically ranging between 8 and 9.5. This elevated \(\text{pH}\) is achieved by increasing the concentration of hydroxide ions (\(\text{OH}^-\)) relative to \(\text{H}^+\) ions.
Alkaline water is commonly created by adding dissolved alkaline minerals, such as calcium, magnesium, or bicarbonate, which naturally raise the \(\text{pH}\) level. These minerals often originate from natural spring sources. The presence of these mineral compounds is responsible for the water’s increased alkalinity.
Alternatively, alkaline water can be produced through water ionization or electrolysis. This process uses electrically charged plates to separate the water into two streams: one acidic and one alkaline. During electrolysis, the concentration of alkaline mineral ions is increased in the resulting alkaline stream, effectively raising the \(\text{pH}\) and generating a higher proportion of \(\text{OH}^-\) ions.
The resulting water’s primary characteristic is its basic nature, a direct consequence of ion manipulation or mineral content. The focus remains on shifting the water’s position on the \(\text{pH}\) scale, making it less acidic than standard tap water.
The Role of Dissolved Gas in Hydrogen Water
Hydrogen water is defined by the presence of dissolved molecular hydrogen gas (\(\text{H}_2\)). Although water’s chemical formula is \(\text{H}_2\text{O}\), the hydrogen in hydrogen water exists as an additional, neutral diatomic gas molecule suspended within the liquid. This dissolved gas is distinct from the hydrogen atoms chemically bonded to oxygen in the water molecule itself.
Production focuses on saturating the liquid with neutral \(\text{H}_2\) gas to achieve therapeutic concentrations. This is often accomplished through high-pressure infusion of the gas into the water. The extremely small size of the \(\text{H}_2\) molecule allows it to dissolve efficiently and remain suspended in the water.
Specialized electrolysis devices can generate \(\text{H}_2\) gas and infuse it directly into the water, often achieving levels of 0.5 to 1.6 parts per million (\(\text{ppm}\)) or higher. Some portable products use magnesium tablets that react with the water (\(\text{Mg} + 2\text{H}_2\text{O} \rightarrow \text{Mg}(\text{OH})_2 + \text{H}_2\)), releasing molecular hydrogen gas into the solution.
Crucially, the presence of dissolved \(\text{H}_2\) gas does not change the water’s \(\text{pH}\) level. Hydrogen water is typically neutral, maintaining a \(\text{pH}\) of around 7, similar to regular water. Its defining characteristic is the concentration of the dissolved neutral gas, not the concentration of charged ions.
Key Differences in Composition and Creation
The fundamental difference is rooted in what defines them chemically: alkaline water is characterized by its \(\text{pH}\), while hydrogen water is characterized by the concentration of a dissolved neutral gas (\(\text{H}_2\)). Alkaline water is a solution containing an increased concentration of charged ions, specifically \(\text{OH}^-\) and alkaline mineral cations. Production aims to shift the equilibrium of hydrogen and hydroxide ions to achieve a \(\text{pH}\) above 7.
Hydrogen water is a supersaturated solution of the neutral molecule \(\text{H}_2\), which does not carry an electrical charge or alter the water’s \(\text{pH}\). Alkaline water production manipulates the ionic strength through mineral addition or ion separation. In contrast, hydrogen water production involves physically dissolving or generating a neutral gas into the liquid.
While some water ionizers produce both alkaline water and a small amount of dissolved hydrogen gas, the primary purpose of an alkaline ionizer is \(\text{pH}\) modification. Conversely, modern hydrogen water generators are engineered to maximize the dissolved \(\text{H}_2\) concentration. They often use technologies like Proton Exchange Membrane (\(\text{PEM}\)) electrolysis to separate the \(\text{H}_2\) from the \(\text{OH}^-\) ions, ensuring a high gas concentration with a neutral \(\text{pH}\).
The resulting compositions reflect these different goals. Alkaline water has an altered \(\text{pH}\) and a higher mineral content, giving it a distinctive taste. Hydrogen water maintains the same \(\text{pH}\) and taste as its source water, but contains \(\text{H}_2\) gas measurable in \(\text{ppm}\). Alkaline water is an ionic solution, while hydrogen water is a gas solution.
Understanding the Health Claims
The marketing narratives reflect the distinct compositions and proposed mechanisms of action. Alkaline water is promoted based on its elevated \(\text{pH}\) level. Proponents claim that drinking alkaline water helps neutralize excess acidity in the body, which is theorized to result from a modern diet high in acidic foods.
These claims often focus on balancing the body’s overall \(\text{pH}\) and supporting digestive health by counteracting stomach acid. The purported benefits are tied directly to the water’s basic properties and its ability to act as a buffer.
Hydrogen water is marketed based on the unique biological activity of the molecular hydrogen molecule. The claims center on \(\text{H}_2\) acting as a selective antioxidant. The tiny gas molecule is believed to neutralize only the most damaging forms of free radicals, such as the hydroxyl radical (\(\cdot \text{OH}\)), without interfering with beneficial signaling molecules. This selective antioxidant effect is promoted for reducing oxidative stress, lowering inflammation, and aiding in muscle recovery.
The claims for hydrogen water focus on cellular protection and anti-inflammatory effects due to the dissolved gas, rather than \(\text{pH}\) modification.