There are many different technologies for creating "live" water. This week, a reader of our blog asked what "oxygen water" is and how it differs from regular water. So, we will try to answer the most common questions on this topic.

However, as a small spoiler, science states that the oxygen in the water we drink is not related to its amount in our blood.

Dissolved oxygen in natural waters

The dissolved oxygen parameter for drinking water is not regulated anywhere in the world because, firstly, it does not affect its quality, and secondly, it does not carry significant indirect information. Below, we will explain why this parameter is important for natural waters but not informative for drinking water.

Regarding natural water bodies, the dissolved oxygen content in water plays a crucial role, essentially serving as an indicator of the viability of the flora and fauna in a body of water.

Water absorbs oxygen through contact with the atmosphere and precipitation, which always contains more gases, as well as through the photosynthesis of algae within the body of water. The oxygen level decreases due to decomposition, organic matter breakdown, and algae overgrowth (water body eutrophication).

In well water, regardless of depth, oxygen is practically absent, meaning there are no aerobic microorganisms. However, dissolved ferrous iron is present, which, upon exposure to air, quickly oxidizes to insoluble ferric iron.

Drinking water should not contain live bacteria or any other living organisms. Therefore, determining oxygen levels in drinking water has no meaningful significance.

What is oxygen water?

Due to its physical and chemical properties, water is a powerful solvent. It can dissolve organic and inorganic salts as well as most gases.

When it comes to oxygen water, it is an example of a system consisting of a liquid (water - H₂O) and a dissolved gas — oxygen (O₂). At 20°C, one liter of water can dissolve 31 ml of oxygen. For comparison, here are the solubility levels of other gases: 879 ml for carbon dioxide and 2.3 liters for chlorine.

Essentially, oxygen water is the same as carbonated water, but instead of carbon dioxide (CO₂), it is artificially enriched with oxygen under excess pressure and sealed with a cap.

What affects oxygen solubility?

The main factors are temperature and pressure. The higher the temperature, the lower the oxygen solubility in water, and vice versa. For this reason, boiled water is almost entirely devoid of dissolved gases. Notably, reverse osmosis membranes can pass dissolved oxygen molecules.

Pressure also plays a significant role: the higher the pressure, the more gas can be dissolved in the water volume. This is why carbon dioxide is injected into plastic bottles under high pressure and then hermetically sealed with a cap. This explains the characteristic "hiss" when opening a bottle, as the trapped undissolved gas is released.

You may have noticed that if a bottle of carbonated water is left in the sun, it expands, and after cooling, it shrinks again. This effect occurs because the solubility of carbon dioxide (or any other gas) decreases, causing it to escape from the water and create excess pressure in the free space of the bottle, while upon cooling, it dissolves again.

Oxygen content in water

In one liter of regular tap water, there are 2.5 - 3.5 milliliters of oxygen, while in clean rivers, the content can reach 20 ml, and in polluted wastewater-affected bodies, oxygen may be completely absent.

As mentioned earlier, water can dissolve even more oxygen. For example, manufacturers of "oxygen water" claim their product contains up to 90 ml O₂/L. A group of scientists conducted a study on five different brands of oxygen water and found that in four out of five, the oxygen concentration was significantly higher than in regular tap water, while in one sample, it was identical. However, at the moment of opening the container, the maximum content dropped to no more than 80 ml O₂/L, as under normal conditions, oxygen tends to escape into the atmosphere.

To determine the oxygen content in water, specific tests must be conducted. In laboratory conditions, the experiment is usually performed using a titration method. For home experiments, test strips and drop tests, commonly found in aquarium supply stores, can be used.

Can humans breathe through their stomach?

Reading various marketing materials might make one believe that oxygen water indeed has certain therapeutic properties. However, all such claims fall apart when revisiting a basic school biology course.

"Every cell in the body can absorb oxygen," they say, and this is true—but somewhat misleading. Anatomy, the science of the human body, tells us that oxygen enters the lungs through inhaled air, where it comes into contact with alveoli lined with a network of thin blood vessels. These vessels absorb oxygen from the air and release carbon dioxide. The oxygen then binds to iron in hemoglobin within red blood cells and is transported throughout the body. Humans do not have any other method of breathing, unlike plants or coelenterates (such as jellyfish).

Now, let’s talk numbers. A single breath at rest is about 500 ml, with oxygen making up 21% of the total volume—approximately 105 ml. The maximum oxygen concentration in artificially enriched water reaches no more than 90 ml/L. To ingest the same amount of oxygen as in a single breath, you would need to drink slightly more than a liter of oxygenated water. Moreover, this must be done in one go, as under normal conditions, gases quickly escape due to the laws of physics.

As for the digestive tract, oxygen is present there even without enriched water—in the form of intestinal gases. It enters through swallowed air during meals. The total volume of these gases ranges from 150 to 500 ml. Oxygen content varies across different parts of the digestive system: in the stomach, it constitutes 15-16%, which is likely even more than in a bottle of oxygen water, while its amount decreases further along the tract