“Oxygenated” water and athletic performance (2025)

A decade or so ago, the idea arose that athletes might gain a competitive edge by drinking water that contained extra dissolved oxygen (O₂). The notion stems from observations that O₂ breathing during exercise enhances athletic performance,1,2 but the connection of O₂ breathing during exercise with drinking “hyperoxygenated” water before exercise conflates physics and physiology in a struthonian visit to placebo land. Fuelled by bottled‐water mavens, who collect testimonials for oxygenated waters, claims abound of ergogenic benefits of water advertised to hold up to 40 times more O₂ than plain water.

The issue of hydration aside, such claims have a flimsy rationale and no rigorous experimental support. On close inspection, three scientific problems immediately arise. Firstly, for all practical purposes, supplemental O₂ improves performance only during exercise, not before or between bouts.3 With normal lungs, breathing of even pure O₂ at sea level increases maximal O₂ uptake (V̇o₂max) by only 5–10% because air breathing alone, except at high intensity work, keeps the arterial O₂ saturation (Sao₂) and content (Cao₂) very high.2

The next problem is that the solubility of O₂ in water (and plasma) is low. The solubility constant obeys Henry's Law: it is directly proportional to O₂ partial pressure at the air‐liquid interface as well as inversely proportional to the temperature—cold water holds more O₂ than warm water.4 At sea level (760 mm Hg) and room temperature (20°C), O₂ solubility in water is ∼0.68 ml/dl. The O₂ content of bottled water can be raised by increasing the O₂ partial pressure, but when the pressure returns to atmospheric—for instance, when the bottle is opened—O₂ off‐gases just like the CO₂ fizz in a carbonated beverage. The aqueous O₂ content rapidly falls to the lower equilibrium.

Problem three is that it is not known whether O₂ is actually absorbed from drinking water, hyperoxygenated or not. Perhaps some O₂ enters the portal circulation, and then the venous circulation, to raise venous Po₂. But the intestine, unlike the lung, is not designed for gas exchange, and O₂ absorbed in this way would have a negligible effect viscerally or on systemic oxygen delivery (Do₂). At a normal Cao₂ of 20 ml/dl, only 0.3 ml/dl (1.5%) is dissolved in plasma. Basal Do₂ is ∼1000 ml/min, and at a Vo₂ of 3.5 ml O₂/kg/min (1 MET), the O₂ extraction ratio is ∼0.25; therefore, to supply this amount for one minute to the average sized person, a drink would have to provide ∼250 ml of rapidly absorbable oxygen.

How much O₂ is present in the oxygenated water sold commercially? Hampson et al5 measured the O₂ content of five brands of “hyperoxygenated” water and compared them with plain water. Four of five brands had values above plain water, and one was similar. The highest values in sealed glass bottles were nine times those of plain water and 80 ml O₂/l (STPD). However, air is 20.9% O₂, and a normal human tidal volume of 500 ml contains roughly 100 ml O₂. Thus a breath of fresh air contains more O₂ than a litre of hyperoxygenated water.

Does this amount of O₂ influence exercise performance? Three controlled studies on oxygenated water and performance say not.5,6,7 Willmert et al6 measured resting, submaximal, and maximal Vo₂, circulatory variables, and blood lactate in 12 subjects who randomly consumed 500 ml of either oxygenated or plain bottled water. No differences were detected between conditions for any variable at rest or in exercise. A second part of the study found nothing to suggest that oxygenated water facilitated recovery from exercise. An independent, randomised, double blind crossover study of 11 subjects found no differences in V̇o₂max or associated cardiorespiratory performance variables after drinking oxygenated or deoxygenated water of the same brand five minutes before exercise.5 Finally, a study of nine male recreational cyclists showed that oxygenated water did not improve performance even in mild acute hypoxia (P_bar  =  641 mm Hg).7 These studies all meet the physiological expectation that oxygenated water would not improve incremental exercise to V̇o₂max or recovery from strenuous exercise.

One abstracted study also found no exercise performance benefit, but noted Sao₂ to be higher with oxygenated water (91.3% v 87.3%) at the end of a standard endurance test.8 The O₂ content of the water was not given, but if 80 ml O₂ as mentioned above instantaneously entered the circulation, basal Do₂ would rise to 1080 ml/min. This would not increase Sao₂ (as haemoglobin is already essentially saturated) but would raise Svo₂ for ∼20 seconds before the O₂ was consumed. At 10 MET, however, 80 ml O₂ is consumed in about two seconds—too short a time to measurably increase Sao₂ or Svo₂. Simply put, minute amounts of dissolved O₂ cannot explain an increase in Sao₂ in an endurance test.

In summary, oxygenated water fails both quantitative analysis and practical physiological tests of exercise performance and recovery. Only miniscule quantities of O₂ can be dissolved in drinking water compared with that required for exercise, and significant intestinal absorption of O₂ is unsubstantiated. Ergogenic claims for oxygenated water therefore cannot be taken seriously.