Introductory remarks

In part 42 of our A–Z series of nutritional supplements, having covered vitamins in parts 39–41, we finish off reviewing V by looking at valine, an essential amino acid (EAA) classified as a branched chain amino acid (BCAA), and vanadium, a trace element marketed as an aid to muscle growth in weight training. We then turn our attention to W, with the first W to be reviewed being ‘water (oxygenated)’. Oxygenated water products are marketed to athletes with a claim that, dependent on the product, they contain 3–30 times the oxygen content of normal tap water, and thereby could potentially be of benefit to health and performance.

It is worth noting that these oxygenated water products are not to be confused with doubly labelled water (DLW). In DLW, the water is generally labelled with the heavy, non-radioactive isotope forms of the elements deuterium (symbol D or ²H, also known as heavy hydrogen) and the isotope of oxygen, oxygen-18 (¹⁸O, as opposed to the normal oxygen-16, ¹⁶O), combining to become deuterium oxide-18 (D₂¹⁸O). DLW is commonly used to measure metabolic rate, particularly ‘in the field’ and for longer periods of measurement, where more accurate direct or indirect calorimetric measurements would be rather difficult.