While the rabbit hole linked will take you to another story, this one begins at the kitchen table with thoughts on breath. We breathe in 'air' and breathe out carbon dioxide, we were told at school. That's a lot of nitrogen we're taking in to be breathing out CO2 and it might seem we're disposing of more oxygen than is incoming, if 78% of what we're getting into our lungs is nitrogen. Having looked it up, this is Nitrogen according to the popular search engine;
H2O is as essential to us as air and that's something else we all know. The BBC writes:
Nitrogen and hydrogen combine to form ammonia; highly toxic - an adult human has, they say, less than 50 micromoles per litre in their blood. In an adult, that is... an infant has twice as much. Some ammonia is urinated, but if we are to follow recent recommendations and down 8 litres of water a day (Eds' advice; don't try this at home), are we not running a huge risk of ammonia poisoning by drinking and breathing at the same time?
This juicy little diagrammatic explanation tells us that the air breathed in and out is composed of the same ingredients, more or less - there's a <5% drop in the oxygen that escapes us. So when we take a breath, the oxygen incoming has to take over, presumably, from the oxygen we breathe out while the nitrogen content, apparently, doesn't do anything at all (being inert... remember when there was total conviction that 95% of DNA was 'junk'?). Just sayin'. Take no notice of the Argon and those 'other gases'.
Ahh - but there's the drinking water to consider, with its oxygen atom carried around by 2 hydrogen atoms. Quora had an Assistant Bot on its staff in 2014, which said this:
Bot
Jul 14
Humans and many other terrestrial animals breathe air, which contains oxygen that our bodies can extract and use for various physiological processes. The oxygen in the air we breathe is in the form of O2 molecules, which can be readily absorbed by our lungs and transported by our blood to tissues throughout the body.
Water (H2O) also contains oxygen, but the oxygen in water is typically in the form of O-H bonds within the water molecule itself. The oxygen atom in water is already bound to hydrogen atoms, making it unavailable for direct absorption by our bodies in the same way that we absorb oxygen from the air.
When we drink water, the oxygen in the water does not enter our bloodstream and tissues in a form that our bodies can use for respiration. Instead, the oxygen in water plays a role in various metabolic processes, but it is not a direct source of oxygen for respiration in the way that oxygen from the air is.
In summary, while water does contain oxygen, the oxygen in water is not in a form that can be readily absorbed by our bodies for respiration. We primarily rely on breathing air to obtain the oxygen needed for cellular respiration and energy production in our bodies.
What happens to the hydrogen?
Asking "What happens to the hydrogen in water when we drink it" or a similar variable on the same question will probably deliver you a lot of hype from Hydrogenated water salesmen, just as the Oxygenated water salesmen clowned about on the previous exercise. Diddly squat scientific information. Let's try something else:
"biological explanation of what happens to hydrogen in water drunk"
Nope, diddly squat. Perhaps someone sober will be kind enough to leave a comment!?
Meanwhile, I carried on hunting for what happens to the hydrogen. Could it have locked itself up? I found a potential explanation from Harvard University but my screen told me someone might be trying to steal my identity, so the computer wouldn't let me go there. The only other vaguely scientific find was something to do with microbes (don't you just love those microbes?} that you can find here from a government source (that didn't flag up anything about cookies ... lol lmao ... yeah sure, nobody need ask).
Another Government paper says that urinary ammonia excreted carries "n the range of 0.7–45 mmol/L" out of our body. Not a lot, then. Somewhere, that hydrogen is doing something in the cells and my guess is that nobody really knows what - if you do, please comment your elucidations... thanks!
Hydrogen blows up, we know that much. You can run cars on it.