@adamh
One thing that breathing H2 gas cannot do, but hydrogen rich water does do, is induce ghrelin release. Ghrelin has mood boosting, antidepressant properties, as well as cognitive enhancing and neuroprotective effects, and I think ghrelin release is most likely responsible for the mood boost that I experience within an hour or two of drinking 500 ml of 5 ppm hydrogen rich water. Ghrelin is being researched for its antidepressant effects.
Indeed, in the following study (which @aconita cited in the first post of this thread), the author says that ghrelin may be responsible for most of the benefits of drinking hydrogen rich water:
Potential ghrelin-mediated benefits and risks of hydrogen water
The possibility that most of the benefits observed with HW in experimental studies are mediated by ghrelin merits consideration. Ghrelin is well known to function as an appetite stimulant and secretagogue for growth hormone, but it influences physiological function throughout the body via interaction with the widely express GHS-R1a receptor. Rodent and, to a more limited extent, clinical studies establish that ghrelin has versatile neuroprotective and cognitive enhancing activity, favorably impacts vascular health, exerts anti-inflammatory activity useful in autoimmune disorders, and is markedly hepatoprotective.
So this is what you miss out on by breathing hydrogen gas, as opposed to drinking water with hydrogen gas dissolved in it (hydrogen rich water).
The benefits of hydrogen rich water appear to derive from the gastric production of ghrelin, and the release of this hormone is triggered by the presence of hydrogen rich water in your stomach. If you don't have hydrogen rich water in your stomach, you won't get any ghrelin.
The following study also tells us something fascinating about hydrogen rich water: you get the same ghrelin-releasing benefits from hydrogen rich water no matter if it is weak or strong in its H2 concentration: the benefits are independent of H2 concentration:
Oral ‘hydrogen water' induces neuroprotective ghrelin secretion in mice
Our findings demonstrate that the neuroprotective effects of oral hydrogen water, which produces negligible levels of H2 in the brain, result from gastric induction of the neuroprotective peptide hormone ghrelin and the subsequent activation of ghrelin receptors. In addition, we have shown an obligate role for β1-adrenergic receptors in hydrogen water-induced ghrelin up-regulation in plasma, consistent with previous reports that adrenergic stimulation regulates ghrelin release in vitro and in vivo.
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We employed three different methods to prepare hydrogen water (see Methods), which resulted in H2 concentration of 0.04–0.8 mM, and we observed that the effects of hydrogen water on ghrelin induction and protection of dopamine neurons were dose-independent over this range.
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The increase in plasma ghrelin levels by oral hydrogen water was eliminated by administration of the β1-adrenergic receptor-specific blocker, atenolol (10 mg/kg i.p.) injected 30 min prior to H2 water administration on each of four days (Figure 3). Thus, activation of β1-adrenergic receptors is required for hydrogen water-induced enhancement of circulating ghrelin.
So this study found that the amount of ghrelin released from drinking hydrogen rich water did not depend on the H2 concentration in the water, at least in the range of H2 concentrations they used in the study, which was concentrations from 0.04 mM to 0.8 mM (this corresponds to H2 concentrations in the water of 0.08 ppm to 1.6 ppm).
So irrespective of whether you drink weak hydrogen rich water at just an 0.08 ppm H2 concentration, or stronger hydrogen rich water at 1.6 ppm H2 concentration, in both cases, you still get the same amount of ghrelin released, and thus exactly the same benefit.
It is not clear whether this dose independence also extends to even higher H2 concentrations of around 5 ppm or 10 ppm, because the study did not examine these very high concentrations. But it is definitely worth bearing in mind that higher ppm concentrations of H2 may not necessarily get you increased effects, when it comes to ghrelin release.
This paradoxical dose independence of hydrogen rich water is also detailed in the following study:
Recent Progress Toward Hydrogen Medicine: Potential of Molecular Hydrogen for Preventive and Therapeutic Applications
When model animals and human subjects consumed H2 by drinking water with dissolved H2, even a very small amount of H2 was extensively effective.
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The amount of administered H2 seems to be, in many cases, independent of the magnitude of effects.
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Intestinal bacteria produce more than 1 liter of hydrogen gas per day, whereas the amount of H2 originating from drinking hydrogen water is less than 50 ml. Nevertheless, additional H2 in drinking hydrogen water is unambiguously effective.
So again this study shows that you don't need to drink very much hydrogen rich water, and you don't need to drink very concentrated hydrogen rich water, in order to get the benefits, which arise from the production of ghrelin in the stomach.
So possibly you may get the best effects from hydrogen rich water if you drink relatively small amounts, but drink it every few hours, in order to provide repeat stimulation of ghrelin release.
This study also implicitly indicates that breathing H2 gas is unlikely to produce much benefit, because your own gut bacteria supply you with over 1 liter of hydrogen gas per day anyway. So if you are only breathing in a few small gulps of H2 gas each day, this is not going to be very much, compared with the liter of H2 gas from your gut bacteria.
And this 1 liter of H2 gas you get from your gut bacteria does not produce the same benefits of drinking hydrogen rich water, because this H2 gas from your gut bacteria will not trigger the release of ghrelin in your stomach, but drinking hydrogen rich water does induce gastric ghrelin release.
So the bottom line is that you have to drink hydrogen rich water orally to get the benefits of H2, because much of the benefits derive from the gastric production of ghrelin, whose release is triggered by the presence of hydrogen rich water in your stomach.
Edited by Hip, 28 January 2017 - 02:36 AM.