What is molecular hydrogen?
Molecular hydrogen (H2) is the lightest and smallest chemical element that exists naturally. It is a colorless and odorless gas. Hydrogen was long thought to have a negligible effect on the human body, but emerging evidence suggests that it may have therapeutic potential as a medical gas. Regardless, research on molecular hydrogen is still in its infancy. While there seems to be promise, it may be too soon to recommend molecular hydrogen for any particular purpose.
What are molecular hydrogen’s main benefits?
Research suggests that molecular hydrogen has antioxidant, anti-inflammatory, and cell-protective properties. These effects may benefit various conditions, particularly those associated with high levels of oxidative stress, but current research is too limited to draw any meaningful conclusions.
One of the most long-standing, albeit niche, uses of molecular hydrogen is for deep-sea diving. Adding hydrogen gas to the breathing mixture as a substitute for nitrogen is one method for reducing the side effects of nitrogen gas in high-pressure environments. This isn’t through any drug-like effects of hydrogen, though; it’s simply because it’s replacing nitrogen gas so that less nitrogen can dissolve into the blood during a dive.[7][8]
Preliminary research also points to potential benefits in metabolic syndrome, nonalcoholic fatty liver disease, recovery following a heart attack or cardiac arrest, rheumatoid arthritis, cancer, exercise capacity, and some respiratory conditions.[1][9][10]
What are molecular hydrogen’s main drawbacks?
Molecular hydrogen is generally considered nontoxic, even at high doses, and side effects have rarely been reported.[9] In one study using hydrogen-rich water, a few participants experienced loose stools, heartburn, and headaches; however, there was no placebo group to compare to.[11] In patients inhaling hydrogen gas for several hours daily, drowsiness and agitation have been reported.[9]
There are some additional risks depending on the administration method. Hydrogen gas at concentrations above 4% can be explosive when mixed with oxygen, and injectable hydrogen-rich saline raises the risk of infection and injury. Furthermore, these dosage forms generally require specialized equipment and medical supervision.[1][12]
How does molecular hydrogen work?
Molecular hydrogen has an incredibly small size and low molecular weight, allowing it to rapidly diffuse throughout the body, including through cell membranes and the blood-brain barrier. While it readily penetrates bodily tissues, it’s also eliminated quickly through exhalation. Overall, hydrogen seems to work by activating various biological pathways in ways that promote cellular homeostasis.[10]
Molecular hydrogen is a unique antioxidant in that it selectively scavenges hydroxyl and peroxynitrite radicals but not other reactive species that play important roles in cellular signaling (e.g., hydrogen peroxide). Its small size allows it to interact directly with mitochondria, possibly benefiting mitochondrial function and energy metabolism. Furthermore, hydrogen seems to increase the body’s own antioxidant mechanisms, resulting in a prolonged antioxidant effect even once it has been cleared from the body.[13]
The anti-inflammatory effects of molecular hydrogen may be related to the antioxidant effects, but hydrogen also seems to inhibit inflammatory pathways directly. Additionally, hydrogen may influence gene expression, lipid metabolism, apoptosis (programmed cell death), and autophagy (the process of breaking down and recycling cellular materials).[1][10]
What are other names for Molecular Hydrogen
- H2
- Hydrogen
- Hydrogen gas
- Hydrogen-rich water
- Hydrogen-rich saline
Dosage information
Molecular hydrogen can be administered in several ways, including inhaling hydrogen gas, drinking or bathing in hydrogen-rich water (HRW), or injecting/infusing hydrogen-rich saline. Injecting, infusing, or inhaling molecular hydrogen is generally done under medical supervision and with specialized equipment. Drinking HRW is probably the safest and most accessible option for most people.[1] Regardless, more research is needed to determine the optimal dosage and administration method of molecular hydrogen.
HRW is simply water with added hydrogen. The extra hydrogen diffuses out of the water fairly quickly; therefore, it’s generally necessary to prepare the HRW immediately before consumption.[1] There are two methods of doing this: effervescent hydrogen-generating tablets, which usually contain magnesium and an acid which will lead to the production of hydrogen when added to a glass of water,[2] and hydrogen-generating water bottles, which use an electric current to produce hydrogen.[3]
In clinical studies, HRW (0.3 mM to 7.5 mM) has been consumed in amounts ranging from 250 mL to 2 L (2,000 mL) per day, usually divided into several daily doses with higher volumes.[1][4]
In metabolic syndrome, HRW (~7.3 mM) at a dose of 750 mL daily may be safe and effective for up to 24 weeks.[5]
When used to reduce fatigue during exercise (an effect possibly relevant in untrained individuals), HRW can be taken as a single dose immediately before exercise.[6]
Frequently asked questions
Molecular hydrogen (H2) is the lightest and smallest chemical element that exists naturally. It is a colorless and odorless gas. Hydrogen was long thought to have a negligible effect on the human body, but emerging evidence suggests that it may have therapeutic potential as a medical gas. Regardless, research on molecular hydrogen is still in its infancy. While there seems to be promise, it may be too soon to recommend molecular hydrogen for any particular purpose.
Research suggests that molecular hydrogen has antioxidant, anti-inflammatory, and cell-protective properties. These effects may benefit various conditions, particularly those associated with high levels of oxidative stress, but current research is too limited to draw any meaningful conclusions.
One of the most long-standing, albeit niche, uses of molecular hydrogen is for deep-sea diving. Adding hydrogen gas to the breathing mixture as a substitute for nitrogen is one method for reducing the side effects of nitrogen gas in high-pressure environments. This isn’t through any drug-like effects of hydrogen, though; it’s simply because it’s replacing nitrogen gas so that less nitrogen can dissolve into the blood during a dive.[7][8]
Preliminary research also points to potential benefits in metabolic syndrome, nonalcoholic fatty liver disease, recovery following a heart attack or cardiac arrest, rheumatoid arthritis, cancer, exercise capacity, and some respiratory conditions.[1][9][10]
Molecular hydrogen might influence several aspects of exercise capacity to a small degree, but whether this is actually meaningful to an exercising person requires more research.
Molecular hydrogen may reduce fatigue, blood lactate levels, and the perception of exertion during high-intensity exercise. However, the reduction in fatigue and perceived exertion may only be significant in untrained individuals, possibly due to the body being less adapted to the stress of exercise. Furthermore, most studies have reported that hydrogen did not affect VO2max (a metric of aerobic exercise performance) or endurance performance in trained or untrained individuals.[6][10]
When benefits have been observed, they appear to be greater in intermittent, high-intensity exercise as opposed to continuous exercise and with molecular hydrogen provided as a single dose immediately before exercise rather than multiple-day dosing or after exercise.[6][14]
Molecular hydrogen is an intriguing option for metabolic conditions which are often associated with high levels of oxidative stress and inflammation. While some trials have pointed to potential benefits, the research is mixed, and all outcomes require replication in further trials.
Hydrogen-rich water (HRW) might improve lipid profiles, more specifically by reducing LDL cholesterol, total cholesterol, and triglycerides. However, the effects appear small or marginally beneficial.[4]
A randomized controlled trial in people with metabolic syndrome reported that HRW reduced oxidative stress biomarkers, improved lipid profiles, and reduced fasting glucose and HbA1c after 24 weeks.[5] The participants consumed 750 mL (0.75 L) of HRW (7.3 millimolar (mM)) daily. Studies providing HRW at lower concentrations and for shorter durations have not found these benefits, aside from reduced oxidative stress biomarkers.[11][15]
In nonalcoholic fatty liver disease (NAFLD), a small trial reported that 1 L (1,000 mL) of HRW (3 mM) daily for 28 days reduced liver fat accumulation compared to a placebo.[16] In another trial, hydrogen gas (66% hydrogen and 33% oxygen) inhaled for 1 hour daily for 13 weeks was reported to reduce liver enzymes, inflammatory markers, and oxidative stress biomarkers compared to baseline, with no changes observed in the control group.[17]
Molecular hydrogen has demonstrated some potentially promising effects in cancer therapy. However, this is based on several small clinical trials and case reports and requires more research.[9]
In 20 patients with stage III or IV non-small-cell lung cancer (NSCLC) who refused standard treatment, inhaled hydrogen reportedly led to significantly reduced respiratory symptoms (e.g., shortness of breath, cough, chest pain) and prolonged progression-free survival time compared to a placebo (7.9 months vs 4.4 months). Hydrogen gas (66.7% hydrogen and 33.3% oxygen) was inhaled for 4 to 6 hours daily over 5 months.[18] Similarly, another clinical trial in patients with stage IV lung cancer reported that inhaled hydrogen (~3 hours daily) in addition to standard treatment (nivolumab) led to prolonged overall survival compared to standard treatment alone.[19][20]
In one clinical trial, patients with liver cancer who were undergoing radiation drank 1.5 L to 2 L (1,500 mL to 2,000 mL) of hydrogen-rich water daily (0.55–0.65 millimolar) for 6 weeks and reported reduced side effects of radiation (appetite loss and altered taste), had improved oxidative stress biomarkers, and showed no difference in tumor response to radiation.[21]
More research is needed to confirm the validity of these findings, but a few trials have suggested that hydrogen may alter immune function in a way that could improve cancer prognosis.[1]
Molecular hydrogen, particularly inhaled hydrogen gas, may be beneficial in various respiratory conditions, including COVID-19, asthma, and chronic obstructive pulmonary disease (COPD). This may be due to its antioxidant and anti-inflammatory properties as well as its low density, which may improve lung airflow.[1]
In a randomized controlled trial, people experiencing persistent symptoms following a COVID-19 infection reported improved physical function (6-minute walking test) and lung function (forced vital capacity and forced expiratory volume) with inhaled hydrogen gas compared to a placebo. Hydrogen gas (100% hydrogen) was inhaled for 1 hour twice a day for 14 days.[22] In an open-label, multicenter trial in hospitalized patients with COVID-19, inhaled hydrogen gas (66.7% hydrogen and 33.3% oxygen) led to reduced disease severity, reduced chest pain, and a faster improvement in shortness of breath and cough compared to participants receiving oxygen gas alone.[23]
Similar benefits have been observed in people with asthma and COPD. In a multicenter randomized controlled trial, patients with an acute exacerbation (a sudden worsening of disease/symptoms) of COPD saw a greater reduction in symptoms when inhaling hydrogen and oxygen gas over 7 days compared to oxygen alone, but there were no differences in lung function.[24] In a study including people with either asthma or COPD, a single dose of hydrogen gas (2.4% hydrogen inhaled for 45 minutes) led to decreased markers of inflammation in the blood and exhaled breath.[25]
This could represent a novel approach to managing respiratory conditions and is certainly worthy of further research.
Molecular hydrogen is generally considered nontoxic, even at high doses, and side effects have rarely been reported.[9] In one study using hydrogen-rich water, a few participants experienced loose stools, heartburn, and headaches; however, there was no placebo group to compare to.[11] In patients inhaling hydrogen gas for several hours daily, drowsiness and agitation have been reported.[9]
There are some additional risks depending on the administration method. Hydrogen gas at concentrations above 4% can be explosive when mixed with oxygen, and injectable hydrogen-rich saline raises the risk of infection and injury. Furthermore, these dosage forms generally require specialized equipment and medical supervision.[1][12]
Molecular hydrogen has an incredibly small size and low molecular weight, allowing it to rapidly diffuse throughout the body, including through cell membranes and the blood-brain barrier. While it readily penetrates bodily tissues, it’s also eliminated quickly through exhalation. Overall, hydrogen seems to work by activating various biological pathways in ways that promote cellular homeostasis.[10]
Molecular hydrogen is a unique antioxidant in that it selectively scavenges hydroxyl and peroxynitrite radicals but not other reactive species that play important roles in cellular signaling (e.g., hydrogen peroxide). Its small size allows it to interact directly with mitochondria, possibly benefiting mitochondrial function and energy metabolism. Furthermore, hydrogen seems to increase the body’s own antioxidant mechanisms, resulting in a prolonged antioxidant effect even once it has been cleared from the body.[13]
The anti-inflammatory effects of molecular hydrogen may be related to the antioxidant effects, but hydrogen also seems to inhibit inflammatory pathways directly. Additionally, hydrogen may influence gene expression, lipid metabolism, apoptosis (programmed cell death), and autophagy (the process of breaking down and recycling cellular materials).[1][10]
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