Hydrogen is the most abundant element in the universe, the fuel that powers every star, and a building block of water, DNA, and nearly every molecule in your body. Its importance spans from the cosmic scale down to the molecular machinery inside your cells. Few elements touch as many aspects of life, industry, and the future of energy.
The Most Common Element in the Cosmos
Hydrogen makes up roughly 75% of all normal matter in the universe. Stars, including our sun, are essentially giant hydrogen reactors. Deep in a star’s core, where temperatures reach at least 10 million degrees, hydrogen atoms fuse together to form helium, releasing enormous amounts of energy in the process. This fusion reaction is what makes stars shine, and it dominates about 99% of a star’s total lifetime. Every heavier element that exists, from the carbon in your bones to the iron in your blood, was originally forged in stars that started by burning hydrogen.
Why Your Body Depends on It
Hydrogen is the third most abundant element in the human body by mass, after oxygen and carbon. It’s a core component of water, which makes up about 60% of your body weight. Beyond water, hydrogen atoms are woven into proteins, fats, carbohydrates, and DNA.
Inside your cells, hydrogen plays a direct role in energy production. Mitochondria, the structures that generate energy for your cells, rely on the movement of hydrogen ions to produce ATP, the molecule your body uses as fuel for virtually everything it does. Electrons pass through a chain of proteins inside the mitochondria, and the resulting flow of hydrogen ions across a membrane drives the assembly of ATP. Without this process, your cells would have no usable energy.
Holding Molecules Together
Hydrogen bonding is one of the most important forces in biology. These bonds form when a hydrogen atom attached to one molecule is attracted to an oxygen or nitrogen atom on another. They’re individually weak compared to the bonds holding atoms together within a molecule, but collectively they’re powerful enough to shape the structures that make life possible.
The two strands of DNA stay paired together largely because of hydrogen bonds between their base pairs. Proteins fold into their functional three-dimensional shapes through hydrogen bonds as well. Research shows that 66 to 69% of the hydrogen bonds within protein chains are strong ones, and these bonds are the primary driving force behind the formation of the alpha helices and beta sheets that give proteins their structure. Without hydrogen bonding, proteins would be shapeless chains and DNA couldn’t store genetic information.
Controlling Your Body’s pH
The concentration of hydrogen ions in a fluid determines its pH, which is a measure of how acidic or basic that fluid is. The pH scale is logarithmic, meaning each whole number represents a tenfold change. Water with a pH of 5 is ten times more acidic than water with a pH of 6.
Your blood maintains a pH between about 7.35 and 7.45, and even small shifts outside this range can disrupt enzyme function, oxygen delivery, and cell signaling. Your body uses several buffer systems to keep hydrogen ion levels tightly controlled. This is why pH balance matters in contexts from exercise (lactic acid buildup increases hydrogen ions in muscles) to kidney function (your kidneys excrete excess hydrogen ions to prevent your blood from becoming too acidic).
Feeding Nearly Half the World
One of hydrogen’s most consequential industrial uses is one most people never think about: making fertilizer. The Haber-Bosch process, developed in 1908 by Fritz Haber, combines nitrogen from the air with hydrogen (traditionally sourced from natural gas) under high pressure and temperature to produce ammonia. About 170 million metric tonnes of ammonia are produced globally each year, and roughly 80% of it goes into fertilizers.
The scale of this is hard to overstate. An estimated 48% of the global population eats food grown with synthetic fertilizers made through this process. Without hydrogen as a feedstock for ammonia production, modern agriculture simply could not support the current world population.
Clean Energy Potential
Hydrogen fuel cells convert hydrogen and oxygen into electricity, and the only byproducts are water and heat. No carbon dioxide, no particulate matter. These fuel cells can exceed 60% energy conversion efficiency, which is higher than traditional combustion engines.
The challenge is how the hydrogen itself gets made. Steam methane reforming, which accounts for 68% of global hydrogen production, produces what’s called “gray hydrogen” at a cost of roughly $1 to $3 per kilogram, but it releases carbon dioxide in the process. “Green hydrogen,” made by splitting water using renewable electricity, costs between $4 and $12 per kilogram, a significant price gap. The U.S. Department of Energy has set a target of $1 per kilogram for net-zero-carbon hydrogen by 2030, which would make it competitive with fossil fuel alternatives.
Hydrogen is especially promising for sectors that are hard to electrify directly, like heavy trucking, shipping, steel manufacturing, and long-duration energy storage. If the cost gap closes, hydrogen could become a practical replacement for fossil fuels in applications where batteries alone aren’t sufficient.
Safety Considerations
Hydrogen is flammable in air at concentrations between 4% and 74%, a much wider range than natural gas or gasoline vapor. Its explosion limits fall between 18.3% and 59%. It’s also colorless and odorless, making leaks hard to detect without sensors.
Storing hydrogen requires specialized infrastructure. In liquid form, it must be kept at extremely low temperatures (below negative 253°C), so containers are double-walled, vacuum-jacketed, and super-insulated. These containers are designed to safely vent hydrogen as gas if a breach in either wall is detected. In compressed gas form, hydrogen is stored in high-pressure tanks rated to withstand significant impact. These engineering requirements add cost and complexity, but they reflect well-understood safety principles rather than unsolvable problems.
Molecular Hydrogen as a Medical Tool
A growing body of research is exploring molecular hydrogen (H₂ gas) as a therapeutic agent. Its key property is selectivity: H₂ appears to neutralize the most damaging types of free radicals in the body while leaving beneficial ones intact. It also activates the body’s own antioxidant defense systems and helps interrupt the chain reaction between oxidative stress and inflammation.
Researchers are studying H₂ therapy across a wide range of conditions, including neurodegenerative diseases like Alzheimer’s, cardiovascular problems such as atherosclerosis and hypertension, lung diseases including COPD and acute lung injury, liver and kidney conditions, and several types of cancer. It was also investigated during the COVID-19 pandemic. Much of this work is still in early stages, but the breadth of interest reflects how fundamental oxidative stress is to disease, and how useful a selective, low-risk antioxidant could be if the results hold up in larger clinical trials.