Why are cells damaged when they receive too little oxygen?
Oxygen deprivation damages cells through multiple simultaneous pathways: energy deficit, toxic accumulation of calcium and lactate, structural deterioration of mitochondria, and membrane damage caused by oxidised fats. Understanding of these processes is scientifically solid, but intervening in them remains confined to the laboratory, not for home use.
When oxygen is scarce, cells can no longer sustain their normal energy production in the mitochondria. They switch to an emergency pathway that yields far less energy and produces large amounts of lactate (lactic acid). That lactate places a chemical tag on a key protein in the energy system, causing the mitochondria to deteriorate further. This creates a vicious cycle: less oxygen leads to more lactate, which in turn damages the cell's power plant even more.
In blood vessel walls, oxygen deprivation also causes structural damage to the inner membrane of the mitochondria. As a result, genetic material (mitochondrial DNA) leaks out of the mitochondria into the cell. The cell's immune system recognises this as an alarm signal and simultaneously activates multiple self-destruction programmes. The outcome is that cells die off through several pathways at the same time.
In the brain, things go wrong especially quickly. Nerve cells consume enormous amounts of energy to maintain the balance of ions inside and outside the cell. The moment that energy fails, the signalling substance glutamate accumulates and too much calcium flows into the cell. At high concentrations, that calcium is toxic to the cell and leads to cell death. Moreover, the damage can continue even after the oxygen supply has been restored. With prolonged deprivation, the brain's immune cells also become overactive, which damages the blood-brain barrier and may contribute to vascular dementia.
Another pathway of damage is called ferroptosis: a form of cell death in which toxic, oxidised fats accumulate in the cell membrane until it breaks down. This process is driven by a sensor the cell normally uses to detect oxygen deficiency. In pre-eclampsia, this plays a role in the placenta: the oxygen shortage causes cells to die through ferroptosis and to release toxic substances that damage the blood vessel wall of the mother.
Finally, there is a paradox in cancer: while oxygen deprivation kills healthy cells, cancer cells can activate multiple survival programmes that actually protect them. This makes tumours harder to treat. That is not a property of oxygen deprivation itself, but of the way cancer cells turn the emergency signals to their own advantage.
All claims are based on cell culture and animal models (rats, laboratory cells) with some mechanistic insights into human conditions such as pre-eclampsia. No large randomised human studies exist on the underlying mechanisms. The strength of evidence is moderate for most claims; one claim concerning nerve cells in a cell culture model is limited.