What are free radicals and what do they do to your cells?
Free radicals arise naturally when your cells produce energy and, in small amounts, do useful work. Only when they overwhelm your body's own defence systems do they damage DNA, proteins, and fats, contributing to ageing and disease.
During normal energy production in your cells, around 95% of oxygen is converted into water. The remaining 5% forms free radicals, also known as reactive oxygen species. They are therefore an unavoidable by-product of ordinary cell metabolism.
Free radicals are not purely harmful. At low concentrations they act as signalling molecules needed for cell growth and other vital processes. In muscles, for example, a certain amount is needed for normal strength development. Switch them off entirely and muscles actually perform worse.
The problems start when the production of free radicals exceeds the cell's own defences. This is called oxidative stress (too many free radicals in your cells). It is estimated that around 10,000 attacks on the DNA of every cell take place each day. In older brains, at least one in three proteins is estimated to be damaged and therefore no longer functioning properly. During intense exercise, the increased production in muscles leads to measurable damage to muscle cells.
The cell's energy generators, the mitochondria, are a major source of free radicals. In animals that age at different rates, the faster they produce free radicals, the more DNA damage accumulates and the shorter the maximum lifespan. Whether free radicals are the primary cause of ageing or are more of a response to damage that is already present has not yet been settled. More recent studies in worms and mice have added nuance to the classic view that they directly drive the ageing process.
Your body defends itself against free radicals through specialised enzymes. That enzyme-based system is by far the most important line of defence. Small antioxidant molecules from food or supplements, such as vitamin C or E, play only a supporting role in this. People who take expensive antioxidant supplements because of ageing are not building on the strongest part of the body's protection.
This answer draws on multiple combined studies by scientists in the fields of cell biology, ageing, and free radical damage. The basic facts about free radicals and cell damage are well supported and widely accepted. On the question of whether free radicals are the primary cause of ageing, views still differ: more recent animal studies have added nuance to the classic theory but have not yet replaced it. The precise role in specific diseases per organ has not yet been fully clarified.
How does air pollution damage your cells from the inside?
Air pollution damages your cells from the inside through oxidative stress: fine particulate matter causes an excess of harmful oxygen molecules that attack your DNA, energy factories, and immune system. Protection begins with limiting exposure, because the damage occurs at the cellular level.
Why do cells lose their ability to repair themselves?
Cells lose their capacity for self-repair through a combination of declining energy supplies, impaired DNA repair and the accumulation of 'burnt-out' cells that release harmful substances. These are well-supported mechanisms, although it is still too early to act on them through supplements or therapies.
What does caffeine do to your cells and their repair process?
Animal studies show that caffeine affects cells in different ways depending on the situation. Until comparable studies in people are available, it remains unclear what this means in practice for everyday use.
Why are cells damaged when you don't get enough oxygen?
Oxygen deprivation damages cells through a chain of mechanisms: energy deficit, overstimulation of nerve cells, and an assault by free radicals, partly triggered precisely when blood flow is restored. How severe the damage turns out to be depends on how long and how serious the deficit is.
What are senescent cells and why are they bad for you?
Senescent cells are damaged cells that stop dividing but continue to live and chronically inflame their surroundings. They accumulate as you age and are strongly linked to age-related diseases, but because they also play a protective role, simply clearing them all away is not an option.
What do zombie cells do to your ageing?
Zombie cells accumulate as you age and accelerate ageing through inflammatory signals; how to tackle them is promising but still very much under investigation.