What are free radicals and what do they do to your cells?
Free radicals are unavoidable by-products of your metabolism that are useful in small amounts but, in excess, damage DNA, proteins and cell membranes. Antioxidant supplements offer little practical benefit; the best protection lies in avoiding external sources such as smoking, fine particulate matter and excessive UV exposure.
Free radicals are small molecules with a single unpaired electron, which makes them extremely reactive. They arise as a normal by-product of your own metabolism: roughly 5% of the oxygen you breathe in is not fully broken down, forming these reactive particles in the process. There is no escaping them, because they are part of life.
In small amounts, free radicals are actually useful. They act as signalling molecules that drive cell division and regulate immune responses. The problem starts when they are present in excess: researchers then speak of oxidative stress. In that state they damage DNA (your genetic material), proteins (the workers inside the cell) and the fats in your cell membrane. That fat damage, called lipid peroxidation, produces toxic waste products that can switch genes off and trigger cell death.
Your body has its own defence systems to keep free radicals in check, consisting of specialised clean-up enzymes. Oxidative stress only occurs when that defence is overwhelmed by production. Additional free radicals from outside sources, through UV radiation, fine particulate matter or exhaust fumes, can further disrupt that balance, particularly in the skin.
Prolonged oxidative stress is associated with serious conditions such as diabetes, atherosclerosis, cancer and brain diseases like Alzheimer's and Parkinson's. Whether oxidative stress is the direct cause or more of a consequence is not always clear; for now this is an association, not a proven causal relationship. A more recent finding from laboratory and animal research is that damaged energy centres of cells can be transferred from one cell to another, where they accumulate additional free radicals in the receiving cell and may cause it to divide more rapidly.
Fighting free radicals with supplements turns out to be disappointing in practice. Antioxidants look promising in laboratory studies, but clinical trials in humans deliver disappointing results. More insight into when and where they intervene is needed before better applications become possible.
All claims come from reviews; no randomised trials or meta-analyses are included in the source set. The link between oxidative stress and chronic disease is based on associations, not demonstrated causality. The mitochondrial transfer to cancer cells comes from laboratory and animal research only.
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.
What does caffeine do to your cells and their repair processes?
Caffeine inhibits important DNA repair processes while simultaneously having protective effects in certain cell types, depending on context. The most concrete consequence for humans has now been demonstrated in blood transfusions: caffeine in donor blood measurably reduces the quality of stored red blood cells.
Why do cells lose their ability to repair themselves over time?
Cells lose their repair capacity through a combination of declining energy stores, impaired DNA repair and the accumulation of 'burned-out' cells that secrete inflammatory substances. These are well-supported mechanisms, although it is still too early to act on them through supplements or therapies.
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.