Can DNA damage in your cells repair itself?
Your cells repair DNA damage continuously and systematically, but the system is not infallible: chronic overload or a defect in the repair routes increases the risk of cancer and age-related diseases.
Every cell in your body sustains tens of thousands of instances of DNA damage every single day. This is not the exception but the rule: both your own metabolism and external triggers such as sunlight, X-rays or chemicals constantly attack your DNA. Your cells repair that damage continuously, and they do so largely without you noticing.
For each type of damage there is a dedicated repair route. The most dangerous kind, a break in both strands of the DNA, is fixed via two different strategies: one that uses an identical copy as a template, and one that simply welds the loose ends back together. The second approach is faster but more prone to errors. Lighter damage, such as a faulty chemical change to a single letter in the DNA code, is handled by yet other repair routes. A protein that plays a central role in this recognises the damage and alerts the rest of the repair system.
How quickly this works in practice was shown by laboratory research with human white blood cells: DNA breaks caused by an excess of iron started to disappear within just one hour and were completely repaired after 24 hours. That is a controlled laboratory setting, not a living body, but it gives a concrete picture of the speed at which cells get to work.
This repair system is impressive, but not infallible. When it falls short, errors accumulate in the genetic material, which is a well-known cause of cancer and age-related diseases. Radiation used in cancer treatment deliberately exploits this: tumour cells that have already partly lost their repair system are unable to recover from additional damage at all and die off. The same principle applies to medicines that block a key protein in the repair process, an approach that is now used in clinical practice for certain types of cancer.
In short: your cells repair DNA damage at remarkable speed and in a highly organised way, but the system has its limits. Chronic exposure to large amounts of damage, or a genetic defect in the repair routes, can overwhelm a cell's ability to keep up.
This answer draws on several broad review studies in the field of DNA repair, supplemented by one laboratory study using human white blood cells. The review studies describe mechanisms that are strongly supported and widely accepted in science. The laboratory study involving iron overload is illustrative but limited to a controlled environment outside a living body. Evidence on the precise interaction between DNA repair and metabolism remains thin.
Can you repair DNA damage, or can you only prevent it?
Your body actively repairs DNA damage through multiple well-studied mechanisms, but that repair is not always perfect and becomes less effective when the cell is under excessive strain or grows older.
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.
Can you protect your DNA from damage through diet?
Diet can both protect and damage your DNA, but the protective effects of supplements often fall short in practice. Make sure you are not deficient in zinc, folate and selenium, eat plenty of vegetables and fruit, and avoid supplements containing high doses of beta-carotene, especially if you smoke.
Can you counteract DNA damage from ageing through your lifestyle?
Quitting smoking, exercising regularly and eating plenty of vegetables demonstrably reduce DNA damage; antioxidant supplements are unlikely to help with this.
Why don't damaged cells always clean themselves up?
Cells have three ways of cleaning themselves up. When all three falter, damaged cells accumulate, and that is linked to ageing and disease.
Can smoking permanently damage your DNA?
Smoking damages your DNA in multiple ways simultaneously, and some of that damage is permanent; quitting genuinely helps, but does not erase earlier mutations.