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.
Caffeine has a direct influence on the repair of damaged DNA. In bacterial studies it blocks two different repair enzymes that clear up UV damage, doing so in two entirely different ways. In human cells, caffeine inhibits two guardian proteins (ATM and ATR) that normally apply the brakes on cell division as soon as DNA is damaged. Without that brake, cells continue to divide despite the damage. In cancer cells this makes them more sensitive to radiation and chemotherapy, with effects up to eighty times stronger in cell-culture models. Whether this is clinically relevant at normal levels of coffee consumption has not yet been established.
On the other hand, caffeine activates a cellular clean-up mechanism in skin cells: autophagy. In this process, damaged proteins and cell structures are broken down and recycled. In cell and animal research, a low dose of caffeine protects skin cells in this way against oxidative damage and UV radiation. Caffeine also triggers the same clean-up mechanism in gastric cancer cells, after which those cells grow less actively and more frequently undergo programmed cell death. In blood vessels it suppresses the excessive cell division that can cause re-blockage after balloon angioplasty. All of these findings come from cell and animal research, and it is too early to draw firm conclusions about humans.
A notable exception is the effect on red blood cells. A study involving more than 13,000 blood donors showed that higher caffeine levels in the blood are associated with more fragile red blood cells: they metabolise sugar less efficiently, accumulate more oxidative stress, and are more fragile during storage. People who received this blood had lower haemoglobin levels after transfusion than expected. Caffeine directly inhibits a protective enzyme (G6PD) in the red blood cell. This effect was also reproducible in animal research and in volunteers after a single cup of coffee, and was stronger in people carrying a particular genetic variant.
The findings on possible chromosomal damage are nuanced. Older cell-culture studies show that caffeine can cause chromosomal abnormalities in plant and mammalian cells in the laboratory, but this effect has not been demonstrated in living mammals, including humans. At present there is no evidence that caffeine is mutagenic in humans at normal intake levels.
This answer is based on reviews, large-scale donor research involving more than 13,000 blood donors, and multiple cell and animal studies. The donor study is the only component with a large human population and confirmation through volunteer experiments; the remaining findings come predominantly from laboratory and animal models, which limits their applicability to everyday coffee consumption. The chromosomal study originates from older research that has not been further indexed.
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.
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 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.
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 pathways increases the risk of cancer and age-related diseases.
What does alcohol do to your cells and DNA in the long term?
Chronic alcohol use damages your DNA, disrupts how genes are read, and increases the risk of several types of cancer. Drinking less or not at all is the only way to reduce this risk.
Can eating too little actually damage your cells?
Eating moderately less does not damage your cells - it actually protects them through a cellular clean-up mechanism. However, eating severely too little for a prolonged period can cause that same clean-up mechanism to overshoot and actually kill cells, so the line is drawn at extreme restriction.