What is oxidative stress and how serious is it really?
Oxidative stress is a real biological process that causes damage to cells and contributes to ageing, but how large a role it plays in specific diseases varies by condition and is by no means always proven. Antioxidant supplements are not a clear answer: their effect in the body is far less certain than in the laboratory.
Every cell in your body continuously produces small, aggressive molecules as a by-product of energy generation. These are known as reactive oxygen species, also called free radicals. Under normal circumstances your body clears them up neatly. But when the build-up exceeds what your cells can handle, oxidative stress develops: the molecules damage fats, proteins, DNA and the cell's energy factories (the mitochondria). This mechanism is well established and is considered causal.
The DNA damage this causes has by now been documented in humans as well: more than twenty types of damaged DNA building blocks have been identified. Whether this always leads to disease is less certain. Findings sometimes contradict one another and the measurement methods have limitations. The role in specific conditions varies. For example, oxidative stress in the heart muscle probably contributes to cardiac damage from prolonged heavy alcohol use, more than 80 grams per day for five years or longer. And in people who simultaneously lose muscle mass and carry excess weight, oxidative stress is considered one of the central culprits. In Alzheimer's disease there is a clear association with damage to the mitochondria in brain cells, but whether oxidative stress is a cause or a consequence here has not yet been proven.
For the skin the link is most strongly demonstrated. UV radiation accelerates oxidative damage and thereby directly contributes to wrinkles, pigmentation spots and loss of elasticity. This is the best-documented external accelerator.
The obvious approach would be: eat more antioxidants or take supplements. That is partly correct, but less straightforward than it sounds. Under laboratory conditions antioxidants demonstrably inhibit oxidative damage. How well that also works in the actual human body is far less certain. Results are not consistent and measurement methods provide insufficient grip. This makes it difficult for now to say which dietary source or supplement makes the most difference.
Based on seven claims, covered by six PMIDs (32105850, 12832285, 38848133, 37380015, 40023293, 32180036, 40232392). For the underlying mechanism the evidence is strong and causal; for the specific disease links it is moderate and in part associative only. For antioxidants as protection the evidence is limited and inconsistent.