What is oxidative stress and how serious is it really?

Oxidative stress is a condition in which cells contain too many so-called 'reactive oxygen species' (ROS). ROS are chemically unstable molecules that arise as a by-product of normal metabolism, but are also generated by external factors such as UV radiation and alcohol. When cells cannot neutralise these substances quickly enough, they damage fats, proteins, DNA and the small organelles inside the cell. This can ultimately lead to premature cell ageing, also known as cellular senescence (PMID 32105850).

In the skin, the link with ageing has been studied most directly. Both the normal, internally driven ageing process and UV radiation from outside cause oxidative stress, contributing to wrinkles, loss of elasticity and pigmentation spots. UV is explicitly described as an accelerating factor on top of the normal ageing process. The process is, however, complex and not yet fully understood; it always involves an interplay of multiple mechanisms (PMID 32105850).

Oxidative stress also plays a role in diseases beyond the skin. In people with obesity, it can contribute to muscle loss, together with fat infiltration in the muscles and poorly functioning mitochondria (the powerhouses of cells). In Alzheimer's disease it is increasingly regarded as a central factor alongside the well-known protein accumulations in the brain. And in cases of prolonged heavy alcohol use (generally more than 80 grams per day for at least five years), oxidative stress damages heart muscle tissue, which can lead to an enlarged, poorly pumping heart. In all of these cases, oxidative stress is one of several interacting causes, not the only one (PMID 37380015, 40023293, 38848133).

In older adults, oxidative stress is also associated with frailty, a condition in which people are more vulnerable to illness and falls. The evidence here is weakest, however: the relationship is for now associative (a link exists, but no proven causal relationship), and there is as yet no reliable blood test or biomarker to measure or monitor oxidative stress in a clinically meaningful way (PMID 38631189).

Then comes the logical follow-up question: do antioxidants help? Antioxidants, both from food and from supplements, can neutralise ROS in the laboratory. However, the measurement methods used for this vary widely and are difficult to compare. The available reviews make no statement about whether this also leads to less disease or a longer lifespan in the human body. The step from 'works in a test tube' to 'protects a human being' is therefore far from proven (PMID 40232392, 32180036).