Small Cellular Stressors May Trigger Protective Responses, but Human Evidence Remains Mixed

Small amounts of cellular stress may sometimes activate defenses that help cells cope with later challenges, according to a Medical Xpress report examining a phenomenon known as hormesis. The idea is being studied in nutrition and drug development, but evidence that particular food compounds produce these effects in people remains mixed.

Cells regularly encounter ultraviolet radiation, alcohol, pollutants and some medicine byproducts. These stressors can damage DNA, proteins and the fatty membranes surrounding cells. In response, cells use specialized systems that alter gene activity and help limit damage, remove harmful chemicals, recycle damaged proteins, repair DNA or slow cell division.

One important pathway involves NRF2, a protein that functions as a molecular switch for hundreds of protective genes. Under certain conditions, a limited challenge can stimulate these defenses and leave cells better prepared for another challenge. A stronger or prolonged exposure, however, can overwhelm those systems and cause lasting harm.

The report compares the process with exercise: temporary strain followed by recovery can produce adaptations that make muscles better able to handle later demands. It also describes a proposed role for plant compounds. When cruciferous vegetables such as broccoli are chopped or chewed, they produce sulforaphane, which has activated NRF2 in laboratory-grown cells and animals.

That laboratory evidence has not established the same effect from eating broccoli or taking sulforaphane in humans. A systematic review of 18 human studies found mixed results, and many of the studies had methodological limitations that could have affected their findings. Researchers are seeking blood-based biomarkers that would make cellular stress responses easier to measure in people.

The same biological defenses are also being investigated as targets for medicines. The report cites omaveloxolone, an NRF2-activating medicine that became the first medicine approved in the United Kingdom specifically for Friedreich’s ataxia in April 2025. In a 48-week clinical trial, participants receiving the medicine performed better on a physical-impairment assessment than those receiving a placebo.

The findings do not make all stress beneficial. Deliberate exposure to pollution or ultraviolet radiation is not supported as a health strategy, and the report says there is no established benefit for healthy people from supplements marketed as NRF2 activators. The response depends on the type, dose and duration of the stress, while excessive activation of cellular defenses may itself create risks. Hormesis therefore remains a framework for understanding some biological responses—not proof that more stress, or a specific supplement, improves health.