More light is not more benefit

It is natural to assume that if some red light is good, more must be better. The research says otherwise.

The biphasic dose response

Researchers at the Wellman Center for Photomedicine at Massachusetts General Hospital reviewed the evidence in 2009 and again in 2011, in the journal Dose-Response.

They described a pattern seen repeatedly: low levels of light often had a better effect on stimulating and repairing tissue than higher levels. Beyond a point, the benefit fell away.

This is often drawn as the Arndt-Schulz curve. It rises, peaks, then falls.

Why it might happen

In cell studies, markers of mitochondrial energy production, such as ATP and membrane potential, followed this rise-and-fall pattern. One explanation involves reactive oxygen species, signalling molecules that are useful in small amounts and harmful in large ones.

An honest caveat

Most of this dose-curve evidence comes from cells and animals. The exact best dose for a person, for any given goal, is not settled.

What it means in practice

• Bigger wattage and longer sessions are not automatically better.
• Consistency at a sensible dose matters more than intensity.
• Follow the device's guidance, and always use eye protection with high-power devices.

This is why the Norge Red Light Bed has a lower-power residential mode alongside its commercial setting. Home use is about a steady routine.

Free: The Norge Longevity Guide. Heat, cold and light after 50, with the evidence and the safety rules in one place. Get the guide.

Sources

1. Huang et al., Biphasic dose response in low level light therapy, Dose-Response, 2009
2. Huang et al., Biphasic dose response in low level light therapy: an update, 2011

This article is general information, not medical advice. If you have a heart condition, low blood pressure or are pregnant, speak with your GP before using heat or cold.