The pigment responsible for red hair, freckles, and sun-sensitive skin may have an unexpected superpower: neutralizing a toxic buildup within cells. New research suggests that pheomelanin, the orange-to-red pigment found in hair and feathers, can convert excess cysteine – an amino acid that becomes harmful in high concentrations – into a harmless, and even beneficial, substance.
The Cysteine Problem
Cysteine is essential for life, but when it accumulates beyond safe levels, it causes oxidative damage – a key factor in aging and disease. This damage happens because cysteine can react with oxygen to form unstable molecules that attack cells. The body must carefully balance cysteine levels, and pheomelanin production appears to be one way nature does this.
How Pheomelanin Helps
Scientists studied zebra finches to understand how pheomelanin works. Male finches that couldn’t produce the pigment showed significantly more oxidative damage when given a high-cysteine diet compared to those able to make it. This suggests pheomelanin acts as a kind of “sink,” absorbing excess cysteine and turning it into pigment.
Notably, female finches don’t naturally produce much pheomelanin, and weren’t significantly affected by blocked production. This reinforces the idea that the benefit is tied to the pigment itself.
Humans and Pheomelanin
Humans with red hair carry genetic variations that increase pheomelanin production. The pigment is concentrated in areas like lips, nipples, and genitals, but also in hair and skin. While higher pheomelanin levels are linked to increased melanoma risk, this new research suggests the genetic drive to produce it may have evolved to protect cells from cysteine toxicity.
“These findings demonstrate that pheomelanin has a physiological role: avoiding the toxicity of excess cysteine,” explain the study authors.
Why This Matters
This isn’t just about redheads. The mechanism by which pheomelanin neutralizes cysteine could apply to other organisms, helping us understand how animals evolved coloration while managing internal toxicity. It also raises questions about why some people accumulate cysteine more easily than others, potentially linking diet, environment, and genetic predisposition to cellular health. The findings may eventually inform strategies for preventing oxidative damage in anyone, not just those with fair skin and fiery locks.
