People with red hair may have a special pigment that helps filter toxic, disease-causing compounds out of their bodies, a study suggests.
Researchers in Spain have honed in on cysteine, an amino acid that, while harmless in normal levels, could inflame and damage the body’s tissues and organs when it accumulates, leading to premature aging and cancer.
However, they believe a yellow-orange pigment in red hair, called pheomelanin, may keep cysteine from building up in the body and damaging vital organs like the kidneys, eyes, muscles, liver and brain.
In a new study, the team, from Spain’s National Museum of Natural Sciences, tested their theory in zebra finches, whose feathers and beaks glow a vibrant orange.
In humans, pheomelanin is produced in the lips, genitals and nipples, but redheads have it in their hair and skin.
The study found that male finches that couldn’t make pheomelanin showed higher levels of damage in their cells when fed excess cysteine for a month than those that could produce the pigment.
The team noted that pheomelanin is not protective against the sun’s harmful UV rays like other types of melanin are, making redheads and people with fair skin more vulnerable to skin cancer.
But they believe that the genes responsible for producing it are likely helping cells balance levels of cysteine and prevent organ damage.
For individuals with genetic variants for red hair, the very pigment that creates their distinctive red or orange hues can help shield vital organs from serious damage (stock image)
Cysteine is found in many protein-rich foods, particularly animal proteins. It is also available as a dietary supplement, often as N-acetylcysteine or NAC, commonly taken for its antioxidant properties.
For the average person eating a balanced diet, it’s unlikely to consume dangerously high levels of cysteine through food alone. The body has efficient systems to metabolize and use it.
Researchers studied 65 zebra finches to understand how pheomelanin and cysteine affect feather color and the body’s internal balance.
Birds were divided into three groups: one group received a supplement called L-cysteine in their water, a second group received both L-cysteine and a drug called ML349 via injection to block the production of pheomelanin, and a third control group received no treatment.
They collected growing feather tissues and blood samples from the birds at the start and again after 30 days of treatment to measure changes.
Then, they analyzed the samples to see how the treatments affected the birds.
They measured stress in the birds’ blood cells, studied color-related genes in their feather follicles and used light reflection to precisely measure the color of their newly grown orange and black feathers.
Their statistical tests specifically compared the group that got both chemicals to the group that got only cysteine and also compared the cysteine-only group to the untreated control birds.
When male birds’ natural antioxidant levels were factored in, those receiving only cysteine showed less cell damage. But males also given ML349, a drug that blocks pheomelanin production, showed increased damage, indicating that producing pheomelanin may help protect the body
The researchers found that, in male birds, when they accounted for their natural antioxidant levels in pigment-producing cells, those that received cysteine alone showed reduced cell damage.
On the other hand, male birds that also received the drug ML349 showed an increase in cellular damage, suggesting that making pheomelanin may serve as a buffer against the potential negative effects of cysteine.
The protective effect was specifically linked to the cells that produce the orange pigment, not those that produce black pigment, eumelanin. There were no clear effects seen in female birds, who do not produce this specific orange pigment.
The study authors said: ‘These findings represent the first experimental demonstration of a physiological role for pheomelanin, namely avoiding the toxicity of excess cysteine, leading to a better understanding of melanoma risk and the evolution of animal coloration.’
The main takeaway of the study, published in the journal PNAS Nexus, is that something as visible as hair or feather color may be tied to how the body manages internal cellular stress that contributes to organ damage and cancer.
Pheomelanin has been linked to an increased risk of melanoma, the most dangerous form of skin cancer expected to strike 235,000 Americans and kill 8,500 in 2026.
Unlike its counterpart, eumelanin, which absorbs UV radiation, pheomelanin is less protective and paradoxically generates harmful reactive oxygen species that damage cells when exposed to UV light.
This, in addition to a lighter skin tone that offers less natural UV protection, is thought to create a prime environment in the skin for the development of cancer cells.
This can lead to greater DNA damage and a higher likelihood of the formation of cancerous moles, which helps explain the elevated melanoma susceptibility observed in individuals with red hair and fair skin.
While these results point to a novel biological mechanism, the research was conducted in birds and further studies are needed to determine if a similar protective process occurs in humans.
