Researchers in Spain focused on cysteine, an amino acid naturally found in the body. While normal levels are safe, an accumulation of cysteine can cause inflammation and damage to tissues and organs, potentially leading to premature aging and an increased risk of cancer.
The team found that an orange-yellow pigment known as pheomelanin, which is found in people with red hair, may prevent the buildup of cysteine and protect vital organs such as the kidneys, eyes, muscles, liver, and brain.
To test this idea, the researchers conducted an experiment on zebra finches, whose feathers and beaks are bright orange. The birds were divided into three groups: the first group received L-cysteine in their drinking water, the second group received L-cysteine along with the drug ML349 to inhibit pheomelanin production, while the third group received no treatment (the control group).
The researchers collected feather tissue and blood samples at the beginning of the experiment and after 30 days, then analyzed them to see the effect of the treatments on cell health and feather color.
The results showed that male birds that did not produce pheomelanin experienced greater cell damage when fed excess cysteine compared to birds capable of producing the orange pigment. This protective effect was associated with pheomelanin-producing cells, not with eumelanin-producing cells. Females that do not produce this pigment showed no significant effects.
The study authors noted that these results represent the first experimental evidence of the role of pheomelanin in protecting the body from the toxicity of excess cysteine, which may help in a better understanding of the risks of developing melanoma and how animal colors evolved.
The researchers also pointed out that "pheomelanin" does not protect against ultraviolet radiation as "eumelanin" does, which makes people with red hair and fair skin more susceptible to skin cancer.
They believe that the genes responsible for producing the pigment help cells balance cysteine levels and prevent organ damage.
In short, it can be said that pheomelanin has an internal protective function against cysteine toxicity, but at the same time it represents an external risk factor when exposed to ultraviolet radiation.
Cysteine is found in many protein-rich foods and is also available as a dietary supplement in the form of N-acetylcysteine (NAC). For people who eat a balanced diet, it is unlikely that cysteine levels in the body will reach toxic levels from food alone, as the body has efficient mechanisms for metabolizing and utilizing it.
The study, published in PNAS Nexus, concludes that visual traits such as hair or feather color may reflect how the body deals with internal cellular stress, affecting organ health and the potential for cancer.
However, the researchers emphasize that the results were obtained from a study on birds, and further studies are needed to determine whether this protective mechanism also occurs in humans.
