Age spots or dark patches in the skin known as hyperpigmentation are caused by an excess of melanin. What is melanin and what contributes to its production?
Humans have three main forms of melanin with many functions including pigmentation. Two pigmenting forms of melanin are produced by melanocytes in skin and hair follicles: eumelanin, a brown-black pigment; and pheomelanin, an orange-to-red pigment. Eumelanin especially protects the skin from ultraviolet (UV) radiations.
Melanocytes in the basal layer of the epidermis insert granules of melanin into their melanosomes, intracellular organelles. The melanosomes are then transferred to the keratinocyte cells – where the melanin-containing melanosomes accumulate to protect cell DNA from solar radiations. This protective melanin gives skin its colour.
The production of melanin called melanogenesis is a “chemical process where the oxidation of the amino acid tyrosine is followed by polymerization.” The primary stimulus for melanogenesis and subsequent melanosome production is UV radiation, which “upregulates melanocyte production of pro-opiomelanocortin (POMC) and its downstream products, alpha-melanocyte-stimulating hormone (alpha-MSH) and adrenocorticotropic hormone (ACTH). The overall effect is to increase eumelanin production.”
Significantly, melanin is an antioxidant. Antioxidants from all sources can help reduce the consequences of sun radiation exposures. Melanin interacts with free radicals and other reactive species readily due to the presence of unpaired electrons in its molecule. Research indicates that "Oxidative stress is implicated in the pathogenesis of hyperpigmentation..."
UV radiation, certain drugs and other toxic exposures contribute to oxidative stress. Improving antioxidant levels through diet and exercise are ways to help regulate melanin production and mitigate the risk of hyperpigmentation.