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The mystery of melanin's role in human physiology, and its potential to confer profound health protective and promoting properties, is explained in the excerpt below from Chapter 3 of Sayer Ji's book REGENERATE: Unlocking Your Body's Radical Resilience Through The New Biology.
Melanin, Radiation, and the Conversion of Light to Metabolic Energy
Melanin, the central pigment within our skin, and distributed throughout our bodies, is one of the most interesting biomolecules identified thus far. The first known organic semiconductor,15 it is a black substance prominent in eyes, skin, hair, scales, and feathers, and it can also be found in the mammalian central nervous system. From the ink of the octopus to the protective colorings of bacteria and fungi, melanin offers protection against a variety of biochemical and predatory threats and chemical stressors, and, most famously, acts as a photoprotective factor against ultraviolet radiation. It absorbs all visible wavelengths of the electromagnetic spectrum, hence its dark coloration, and, most notably, converts and dissipates potentially harmful ultraviolet radiation into heat. It serves a wide range of additional physiological roles, including free radical scavenging, charge transfer, toxicant chelation, endocrine functions,16 and gene protection. Melanin's proposed ability to convert sunlight into metabolic energy--akin to the way chlorophyll harvests sunlight in plants--means that our species should be reclassified from heterotrophic to photoheterotrophic, and, even more significantly, may raise the prospect that melanin offers protection against ionizing radiation while transforming it into metabolically useful energy.
As the molecule that is crucial in determining skin color, melanin has fundamentally shaped the way we humans perceive ethnic and racial differences and tribal affiliation. Given its function as an evolutionarily encoded heuristic that has allowed the human brain to rapidly identify in-group versus out-group dynamics, it has played a role in genocide, slavery, and the rise and fall of civilizations, all of which have been at least partly due to misperceptions about what it means to have more or less melanin in the skin.
The variation in human skin from dark, melanin-saturated African skin to light, relatively melanin-depigmented Caucasian skin may merely be a direct by-product of our last common ancestor from Africa migrating toward sunlight-impoverished higher latitudes 60,000 years ago. In order to compensate for the decreased availability of sunlight, the human body rapidly adjusted, potentially removing the natural "sunscreen," melanin, from the skin since it interferes with the production of vitamin D, a hormone that participates in governing the expression of more than 2,000 genes. Without adequate vitamin D, our genome would completely destabilize, and immune balance would become disturbed, so the reduction of melanin to augment vitamin D status likely saved the lives of humans who migrated to cooler climates. But this evolutionary adjustment may have come at a significant cost. Humans with lighter skin tones may have gained vitamin D accessibility at the expense of the ability to convert sunlight into metabolic energy.
The resolution to this energy paradox might be found in the discovery that melanin has the intrinsic ability to transform light energy into chemical energy through the hydrolysis of the water molecule, a function formerly consigned to the domain of the plant kingdom. The chemical energy liberated via the dissociation and subsequent charge separation of the water molecule by melanin, in fact, has been estimated to meet over 90 percent of cellular energy needs.17
Research on the melanin-rich intraocular organ pecten in birds explains many phenomena that have eluded scientific explanation, including avian metabolism, bioenergetics, and flight mechanics, and gives us clues about our own bodies' ability to use melanin for the purposes of energy. The albatross, for instance, is capable of traveling 10,000 miles in a single flight, a bioenergetic feat that has long baffled the scientific community. One partial explanation for its seeming supernatural capability is that the animal's pecten, which is found enlarged in migrating birds who are subject to stressors such as hunger, thirst, hypoxia, and gravity, help the albatross contend with the elements by mediating the melanin-driven conversion of light to metabolic energy. This is one example among several that challenge the widely held assumption that animals are incapable of directly utilizing light energy.18
Hairlessness, Sunlight, and Paleo - Deficit Disorder
Melanin may also explain another curious fact: that humans are the only species among hundreds of different primates who are almost completely hairless, which is why we are known in biology as the "naked ape." Approximately 6 million years ago, the mutation for human hairlessness was introduced into the genome, causing us to diverge from hairy chimpanzee lineages. The evolutionary reason, however, is hard to pin down. Being hairless left us vulnerable to fluctuations in weather since, in comparison to other primates, we must expend significant extra energy to produce body heat to stay warm. We are also more exposed to ultraviolet light, which degrades folate in the human body, leaving fetuses more likely to develop neural tube defects. What advantages, then, could hairlessness impart?
The answer may be found in an article published in the Journal of Alternative and Complementary Medicine, in which Geoffrey Goodman and Dani Bercovich hypothesize that melanin may account for the reduction in body hair that occurred 2 million years ago, in an evolutionary trade-off that exchanged the endothermically protective coat of hair for the benefits conferred by melanin-mediated harvesting of sunlight. Human hairlessness occurred concurrently with an augmentation in the melanin content of the skin, paving the way for a process called photomelanometabolism.19 In what is known as "ultrafast internal conversion," melanin can convert 99.9 percent of potentially gene-damaging ultraviolet light into harmless heat, fulfilling both sun blocking and energy-generating functions.20
As explained in a paper published in Medical Hypotheses by retired medical practitioner Iain Mathewson, new research on low-level light therapy, also known as photobiomodulation, may explain the immediate benefit conferred by hairlessness, as it shows that exposure to the red and near-infrared radiation found at sunset increases mitochondrial respiratory chain activity and results in extra synthesis of ATP in all superficial tissue sites, including those of the brain.21 Under Mathewson's hypothesis, a random mutation for hairlessness occurring in one of our African forebearers millions of years ago would have conferred an immediate survival advantage over her hairy relatives by enabling her body, especially her brain, to access the red and near-infrared wavelengths generated by ancient sunsets.
The rapid expansion of our species's brain volume, known as encephalization, occurred at the same time as the adaptive event of human hair loss, around 2 million years ago. Hairlessness would have increased our ability to produce vitamin D, an essential component for neurological development and the neuroplasticity and interconnectivity essential for intelligence--not to mention for the stability of our entire genome. This could have further increased brain development in the sheer size and complexity of neural circuits. Most significant, however, is the resulting necessity for the increased production of melanin, first as a sun protectant but secondarily as a means to endow humans with the ability to harness electromagnetic radiation for metabolic energy in a fashion similar to chlorophyll.
The ability to use melanin to absorb electromagnetic radiation and utilize its energy to dissociate the water molecules in our bodies (producing what Gerald Pollack says "amounts to a light-energy driven proton pump")22 may have reduced the energy expenditure required for hunting and foraging food. In other words, the energy freed up by using melanin in this novel way may have enabled the expansion of energetically intensive brain tissues such as the cerebral cortex, which is responsible for the higher thought processes of speech, information processing, impulse control, and decision making.23
The development of these higher cognitive processes allowed for the materialization of sophisticated technologies, the agrarian revolution, hierarchical social structure, and advanced human civilizations. This turning point--first the hairlessness, then the expansion of the brain--may be directly traced back to melanin, exemplifying how paramount it is to our species' resilience and survival.
Melanin and the Holy Grail of Radioprotective Foods
Not only can melanin convert light into heat, but new research raises the possibility that it can also transform other forms of radiation into metabolically useful forms of energy. Hints at this phenomenon arose when scientists noticed that a group of fungi had colonized within the walls of the still-hot site of the Chernobyl nuclear meltdown.24 Fungi were also found at a nuclear test site in Nevada in the 1960s, where they had survived radiation doses of up 6,400 grays, around 2,000 times the dose that is lethal for humans,25 suggesting that certain kinds fungi are not deterred by radiation but, on the contrary, seem to thrive on it. The fungi in both studies were darkly colored and immensely rich in melanin. 
Taken alongside evidence that bacteria that produce pyomelanin, a cousin to melanin, thrive in soil contaminated with uranium,26 and the findings that exposure to ionizing radiation actually promotes the growth of certain melanized fungal species inhabiting nuclear reactors, space stations, and the Antarctic mountains, it seems plausible that melanin allows certain organisms to "eat" radiation.27 A study published in PLOS ONE revealed that melanin-containing fungal cells saw increased growth relative to nonmelanized cells after exposure to ionizing radiation and that the irradiated melanin from these fungi also changed its electronic properties, which the study noted raised "intriguing questions about a potential role for melanin in energy capture and utilization."28
Collectively, this research suggests that, more than surviving radiation exposure that is normally lethal to most forms of life, fungi may be using melanin to feast on the free lunch of anthropogenic radioactivity. Therefore it is logical to ask whether the consumption of melanin from fungi might protect those higher on the food chain--like humans--from radiation exposure.
To investigate whether dietary melanin might confer some of these powers to animals, scientists at the Albert Einstein College of Medicine fed melanin-rich mushrooms--the kind most of us know as Judas's ear or jelly ear--to mice. A second group of mice was fed white, melanin-poor porcini mushrooms, a third group ate white porcini mushrooms that were supplemented with melanin, and a final control group received no mushrooms or melanin at all. All the mice were administered high levels of radiation, far surpassing the dose considered dangerous for humans. After 13 days, all the mice in the control group had died, and the mice that ate the nonmelaninized porcini mushrooms died almost as fast as the controls. Impressively, however, 90 percent of the mice that had been given melanin-rich mushrooms or white mushrooms supplemented with melanin survived.29
In another provocative study published in the journal Toxicology and Applied Pharmacology, researchers extracted melanin from the fungus Gliocephalotrichum simplex and gave it to mice just before exposing them to gamma radiation, increasing their 30-day survival by 100 percent. The probable mechanism of action was suggested by a study published in Bioelectrochemistry,30 in which ionizing radiation was found to alter melanin's oxidation-reduction potential. Whereas most other biomolecules experience a destructive form of oxidative damage as a result of radiation exposure, melanin remained structurally and functionally intact, appearing capable of producing a continuous electric current that could theoretically be used to produce metabolic energy in living systems. This would explain the increased growth rate, even under low nutrient conditions, in certain kinds of gamma-irradiated fungi.
In an eye-opening statement, researchers noted that these effects need to be studied in humans but that in nuclear emergencies, "diets rich in melanin may be beneficial to overcome radiation toxicity in humans."31
Learn more by reading the entire Chapter 3, The New Biophysics of Energy Synthesis: How the Body Harvests Nature’s Alternative Energy Sources to Power Cellular Pathways, Build Resilience, and Promote Our Evolutionary Edge.
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References
15. Albertus B. Mostert et al., "Role of Semiconductivity and Ion Transport in the Electrical Conduction of Melanin," Proceedings of the National Academy of Sciences 109, no. 23 (2012): 8943-47, https://doi.org/10.1073/pnas.1119948109.
16. Motohiro Takeda et al., "Biophoton Detection as a Novel Technique for Cancer Imaging," Cancer Science 95, no. 8 (August 2004): 656- https://doi.org/10.1111/j.1349-7006.2004.tb03325.x.
17. Arturo S. Herrera et al., "Beyond Mitochondria, What Would Be the Energy Source of the Cell?," Central Nervous System Agents in Medicinal Chemistry 15, no. 1 (2015): 32-41, https://doi.org/10.2174/1871524915666150203093656.
18. Geoffrey Goodman and Dani Bercovich, "Melanin Directly Converts Light for Vertebrate Metabolic Use: Heuristic Thoughts on Birds, Icarus and Dark Human Skin," Medical Hypotheses 71, no. 2 (August 2008): 190-202, https://doi.org/10.1016/j.mehy.2008.03.038.
19. Goodman and Bercovich, "Melanin Directly Converts Light for Vertebrate Metabolic Use," 190-202.
20. Sheng Meng and Efthimios Kaxiras. "Mechanisms for Ultrafast Nonradiative Relaxation in Electronically Excited Eumelanin Constituents," Biophysics Journal 95, no. 9 (2008): 4396-402, https://doi.org/10.1529/biophysj.108.135756.
21. Iain Mathewson, "Did Human Hairlessness Allow Natural Photobiomodulation 2 Million Years Ago and Enable Photobiomodulation Therapy Today? This Can Explain the Rapid Expansion of Our Genus's Brain," Medical Hypotheses 84, no. 5 (May 2015): 421-28, https://doi.org/10.1016/j.mehy.2015.01.032.
22. Gerald H. Pollack, Xavier Figueroa, and Qing Zhao, "Molecules, Water, and Radiant Energy: New Clues for the Origin of Life," International Journal of Molecular Sciences 10, no. 4 (April 2009): 2009 Apr; 10(4): 1419-1429, https://doi.org/10.3390/ijms10041419.
23. Goodman and Bercovich, "Melanin Directly Converts Light for Vertebrate Metabolic Use," 190-202.
24. V. Vember and N. Zhdanova, "Peculiarities of Linear Growth of the Melanin-Containing Fungi Cladosporium sphaerospermum Penz. and Alternaria alternata (Fr.) Keissler" [in Russian], Mikrobiolohichnyĭ Zhurnal 63, no. 3 (May-June 2001): 3-12.
25. Lora Mangum Shields, L. W. Durrell, and Arnold H. Sparrow, "Preliminary Observations on Radiosensitivity of Algae and Fungi from Soils of the Nevada Test Site," Ecology 42, no. 2 (April 1961): 440-41, https://doi.org/10.2307/1932103.
26. Charles E. Turick et al., "In Situ Uranium Stabilization by Microbial Metabolites," Journal of Environmental Radioactivity 99, no. 6 (June 2008): 890-99, https://doi.org/10.1016/j.jenvrad.2007.11.020.
27. Ekaterina Dadachova and Arturo Casadevall, "Ionizing Radiation: How Fungi Cope, Adapt, and Exploit with the Help of Melanin," Current Opinion in Microbiology 11, no. 6 (December 2008): 525-31, https://doi.org/10.1016/ j.mib.2008.09.013.
28. Ekaterina Dadachova et al., "Ionizing Radiation Changes the Electronic Properties of Melanin and Enhances the Growth of Melanized Fungi," PLoS ONE 2, no. 5 (2007): e457, https://doi.org/10.1371/journal.pone.0000457.
29. Ekaterina Revskaya et al., "Compton Scattering by Internal Shields Based on Melanin-Containing Mushrooms Provides Protection of Gastrointestinal Tract from Ionizing Radiation," Cancer Biotherapy and Radiopharmaceuticals 27, no. 9 (November 2012): 570-76, https://doi.org/10.1089/cbr.2012.1318.
30. Charles E. Turick et al., "Gamma Radiation Interacts with Melanin to Alter Its Oxidation-Reduction Potential and Results in Electric Current Production," Bioelectrochemistry 82, no. 1 (August 2011): 69-73, https://doi.org/10.1016/j.bioelechem.2011.04.009.
31. A. Kunwar et al., "Melanin, a Promising Radioprotector: Mechanisms of Actions in a Mice Model," Toxicology and Applied Pharmacology 264, no. 2 (2012): 202-11, https://doi.org/10.1016/j.taap.2012.08.002.
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