Beautiful women don’t like strong sunlight because it darkens their skin. But melanin also has its own biological role. 1, For humans, melanin is undoubtedly the main barrier against UV damage to the skin. 2, At the same time, melanin synthesis can increase the heat load of people in hot climates, so that black people absorb 30% more heat from the sun than white people do. 3, and melanin synthesis can also prevent the synthesis of vitamin D in the skin, and vitamin D is a key substance to promote calcium absorption, so rickets is more common in malnourished black children. 4, in addition, melanin is also a stable free radical, can participate in some redox reactions in the body.