eli5: If more melanin is advantageous in warm climates, why is less of it advantageous in colder climates? Wouldn’t darker skin still be most advantageous in cold climates where it might occasionally be hot?
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Melanin protects against UV damage, but as a result it also decreases the amount of UV available for vitamin D production. Near the equator, that’s fine because there’s more than enough sun. Near the poles, having a lot of melanin increases risk of vitamin D deficiency.
Melanin protects against UV damage, but as a result it also decreases the amount of UV available for vitamin D production. Near the equator, that’s fine because there’s more than enough sun. Near the poles, having a lot of melanin increases risk of vitamin D deficiency.
It’s because their melanin acts like a shield against ultraviolet radiation but in cold climates it is too much of a shield for them to be able to get all the VIT D that they need!
“It would be harmful if melanin acted as a complete shield. A certain amount of shortwave ultraviolet radiation (UVB) must penetrate the outer skin layer in order for the body to produce vitamin D. Approximately 90% of this vitamin in people normally is synthesized in their skin and the kidneys from a cholesterol-like precursor chemical with the help of ultraviolet radiation. The remaining 10% comes from foods such as fatty fish and egg yolks. Simple vitamin D is converted by our bodies into two sequential forms. The last form, commonly referred to as vitamin D3, is needed for the intestines to absorb calcium and phosphorus from food for bone growth and repair. “
“In such an environment, very dark skin is a disadvantage because it can prevent people from producing enough vitamin D, potentially resulting in rickets disease in children and osteoporosis in adults. Contributing to the development of osteoporosis in older people is the fact that their skin generally loses some of its ability to produce vitamin D. Women who had prolonged vitamin D deficiencies as girls have a higher incidence of pelvic deformities that prevent normal delivery of babies.”
Source: https://www.palomar.edu/anthro/adapt/adapt_4.htm
Human skin produces vitamin D in response to sunlight. We need that. But Melanin also obstructs that sunlight, which is a natural defense against UV light.. sun burns, skin cancer, etc.
It’s not the colder temperature so much as it is the reduced sun exposure. To get more vitamin D, evolution took away some of the Melanin. We traded off some of the UV protection to get better vitamin D production.
So, if you’re not getting much sun exposure, consider taking a vitamin D supplement. (talk to your doctor, blah blah blah, not medical advice)
Melanin protects against UV damage, but as a result it also decreases the amount of UV available for vitamin D production. Near the equator, that’s fine because there’s more than enough sun. Near the poles, having a lot of melanin increases risk of vitamin D deficiency.
It’s because their melanin acts like a shield against ultraviolet radiation but in cold climates it is too much of a shield for them to be able to get all the VIT D that they need!
“It would be harmful if melanin acted as a complete shield. A certain amount of shortwave ultraviolet radiation (UVB) must penetrate the outer skin layer in order for the body to produce vitamin D. Approximately 90% of this vitamin in people normally is synthesized in their skin and the kidneys from a cholesterol-like precursor chemical with the help of ultraviolet radiation. The remaining 10% comes from foods such as fatty fish and egg yolks. Simple vitamin D is converted by our bodies into two sequential forms. The last form, commonly referred to as vitamin D3, is needed for the intestines to absorb calcium and phosphorus from food for bone growth and repair. “
“In such an environment, very dark skin is a disadvantage because it can prevent people from producing enough vitamin D, potentially resulting in rickets disease in children and osteoporosis in adults. Contributing to the development of osteoporosis in older people is the fact that their skin generally loses some of its ability to produce vitamin D. Women who had prolonged vitamin D deficiencies as girls have a higher incidence of pelvic deformities that prevent normal delivery of babies.”
Source: https://www.palomar.edu/anthro/adapt/adapt_4.htm
Human skin produces vitamin D in response to sunlight. We need that. But Melanin also obstructs that sunlight, which is a natural defense against UV light.. sun burns, skin cancer, etc.
It’s not the colder temperature so much as it is the reduced sun exposure. To get more vitamin D, evolution took away some of the Melanin. We traded off some of the UV protection to get better vitamin D production.
So, if you’re not getting much sun exposure, consider taking a vitamin D supplement. (talk to your doctor, blah blah blah, not medical advice)
It’s because their melanin acts like a shield against ultraviolet radiation but in cold climates it is too much of a shield for them to be able to get all the VIT D that they need!
“It would be harmful if melanin acted as a complete shield. A certain amount of shortwave ultraviolet radiation (UVB) must penetrate the outer skin layer in order for the body to produce vitamin D. Approximately 90% of this vitamin in people normally is synthesized in their skin and the kidneys from a cholesterol-like precursor chemical with the help of ultraviolet radiation. The remaining 10% comes from foods such as fatty fish and egg yolks. Simple vitamin D is converted by our bodies into two sequential forms. The last form, commonly referred to as vitamin D3, is needed for the intestines to absorb calcium and phosphorus from food for bone growth and repair. “
“In such an environment, very dark skin is a disadvantage because it can prevent people from producing enough vitamin D, potentially resulting in rickets disease in children and osteoporosis in adults. Contributing to the development of osteoporosis in older people is the fact that their skin generally loses some of its ability to produce vitamin D. Women who had prolonged vitamin D deficiencies as girls have a higher incidence of pelvic deformities that prevent normal delivery of babies.”
Source: https://www.palomar.edu/anthro/adapt/adapt_4.htm
Human skin produces vitamin D in response to sunlight. We need that. But Melanin also obstructs that sunlight, which is a natural defense against UV light.. sun burns, skin cancer, etc.
It’s not the colder temperature so much as it is the reduced sun exposure. To get more vitamin D, evolution took away some of the Melanin. We traded off some of the UV protection to get better vitamin D production.
So, if you’re not getting much sun exposure, consider taking a vitamin D supplement. (talk to your doctor, blah blah blah, not medical advice)
Melanin keeps UV light from penetrating your skin. You need a little UV light to make vitamin D, but too much and you’ll get sunburned.
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