Who gets them? Why do people get them? Whats the relationship to vitamin D production?
Have always always had some freckles, mostly faint on the face. Historically have always burned slightly in early summer then gotten very dark. Now, since going paleo and taking more vitamin D, I get more freckles on my body. Now coming up with theories for why - such as skin isn't producing vitamin D on its own since taking the supplement so it is trying to make more, or such as my skin is protecting itself since i get plenty of D as a supplement. low carb 100% paleo for 1.5 years. There really isnt much literature out there on freckles and sun and vitamin D.
If I understand correctly, freckles are just the result of a uneven distribution of melanocytes, and it's genetic whether you have this distribution or not.
I'm not sure this makes sense, but maybe the progression with increasing sunlight exposure goes like this: first, the areas with more melanocytes produce melanin, making freckles. Then, since the freckled areas are now more protected from exposure, the in-between areas start to catch up, eventually producing an even tan. In some people, this never happens, the freckles just get more numerous and darker. Maybe this represents a more extreme unevenness in distribution, with some areas completely without melanocytes, like albino skin, that can't ever darken.
If this is how it works, then your speculation above that you have freckles now from lower than usual sun exposure would fit.
ETA: From Wikipedia:
Lentigines are distinguished from freckles (ephelis) based on the proliferation of melanocytes. Freckles have a relatively normal number of melanocytes but an increased amount of melanin. A lentigo has an increased number of melanocytes. Freckles will intensify and fade with sunlight exposure, whereas lentigines will stay stable in their color regardless of sunlight exposure.
So it's uneven production, not the cells themselves, except in the case of lentigines. HT gingernaut.
The darkest freckles on my body are located on spots that almost never see the sunlight - namely my shoulders - and it's been like that my entire life, regardless of sun exposure.
Freckles are determined by a mix of genetics and sun exposure, due to an uneven distribution of melanin (the skin pigment, not melanocytes, the cells that produce the pigment). It could simply be that going Paleo has made you hyper aware of changes. As in, you may just be overthinking the whole thing. Sometimes the simplest answer is the best one!
I'm thinking the main reason you're freckling on your body these days is because you're getting more sun exposure for some reason. It doesn't take much.
I don't think freckles have anything to do with vitamin D status. Certainly I've never heard of any evidence linking the two things.
It's almost entirely genetics and sun exposure. Mostly it's white/European people who freckle (duh). And more usually people with red, blond, or light brown hair and the corresponding very light skin.
I'm from a blondish, pale family. My one sister, father, and I have never freckled at all (we have light but yellowish skin and tan golden). My mother and other sister have pale rosy skin and freckle quite a bit (as well as burning easily). The more sun, the more freckles.
Vitamin D: friend or foe? 12 Answers
Redheaded toddler and vitamin D 6 Answers
Skin Cancer Danger 8 Answers