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Comment by amanaplanacanal | Hacker News Reader

Better just to get some sun. Your body will self regulate how much is produced in your skin from the ultraviolet that reaches it. Just don’t stay out so long you get burnt.

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Unless you live in a northern hemisphere and have darker skin.

Probably best to ask PCP after getting some blood work.

> Unless you live in a northern hemisphere and have darker skin.

Why is this a problem for darker skinned people living in northern hemisphere? Their bodies dont make enough vitamin D even after exposure to the sun?

Yes, people with darker skin is at higher risk of vitamin D deficiency in northern territories.

"Vitamin D synthesis is highly dependent on the concentration of melanin in the skin as melanin absorbs and scatters UVR-B, resulting in a less efficient conversion of 7-dehydrocholesterol to previtamin D3[3]. Therefore, dark-skinned individuals will experience slower vitamin D synthesis than light-skinned ones. "

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4067096/

Not really "northern hemisphere", but rather northern (and, at least in theory, southern) enough latitudes. The amount UV-B exposure needed for vitamin D synthesis depends on the season and the latitude, as well as probably cloud cover etc.

Anecdotal article I found about latitude vs. UV-B exposure: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5037520/

I live at ~60° of northern latitude, and AFAIK people around here commonly don't get enough UV-B exposure for sufficient vitamin D synthesis for half of the year or so, so you need to get it either from nutrition or supplements.

Darker complexion mean you need to stay out much longer to get the vitamin D you need. This is why humans lost their natural pigmentation when they migrated to Europe and Asia.

I went on vacation in Costa Rica, leaving my Vitamin D pills at home, thinking the same thing.

Not true! I had to shell out like $30 to buy imported Vitamin D tablets because I could feel the positive effects of my Vitamin D supplementation wearing off within 4 days.

And I had gotten enough sun to get a serious tan already.

People process sunlight and synthesize Vitamin D at different levels.

Could that be in your head? Vitamin D lasts a long time in the body, seems unlikely you'd be able to notice any difference after four days.

Does it have such a short run effect? My impression is sun/supplementation build up circulating blood levels, and then what’s in the blood is converted to an active substance the body can actually use.

For a week long vacation your body would just draw down those stores.

Sorry but there's no way your Vitamin D levels would wear off in 4 days.

Sunlight generation declines with age and skin color.

Often I pack a sandwich for lunch and bring it with me on a walk in the park; it's an easy way to get some sunlight without having to carve time out of your schedule (presuming most of your lunches aren't scheduled as work meetings...)

Even outside of the fact that this isn't an option for a huge portion of the population, for those that it is possible for, is it better? Aren't there all sorts of harmful associations with sunlight exposure?

I can't find it, but I remember reading a study posted here that said the downsides from sun exposure are outweighed by the upsides of getting enough vitamin D. The reasoning was that the issues caused by vitamin D deficiency aren't visible, while skin cancer from too much sunlight is easy to detect at home, and is rarely fatal if you catch it early.

In the US the five year survival rate of melanoma, the most dangerous sort of skin cancer, is something like 99%. In 2015 only 60k people died from it globally; compare that to the billions of people who got more sunlight than the average software engineer practicing sunlight avoidance and I think it's clear there are better things to worry about (for instance, the misery of spending your life in the dark popping pills instead of getting some fresh air for an hour or so a day.)

Not an option for everyone. Some people ate sensitive to the sun due to medical conditions and/ or medications. Some people work night shift.

If you have darker skin or you’re in a high latitude (or winter) things get trickier.

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