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Comment by StavrosK | Hacker News Reader

Why not just go out and walk more?

Which is a great idea for more than just the sun exposure, but unfortunately at Los Angeles's latitude, there isn't sufficient UVB to trigger vitamin D production in the skin from around the beginning of October through the beginning of March. During these months vitamin D supplementation is pretty much a necessity for anyone who's ordinarily vitamin D deficient.

The root cause here is probably high stress, to which walking more is probably going to be helpful, but for people under chronic stress (as I am from time to time) it can be hard to see how to make the time for that.

I used to walk when I lived in a different neighborhood of a southern city. We get lots of sun, but way more heat & pollution. My neighborhood's simply not great for walking.

You can do both! But if you supplement vitamin D you wouldn't need to worry about making it out for your walk every day. IANA nutritionist, but I also believe GP's prescribed dose would be unfeasible to get reliably from the sun, especially at northern latitudes.

Hmm, I see. I live in Greece, so I don't really have an intuition for how much sun one needs (we get eight months of sun or so). What you say makes sense, thank you.

The Norwegian Institute for Air Research has a fairly simple online calculator: https://fastrt.nilu.no/VitD-ez_quartMED.html

I can't personally vouch for its accuracy though.

Doesn't sun exposure cause skin ageing and increase your risk of skin cancer?

It does - so much so that fair skinned people are suggested to avoid sun exposure and get vitamin d from supplements.

Not unless you overdo it.

Agreed - I think this is another myth that has gone mainstream. The biggest issue from my reading is damage to the skin. If you are constantly getting burned you are increasing your risk. If you slowly increase your exposure and avoid burning you get the benefits of sun plus (almost) none of the drawbacks. I say almost b/c you cannot discount genetic predisposition. Also, time of day is critical too - with mid-day being the best time.

I'm not sure if there are studies that take this variable into consideration. The tin foil hatter in me tends to think the results are probably different than the current common belief. BUT we can't have sunscreen sales dropping to zero ;) BTW I'm also weary of the effects of sunscreen itself - does slathering chemicals on your skin to protect against sun contributing to cancer?

Th truth is there is probably a happy medium somewhere between the "sun is evil! It causes cancer!" and "don't worry worshipping the sun is OK". However we tend to knee jerk react in one direction or the other...

It's not always that simple - in Dunedin, NZ, burn time can be under ten minutes. It's quite similar in Australia, too.

Another consideration is the pollution you're breathing when walking or deeply breathing while running. Particulate matter, ozone, and carbon monoxide could very well cancel out the benefits of receiving that Vitamin D production you get in some months.

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