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The survey in the article that assessed vitamin D deficiency was a bit odd: >Because physical exams are performed in mobile vans in NHANES, data could not be c
by Aerroon 4mo ago
The survey in the article that assessed vitamin D deficiency was a bit odd:
>Because physical exams are performed in mobile vans in NHANES, data could not be collected in northern latitudes during the winter; instead data were collected in northern latitudes during summer and in southern latitudes in winter. To address this season-latitude aspect of the NHANES design, we stratified the sample into two seasonal subpopulations (winter/lower latitude and summer/higher latitude) before examining vitamin D status.
Yeah, I'm not surprised that the rates for vitamin D deficiency were low.
>Less than 1% of the winter/lower latitude subpopulation had vitamin D deficiency (25-OHD <17.5 nmol/L). However, the prevalence of vitamin D insufficiency in this group ranged from 1%–5% with 25-OHD <25 nmol/L /.../, even though the median latitude for this subsample (32°N) was considerably lower than the latitude at which vitamin D is not synthesized during winter months (∽42°N).
and the more northern latitude in summer:
>With the exception of elderly women, prevalence rates of vitamin D insufficiency were lower in the summer/higher latitude subpopulation (<1%–3% with 25-OHD <25 nmol/L)
Now imagine if you lived in northern Europe around the 60th parallel, where the sun doesn't get high enough in winter to produce vitamin D.
- qurren 4mo agoNot to mention, northern latitudes get more sun that average in summer, and most northern countries have more reasonable working hours so people actually do go outside.
- HPsquared 4mo agoMore hours of sun, but it's less intense.
- codethief 4mo agoThe sun in northern countries in summer is less intense?
- pdonis 4mo agoYes, because it's lower in the sky so more of the UV in it gets absorbed by the atmosphere before reaching the ground. For example, in Florida in the summer, the sun is close to directly overhead at noon. In Scandinavia in the summer, the sun is only about halfway up the sky from the horizon at noon.
- NoPicklez 4mo agoCome to Australia during the summer and watch how quickly you burn outside without sunscreen.
- tremon 4mo agoYes, it's crazy to consider how far north Earth's entire land mass is skewed. Australia is basically the southernmost landmass (apart from Tierra del fuego), yet it is located squarely under the Tropic of Capricorn; at the same distance north of the equator (Tropic of Cancer), you've merely reached Mexico, the Sahara desert, and the Himalayas.
- pocksuppet 3mo agoMost of Europe is at the latitudes of Canada. The whole UK is squarely north of Vancouver. https://vividmaps.com/comparing-latitude-of-europe-and-america/ https://vividmaps.com/comparing-latitude-of-europe-and-ameri...
- pseudohadamard 4mo agoFor non-Australians, that's burn as in "burst into flames", not "your skin goes red". Go to somewhere like Cairns and you can hear people crackling as they walk down the street.
- NoPicklez 4mo agoSmells like pork everywhere
- SJC_Hacker 4mo ago
- calgoo 4mo agoSure but i hide a lot more from the intense sun in spain then i do for the softer sun in sweden. In general i think it balances out quite well.
- fluoridation 4mo agoDoes vitamin D synthesis require direct sunlight, or does it work with scattered light as well?
- lukan 4mo agoNot really, it requires direct sunlight above 45 degree, so northern sweden for example gets plenty of sun in summer, but only for a very short time intense enough sun.
- bryanrasmussen 4mo agoIs it really less intense? When I go out on a sunny day in Denmark it is murder. When I go out on a sunny day in Italy it's generally just overall warm. At any rate another factor is that in the Northern regions it's my experience people do their best to soak up as much sun as possible.
- HPsquared 4mo agoThe sun is at a lower angle from the horizon at higher latitudes. It passes through more atmosphere, losing some UV, and also the surface irradiance on the ground (energy per unit land area) is lower.
- flossly 4mo agoThis. What I've learned for VitD conversion in the skin the sun needs to be more than 45° "high". Below that it's not much effective. Those long summer evenings in northern Europe are thus not all that useful for VitD.
- da_chicken 4mo agoI could believe that if you were near the coast. I grew up in central Michigan and thought the same about the sun until I spent a few years in southern Arizona. The sun there feels like a heat lamp in summer. The low humidity makes the atmosphere absorb less energy. Although it feels like it's about 5 C cooler than it actually is because sweat evaporates so quickly, but once it gets to 43 C you actually just feel vaguely ill just going outside. Standing in the sun is just not something you do. It's a very unique experience to lick your lips and have your tongue feel cold. Of course, neither of those were as bad as Houston in August. It was 38 C and 98 % relative humidity. And, I will point out, it had not rained. That's just what it's like. You walk outside and your glasses instantly fog up and you feel like you desperately need to shower.
- chasd00 4mo agoI live in Dallas and remember going hiking in Arizona and then getting in the car and the windows fogged up from sweat evaporating. Someone from a humid summer climate being outdoors in a dry summer climate has to really watch their water intake. It doesn't feel as hot because it's sucking all the moisture out of you and by the time you realize what's happening you're already not feeling so great. If you're 5 miles from water you're in a bad spot.
- galleywest200 4mo agoCould this be why evidence suggests that redheads synthesize Vitamin D more efficiently? Red hair is more prevalent at higher latitudes (I think). Can redheads produce Vitamin D in these darker conditions while others cannot do so effectively? https://www.sciencealert.com/evolution-favored-genes-linked-to-red-hair-and-vitamin-d-may-be-why https://www.sciencealert.com/evolution-favored-genes-linked-...
- annzabelle 4mo agoPale skin in general helps synthesize Vitamin D. The less melanin you have the more you absorb, this is why lighter skin happens at northern latitudes. Darker skinned people are more likely to need to supplement it.
- galleywest200 4mo agoMakes sense, thanks for the reply and clarification!
- bakul 4mo agoDarker skinned people in northern latitudes. Made worse for vegetarians like Ramanujan in England.
- chrisweekly 4mo ago"vegetarians" relevance?
- bostik 4mo ago> Now imagine if you lived in northern Europe around the 60th parallel, where the sun doesn't get high enough in winter to produce vitamin D. Like... all of Finland? And most of Norway? Both countries where the answer to "when does the sun rise?" can be "at the end of January".
- b112 4mo agoThis is why you're supposed to fatten up in the summer. In nature, mammals fatten up all summer long, and fat soluable vitamins such as D, are stored in your fat. As animals basically slowly starve over the winter, they consume their fat and also get some vitamin D back. It helps shore up the lack of sun in the winter.
- normie3000 4mo ago> data were collected in northern latitudes during summer and in southern latitudes in winter And what were they doing for the other 9 months of the year?