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Except during the summer months, the skin makes little if any vitamin D from the sun at latitudes above 37 degrees north (in the United States, the shaded regio
by exhilaration 9y ago
Except during the summer months, the skin makes little if any vitamin D from the sun at latitudes above 37 degrees north (in the United States, the shaded region in the map) or below 37 degrees south of the equator. People who live in these areas are at relatively greater risk for vitamin D deficiency.
Check out the map: https://www.health.harvard.edu/staying-healthy/time-for-more-vitamin-d https://www.health.harvard.edu/staying-healthy/time-for-more...
- pcarolan 9y agoThat's me. Any idea how well supplements are absorbed? Which are better or worse?
- exhilaration 9y agoGet a blood test first so you know your Vitamin D level (they're cheap: https://news.ycombinator.com/item?id=15869485 https://news.ycombinator.com/item?id=15869485), maybe you already get enough from your diet. If you do need supplementation, then Vitamin D3 (specifically Cholecalciferol) is vastly better absorbed than Vitamin D2. If you want a specific recommendation, buy this: https://www.amazon.com/gp/product/B07234TTCC https://www.amazon.com/gp/product/B07234TTCC and take it twice per week (Sunday & Thursday for example), that'll average to about 1400 IU per day.
- triangleman 9y agoAccording to the article, it is safe and recommended to take one of those 5000 IU capsules per day.
- WillPostForFood 9y agoI see 8000 IU for adults: This could lead to a recommendation of 1000 IU for children <1 year on enriched formula and 1500 IU for breastfed children older than 6 months, 3000 IU for children >1 year of age, and around 8000 IU for young adults and thereafter.
- seanmcdirmid 9y agoSupposedly this is why Northern Europeans evolved lactose tolerance. Asians got the D they needed from the sun and leafy veggies.
- hyperpape 9y agoLactose tolerance evolved in several different populations independently (including African populations), so I think Vitamin D can only be part of the story. Lactose tolerance gives you access to nutrients from milk, which has a huge impact.
- 52-6F-62 9y agoI don't know any of the history, but I would wager high protein content as that's also the huge benefit meat-eating brought humans.
- Tharkun 9y agoSeems odd, considering cow milk contains virtually no vitamin D. It is often enriched with vitamin D, but that practice likely does not predate the evolution of lactose tolerance.
- StevePerkins 9y agoWhen it comes to nutrition, the majority of unsourced information on web forums is made-up nonsense. Perhaps not maliciously in bad-faith (i.e. maybe OP really has heard this before)... but usually someone repeating something they heard 3rd or 4th-hand without any real fact-checking. Milk is high in vitamin D because it's intentionally added. Like iodine in table salt, or fluoride in drinking water. Obviously these things had no role in human evolution before they started in the 20th century.
- jessaustin 9y agoVitamin D is only absorbed in the presence of fat in the intestine. Milk is a source of fat. Of course it isn't the only source of fat, but the hypothesized explanation is more plausible than you might think. I have observed 'seanmcdirmid to be a thoughtful commentator. It would be uncharitable to suggest that he thinks that USDA has regulated milk drinking for millennia. Most "1st-hand" nutritional research is also wrong. That has been the case for decades, which explains the field's relative lack of progress. The reason is that most nutritional research is funded by large commercial food interests.
- chadgeidel 9y agoThat line was a lot lower than I imagined! Surprised that Denver is “too far north”.
- jessaustin 9y agoIt is silly to go through the trouble of including a map, only to reinforce the imprecision of the parallel approximation. Obviously People in Denver get more sunlight than e.g. people in Nashville, given the altitude and weather patterns. More detailed maps don't limit themselves to drawing a straight line.
- neves 9y agoBTW, here is the equivalent South Parallel: https://en.wikipedia.org/wiki/37th_parallel_south https://en.wikipedia.org/wiki/37th_parallel_south Argentina and Southern Chile in it. Buenos aAires looks ok. Bu
- ptero 9y agoI saw the quoted text, but missed any explanation. I would love a clarification on whether they claim the skin is not getting exposed to sun or, even when exposed, does not make any vitamin D, which is how I read the above. This is an honest question -- if it is the first, I am not too concerned. I grew up in a colder climate and, while living far in the shaded area today, routinely wear short sleeves and walk a lot outside from early spring to late fall. If it is the second, I would love to learn the underlying causes at least as a scientific curiosity (and start thinking about vitamin D supplements).
- exhilaration 9y agoThe sun is too low in winter and the atmosphere blocks the UVB rays our skin needs to produce Vitamin D. The same thing happens around sunrise and sunset even in summer. Here's a good explanation from HN's favorite site: https://physics.stackexchange.com/questions/268509/why-is-there-less-uv-light-on-earth-in-winter https://physics.stackexchange.com/questions/268509/why-is-th...