400 IU per 5 minutes is 8000 IU per hour is 32,000 IU (800 micrograms) per day by this estimate.
That’s not how it works. When Vitamin D3 gets produced it’s first on the skin. If you just stay longer outside then a lot of the Vitamin D3 that gets produced gets destroyed by radiation before it enters the bloodstream if you stay longer in the sun.
If someone wants to pay some people to have their blood drawn and analyzed before and after a full sunny day at the beach, great, but I can’t be bothered. It would also be nice to see a study done on black people.
That’s again not how things work. Vitamin D blood tests measure calcifediol and not cholecalciferol (Vitamin D3). It takes time for the cholecalciferol to be transformed, so you won’t get the answer you are seeking by measuring after a single day.
That’s not how it works. When Vitamin D3 gets produced it’s first on the skin. If you just stay longer outside then a lot of the Vitamin D3 that gets produced gets destroyed by radiation before it enters the bloodstream if you stay longer in the sun.
That’s again not how things work. Vitamin D blood tests measure calcifediol and not cholecalciferol (Vitamin D3). It takes time for the cholecalciferol to be transformed, so you won’t get the answer you are seeking by measuring after a single day.
I did write more about Vitamin D: https://www.lesswrong.com/posts/c5aycbSsSc38XWPEc/taking-vitamin-d3-with-k2-in-the-morning