[poizan42]

Not OP, but the paper says on page 8

> An adult in a bathing suit exposed to 1 minimal erythemal dose of ultraviolet radiation (a slight pinkness to the skin 24 h after exposure) was found to be equivalent to ingesting between 10,000 and 25,000 IU of vitamin D (Fig. 6).

Doesn't say 30 minutes, but it may be 30 minutes depending on your skin colour and the local strength of the sun.

[zelphirkalt]

I think the OP's interpretation of this is wrong. Just because someone was found to have an equivalent of ingesting so and so much, after UV radiation, doesn't automatically imply that it a good idea to ingest any amount of vitamin D. Ingestion is different from exposing skin to UV/sun. The paper probably doesn't state, that ingesting that much will make a person absorb that much from that ingestion, nor does it state, that ingesting some equivalent amount will be safe and without side-effects.

So the paper may be well researched or whatever, but the interpretation of it is questionable.

[poizan42]

I can't make any assesment on the quality of the paper as that is far outside my expertise, but as far as I can tell from a quick skim it does indeed make the claim that recommendations for supplements should be significantly increased.

From the abstract:

> The safe upper limit for children can easily be increased to 2,000 IU of vitamin D/day, and for adults, up to 10,000 IU of vitamin D/day has been shown to be safe. The goal of this chapter is to give a broad perspective about vitamin D and to introduce the reader to the vitamin D deficiency pandemic and its insidious consequences on health that will be reviewed in more detail in the ensuing chapters

The full article is available on researchgate[1]. Direct link to PDF [2].

[1] https://www.researchgate.net/publication/226676251_Vitamin_D...

[2] https://www.researchgate.net/profile/Michael-Holick/publicat...

EDIT: I just looked up the author, Michael F. Holick. Apparently he is one the people who identified calcitriol in 1971. I know appeal to authority doesn't prove anything, but it might be prudent to at least consider his findings.