I was surprised to see that there was a separate definition for "deficiency" and "insufficiency" in vitamin intake. I think these words are too similar and so could cause confusion to the general public
As far as vitamin D goes I think there is (or was) a genuine issue with definitions. Deficiency was used to describe levels of vitamin D that cause rickets (and similar), where as "insufficiency" was related to higher levels of osteoporosis (the clinical significance of which is unclear to me, but in terms of dietary choices seems to be something that one would choose to avoid).
But I think a simple number (RDA, or even 4 numbers) is probably not useful. For example different races may have different needs for vitamin D (the reason for which are not all known yet). Different people (within the same ethnic group) can metabolize vitamin D differently. Women are also much more prone to osteoporosis than men. Thus epidemiologists seem to use serum concentrations to assess if someone has sufficient vitamin D intake for themselves, rather than say dietary intake, or sun exposure, both of which are tricky to measure.
I (and I assume others) queried the Marshall Protocol related research used in Science or Fiction. Which further muddies the vitamin D story. Marshall had a condition which is (now recognised to be - at least sometimes) worsened by Vitamin D, but was thought to be autoimmune in nature when Marshall was diagnosed. Marshall's protocol assumes vitamin D is bad for many autoimmune diseases, where as other scientists have concluded that vitamin D helps regulate the immune response preventing the development of autoimmune disorders (hence the use mentioned in MS earlier in this episodes thread, and is why I thought the reference in Science or Fiction was so suspect).
This improved regulation of the immune response is why the regulators have upped the vitamin D content of baby formula, and encouraged other forms of vitamin D supplementation. To prevent insufficiency/deficiency of vitamin D.
However whilst Steve said he wouldn't have used the Marshall Protocol research if he'd recognised the agenda behind it, I don't mean to be too critical of it. Clearly there were unrecognised issues relating to vitamin D in Sarcoidosis. Some other autoimmune complaints are aggravated by sunlight (famously Lupus). And vitamin D metabolism is known to be affected by genes that correlate with some other autoimmune disorders (the convention assumption is that the enhanced immune regulation from vitamin D is lost by these mutations).
The problem with the Marshall Protocol research is more that the researchers have assumed their conclusion are right (avoiding vitamin D fixes certain autoimmune disorders), and suffer from the usual issues of understanding like confirmation bias. Certainly some people have avoided vitamin D and got better from complaints, in some cases this may be coincidence (natural progression), in a few cases it may be clinically significant. But till the mechanisms are better understood, and the results replicated in independent trials the message on vitamin D remains "a little sunshine each day is good for your metabolism but bad for your risk of skin cancer".
Some times there aren't easy answers to give, we aren't perfectly adapted to life on earth.
