"Toxic effects" of high vitamin D [ - Vieth, 2006]

The actual one line quote is: "High doses of oral vitamin D supplements, however, have been shown to have toxic effects (Vieth, 2006)."

This followed a ( - clearly questionable?) view on the safety (for ALL?) of vitamin D formed by sun-exposure:

"The cutaneous conversion of 7-dehydrocholesterol to previtamin D3, which spontaneously isomerizes to cholecalciferol, is regulated so that prolonged sunlight exposure does not lead to excess production; both precholecalciferol and cholecalciferol can be photolysed to inert compounds."

[ - does that apply to ALL, . . . . . . withOUT qualification ? ? ? See below !]

The above from paragraph 30 on p. 11 of "Update on Vitamin D Position statement by the Scientific Advisory Committee on Nutrition" of 2007 - SACN report available FREE online online ( - hurray !):


As we know from other posts on this forum, there are (seemingly ?) credible and significant reports of well over a decade of a sub-group of the population, which is affected by or exhibit a "vitamin D dysfunction" found in those with a range of medical conditions: for this group, it might be said that even limited amounts of sun exposure can further elevate the already (relatively) higher calcitriol levels, which inflame an already poor situation further, unlike in their healthy counterparts, aggravating the (often unidentified) disease process ! These are said to be or include Th1 inflammation causing conditions. This knowledge is POWER ( - I dare say !) for those so affected !

I remain unsure whether Prof Vieth even adequately ( -or at all) acknowledges the existence of this sub-group, the size of which, I fear may be increasing, year by year as the number of people with this dysfunction rises ! The level of supplementation Vieth considers as safe would NOT appear to apply to this sub-group, for which one body of opinion recommends reducing calcidiol, or 25(OH)D levels . . . . . and hence ANY supplementation would be seen as counter-indicated ! A HIGH vitamin D level, as assessed by the standard calcidiol [ - or 25(OH)D] blood test, for this SUB-GROUP would, it seems to be at levels considered low ( - either as inadequate or insufficient) for those in the portion of the population not so affected.

[As clear as . . . . . . . mud ? ? ? It is, it seems for most of the UK medical profession, sadly at present ! ! !].

Just ONE more viewpoint of this complex endo-immunological bio-landscape to consider !

Warm regards to all, on a sunny cold autumn afternoon,

Epictetus x

Sat 7 Nov 2015


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2 Replies

  • Strange that the abstract of the quoted paper doesn't mention problems with high doses - ncbi.nlm.nih.gov/pubmed/167...

  • Hi fbirder,

    The reference in the SACN report is:

    "Vieth R (2006) Critique of the Considerations for Establishing the Tolerable Upper Intake Level for Vitamin D: Critical Need for Revision Upwards. J Nutr 136, 1117-1122." ( - on p.60)

    However, am concerned to read in the 2006 paper, "What is the optimal vitamin D status for health?" you cite:

    "Based upon these studies, 25(OH)D concentrations should exceed 75 nmol/L."

    [ - does NOT mean that level is OK for ALL . . . . . . . I suggest !]

    Well AT LEAST the qualification, "based upon these studies, . . . " is included.

    So, there could be/are other views . . . . . . of which we know something ! However, the above sentence does/may suggest Prof Vieth isn't giving much credence to those with "vit D ( - or specifically calcidiol) hypersensitivity". I suspect his recommended maximum daily dose will not be appropriate AT ALL for this important sub-group.

    25(OH)D concentrations at or HIGHER THAN 75nmol/L are certainly NOT recommended for those with the described "vit D dysfunction" by any authoritative source I know of ( - so far !).

    In fact, those with this dysfunction would, in many ( - if not all) cases, have a hard time raising their blood calcidiol levels to this figure, even with copious supplementation . . . . . with either the level simply not rising . . . . . . or the person FEELING ill/unwell as a result ( - as I understand it at present !).

    Any credible views to the contrary would be interesting to consider, based of their cited evidence. Far more commonly, it seems this SIGNIFICANT sub-group is simply NOT being acknowledged.

    Good to have your pointer, though - thanks !

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