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Matti Narkia

The solar UV radiation level needed for cutaneous production of vitamin D3 in the face.... - 0 views

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    The solar UV radiation level needed for cutaneous production of vitamin D3 in the face. A study conducted among subjects living at a high latitude (68 degrees N).
    Edvardsen K, Brustad M, Engelsen O, Aksnes L.
    Photochem Photobiol Sci. 2007 Jan;6(1):57-62. Epub 2006 Nov 10.
    PMID: 17200737
Matti Narkia

VitD-ez Easy Duration of Vitamin D Synthesis in Human Skin - 0 views

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    Vitamin D production in human skin occurs only when UV radiation exceeds a threshold. From simulations of UV irradiances, the VitD-ez www page ( http://zardoz.nilu.no/~olaeng/fastrt/VitD-ez.html) computes the daily duration of dermal vitamin D production at midday when UV radiation exceeds the required threshold. The VitD-ez www page is a simplified version of the more complex VitD web page ( http://zardoz.nilu.no/~olaeng/fastrt/VitD.html). The simplified VitD-ez www page is convenient for users unfamiliar to radiative transfer modelling, because the model input is limited and more intuitive.
Matti Narkia

Daily duration of vitamin D synthesis in human skin with relation to latitude, total oz... - 1 views

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    Daily duration of vitamin D synthesis in human skin with relation to latitude, total ozone, altitude, ground cover, aerosols and cloud thickness.
    Engelsen O, Brustad M, Aksnes L, Lund E.
    Photochem Photobiol. 2005 Nov-Dec;81(6):1287-90.
    PMID: 16354110

    Vitamin D production in human skin occurs only when incident UV radiation exceeds a certain threshold. From simulations of UV irradiances worldwide and throughout the year, we have studied the dependency of the extent and duration of cutaneous vitamin D production in terms of latitude, time, total ozone, clouds, aerosols, surface reflectivity and altitude. For clear atmospheric conditions, no cutaneous vitamin D production occurs at 51 degrees latitude and higher during some periods of the year. At 70 degrees latitude, vitamin D synthesis can be absent for 5 months. Clouds, aerosols and thick ozone events reduce the duration of vitamin D synthesis considerably, and can suppress vitamin D synthesis completely even at the equator. A web page allowing the computation of the duration of cutaneous vitamin D production worldwide throughout the year, for various atmospheric and surface conditions, is available on the Internet at http://zardoz.nilu.no/~olaeng/fastrt/VitD.html and http://zardoz.nilu.no/~olaeng/fastrt/VitD-ez.html. The computational methodology is outlined here.
Matti Narkia

Vitamin D effective ultraviolet wavelengths due to scattering in shade - ScienceDirect ... - 0 views

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    Vitamin D effective ultraviolet wavelengths due to scattering in shade.
    Turnbull DJ, Parisi AV, Kimlin MG.
    J Steroid Biochem Mol Biol. 2005 Sep;96(5):431-6. Epub 2005 Jul 6.
    PMID: 16005208
Matti Narkia

Aging decreases the capacity of human skin to produce vitamin D3. - Journal of Clinical... - 0 views

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    Aging decreases the capacity of human skin to produce vitamin D3.
    MacLaughlin J, Holick MF.
    J Clin Invest. 1985 Oct;76(4):1536-8.
    PMID: 2997282
    doi:10.1172/JCI112134

    An evaluation of surgically obtained skin (age range, 8-92 yr) revealed that there is an age-dependent decrease in the epidermal concentrations of provitamin D3 (7-dehydrocholesterol). To ascertain that aging indeed decreased the capacity of human skin to produce vitamin D3, some of the skin samples were exposed to ultraviolet radiation and the content of previtamin D3 was determined in the epidermis and dermis. The epidermis in the young and older subjects was the major site for the formation of previtamin D3, accounting for greater than 80% of the total previtamin D3 that was produced in the skin. A comparison of the amount of previtamin D3 produced in the skin from the 8- and 18-yr-old subjects with the amount produced in the skin from the 77- and 82-yr-old subjects revealed that aging can decrease by greater than twofold the capacity of the skin to produce previtamin D3. Recognition of this difference may be extremely important for the elderly, who infrequently expose a small area of skin to sunlight and who depend on this exposure for their vitamin D nutritional needs.
Matti Narkia

Sunlight Regulates the Cutaneous Production of Vitamin D3 by Causing Its Photodegradati... - 0 views

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    Sunlight regulates the cutaneous production of vitamin D3 by causing its photodegradation.
    Webb AR, DeCosta BR, Holick MF.
    J Clin Endocrinol Metab. 1989 May;68(5):882-7.
    PMID: 2541158
    doi:10.1210/jcem-68-5-882

    Vitamin D3 proved to be exquisitely sensitive to sunlight, and once formed in the skin, exposure to sunlight resulted in its rapid photodegradation to a variety of photoproducts, including 5,6-transvitamin D3, suprasterol I, and suprasterol II.suprasterol I, and suprasterol II.
Matti Narkia

VitD Duration of Vitamin D Synthesis in Human Skin - 0 views

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    Vitamin D production in human skin occurs only when UV radiation exceeds a threshold. From simulations of UV irradiances, the VitD www page ( http://zardoz.nilu.no/~olaeng/fastrt/VitD.html) computes the daily duration of dermal vitamin D production at midday when UV radiation exceeds the required threshold. The daily duration depends on latitude, time, total ozone, clouds, aerosols, surface reflectivity and altitude all of which can be specified by the user
Matti Narkia

Schematic diagram of cutaneous production of vitamin D and its metabolism and regulatio... - 0 views

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    Schematic diagram of cutaneous production of vitamin D and its metabolism and regulation for calcium homeostasis and cellular growth - Figure 3 from the study

    Holick MF. Sunlight and vitamin D for bone health and prevention of autoimmune diseases, can
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