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Matti Narkia

sunlightD.org - Main -sunlightandvitamind.com - 1 views

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    sunlightD.org

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Matti Narkia

Hyperlipid: Vitamin D and UV fluctuations (2) - 0 views

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    "I discussed in my last post how Dr Vieth has a model of tissue 1,25(OH)2D synthesis and degradation in which the level of active substance is pretty well independent of blood vitamin D level, provided the level is either rising or stable. I think it is also worth pointing out that he is talking, hypothetically, about tissue 1,25(OH)2D, not plasma level... As we know, almost nothing is known about tissue 1,25(OH)2D control.

    By Vieth's hypothesis tissue 1,25(OH)2D is OK so long as there is at least SOME vitamin D present in plasma and the level dose not vary too much. Obviously there is a level below which you can have as much of the enzyme for converting vitamin D to the active form as you like, if there is no vitamin D in your blood you can't make any 1,25(OH)2D in your tissues, or in your kidneys for export to your blood to control calcium levels. At the lower extremes we have rickets and osteomalacia. These are clear cut, unarguable markers of vitamin D deficiency, in the absence of confounding factors (there are a few)."
Matti Narkia

Seasonality of UV-radiation and vitamin D status at 69 degrees north. - Photochem Photo... - 1 views

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    Seasonality of UV-radiation and vitamin D status at 69 degrees north.
    Brustad M, Edvardsen K, Wilsgaard T, Engelsen O, Aksnes L, Lund E.
    Photochem Photobiol Sci. 2007 Aug;6(8):903-8. Epub 2007 Jun 27.
    PMID: 17668121

    The generally high dietary intakes of vitamin D, especially in winter, mask largely the effect of seasonal variation in UV-exposure, causing an atypical seasonal variation in vitamin D status. The UV-hour variable significantly predicted 25(OH)D levels in blood when adjusted for intakes and artificial UV-radiation exposure and sun holidays abroad.
Matti Narkia

The High Prevalence of Vitamin D Insufficiency across Australian Populations Is Only Pa... - 1 views

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    The high prevalence of vitamin D insufficiency across Australian populations is only partly explained by season and latitude.
    van der Mei IA, Ponsonby AL, Engelsen O, Pasco JA, McGrath JJ, Eyles DW, Blizzard L, Dwyer T, Lucas R, Jones G.
    Environ Health Perspect. 2007 Aug;115(8):1132-9.
    PMID: 17687438
    doi: 10.1289/ehp.9937.

    Conclusion
    Vitamin D insufficiency is common over a wide latitude range in Australia. Season appears to be more important than latitude, but both accounted for less than one-fifth of the variation in serum 25(OH)D levels, highlighting the importance of behavioral factors. Current sun exposure guidelines do not seem to fully prevent vitamin D insufficiency, and consideration should be given to their modification or to pursuing other means to achieve vitamin D adequacy.
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

Ultraviolet exposure scenarios: risks of erythema from recommendations on cutaneous vit... - 0 views

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    Ultraviolet exposure scenarios: risks of erythema from recommendations on cutaneous vitamin D synthesis.
    Webb AR, Engelsen O.
    Adv Exp Med Biol. 2008;624:72-85.
    PMID: 18348448
    DOI: 10.1007/978-0-387-77574-6_6
Matti Narkia

Daily duration of vitamin D synthesis in human skin with relation to latitude, total oz... - 0 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."
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

Hyperlipid: Vitamin D and UV fluctuations - 0 views

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    "Under year round UV exposure conditions (low latitudes, broken line, "High UV") there is no association between 25(OH)D and either prostate or pancreatic cancer. At high latitudes (Solid line, "Low UV") there is a positive association between blood levels of 25(OH)D and these cancers. The average year round levels of 25(OH)D actually tend to be higher in northern latitudes, higher than those where there is year-round solar UVB.

    Vieth explains that we know almost nothing about the enzymes controlling tissue 1,25(OH)2D levels and much of his discussion is extrapolated from renal enzyme activity."
Matti Narkia

Vitamin D and multiple sclerosis. [Proc Soc Exp Biol Med. 1997] - PubMed Result - 0 views

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    Vitamin D and multiple sclerosis.
    Hayes CE, Cantorna MT, DeLuca HF.
    Proc Soc Exp Biol Med. 1997 Oct;216(1):21-7. Review.
    PMID: 9316607
Matti Narkia

Vitamin D and living in northern latitudes--an endemic risk area for vitamin D deficien... - 0 views

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    Vitamin D and living in northern latitudes--an endemic risk area for vitamin D deficiency.
    Huotari A, Herzig KH.
    Int J Circumpolar Health. 2008 Jun;67(2-3):164-78. Review.
    PMID: 18767337

    CONCLUSIONS: Vitamin D plays a fundamental role in calcium and phosphate homeostasis. A deficiency of vitamin D has been attributed to several diseases. Since its production in the skin depends on exposure to UVB-radiation via the sunlight, the level of vitamin D is of crucial importance for the health of inhabitants who live in the Nordic latitudes where there is diminished exposure to sunlight during the winter season. Therefore, fortification or supplementation of vitamin D is necessary for most of the people living in the northern latitudes during the winter season to maintain adequate levels of circulating 25(OH)D3 to maintain optimal body function and prevent diseases.
Matti Narkia

In vivo threshold for cutaneous synthesis of vitamin D3. - [J Lab Clin Med. 1989] - Pub... - 0 views

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    In vivo threshold for cutaneous synthesis of vitamin D3.
    Matsuoka LY, Wortsman J, Haddad JG, Hollis BW.
    J Lab Clin Med. 1989 Sep;114(3):301-5.
    PMID: 2549141
Matti Narkia

Regulation of cutaneous previtamin D3 photosynthesis in man: skin pigment is not an ess... - 0 views

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    Holick, M. F., MacLaughlin, J. A. & Doppelt, S. H. (1981)
    Factors that influence the cutaneous photosynthesis of previtamin D3. Science 211:590-593

    When human skin was exposed to simulated solar ultraviolet radiation, epidermal 7-dehydrocholesterol was converted to previtamin D3. During prolonged exposure to simulated solar ultraviolet radiation, the synthesis of previtamin D3 reached a plateau at about 10 to 15 percent of the original 7-dehydrocholesterol content, and previtamin D3 was photoisomerized to two biologically inert isomers, lumisterol3 and tachysterol3. Increases either in skin melanin concentration or in latitude necessitated increases in the exposure time to simulated solar ultraviolet radiation required to maximize the formation, but not the total content, of previtamin D3. In order of importance, the significant determinants limiting the cutaneous production of previtamin D3 are (i) photochemical regulation, (ii) pigmentation, and (iii) latitude.
Matti Narkia

An ecologic study of dietary and solar ultraviolet-B links to breast carcinoma mortalit... - 0 views

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    An ecologic study of dietary and solar ultraviolet-B links to breast carcinoma mortality rates.
    Grant WB.
    Cancer. 2002 Jan 1;94(1):272-81.
    PMID: 11815987

    CONCLUSIONS
    It is hypothesized that animal products are associated with risk for breast carcinoma because they are associated with greater amounts of insulin-like growth factor-1and lifetime doses of estrogen. Vegetable products contain several risk reduction components including antioxidants and phytoestrogens. The association with latitude is very likely because of solar UV-B radiation and vitamin D. Alcohol modulates estrogen's effects on breasts. Fish intake is associated with risk reduction through vitamin D and n-3 oils. These results are consistent with those of many case-control and cohort studies but should be assessed in well designed cohort studies.
Matti Narkia

Geographic variation of prostate cancer mortality rates in the United States: Implicati... - 0 views

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    Geographic variation of prostate cancer mortality rates in the United States: Implications for prostate cancer risk related to vitamin D.
    Grant WB.
    Int J Cancer. 2004 Sep 1;111(3):470-1; author reply 472. No abstract available.
    PMID: 15221981
    10.1002/ijc.20220

    The implications of our results and those of Tuohimaa et al.[1] include the following. Vitamin D supplementation should be undertaken in wintertime, a period when it is impossible to produce vitamin D by solar UVB exposure in northeastern states.[13] Given these new results, the optimal vitamin D intake and production and serum 25(OH)-vitamin D3 levels for prostate cancer appear to be lower than for other cancers. However, when developing guidelines for vitamin D fortification, many factors should be included in the analysis, including all of the potential health benefits and possible risks of vitamin D, as well as age, sex, residence, child-bearing status, etc.[14] Also, the suggestion that daily vitamin D3 supplement doses of 100 g (4,000 IU)/day are safe[15] should be reexamined. Finally, in terms of preventing prostate cancer, more attention should be given to diet, which has the greatest environmental impact on risk of prostate cancer, with animal products being important risk factors and vegetable products, especially onions and other allium family members, being important risk-reduction factors.[16]
Matti Narkia

Evolution and function of vitamin D. [Recent Results Cancer Res. 2003] - PubMed Result - 0 views

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    Evolution and function of vitamin D.
    Holick MF.
    Recent Results Cancer Res. 2003;164:3-28. Review.
    PMID: 12899511
Matti Narkia

Vitamin D and skin physiology: a D-lightful story - JBMR Online - Journal of Bone and M... - 0 views

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    Vitamin D and skin physiology: a D-lightful story.
    Holick MF, Chen TC, Lu Z, Sauter E.
    J Bone Miner Res. 2007 Dec;22 Suppl 2:V28-33.
    PMID: 18290718
    doi: 10.1359/jbmr.07s211

    Very few foods naturally contain vitamin D, and those that do have a very variable vitamin D content. Recently it was observed that wild caught salmon had between 75% and 90% more vitamin D(3) compared with farmed salmon. The associations regarding increased risk of common deadly cancers, autoimmune diseases, infectious diseases, and cardiovascular disease with living at higher latitudes and being prone to vitamin D deficiency should alert all health care professionals about the importance of vitamin D for overall health and well being.

    Humans have depended on sunlight for their vitamin D requirement. The impact of season, time of day, and latitude on vitamin D synthesis is well documented.(2,3) We now report that altitude also has a dramatic influence on vitamin D3 production and that living at altitudes above 3500 m permits previtamin D3 production at a time when very little is produced at latitudes below 3400 m. It was surprising that, at 27° N in Agra (169 M), little previtamin D3 production was observed. However, there was significant air pollution that caused a haze over the city. It is likely the ozone and other UVB-absorbing pollutants in the air prevented the solar UVB photons from reaching the earth's surface to produce previtamin D3.
Matti Narkia

Influence of Season and Latitude on the Cutaneous Synthesis of Vitamin D3: Exposure to ... - 0 views

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    nfluence of season and latitude on the cutaneous synthesis of vitamin D3: exposure to winter sunlight in Boston and Edmonton will not promote vitamin D3 synthesis in human skin.
    Webb AR, Kline L, Holick MF.
    J Clin Endocrinol Metab. 1988 Aug;67(2):373-8.
    PMID: 2839537
    doi:10.1210/jcem-67-2-373

    These results quantify the dramatic influence of changes in solar UVB radiation on cutaneous vitamin D3 synthesis and indicate the latitudinal increase in the length of the "vitamin D winter" during which dietary supplementation of the vitamin may be advisable.
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