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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

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.
Matti Narkia

Factors that Influence the Cutaneous Synthesis and Dietary Sources of Vitamin D - 0 views

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    Factors that influence the cutaneous synthesis and dietary sources of vitamin D. Chen TC, Chimeh F, Lu Z, Mathieu J, Person KS, Zhang A, Kohn N, Martinello S, Berkowitz R, Holick MF. Arch Biochem Biophys. 2007 Apr 15;460(2):213-7. Epub 2007 Jan 8. PMID: 17254541 doi: 10.1016/j.abb.2006.12.017 Vitamin D is rare in food. Among the vitamin D-rich food, oily fish are considered to be one of the best sources. Therefore, we analyzed the vitamin D content in several commonly consumed oily and non-oily fish. The data showed that farmed salmon had a mean content of vitamin D that was ~25% of the mean content found in wild caught salmon from Alaska, and that vitamin D2 was found in farmed salmon, but not in wild caught salmon. The results provide useful global guidelines for obtaining sufficient vitamin D3 by cutaneous synthesis and from dietary intake to prevent vitamin D deficiency and its health consequences.ensuing illness, especially, bone fractures in the elderly.
Matti Narkia

Effects of Atorvastatin on Vitamin D Levels in Patients With Acute Ischemic Heart Disease - 0 views

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    Effects of Atorvastatin on vitamin D levels in patients with acute ischemic heart disease. Pérez-Castrillón JL, Vega G, Abad L, Sanz A, Chaves J, Hernandez G, Dueñas A. Am J Cardiol. 2007 Apr 1;99(7):903-5. Epub 2007 Feb 8. PMID: 17398180 In conclusion, atorvastatin increases vitamin D levels. This increase could explain some of the beneficial effects of atorvastatin at the cardiovascular level that are unrelated to cholesterol levels. The mechanism by which atorvastatin increases vitamin D levels is related to inhibition of 3-hydroxy-3 methylglutaryl coenzyme A (HMG-CoA) reductase. Cholesterol is synthesized from 7-dehydrocholesterol, which is also a precursor of vitamin D3. For this reason, we initially observed a statistically significant relation between total cholesterol and vitamin D. HMG-CoA enzyme reductase is key to the synthesis of cholesterol, whereas ultraviolet radiation causes the formation of 25-hydroxyvitamin D. Inhibition of the enzyme may increase levels of 7-dehydrocholesterol and increase the synthesis of 25-hydroxycholecalciferol, thereby increasing vitamin D levels,10 although we observed no relation between lower cholesterol and increased vitamin D. In addition, 25-hydroxyvitamin D has been shown to inhibit HMG-CoA enzyme reductase activity in in vitro studies.11 A greater concentration of vitamin D could increase enzymatic inhibition, acting in synergy with the statin in decreasing total cholesterol.
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

Factors that influence the cutaneous synthesis and dietary sources of vitamin D. - Scie... - 0 views

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    Factors that influence the cutaneous synthesis and dietary sources of vitamin D.\nChen TC, Chimeh F, Lu Z, Mathieu J, Person KS, Zhang A, Kohn N, Martinello S, Berkowitz R, Holick MF.\nArch Biochem Biophys. 2007 Apr 15;460(2):213-7. Epub 2007 Jan 8.\nPMID: 17254541\ndoi:10.1016/j.abb.2006.12.017\n
Matti Narkia

Factors that influence the cutaneous synthesis and dietary sources of vitamin D - Scien... - 0 views

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    Chen TC, Chimeh F, Lu Z, Mathieu J, Person KS, Zhang A, Kohn N, Martinello S, Berkowitz R, Holick MF. Factors that influence the cutaneous synthesis and dietary sources of vitamin D. Arch Biochem Biophys. 2007 Apr 15;460(2):213-7. Epub 2007 Jan 8. PMI
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

Duration of vitamin D synthesis from weather model data for use in prospective epidemio... - 0 views

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    Duration of vitamin D synthesis from weather model data for use in prospective epidemiological studies. Edvardsen K, Engelsen O, Brustad M. Int J Biometeorol. 2009 Sep;53(5):451-9. Epub 2009 May 15. PMID: 19444487
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

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

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

Season of diagnosis is a prognostic factor in Hodgkin's lymphoma: a possible role of su... - 0 views

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    SSeason of diagnosis is a prognostic factor in Hodgkin's lymphoma: a possible role of sun-induced vitamin D. Porojnicu AC, Robsahm TE, Ree AH, Moan J. Br J Cancer. 2005 Sep 5;93(5):571-4. PMID: 16136030 doi:10.1038/sj.bjc.6602722 Epidemiological data for this period indicate that season of diagnosis is a strong prognostic factor for Hodgkin's lymphoma, with approximately 20% lower case fatality for patients diagnosed during autumn vs winter diagnosis (RR = 0.783, 95% CI,-0.62 to 0.99; P = 0.041). Notably, the improved autumnal survival rate was higher than 60% (RR = 0.364, 95% CI, -0.15 to 0.87; P = 0.025) for patients younger than 30 years. This finding may be related to higher endogenous levels of vitamin D in autumn, with a favourable influence on the conventional therapy. In conclusion, we have found that the prognosis of Hodgkin's lymphoma is significantly correlated with the season of diagnosis, particularly for patients younger than 30 years. This seasonal effect is presumably due to the vitamin D3 synthesis in skin during sun exposure. The present findings should encourage further investigations of the possible adjuvant role of vitamin D derivatives in cancer therapy
Matti Narkia

JNNP -- eLetters for Soilu-Hänninen et al., 79 (2) 152-157 - 0 views

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    Vitamin D may suppress infections which lead to development of Multiple Sclerosis Steven R Brenner, None (16 August 2007) J Neurol Neurosurg Psychiatry 2008 I read the article with reference to the inverse relationship between multiple sclerosis clinical activity and deficiency of vitamin D by Soilu-Hannienen (1) with interest, and was considering what mechanism could be in play to cause such a relationship. 25-hydroxylated metabolites of vitamin D act as intracellular regulators of the synthesis and action of defensin (2) molecules against bacterial antigens, defensin being an endogenously synthesized antimicrobial substance (2). Human cathelicidin antimicrobial peptide gene is a target of vitamin D receptor and is strongly up-regulated by 1,25-dihydroxyvitamin D3, indicating vitamin D receptor and the 1,25-dihydroxyvitaminD3 regulate primate innate immunity (3)
Matti Narkia

Role of vitamin D in the pathogenesis of type 2 diabetes mellitus. - Wiley InterScience... - 0 views

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    Role of vitamin D in the pathogenesis of type 2 diabetes mellitus. Palomer X, González-Clemente JM, Blanco-Vaca F, Mauricio D. Diabetes Obes Metab. 2008 Mar;10(3):185-97. Review. PMID: 18269634 DOI: 10.1111/j.1463-1326.2007.00710.x Vitamin D deficiency has been shown to alter insulin synthesis and secretion in both humans and animal models. It has been reported that vitamin D deficiency may predispose to glucose intolerance, altered insulin secretion and type 2 diabetes mellitus. Vitamin D replenishment improves glycaemia and insulin secretion in patients with type 2 diabetes with established hypovitaminosis D, thereby suggesting a role for vitamin D in the pathogenesis of type 2 diabetes mellitus.
Matti Narkia

The roles of calcium and vitamin D in skeletal health: an evolutionary perspective - Ro... - 0 views

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    Robert P. Heaney is John A. Creighton University Professor, Creighton University, Omaha, Nebraska, United States. Hominid evolution took place in an environment (equatorial East Africa) that provided a superabundance of both calcium and vitamin D, the first in available foods and the second through conversion of 7-dehydrocholesterol to pre-vitamin D in the skin, a reaction catalysed by the intense solar ultraviolet (UV) radiation. Seemingly as a consequence, the evolving human physiology incorporated provisions to prevent the potential of toxic excesses of both nutrients. For vitamin D the protection was of two sorts: skin pigmentation absorbed the critical UV wavelengths and thereby limited dermal synthesis of cholecalciferol; and slow delivery of vitamin D from the skin into the bloodstream left surplus vitamin in the skin, where continuing sun exposure led to its photolytic degradation to inert compounds. For calcium, the adaptation consisted of very inefficient calcium absorption, together with poor to absent systemic conservation. The latter is reflected in unregulated dermal calcium losses, a high sensitivity of renal obligatory calcium loss to other nutrients in the diet and relatively high quantities of calcium in the digestive secretions. Today, chimpanzees in the original hominid habitat have diets with calcium nutrient densities in the range of 2 to 2.5 mmol per 100 kcal, and hunter-gatherer humans in Africa, South America and New Guinea still have diets very nearly as high in calcium (1.75 to 2 mmol per 100 kcal) (Eaton and Nelson, 1991). With energy expenditure of 3 000 kcal per day (a fairly conservative estimate for a contemporary human doing physical work), such diets would provide substantially in excess of 50 mmol of calcium per day. By contrast, median intake in women in North America and in many European countries today is under 15 mmol per day. Two factors altered the primitive situation: the migration of humans from Africa to higher latitude
Matti Narkia

Vitamin D: a D-Lightful health perspective. - Nutr Rev. 2008 Oct;66(10 Suppl 2):S182-94... - 0 views

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    Vitamin D: a D-Lightful health perspective. Holick MF. Nutr Rev. 2008 Oct;66(10 Suppl 2):S182-94. Review. PMID: 18844847 DOI: 10.1111/j.1753-4887.2008.00104.x Sunlight provides most humans with their vitamin D requirement. Adequate vitamin D(3) by synthesis in the skin or from dietary and supplemental sources is essential for bone health throughout life. Vitamin D deficiency is defined as a 25(OH)D concentration 30 ng/mL (75 nmol/L), and insufficiency as 21-29 ng/mL. Vitamin D deficiency and insufficiency has been linked to a wide variety of chronic diseases including common cancers, autoimmune, cardiovascular, and infectious diseases. Healthcare professionals need to be aware of the vitamin D deficiency pandemic. Guidelines for sensible sun exposure and supplemental vitamin D of 800-1000 IU/day are needed.
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

Vitamin D - Linus Pauling Institute at Oregon State University - 0 views

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    Vitamin D is a fat-soluble vitamin that is essential for maintaining normal calcium metabolism (1). Vitamin D3 (cholecalciferol) can be synthesized by humans in the skin upon exposure to ultraviolet-B (UVB) radiation from sunlight, or it can be obtained from the diet. Plants synthesize ergosterol, which is converted to vitamin D2 (ergocalciferol) by ultraviolet light. Vitamin D2 is less active in birds than vitamin D3 and may also be less active in humans (2). When exposure to UVB radiation is insufficient for the synthesis of adequate amounts of vitamin D3 in the skin, adequate intake of vitamin D from the diet is essential for health.
Matti Narkia

Vitamin D deficiency is the cause of common obesity - 0 views

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    Vitamin D deficiency is the cause of common obesity. Foss YJ. Med Hypotheses. 2009 Mar;72(3):314-21. Epub 2008 Dec 2. PMID: 19054627 doi:10.1016/j.mehy.2008.10.005 Common obesity and the metabolic syndrome may therefore result from an anomalous adaptive winter response. The stimulus for the winter response is proposed to be a fall in vitamin D. The synthesis of vitamin D is dependent upon the absorption of radiation in the ultraviolet-B range of sunlight. At ground level at mid-latitudes, UV-B radiation falls in the autumn and becomes negligible in winter. It has previously been proposed that vitamin D evolved in primitive organisms as a UV-B sensitive photoreceptor with the function of signaling changes in sunlight intensity. It is here proposed that a fall in vitamin D in the form of circulating calcidiol is the stimulus for the winter response, which consists of an accumulation of fat mass (obesity) and the induction of a winter metabolism (the metabolic syndrome). Vitamin D deficiency can account for the secular trends in the prevalence of obesity and for individual differences in its onset and severity. It may be possible to reverse the increasing prevalence of obesity by improving vitamin D status.
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