I love Zhang translation and Naughton Nutrition, Journal 2010 9: 65
http: / / www.nutritionj.com / content / 9 / 1 / 65 Page 3 of 13
patients. With chronic granulomatous disorders should be cautious with the dose of vitamin D since macrophage production, of 1 25-dihydroxyvitamin. D causes hypercalce - mia and hyperphosphatemia [8 9 23,,]. 2.1 Causes of vitamin D deficiency There are many causes of vitamin D deficiency. Gener - ally they can, be divided into two. Groups: UVB-related deficiency and medical / physical condition-related deficiency.
2.1.2 UVB-related deficiency The elderly. The elderly due to, the decreased presence of skin 7-dehydrocholesterol which is the precursor for UVB mediated synthesis. Of, vitamin DAre particularly at risk of vitamin D deficiency. Moreover reduced mobility, or institutionalization that discourages. Sun exposure reduced renal, production, of 1 25-dihydroxy - vitamin D as well as decreased intake of fortified foods pose. Great difficulties in vitamin D formation in, body [25 26].
Dark skin People with dark skin have great amounts of melanin. In their epidermis.Melanin competes with 7-dehydrocholesterol for absorption of UVB photons. Therefore people of, color are less efficient. In produ - cing vitamin D than are whites. It is reported that a person with skin type 5 / 6 (dark skin) requires 10-50 times. The exposure to sunlight to produce the same amount of vitamin D as does a white person with skin type 2 / 3 [27].
Season,, Latitude.And the time of day It has been established that the ozone layer can absorb UVB radia - tion above 290 nm which is responsible. For generating previtamin D3. Zenith angle defined as, the angle of the sunlight reaching the Earth ', s surface decides the. Thick - ness of ozone layer which sunlight needs to penetrate. The thicker the ozone, layer is the fewer amounts of UVB photons. Can reach, the earthThus few previtamin D3 can be produced. Zenith angle is dependent on factors such as time of day season of the year,,, And lati - tude. Thus those factors have great effects on vitamin D production [,]. For 28 29 example residents of, Boston. (42 ° N), Edmonton Canada (, 52 ° N), andBergen Norway (61 ° N) can not produce sufficient quantities of vitamin D in their skin for 4 5 and months 6,,,, 6 respectively [].Sunscreen users Sunscreens can efficiently absorb UVB radiation. This dramatically prevents the interaction of UVB with. 7-dehydrocholesterol the process, of previta - min D3 generation. It has been shown that when used properly a sunscreen,, With a sun protection factor of 8 reduces the production of previtamin D3 by 95% and 99%, by a sun protection factor of, 15 [30 31]. 2.1.2 Medical / physical condition-related deficiency Fat malabsorption As a, fat-soluble vitamin vitamin D requires the presence. Of dietaryfatinthegutfor absorption. Certain pathological conditions such as,,
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