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 ====== Latitude studies on vitamin D and disease ====== ====== Latitude studies on vitamin D and disease ======
  
-<relatedarticle> [[home:othertreatments:antidepressants|Sunshine/light exposure as therapy]] </article>+<relatedarticle> [[home:othertreatments:sunshine|Sunshine/light exposure as therapy]] </article>
  
 The "latitude studies" are [[home:pathogenesis:vitamind:observational_bias|observational]] - as opposed to interventional - studies  that use ambient solar UV radiation as a proxy for latitude and vitamin D status. For these studies, researchers compare rates of certain major cancers - most notably breast, colorectal and prostate cancer - to rates of sunlight exposure. This group of research has the liability of being wildly inconsistent. The choice to publish research on a specific latitude gradient may be a better proxy for a researcher's bias. There is sufficient variability in the prevalence of disease among countries and ethnicities that different researchers have come to different conclusions even those looking at the same data source. The "latitude studies" are [[home:pathogenesis:vitamind:observational_bias|observational]] - as opposed to interventional - studies  that use ambient solar UV radiation as a proxy for latitude and vitamin D status. For these studies, researchers compare rates of certain major cancers - most notably breast, colorectal and prostate cancer - to rates of sunlight exposure. This group of research has the liability of being wildly inconsistent. The choice to publish research on a specific latitude gradient may be a better proxy for a researcher's bias. There is sufficient variability in the prevalence of disease among countries and ethnicities that different researchers have come to different conclusions even those looking at the same data source.
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   *Legacy content   *Legacy content
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 +<blockquote>need a new article? vitamin D production on skin
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 +Trevor talks about this here: http://www.marshallprotocol.com/view_topic.php?id=13471
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 +
 +J Invest Dermatol. 2010 Feb;130(2):546-53. Epub 2009 Oct 8.
 +Vitamin D production after UVB exposure depends on baseline vitamin D and total cholesterol but not on skin pigmentation.
 +
 +Bogh MK, Schmedes AV, Philipsen PA, Thieden E, Wulf HC.
 +Department of Dermatology, Copenhagen University Hospital, Bispebjerg, Copenhagen NV Vejle, Denmark. bogh@dadlnet.dk
 +Erratum in:
 +J Invest Dermatol. 2010 Jun;130(6):1751.
 +Comment in:
 +J Invest Dermatol. 2010 Feb;130(2):330.
 +J Invest Dermatol. 2010 Aug;130(8):2139-41.
 +J Invest Dermatol. 2010 Feb;130(2):346-8.
 +Abstract
 +UVB radiation increases serum vitamin D level expressed as 25-hydroxyvitamin-D(3) (25(OH)D), but the influence of skin pigmentation, baseline 25(OH)D level, and total cholesterol has not been well characterized. To determine the importance of skin pigmentation, baseline 25(OH)D level, and total cholesterol on 25(OH)D production after UVB exposure, 182 persons were screened for 25(OH)D level. A total of 50 participants with a wide range in baseline 25(OH)D levels were selected to define the importance of baseline 25(OH)D level. Of these, 28 non-sun worshippers with limited past sun exposure were used to investigate the influence of skin pigmentation and baseline total cholesterol. The participants had 24% of their skin exposed to UVB (3 standard erythema doses) four times every second or third day. Skin pigmentation and 25(OH)D levels were measured before and after the irradiations. Total cholesterol was measured at baseline. The increase in 25(OH)D level after UVB exposure was negatively correlated with baseline 25(OH)D level (P<0.001) and positively correlated with baseline total cholesterol level (P=0.005), but no significant correlations were found with constitutive or facultative skin pigmentation. In addition, we paired a dark-skinned group with a fair-skinned group according to baseline 25(OH)D levels and found no differences in 25(OH)D increase after identical UVB exposure.
 +PMID: 19812604</blockquote>
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 +<blockquote>J Hum Evol. 2000 Jul;39(1):57-106.
 +
 +The evolution of human skin coloration.
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 +Jablonski NG, Chaplin G.
 +Department of Anthropology, California Academy of Sciences, Golden Gate Park, San Francisco, CA 94118-4599, USA. njablonski@calacademy.org
 +Abstract
 +Skin color is one of the most conspicuous ways in which humans vary and has been widely used to define human races. Here we present new evidence indicating that variations in skin color are adaptive, and are related to the regulation of ultraviolet (UV) radiation penetration in the integument and its direct and indirect effects on fitness. Using remotely sensed data on UV radiation levels, hypotheses concerning the distribution of the skin colors of indigenous peoples relative to UV levels were tested quantitatively in this study for the first time. The major results of this study are: (1) skin reflectance is strongly correlated with absolute latitude and UV radiation levels. The highest correlation between skin reflectance and UV levels was observed at 545 nm, near the absorption maximum for oxyhemoglobin, suggesting that the main role of melanin pigmentation in humans is regulation of the effects of UV radiation on the contents of cutaneous blood vessels located in the dermis. (2) Predicted skin reflectances deviated little from observed values. (3) In all populations for which skin reflectance data were available for males and females, females were found to be lighter skinned than males. (4) The clinal gradation of skin coloration observed among indigenous peoples is correlated with UV radiation levels and represents a compromise solution to the conflicting physiological requirements of photoprotection and vitamin D synthesis. The earliest members of the hominid lineage probably had a mostly unpigmented or lightly pigmented integument covered with dark black hair, similar to that of the modern chimpanzee. The evolution of a naked, darkly pigmented integument occurred early in the evolution of the genus Homo. A dark epidermis protected sweat glands from UV-induced injury, thus insuring the integrity of somatic thermoregulation. Of greater significance to individual reproductive success was that highly melanized skin protected against UV-induced photolysis of folate (Branda & Eaton, 1978, Science201, 625-626; Jablonski, 1992, Proc. Australas. Soc. Hum. Biol.5, 455-462, 1999, Med. Hypotheses52, 581-582), a metabolite essential for normal development of the embryonic neural tube (Bower & Stanley, 1989, The Medical Journal of Australia150, 613-619; Medical Research Council Vitamin Research Group, 1991, The Lancet338, 31-37) and spermatogenesis (Cosentino et al., 1990, Proc. Natn. Acad. Sci. U.S.A.87, 1431-1435; Mathur et al., 1977, Fertility Sterility28, 1356-1360).As hominids migrated outside of the tropics, varying degrees of depigmentation evolved in order to permit UVB-induced synthesis of previtamin D(3). The lighter color of female skin may be required to permit synthesis of the relatively higher amounts of vitamin D(3)necessary during pregnancy and lactation. Skin coloration in humans is adaptive and labile. Skin pigmentation levels have changed more than once in human evolution. Because of this, skin coloration is of no value in determining phylogenetic relationships among modern human groups.
 +Copyright 2000 Academic Press.
 +
 +PMID: 10896812</blockquote>
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 +
 +
 +<blockquote>Am J Phys Anthropol. 2009 Aug;139(4):447-50.
 +The evolution of light skin color: role of vitamin D disputed.
 +Robins AH.
 +Department of Medicine, Division of Pharmacology, University of Cape Town Medical School, Observatory, South Africa 7925. ashley.robins@uct.ac.za
 +Comment in:
 +Am J Phys Anthropol. 2009 Aug;139(4):451-61.
 +
 +PMID: 19425095</blockquote>
 +
 +
 +  * **atherosclerosis in African Americans** – Vitamin D is widely used to treat patients with osteoporosis and/or low vitamin D levels based on a medically accepted normal range. This "normal" range is typically applied to all race groups, although it was established predominantly in whites. It is thought that as low vitamin D levels rise to the normal range with supplementation, protection from bone and heart disease (atherosclerosis) may increase, as well. Blacks generally have lower vitamin D levels than whites, partly because their darker skin pigmentation limits the amount of the vitamin produced by sunlight. "Despite" these lower vitamin D levels and dietary calcium ingestion, blacks naturally experience lower rates of osteoporosis and have far less calcium in their arteries. Studies further reveal that black patients with diabetes have half the rate of heart attack as whites, when provided equal access to health care. A 2010 study (explained [[http://www.sciencedaily.com/releases/2010/03/100315091259.htm|here]]) determined the relationship between circulating vitamin D levels and arterial calcium in 340 black men and women with type 2 diabetes.(({{pubmed>long:20061416}})) The team concluded that higher circulating levels of 25-D in blacks were associated with higher levels of calcified atherosclerotic plaque. 
  
 ===== References ===== ===== References =====
home/pathogenesis/vitamind/latitude.txt · Last modified: 09.14.2022 by 127.0.0.1
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