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Commonly recommended daily intake of vitamin D is not sufficient if sunlight exposure is limited. Glerup H, Mikkelsen K, Poulsen L, Hass E, Overbeck S, Thomsen J, Charles P, Eriksen EF. J Intern Med. 2000 Feb;247(2):260-8. PMID: 10692090 Conclusions. Severe vitamin D deficiency is prevalent amongst sunlight-deprived individuals living in Denmark. In veiled Arab women, vitamin D deficiency is the result of a combination of limitations in sunlight exposure and a low oral intake of vitamin D. The oral intake of vitamin D amongst veiled ethnic Danish Moslems was, however, very high, at 13.53 µg (approximately 600 IU), but they were still vitamin D-deficient. Our results suggest that the daily oral intake of vitamin D in sunlight-deprived individuals should exceed 600 IU; most probably it should be 1000 IU day-1 to secure a normal level of 25-hydroxyvitamin D. This finding is in contrast with the commonly used RDA (recommended daily allowance) for adults in Europe: 200 IU day-1.

Geographic variation in breast cancer mortality in the United States: a hypothesis involving exposure to solar radiation. Garland FC, Garland CF, Gorham ED, Young JF. Prev Med. 1990 Nov;19(6):614-22. PMID: 2263572 doi:10.1016/0091-7435(90)90058-R Vitamin D from sunlight exposure may be associated with low risk for fatal breast cancer, and differences in ultraviolet light reaching the United States population may account for the striking regional differences in breast cancer mortality. The ecological nature of this study is emphasized, and the possibility that an indirect association with dietary and socioeconomic factors could explain these findings is discussed.

The European Food Safety Authority's Panel on contaminants in the food chain has set a reduced tolerable weekly intake (TWI)[1] for cadmium of 2.5 micrograms per kilogram of body weight (µg/kg bw), based on an analysis of new data. The TWI is the level at which adverse effects are not expected. Average dietary exposure to cadmium for adults across Europe is around this level. Some population groups - vegetarians, children, smokers and people living in highly contaminated areas - can have a higher level of exposure up to twice the TWI. However, the Panel concluded that even for these groups the risk of adverse effects would be very low. The Panel concluded that current exposure to cadmium at the level of the population should be reduced.

Vitamin D and breast cancer. Bertone-Johnson ER. Ann Epidemiol. 2009 Jul;19(7):462-7. Epub 2009 Feb 20. Review. PMID: 19230714 Though the relationship between vitamin D and breast cancer remains unclear, a growing body of evidence suggests that vitamin D may modestly reduce risk. A large number of in vitro studies indicate that vitamin D can inhibit cell proliferation and promote apoptosis and cell differentiation in breast tumor tissue. Results from analytic studies of sunlight exposure and dietary intake have been inconsistent but together generally support a modestly protective role of vitamin D, at least in some population subgroups. Studies using blood vitamin D metabolites to assess vitamin D status may be less prone to misclassification than those of diet and sunlight exposure. Overall, the two prospective and four case-control studies of 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D tend to support a protective effect in older women. The relationship between common vitamin D receptor polymorphisms and risk remains unclear. Many questions about this relationship clearly remain, including the utility of assessing vitamin D through diet and sunlight exposure, the relationship between plasma metabolites, and the potential modifying effects of age, menopausal status and tumor characteristics. Given that vitamin D status is modifiable, additional prospective studies are necessary to determine if vitamin D may have important potential for breast cancer prevention.

Quantitative analysis of the benefits and risks of consuming farmed and wild salmon. Foran JA, Good DH, Carpenter DO, Hamilton MC, Knuth BA, Schwager SJ. J Nutr. 2005 Nov;135(11):2639-43. PMID: 16251623 Contaminants in farmed Atlantic and wild Pacific salmon raise important questions about the competing health benefits and risks of fish consumption. A benefit-risk analysis was conducted to compare quantitatively the cancer and noncancer risks of exposure to organic contaminants in salmon with the (n-3) fatty acid-associated health benefits of salmon consumption. Recommended levels of (n-3) fatty acid intake, as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), may be achieved by consuming farmed or wild salmon while maintaining an acceptable level of noncarcinogenic risk. However, the recommended level of EPA+DHA intake cannot be achieved solely from farmed or wild salmon while maintaining an acceptable level of carcinogenic risk. Although the benefit-risk ratio for carcinogens and noncarcinogens is significantly greater for wild Pacific salmon than for farmed Atlantic salmon as a group, the ratio for some subgroups of farmed salmon is on par with the ratio for wild salmon. This analysis suggests that risk of exposure to contaminants in farmed and wild salmon is partially offset by the fatty acid-associated health benefits. However, young children, women of child-bearing age, pregnant women, and nursing mothers not at significant risk for sudden cardiac death associated with CHD but concerned with health impairments such as reduction in IQ and other cognitive and behavioral effects, can minimize contaminant exposure by choosing the least contaminated wild salmon or by selecting other sources of (n-3) fatty acids.

Addressing the health benefits and risks, involving vitamin D or skin cancer, of increased sun exposure.\nMoan J, Porojnicu AC, Dahlback A, Setlow RB.\nProc Natl Acad Sci U S A. 2008 Jan 15;105(2):668-73. Epub 2008 Jan 7.\nPMID: 18180454

According to a study conducted by University of Wisconsin researchers, even people who are regularly exposed to sunlight can have low vitamin D levels.\n\nThe study focused on subjects who lived in sunny Hawaii and spent an average of 11.1 hours in the sun each week. (None of the participants in the study used any type of sunscreen.) Despite the exposure, 51 percent of participants were found to be deficient in vitamin D.

Circulating vitamin D3 and 25-hydroxyvitamin D in humans: An important tool to define adequate nutritional vitamin D status. Hollis BW, Wagner CL, Drezner MK, Binkley NC. J Steroid Biochem Mol Biol. 2007 Mar;103(3-5):631-4. Epub 2007 Jan 10. PMID: 17218096 In the present study, we sought to investigate what circulating 25(OH)D levels would result in populations exhibiting no substrate limitations to the vitamin D-25-hydroxylase. To perform this, we chose two distinct populations. The first were individuals from a year-found sunny environment who spent a good deal of time outdoors. The second were a group of lactating women receiving a substantial daily oral dose of vitamin D3. Surprisingly, a study such as this previously had not been undertaken. There are several reasons for this. First, finding a group of sun-exposed individuals is not an easy task; in fact, we had to go to Hawaii to find them. Secondly, very few studies have been performed where subjects actually received adequate vitamin D3 supplementation to make them replete. Finally, it is very difficult and costly to measure circulating vitamin D3 and relate it to circulating 25(OH)D. The results of our study are far-reaching. This study also demonstrates that individuals can be vitamin D deficient with significant sun exposure if the skin area exposed is limited as was suggested several years ago (19). Finally, whether one receives their vitamin D3 orally or through UV exposure, the vitamin D-25-hydroxylase appears to handle it in an equivalent fashion with respect to maintaining circulating 25(OH)D levels. Thus, we believe that the relationship between circulating vitamin D and 25(OH)D may define adequate nutritional vitamin D status.

Barger-Lux MJ, Heaney RP. Effects of above average summer sun exposure on serum 25-hydroxyvitamin D and calcium absorption.J Clin Endocrinol Metab. 2002 Nov;87(11):4952-6.PMID: 12414856 [PubMed - indexed for MEDLINE]

Glerup H, Mikkelsen K, Poulsen L, Hass E, Overbeck S, Thomsen J, Charles P, Eriksen EF. Commonly recommended daily intake of vitamin D is not sufficient if sunlight exposure is limited.J Intern Med. 2000 Feb;247(2):260-8.PMID: 10692090 [PubMed - indexed f

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.

An evaluation of the relative contributions of exposure to sunlight and of diet to the circulating concentrations of 25-hydroxyvitamin D in an elderly nursing home population in Boston. Webb AR, Pilbeam C, Hanafin N, Holick MF. Am J Clin Nutr. 1990 Jun;51(6):1075-81. PMID: 2349922

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.

Comment: Although lower risk associated with vitamin D exposure was shown most consistently for ER+/PR+ tumors, the result might simply reflect that this tumor subtype was the most common. Nonetheless, these findings support vitamin D's beneficial effects on breast cancer risk, regardless of hormone-receptor status. Sun exposure and dietary intake (Table 1) are key sources of vitamin D.

Vitamin D from dietary intake and sunlight exposure and the risk of hormone-receptor-defined breast cancer. Blackmore KM, Lesosky M, Barnett H, Raboud JM, Vieth R, Knight JA. Am J Epidemiol. 2008 Oct 15;168(8):915-24. Epub 2008 Aug 27. PMID: 18756015 doi:10.1093/aje/kwn198 This study suggests that vitamin D is associated with a reduced risk of breast cancer regardless of ER/PR status of the tumor. Future studies with a larger number of receptor-negative and mixed tumors are required.

Explaining multiple sclerosis prevalence by ultraviolet exposure: a geospatial analysis. Beretich B, Beretich T. Mult Scler. 2009 Aug;15(8):891-8. PMID: 19667017 DOI: 10.1177/1352458509105579 Conclusion This analysis suggests a strong association between UV radiation and MS distribution, and an increase in risk for MS in those areas with a low UVI.

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.

Cod liver oil, vitamin A toxicity, frequent respiratory infections, and the vitamin D deficiency epidemic. Cannell JJ, Vieth R, Willett W, Zasloff M, Hathcock JN, White JH, Tanumihardjo SA, Larson-Meyer DE, Bischoff-Ferrari HA, Lamberg-Allardt CJ, Lappe JM, Norman AW, Zittermann A, Whiting SJ, Grant WB, Hollis BW, Giovannucci E. Ann Otol Rhinol Laryngol. 2008 Nov;117(11):864-70. Review. PMID: 19102134 Until we have better information on doses of vitamin D that will reliably provide adequate blood levels of 25(OH)D without toxicity, treatment of vitamin D deficiency in otherwise healthy children should be individualized according to the numerous factors that affect 25(OH)D levels, such as body weight, percent body fat, skin melanin, latitude, season of the year, and sun exposure.2 The doses of sunshine or oral vitamin D3 used in healthy children should be designed to maintain 25(OH)D levels above 50 ng/mL. As a rule, in the absence of significant sun exposure, we believe that most healthy children need about 1,000 IU of vitamin D3 daily per 11 kg (25 lb) of body weight to obtain levels greater than 50 ng/mL. Some will need more, and others less. In our opinion, children with chronic illnesses such as autism, diabetes, and/or frequent infections should be supplemented with higher doses of sunshine or vitamin D3, doses adequate to maintain their 25(OH)D levels in the mid-normal of the reference range (65 ng/mL) - and should be so supplemented year round. Otolaryngologists treating children are in a good position to both diagnose and treat vitamin D deficiency.

Investigating the links between muscle strength, sun exposure, dietary vitamin D intake and the vitamin D status of ambulatory older adults in South East Queensland Borradale, David (2008) QUT Thesis]

In 1939, Dr. Abraham Myerson measured initial levels of circulating testosterone in men and exposed their various body parts to UVB light. After five days of chest exposure sufficient to cause reddening, circulating testosterone increased by 120%. After eight days without additional UV exposure, testosterone returned to initial levels. When the genital area was exposed, testosterone levels increased by 200%!