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Vitamin D

Vitamin D and the Sun

In a change to previous advice, SACN now recommends a Reference Nutrient Intake (RNI, meaning the intake that will be adequate to meet the needs of 97.5% of the population) of 10 μg/d (400 IU/d) vitamin D, year-round, for all over-4’s. The RNI for vitamin D refers to intakes from all dietary sources: natural food sources; fortified foods (including infant formula milk); and supplements. Exposure of skin to UVB radiation is affected by a number of factors such as time of day, season, latitude, altitude, cloud cover, air pollution, as well as clothing and sunscreen use. You can find the full SACN report here

British Phototherapy Group/ British Association of Dermatologists, 2013

Background

Vitamin D is essential for bone health. The sources of vitamin D are diet and sunlight exposure, with sunlight being a major source in most people1. However, the ultraviolet radiation in sunlight is the main cause of both melanoma and non melanoma skin cancer. The sunlight exposure time to make significant vitamin D varies according to a number of environmental, physical and personal factors, but is typically short and less than the amount of time needed for skin to redden and burn 2,3. In fact, long exposures can break down vitamin D, reducing benefit whilst increasing risk of skin cancer4. Casual brief sun exposures, while taking care not to burn and avoiding deliberate tanning, can help the body become vitamin D sufficient. Apart from oily fish, natural foods contain little vitamin D, but it can also be obtained through fortified foods and vitamin D supplements, the latter being particularly needed in those at risk of low levels. Presently, there is still uncertainty regarding vitamin D, including what levels qualify as “optimal” or “sufficient”, the risk/benefit balance of sunlight in people of different skin types and colours, whether vitamin D protects against chronic diseases such as cancer, heart disease and diabetes, and the benefits and risks of widespread supplementation. These and related areas are currently under review in the UK5.

Recommendations

1) Vitamin D and health

  • Everyone needs vitamin D, which is essential for good bone health. Low levels are linked to bone disorders including rickets in children, and osteomalacia and osteoporosis in adults4.
  • The evidence suggesting vitamin D might protect against cancer, heart disease, diabetes, multiple sclerosis and other chronic diseases is still inconclusive6. Some studies have supported that high levels of vitamin D are associated with a reduced risk of bowel cancer. However, even for bowel cancer, it is too early to say if vitamin D directly protects against this cancer or if it reflects another aspect of our health7.

2) Vitamin D status and levels

  • There is currently no accepted ‘optimal’ level of vitamin D. However, blood levels of 25(OH)D below 5-10 ng/ml (12.5-25 nmol/L) are agreed to be “deficient” since the severe bone disorders of rickets and osteomalacia can occur below these levels1,4. Some authorities state that a 25(OH)D level of 20 ng/ml (50 nmol/L) represents a “sufficient” level, based on bone health findings6.
  • Levels of 25(OH)D greater than 50 ng/ml (125 nmol/l) are not recommended6,8.

3) Sunlight/ultraviolet radiation, skin cancer and vitamin D

  • Sun exposure is a major source of vitamin D in the UK2,9, but particularly when excessive, is known to be the main cause of both melanoma and non melanoma skin cancers, which continue to escalate in number in the UK10.
  • Environmental, physical and personal factors influence risk/benefit of sunlight exposure4. In white-skinned people, casual short sun exposures a few times per week, taking particular care not to burn and avoiding deliberate tanning, can help provide the benefits of vitamin D while minimising risks2,3.
  • Sunbed use increases the risk of skin cancer, and is not recommended as a method for enhancing vitamin D status11.

4) Dietary vitamin D and vitamin D supplements

  • Vitamin D supplements, fortified foods such as fat spreads, and natural dietary sources particularly oily fish (including salmon, trout and sardines) can be useful for helping to maintain levels of vitamin D. These sources are particularly important during the winter and among people at higher risk of low vitamin D1.
  • Population groups at particular risk of low vitamin D include pregnant and breastfeeding women, young children, older people, darker-skinned people, those who wear whole-body coverings or live in institutions. The Government currently recommends these groups take a 10 microgram (400 iu) vitamin D supplement a day (7 micrograms a day for children 6 months - 5 years)1,12.
  • Certain patient groups are also at particular risk of low vitamin D. This includes patients medically advised to minimise sunlight exposure, i.e. those with photosensitivity/ photodermatoses (sun rashes), patients with skin cancer, and with increased risk of skin cancer including individuals who are immunosuppressed or genetically prone. It is recommended that a blood test for vitamin D level is taken before and during treatment, to assess need for supplements and response to these.
  • Currently in the UK there is no recommendation for widespread vitamin D supplementation for the general population. Unlike vitamin D produced in the skin, which is biologically regulated, there is the potential that vitamin D from supplements and fortified foods could build up to high levels4.

Reviews and recommendations on vitamin D

  • Vitamin D in the UK is an area under active research and debate, and is under current review by Government authorities5.

References

  1. Ashwell M, Stone EM, Stolte H et al. UK Foods Standards Agency Workshop Report: an investigation of the relative contributions of diet and sunlight to vitamin D status. Br J Nutr 2010; 104: 603-11.
  2. Webb AR, Kift R, Durkin MT et al. The role of sunlight exposure in determining the vitamin D status of the UK white adult population. Br J Dermatol 2010; 163: 1050-55.
  3. Rhodes LE, Webb AR, Fraser HI et al. Recommended summer sunlight exposure levels can produce sufficient (≥20 ng/ml) but not the proposed optimal (≥32 ng/ml) 25(OH)D levels at UK latitudes. J Invest Dermatol. 2010; 130: 1411-8.
  4. National Radiological Protection Board. Health effects from ultraviolet radiation. Report of an advisory group on non-ionising radiation. Vol. 13. Didcot, United Kingdom: NRPB, 2002.
  5. Scientific Advisory Committee on Nutrition. http://www.sacn.gov.uk/
  6. Institute of Medicine. Dietary reference intakes for calcium and vitamin D. Washington, DC: The National Academy Press, 2011.
  7. International Agency for Research on Cancer. 2008. Vitamin D and Cancer. IARC Working Group Reports. vol. 5. Lyon: International Agency for Research on Cancer. World Health Organisation.
  8. Michaelsson K, Baron JA, Snellman G et al. Plasma vitamin D and mortality in older men: a community-based prospective cohort study. Am J Clin Nutr 2010; 92: 841-8.
  9. Macdonald HM, Mavroeidi A, Fraser WD et al. Sunlight and dietary contributions to the seasonal vitamin D status of cohorts of healthy postmenopausal women living at northerly latitudes: a major cause for concern? Osteoporos Int 2011; 22: 2461-72.
  10. Cancer Research UK. http://www.cancerresearchuk.org/
  11. International Agency for Research on Cancer Working Group on artificial ultraviolet (UV) light and skin cancer. The association of use of sunbeds with cutaneous malignant melanoma and other skin cancers: A systematic review. Int J Cancer. 2007; 120: 1116-22.
  12. Department of Health (Great Britain). Nutrition and bone health with particular reference to calcium and vitamin D: report of the Subgroup on Bone Health, Working Group on the Nutritional Status of the Population of the Committee on Medical Aspects of Food and Nutrition Policy. London, United Kingdom: Stationery Office, 1998.

Consensus statment, December 2010

This consensus statement represents the unified views of the British Association of Dermatologists, Cancer Research UK, Diabetes UK, the Multiple Sclerosis Society, the National Heart Forum, the National Osteoporosis Society and the Primary Care Dermatology Society.

Vitamin D is essential for good bone health and for most people sunlight is the most important source of vitamin D. The time required to make sufficient vitamin D varies according to a number of environmental, physical and personal factors, but is typically short and less than the amount of time needed for skin to redden and burn. Enjoying the sun safely, while taking care not to burn, can help to provide the benefits of vitamin D without unduly raising the risk of skin cancer. Vitamin D supplements and specific foods can help to maintain sufficient levels of vitamin D, particularly in people at risk of deficiency. However, there is still a lot of uncertainty around what levels qualify as “optimal” or “sufficient”, how much sunlight different people need to achieve a given level of vitamin D, whether vitamin D protects against chronic diseases such as cancer, heart disease and diabetes, and the benefits and risks of widespread supplementation. 

Summary

  • Everyone needs vitamin D, which is essential for good bone health. Low levels are linked to bone conditions such as rickets in children, and osteomalacia and osteoporosis in adults. 
  • There is currently no standard definition of an ‘optimal’ level of vitamin D. The consensus is that levels of 25(OH)D below 25nmol/L indicate ‘deficiency’. Some have argued that this level is conservative. Raising the definition of “deficiency” or “sufficiency” to higher levels is inappropriate until results from randomised trials can show that maintaining such levels has clear health benefits and no health risks.
  • The evidence suggesting that vitamin D might protect against cancer, heart disease, diabetes, multiple sclerosis and other chronic diseases is still inconclusive. Some studies have suggested that high levels of vitamin D are associated with a reduced risk of bowel cancer although the mechanism has yet to be elucidated. For other cancers, the evidence is inconsistent or limited. Even for bowel cancer, it is too early to say if vitamin D directly protects against this cancer or if it reflects another aspect of our health.
  • Sun exposure is the main source of vitamin D, but excessive sun exposure is the main cause of skin cancer, including melanoma, the fastest rising type of cancer in the UK. Enjoying the sun safely, while taking care not to burn, can help to provide the benefits of vitamin D without unduly raising the risk of skin cancer. 
  • It is impractical to offer a one-size-fits-all recommendation for the amount of sun exposure that people need to make sufficient vitamin D, because this varies according to a number of environmental, physical and personal factors. 
  • The time required to make sufficient vitamin D is typically short and less than the amount of time needed for skin to redden and burn. Regularly going outside for a matter of minutes around the middle of the day without sunscreen should be enough. When it comes to sun exposure, little and often is best, and the more skin that is exposed, the greater the chance of making sufficient vitamin D before burning. However, people should get to know their own skin to understand how long they can spend outside before risking sunburn under different conditions. 
  • Vitamin D supplements, fortified fat spreads and dietary sources such as oily fish (including salmon, trout and sardines) can be useful for helping to maintain sufficient levels of vitamin D. These sources are particularly important during the winter and among people at higher risk of vitamin D deficiency, including pregnant and breastfeeding women, young children, older people, darker-skinned people, those who wear whole-body coverings, those living in institutions, skin cancer patients and those who avoid the sun. People at risk of low sun exposure should take a 10 microgram supplement of vitamin D a day (7 micrograms a day for children aged 6 months to 5 years), which is the Government-recommended dose. 
  • There is not enough evidence to support a recommendation for food fortification or widespread vitamin D supplementation for the general population. Unlike vitamin D produced in the skin, there is the potential that vitamin D from supplements and fortificants could build up to toxic levels and there is not enough evidence about the possible risks of raised vitamin D blood levels in the general population over a long period of time.

Vitamin D requirements 

The level of 25-hydroxyvitamin D (25(OH)D) in the blood is the best indicator of vitamin D status. There is consensus that levels below 25nmol/L (10ng/ml) qualify as ‘deficient’,1, 2 but beyond this there is currently no standard definition of ‘optimal’ 25(OH)D levels.3, 4 There is also lack of standardization of methods used to measure 25(OH)D status, with different tests producing very different results.5
Some scientists suggest that levels above 50nmol/L (20ng/ml) are ‘sufficient’, while 70–80nmol/L (28-32ng/ml) is ‘optimal’.1, 6, 7 However, raising the definition of “deficiency” or “sufficiency” is currently inappropriate since no results from randomised trials suggest that maintaining such levels of 25(OH)D prevents chronic diseases. It is also unclear whether these levels are practical for all individuals, given that various studies have found that that 25(OH)D levels plateau at around 70-80nmol/L, with wide variation across individuals.8, 9 For example, a Hawaiian study found that half of healthy, young surfers had levels below 75nmol/L despite extensive unprotected outdoor exposure and tanned complexions.9
The Department of Health currently recommends a daily 10 microgram vitamin D supplement for those at risk of vitamin D deficiency, including all pregnant and breastfeeding women, older people and those at risk of inadequate sun exposure (for example those who cover their skin for cultural reasons or those confined indoors). A daily vitamin D supplement of 7 micrograms is also recommended for all children aged 6 months to 5 years. 2 The National Institute for Health and Clinical Excellence (NICE) also emphasises the importance of maintaining adequate vitamin D during pregnancy and breastfeeding, and suggests that women may choose to take up to 10 µg of vitamin D a day during these periods.10


Factors affecting vitamin D levels and groups at high risk of vitamin D deficiency

The amount of UVB in sunlight changes substantially with season, latitude and time of day.11 These factors greatly affect vitamin D production, which is greatest around two hours either side of solar noon, and during summer months. Physical characteristics can also affect vitamin D production, with darker skin requiring longer UV exposures to produce the same amount of vitamin D.12, 13 Older people have a reduced ability to make vitamin D through their skin.14 Obese people have lower 25(OH)D levels, which may be due to less sun exposure or greater uptake of vitamin D in fat tissue, which may be more inaccessible.15
Certain groups of people have a higher risk of vitamin D deficiency including those with darker skin,12, 13 those who wear whole-body coverings,16, 17 older people,14 pregnant women,18 infants born to vitamin D-deficient mothers,19 skin cancer patients, those who are housebound or in institutions, and those who avoid the sun.20
Some studies have found that sunscreen use reduces vitamin D production.21 However, sunscreens do not provide complete protection against UVB and there is great variation in the way people use these products. Based on studies and trials that reflect actual sun exposure habits, it is unlikely that these products contribute significantly to vitamin D deficiency.22, 23

Sun exposure 

Exposure to ultraviolet B (UVB) radiation in sunlight is the most efficient way to boost vitamin D supply but it is still unclear how much sunlight is required to produce a given level of 25(OH)D. Environmental and personal factors greatly affect vitamin D production in the skin, making it difficult to recommend a one-size-fits-all level of exposure for the general population.
However, the best estimates suggest that for most people, everyday casual exposure to sunlight is enough to produce vitamin D in the summer months, provided optimal environmental conditions.24, 25 The area of skin exposed will also influence the amount of vitamin D made after sun exposure. In a recent study, Caucasian British people were given a simulated dose of a summer exposure to sunlight, while dressed in casual summer clothes that revealed a third of their skin. These controlled conditions (the equivalent of 13 minutes of midday exposure to the summer sun given three times a week for six weeks during winter) raised 25(OH)D levels to greater than 50nmol/L in 90% of people and greater than 70nmol/L in 26% of people 8. The true amount of time may be greater and will vary depending on other factors including posture, time of day, outdoor activities, and the presence of shading structures.
It has been consistently shown that vitamin D can be efficiently and sufficiently produced at doses of UV below those which cause sunburn (i.e. reddening of the skin).21, 26-31 After prolonged UV exposure, vitamin D is converted into inert substances in the skin.11, 32 Thus, additional UV exposure provides no additional vitamin D but linearly increases levels of DNA damage and risk of skin cancer. Some unprotected exposure in the hours close to solar noon may be necessary, but people should not be advised to deliberately sunbathe or expose themselves to the sun for long periods of time in order to produce more vitamin D. When it comes to sun exposure, little and often is best.31, 33
During winter months in the UK, there is not enough UVB for vitamin D synthesis and people rely on tissues stores, supplements and dietary sources.11 If people achieve a sufficient supply of vitamin D in the summer most should keep levels greater than 25nmol/l in winter even without supplements; in others supplementation with vitamin D can help to maintain these levels in the winter. 34-36 
Dietary sources 
Vitamin D is found in only a few foods, with oily fish and fish oils, liver, meat and eggs being the main natural sources. In the UK, processed and some powdered milks, margarine, fat spreads and breakfast cereals are often voluntarily fortified with vitamin D. On average, UK men and women get 3.7 µg and 2.8 µg of vitamin D per day through diet.
The potential contribution of diet to vitamin D supply is a topic of debate. Widely quoted estimates suggest that more than 90% of vitamin D requirements come from exposure to sunlight.37 The International Agency for Research on Cancer (IARC) concluded that results do not support this, noting that many studies from around the world have found that use of vitamin D supplements and oily fish consumption predicted vitamin D levels as well as outdoor activities, holidays in sunny areas and sunbed use.38 Even people with genetic disorders that necessitate sun avoidance can maintain sufficient vitamin D levels through diet.39
The Food Standards Agency has funded three studies investigating the contribution of diet and sunlight to vitamin D status in the adult and elderly population. One of these, the Vitamin D, Food Intake, Nutrition and Exposure to Sunlight in Southern England study (D-FINES; currently unpublished), concluded that dietary vitamin D intake currently makes little contribution to the 25(OH)D status of British Caucasians and Asians living in the South of England, and that too few foods provide a valuable source. Foods can certainly contribute to vitamin D status, but on their own, it is unclear if they can sufficiently raise levels of 25(OH)D in people who experience deficiency. 
Supplements 
Vitamin D is present in a range of unlicensed dietary supplements (including fish oil products) and licensed medicines, which can help to boost vitamin D levels.34 A study commissioned by the FSA concluded that it takes 9 µg/day of supplements for the vast majority of the population to achieve 25(OH)D levels greater than 25nmol/L in the winter. To achieve levels greater than 50nmol/L and 80 nmol/L, predictive modelling suggests it would take on average 28 µg/day (1120 IU) and 41 µg/day (1640 IU) of supplements respectively.40
Supplements may be warranted for groups with high-risk of vitamin D deficiency and the Department of Health already recommends vitamin D supplements (10 micrograms/day or less) for all pregnant and breastfeeding women, young children, older people and those at risk of low sunlight exposure. 
 Supplements containing vitamin D3 (cholecalciferol) are preferable to those containing vitamin D2 (ergocalciferol). And supplements that contain only vitamin D are preferable over multivitamins, since other trials have shown that most vitamin supplements are ineffective for cancer prevention, and some can increase the risk of cancer.41 Supplements that contain vitamin A, including cod liver oil, are unsuitable for older people and pregnant women.
The human body avoids building up toxic levels of vitamin D by limiting the amount that is produced in the skin in response to UV light. Vitamin D taken through supplements is not subject to the same controls that prevent the build-up of toxic levels of vitamin D in response to UV light. As such, it is premature to recommend vitamin D supplements for the general population. Trials have suggested that vitamin D supplementation of 10-20 µg/day (400-800 IU) could reduce all-cause mortality in elderly people with low vitamin D status,42 but there is still a lack of evidence about the possible risks of chronically raising levels of vitamin D in healthy people through supplementation.38 Studies like National Health and Nutrition Examination Survey (NHANES III) and the Cohort Consortium Vitamin D Pooling Project of Rarer Cancers (VDPP) suggest that high levels of vitamin D beyond the threshold of 75nmol/L could be associated with negative effects,43, 44 and past experience has shown that high-dose supplements of other micronutrients have led to increased risk of cancer, despite promising early studies.
In 2003, the Food Standards Agency’s Expert Group on Vitamins and Minerals cautioned that excess vitamin D intake may lead to hypercalcaemia and hypercalciuria and that moderate levels (0.025-0.05 mg/day) of intake may enhance renal stone formation in predisposed individuals.45 The Group also set an upper guidance level for supplemental intake of 25 µg/day, which would not be expected to cause adverse effects in the general population.

Vitamin D and the risk of diseases

Bone health

Prolonged deficiency leads to rickets in infants and children and osteomalacia in adults. It is also associated with osteoporosis, hip fractures and falls in older people. Low levels of 25(OH)D are associated with secondary hyperparathyroidism and low bone mineral density and, thus, a higher risk of fractures. Some studies have suggested that low vitamin D levels are associated with an increased risk of certain cancers and other chronic diseases but evidence for a causal association is weak and inconclusive.
Cancer
Levels of 25(OH)D in the blood are the only reliable indicators of vitamin D status.46 IARC recently concluded that low vitamin D levels are associated with a higher risk of bowel cancer, but the evidence is limited for breast cancer, non-existent for prostate cancer and too sparse for all other cancer types to draw firm conclusions.38 These results are consistent with other meta-analyses and systematic reviews.47, 48 A pooled analysis of 10 cohort studies found that levels of 25(OH)D greater than 75 nmol/L do not reduce the risk of womb, oesophageal, stomach, kidney or ovarian cancers, nor non-Hodgkin lymphoma.49 The analysis also found that levels of 25(OH)D greater than 100 nmol/L was associated with a doubling of pancreatic cancer risk.50 Even where bowel cancer is concerned, it is unclear if a lack of vitamin D causes an increased risk of cancer, or is simply a consequence of poor health or bowel malfunction. Two clinical trials have assessed the effects of vitamin D supplementation. Both showed that such supplements are ineffective at reducing the risk of cancer,51, 52 but both have been criticised for methodological weaknesses.38 Further trials are needed.


Much of the support for a protective role of vitamin D against cancer comes from laboratory, animal and ecological studies.53 Ecological studies report that several cancers are more common at higher latitude, which is taken as a proxy for lower UV exposure and lower vitamin D levels.54, 55 However, this approach is prone to confounding by other factors such as socioeconomic status and skin type and it does not account for variations in individual behaviour, which are stronger predictors of UV exposure than latitude.38, 56
Other chronic diseases
Vitamin D deficiency has also been linked to a variety of other chronic diseases, including multiple sclerosis, heart disease and diabetes. As with cancer, all of these links are still inconclusive and causal relationships cannot be drawn from existing evidence. 
Sunbeds 
Sunbeds do not grant protection against vitamin D deficiency.57 Sunbed use is accompanied by a high frequency of sunburns, which are linked to a higher risk of melanoma.58 While any exposure to UVB radiation can increase vitamin D levels, such increases through sunbed exposures plateau rapidly and are outweighed by the risks. Sunbeds also emit high levels of UVA, which can cause melanoma but do not contribute to vitamin D production.59

Further research 

There are many questions around vitamin D that still need to be answered.

  • What is the optimal level of 25(OH)D for various health outcomes?
  • Can higher levels of 25(OH)D directly reduce the risk of cancer or other chronic diseases, and can supplementation achieve the same effects?
  • How much sun exposure is needed to ensure optimal levels of vitamin D in people of different skin types and under different environmental conditions? 
  • What roles do dietary sources and supplements have in achieving optimal vitamin D levels, particularly in the winter? 
  • Are there any adverse consequences of chronically high levels of 25(OH)D, raised through supplementation or food fortification?
  • Does body fat act as a sink or source of vitamin D in winter?

References

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  2. SACN. Update on Vitamin D: Position Statement by the Scientific Advisory Committee on Nutrition. London: TSO; 2007.
  3. Willett AM. Vitamin D status and its relationship with parathyroid hormone and bone mineral status in older adolescents. Proc Nutr Soc. 2005 May;64(2):193-203
  4. Lanham-New S. Br J Nutr. 2010;In Press.
  5. Snellman G, Melhus H, Gedeborg R, Byberg L, Berglund L, Wernroth L, et al. Determining Vitamin D Status: A Comparison between Commercially Available Assays. PLoS ONE. 2010;5(7):e11555.
  6. Bischoff-Ferrari HA, Giovannucci E, Willett WC, Dietrich T, Dawson-Hughes B. Estimation of optimal serum concentrations of 25-hydroxyvitamin D for multiple health outcomes. Am J Clin Nutr. 2006 Jul;84(1):18-28.
  7. Dawson-Hughes B, Heaney RP, Holick MF, Lips P, Meunier PJ, Vieth R. Estimates of optimal vitamin D status. Osteoporos Int. 2005 Jul;16(7):713-6.
  8. Rhodes LE, Webb AR, Fraser HI, Kift R, Durkin MT, Allan D, et al. Recommended Summer Sunlight Exposure Levels Can Produce Sufficient (>/=20 ng ml(-1)) but Not the Proposed Optimal (>/=32 ng ml(-1)) 25(OH)D Levels at UK Latitudes. J Invest Dermatol. 2010 Jan 14.
  9. Binkley N, Novotny R, Krueger D, Kawahara T, Daida YG, Lensmeyer G, et al. Low vitamin D status despite abundant sun exposure. J Clin Endocrinol Metab. 2007 Jun;92(6):2130-5.
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  11. Webb AR, Kline L, Holick MF. Influence 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. J Clin Endocrinol Metab. 1988 Aug;67(2):373-8.
  12. Lo C, Paris P, Holick M. Indian and Pakistani immigrants have the same capacity as Caucasians to produce vitamin D in response to ultraviolet irradiation. Am J Clin Nutr. 1986;44:683-5.
  13. Dawson-Hughes B. Racial/ethnic considerations in making recommendations for vitamin D for adult and elderly men and women. Am J Clin Nutr. 2004 80:1763S-6S.
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  15. Wortsman J, Matsuoka LY, Chen TC, Lu Z, Holick MF. Decreased bioavailability of vitamin D in obesity. Am J Clin Nutr. 2000 Sep;72(3):690-3.
  16. Dawodu A, Absood G, Patel M, Agarwal M, Ezimokhai M, Abdulrazzaq Y, et al. Biosocial factors affecting vitamin D status of women of childbearing age in the United Arab Emirates. J Biosoc Sci. 1998;30:431-7.
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  18. Dawodu A, Agarwal M, Hossain M, Kochiyil J, Zayed R. Hypovitaminosis D and vitamin D deficiency in exclusively breast-feeding infants and their mothers in summer: a justification for vitamin D supplementation of breast-feeding infants. J Pediatr. 2003 Feb;142(2):169-73.
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  20. Glass D, Lens M, Swaminathan R, Spector TD, Bataille V. Pigmentation and vitamin D metabolism in Caucasians: low vitamin D serum levels in fair skin types in the UK. PLoS One. 2009;4(8):e6477.
  21. Matsuoka L, Wortsman J, Hanifan N, Holick M. Chronic sunscreen use decreases circulating concentrations of 25-hydroxyvitamin D. A preliminary study. Arch Dermatol. 1988;124:1802-4.
  22. Marks R, Foley P, Jolley D, Knight K, Harrison J, Thompson S. The effect of regular sunscreen use on vitamin D levels in an Australian population. Results of a randomized controlled trial. Arch Dermatol. 1995;131:415-21.
  23. Farrerons J, Barnadas M, Lopez-Navidad A, Renau A, Rodriguez J, Yoldi B, et al. Sunscreen and risk of osteoporosis in the elderly: a two-year follow-up. Dermatology. 2001;202(1):27-30.
  24. Holick M. Sunlight "D"ilemma: risk of skin cancer or bone disease and muscle weakness. Lancet. 2001;357:4-6.
  25. Samanek AJ, Croager EJ, Giesfor Skin Cancer Prevention P, Milne E, Prince R, McMichael AJ, et al. Estimates of beneficial and harmful sun exposure times during the year for major Australian population centres. Med J Aust. 2006 Apr 3;184(7):338-41.
  26. Webb AR, Engelsen O. Calculated Ultraviolet Exposure Levels for a Healthy Vitamin D Status. Photochem Photobiol. 2006 Sep 1.
  27. Matsuoka L, Ide L, Wortsman J, MacLaughlin J, Holick M. Sunscreens suppress cutaneous vitamin D3 synthesis. J Clin Endocrinol Metab. 1987;64:1165-8.
  28. Matsuoka L, Wortsman J, Hollis B. Use of topical sunscreen for the evaluation of regional synthesis of vitamin D3. J Am Acad Dermatol. 1990;22:772-5.
  29. Matsuoka LY, Wortsman J, Haddad JG, Hollis BW. Skin types and epidermal photosynthesis of vitamin D3. J Am Acad Dermatol. 1990 Sep;23(3 Pt 1):525-6.
  30. Matsuoka LY, Wortsman J, Haddad JG, Kolm P, Hollis BW. Racial pigmentation and the cutaneous synthesis of vitamin D. Arch Dermatol. 1991 Apr;127(4):536-8.
  31. Rhodes LE. Recommended summer sunlight exposure levels can produce sufficient (> or =20 ng ml(-1)) but not the proposed optimal (> or =32 ng ml(-1)) 25(OH)D levels at UK latitudes. J Invest Dermatol. 2010;130(5):1411-8.
  32. MacLaughlin JA, Anderson RR, Holick MF. Spectral character of sunlight modulates photosynthesis of previtamin D3 and its photoisomers in human skin. Science. 1982 May 28;216(4549):1001-3.
  33. Moan J, Dahlback A, Porojnicu AC. At what time should one go out in the sun? Adv Exp Med Biol. 2008;624:86-8.
  34. Heaney RP. The Vitamin D requirement in health and disease. J Steroid Biochem Mol Biol. 2005 Oct;97(1-2):13-9.
  35. Heaney RP, Davies KM, Chen TC, Holick MF, Barger-Lux MJ. Human serum 25-hydroxycholecalciferol response to extended oral dosing with cholecalciferol. Am J Clin Nutr. 2003 Jan;77(1):204-10.
  36. Holick M. McCollum Award Lecture, 1994: vitamin D – new horizons for the 21st century. Am J Clin Nutr. 1994;60:619-30.
  37. Holick MF. The vitamin D epidemic and its health consequences. J Nutr. 2005 Nov;135(11):2739S-48S.
  38. IARC. Vitamin D and Cancer. Lyon: IARC; 20008.
  39. Sollitto RB, Kraemer KH, DiGiovanna JJ. Normal vitamin D levels can be maintained despite rigorous photoprotection: six years' experience with xeroderma pigmentosum. J Am Acad Dermatol. 1997 Dec;37(6):942-7.
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  43. Melamed ML, Michos ED, Post W, Astor B. 25-hydroxyvitamin D levels and the risk of mortality in the general population. Arch Intern Med. 2008 Aug 11;168(15):1629-37.
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BAD position statment 2009

On this page you will find some advice about the sun, skin cancer prevention and vitamin D. As well as some general advice, you can also read a summary of the evidence (click here) on which we base our advice.
2009: BAD position of vitamin D: In recent months there has been much debate about the pros and cons of sunshine for your health.
We know that UV light from the sun and sunbeds can increase risk of skin cancer. However, sunlight also helps the skin on our body to produce vitamin D.

A lack of vitamin D may cause health issues in some people. There is good evidence that vitamin D helps to keep bones healthy. It has also been suggested that vitamin D may help to prevent serious diseases such as cancer, various forms of arthritis and autoimmune diseases. This is an area of considerable research, as there are a large number of questions that still need to be answered, including whether enough vitamin D can be made from sunlight on our skin to reduce the risk of getting these diseases. On the other hand the link between skin cancer and the sun, is proven and well documented.

We recognize that it can be hard to get the required level of vitamin D from the diet alone, which is why we do not say you should avoid the sun altogether.

Unfortunately, we can’t give a precise level of sun exposure that will safely provide you with vitamin D, while also not putting you at risk of skin cancer. This is because there are so many variables – for example, your personal skin type, the geographical location, time of day, weather conditions and more.

It is therefore difficult to quantify how much sun it takes to damage the skin, how much sun it takes for each individual to make optimum amounts of vitamin D, or furthermore to combine the two and define a safe level of sun exposure that allows each person to get the recommended level of vitamin D without suffering skin damage. We do know, however, that once your body has produced its maximum level of vitamin D, extra sunlight does not increase production and will result in skin damage.

Dermatologists are at the forefront of treating skin cancer, and therefore cannot recommend deliberate sun exposure as a safe means of getting vitamin D. A few points to consider are that:

  1. You can get vitamin D from other sources, such as your diet and supplements
  2. It is a fact that UV light from the sun causes skin cancer
  3. Much of the evidence regarding health benefits of high levels of vitamin D require much more research to define what the optimum levels are and how best to achieve these levels. 

We therefore currently advise that you should not sunbathe to increase your vitamin D levels as you may increase your risk of skin cancer in doing so. Small amounts of incidental sunlight, as you might get through your daily activities, may help to boost your vitamin D levels.

However, if you are at high risk of skin cancer, you should make protecting your skin in the sun a priority, and look to get as much vitamin D as possible from other sources, such as your diet and supplements, rather than placing yourself at higher risk from skin cancer. Those at high risk include:

  • people with very fair skin that easily burns
  • people with a personal or family history of skin cancer
  • people with lots of moles (more than 50) or 
  • if you are being treated with immunosuppressive drugs.

Much research is being done by dermatologists and other doctors in this area and into the role of vitamin D in disease prevention. So the sensible advice is to get some sunshine as you go about your daily life without getting a heavy tan or burning, and to get vitamin D through your diet. Some foods are fortified with vitamin D (for example some yoghurts, margarine and cereals) and others, such as oily fish, are naturally rich in vitamin D. You can also take a vitamin supplement containing vitamin D, such as a multivitamin or cod liver oil, available from a pharmacist.
Remember that your skin will produce plenty of vitamin D long before it starts to burn.


Weighing up the evidence

Evidence relating to sun safety cannot be interpreted in isolation from the increasing, but sometimes contradictory, volume of evidence surrounding the risks to health from vitamin D deficiency and its link to sun avoidance.
The message itself is not easily definable, as a number of variables, such as the geographical location, time of day, weather conditions and the individual’s skin colour, all contribute to the net effect of the sun on the skin.
It is therefore difficult to quantify how much sun it takes to damage the skin, how much sun it takes to obtain an individual’s optimum vitamin D level, or furthermore to combine the two and define a safe level of sun exposure that allows a person to obtain the recommended level of vitamin D without suffering skin damage.


i) Physiology of Vitamin D

Vitamin D is produced in the skin in response to ultraviolet radiation (UVR). This action of UVR on the skin is the main source of vitamin D in humans, and vitamin D status reflects sun exposure over the preceding month or so. There is seasonal variation in UVR, and vitamin D levels reflect changes in outdoor behaviour as well as UVR levels. Production of vitamin D due to UV exposure is limited, because pre-vitamin D and vitamin D are photolabile, no matter how long someone is exposed to sunlight. Hence it is simply not possible to synthesize large stocks of vitamin D by prolonged exposure to the sun (Webb et al., 1989, Dahl, 2004). That is, there is not a clear consistent linear dose - response relationship between UVR exposure and vitamin D levels. Indeed with prolonged sunlight exposure the production of vitamin D actually stops after a certain period. There is considerable debate as to the level of vitamin D required for normal physiological function. Some authorities have the view that plasma levels of above 30 microgram/l of 25 hydroxyvitamin D are required for normal physiological function (Feskanich et al., 2004). This includes calcium homeostasis and normal bone health. In northern latitudes, and in winter, many individuals are vitamin D deficient by these definitions. Some groups are more susceptible to vitamin D deficiency and these include breast fed babies, the elderly, persons with limited sun exposure, and those with malabsorption syndromes, obesity or dark skin.


ii) Health benefits of vitamin D and health risks from vitamin D deficiency

Higher vitamin D levels may have health benefits, and so it has been suggested that additional UVR exposure and / or vitamin D supplements may be necessary; for example, vitamin D supplements of 25 micrograms (µg) (1,000 IU) in those under one year, 50 µg in children up to 13, and 50 µg (2000 IU) in adults, including during pregnancy and lactation (Cranney, 2007). It is clear that high vitamin D levels benefit bone health. A recent evidence-based review of research concluded that supplements of both vitamin D3 (at around 20 micrograms/day) and calcium (500-1200 micrograms/day) decreased the risk of falls, fractures, and bone loss in elderly individuals aged 62 to 85 years (Cranney, 2007). It has been suggested that vitamin D may also reduce the risk of internal malignancy (Giovannucci, 2005; Freedman et al., 2007; Skinner, 2008; Lu et al., 2008; Stolzenberg-Solomon, 2009; Ahn et al., 2008; Khazai et al., 2008). However, a WHO IARC working group paper concluded that there was insufficient evidence to support conclusively the relationship between vitamin D levels and colo-rectal and breast cancer, and none to support a relationship to prostatic cancer. Two studies of dietary supplementation with 10 and 21 micrograms of vitamin D failed to influence the incidence of colo-rectal or breast cancer, but supplementation with up to 20 micrograms of vitamin D reduced all cause mortality in the over 50 age group. It is possible, but unproven, that high vitamin D levels may reduce disease progression in established malignancy. Controversially, very high levels of vitamin D are associated with increased mortality from cardiovascular disease (IARC Reports, 2008). Other adverse health issues associated with low vitamin D levels include multiple sclerosis, hypertension, diabetes and autoimmune disorders (Moan et al., 2008; Diffey, 2006). Whilst there are suggestions of benefit from high vitamin D levels, these health benefits are as yet unproven. The 2008 IARC report concluded that for the time being, the definition of vitamin D deficiency should relate to the prevention of rickets, osteomalacia or muscular pain as opposed to internal malignancies. However, this is an emerging area of research which may support the role of vitamin D in disease prevention in future studies.

iii) The arguments

a) It has been suggested that the potential benefits of exposure to sunlight may outweigh the widely publicized adverse effects on the incidence of skin cancer (Ness et al., 1999). As indicated above, the evidence for benefit of UVR exposure acting through vitamin D is contradictory, whilst the evidence for UVR exposure as a cause of skin cancer is incontrovertible.
b) Some have argued that there is little evidence that sun avoidance measures prevent melanoma (Shuster, 2008) and that there is no reduction in the incidence of melanoma with sunscreen use. Almost all authorities accept that there is a direct link between UVR exposure and melanoma (Menzies, 2008). There are convincing data that sunscreen use has little influence on vitamin D status (Marks, 1995).
c) At the same time, it has been suggested that advice aimed at reducing the frequency of episodes of sunburn may have the net effect of reducing vitamin D levels. As indicated above, this is unlikely to be a significant factor because of the very short period of time in the sun needed for maximum vitamin D synthesis.
d) Finally, a lack of good prospective studies that quantify the potential benefits versus the risks of increasing vitamin D by UVR exposure to allow clinicians, patients, healthy individuals and policy makers to decide on personal and population guidance on this issue, is a major current limitation.

iv) Vitamin D Recommended Daily Allowance (RDA)

The minimal requirement for vitamin D is dependent on many factors such as latitude, personal lifestyle (including smoking and body mass index) skin type and the season. It is thus not possible to give a precise figure of dietary supplementation to avoid vitamin D deficiency but the range of vitamin D intakes required to ensure maintenance of wintertime vitamin D status of 20 to 40 year old adults, considering a variety of sun exposure preferences, is between 7.2 and 41.1 micrograms/day. Government guidelines say people between the ages of 51 and 70 should get 400 International Units (IU) (10 micrograms) of vitamin D daily, and those ages 71 and older, 600 IU. In adult patients at high risk, daily vitamin D3 intake should be 800–1000 IU or 50,000 IU vitamin D3 per month (Kullavanijaya and Lim 2005).

v) The need for balance

There are clear and robust data linking skin cancer and UVR. The data regarding the health benefits of vitamin D are emerging, but are still unclear. Sun safety messages must therefore be tailored to take into account this growing area of research, and should influence but not replace sun safety messages.
People should not be advised to forsake photoprotection for cutaneous vitamin D supplementation. Oral supplementation of vitamin D, through diet or dietary supplements is an additional means of achieving adequate vitamin D levels.

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