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Do vitamin A serum levels moderate outcome or the protective effect of vitamin D on outcome from malignant melanoma?
Clinical Nutrition 32 (2013) 1012e1016
Contents lists available at SciVerse ScienceDirect
Clinical Nutrition journal homepage: http://www.elsevier.com/locate/clnu
Original article
Do vitamin A serum levels moderate outcome or the protective effect of vitamin D on outcome from malignant melanoma?q Sinead Field*, Faye Elliott, Juliette Randerson-Moor, Kairen Kukalizch, Jennifer H. Barrett, D. Timothy Bishop, Julia A. Newton-Bishop Section of Epidemiology & Biostatistics, Leeds Institute of Cancer Studies and Pathology, University of Leeds, Cancer Genetics Building, St. James’s University Hospital, Leeds LS9 7TF, United Kingdom
a r t i c l e i n f o
s u m m a r y
Article history: Received 28 November 2012 Accepted 8 April 2013
Background & aims: Low serum vitamin D levels (25-OH-vit D2/3) are reported to be associated with thicker melanomas and poorer outcome. Vitamin A metabolites and vitamin D bind to the same heterodimeric receptor. We report a study testing the hypothesis that high vitamin A levels may reduce the protective effect of vitamin D on outcome. Methods: Serum vitamin A levels were measured in 795 melanoma cases and assessed for association with Breslow thickness, overall (OS) and melanoma-specific survival (MSS), and modification of the effect of vitamin D levels on survival. Results: Higher vitamin A levels (2.2 mmol/l) conferred a non-significant increased risk of melanomaspecific death (adjusted HR ¼ 1.11, 95%CI(0.74e1.67), p ¼ 0.60) but not for death overall (adjusted HR ¼ 0.95, 95%CI(0.65e1.39), p ¼ 0.79). There was reduction in the protective effect of vitamin D on OS in patients with high vitamin A levels (2.2 mmol/l)(HR ¼ 0.99, 95%CI(0.72e1.36),p ¼ 0.93) compared to patients with low levels (<2.2 mmol)(HR ¼ 0.77, 95%CI(0.64e0.93),p ¼ 0.007), although the difference was not statistically significant (p ¼ 0.26). Conclusions: High vitamin A levels may reduce the protective effect of vitamin D. As sub-optimal levels of vitamin D are common in temperate climates, and are usually managed by dietary supplementation, we suggest vitamin D3 supplementation alone might be preferable for melanoma patients than preparations containing vitamin D and A. Ó 2013 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.
Keywords: Vitamin A Vitamin D Melanoma Survival Dietary supplements
1. Introduction Low serum levels of vitamin D have been reported to be associated with thicker tumours and poorer outcome for melanoma patients.1 Vitamin D has pleiotropic effects and there is strong evidence suggesting vitamin D has antiproliferative effects in cancer, therefore the role for vitamin D in primary and secondary cancer prevention in a number of cancers has been investigated. A recent meta-analysis showed that low vitamin D serum levels were associated with poorer outcome in prostate, breast and colon cancer.2 However, the beneficial effects of vitamin D in cancer
q Conference presentation: Presented as poster at the International Melanoma Congress, Tampa, Florida. * Corresponding author. Tel.: þ44 113206532; fax: þ44 1132340183. E-mail addresses: s.fi[email protected] (S. Field), [email protected] (F. Elliott), [email protected] (J. Randerson-Moor), [email protected] (K. Kukalizch), [email protected] (J.H. Barrett), [email protected] (D.T. Bishop), [email protected] (J.A. Newton-Bishop).
remain controversial. Vitamin D levels are higher in leaner fitter individuals, and although there are some data that lower levels are causally related to the metabolic syndrome,3 there is a concern that the association between higher vitamin D levels and survival in the healthy or the cancer population may not be a direct result of vitamin D but may be explained by confounding factors. Nonetheless many patients diagnosed with a melanoma are vitamin D insufficient at diagnosis,1 and avoidance of sunburn and excess sun exposure in these individuals can potentially lead to further subsequent reduction in vitamin D levels4 with likely adverse effects on overall health. Supplementation is therefore becoming more common; many sources of vitamin D (including cod-liver oil and multivitamins) also contain vitamin A (retinol). The transcriptional effects of vitamin D are mediated by binding to the vitamin D receptor (VDR), which forms a heterodimer with the retinoid receptor alpha (RXR-alpha). Vitamin A is the name for a group of fat-soluble retinoids. Structurally, retinoids are similar except for their polar end; a hydroxyl group in retinols, an aldehyde in retinals, and a carboxylic moiety in retinoic acids. Dietary
0261-5614/$ e see front matter Ó 2013 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved. http://dx.doi.org/10.1016/j.clnu.2013.04.006
S. Field et al. / Clinical Nutrition 32 (2013) 1012e1016
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Table 1 Vitamin A and D levels in melanoma patients taking single and multiple oral supplements.
Number of casesa (%) Vitamin A mmol/l median (range) Vitamin D nmol/l median (range)
Multivitamin alone
Cod liver oil alone
Multivitamin & cod liver oil
p-value for trend
65 (27.1) 1.79 (0.85e3.42) 51.9 (7.9e111.2)
132 (55.0) 1.94 (0.96e3.43) 59.1 (26.6e121.5)
29 (12.1) 2.03 (1.11e4.06) 62.2 (36.6e109.5)
e 0.02 0.01
a 14 patients (5.8%) were excluded; 4 who took pure vitamin D only, 2 who took pure vitamin D and cod liver oil, 5 who took pure vitamin D and multivitamin, 3 who took pure vitamin D, multivitamin and cod liver oil.
vitamin A is absorbed in the form of retinol (directly from animal source and metabolized from vegetable sourced carotenoids). Vitamin A metabolites bind to the RXR-alpha receptor. It has been hypothesised that high retinol levels may moderate the effect of vitamin D by metabolites competitively binding RXR-alpha rendering it unavailable to form a heterodimer with VDR.5 Despite uncertainty of the mechanism, evidence suggests high retinol levels can antagonise vitamin D induced calcium absorption in the human gut,6 and high levels have been associated with a higher risk of hip fractures and reduced bone mineralization in rats.7 These laboratory data have been supplemented by clinical studies. Oh et al. reported that high retinol intake (4800 IU/day) countered the beneficial effect of vitamin D on distal colorectal adenoma risk8 in humans. A Cochrane meta-analysis in 2007 showed an increase in allcause mortality with vitamin A supplementation,9 and a systematic review of betacarotene supplementation showed no preventive effect on melanoma risk and indeed an increased risk of stomach and lung cancer.10 A recent meta-analysis in cervical cancer suggests an inverse relationship with cervical cancer risk and vitamin A intake and blood levels.11 Overall, the data on the relationship between vitamin A and melanoma specifically are conflicting.
Table 2 Associations between vitamin A level, demographic characteristics and Breslow thickness. Statistic Age at diagnosis Mean (s.d) (years) Sex Female Number (%) Male BMI at diagnosis (kg/m2) <25 Number (%) 25 < 30 30 Educational level 2nd level Number (%) education 6th form/ vocational University education Breslow (mm) 1 Number (%) >1 2 >2 4 >4 Site of primary tumour Trunk Number (%) Head & neck Limbs Acral/rare
Vitamin A <2.2 mmol
Vitamin A 2.2 mmol
t or c2
p-value
52.5 (13.8)
55.6 (13.4)
2.75
0.006a
379 (78.8) 220 (70.1)
102 (21.2) 94 (29.9)
7.79
0.005b
236 (79.2) 226 (72.2) 129 (74.1)
62 (20.8) 87 (27.8) 45 (25.9)
4.17
0.12b
220 (75.6)
71 (24.4)
0.09
0.96b
244 (75.1)
81 (24.9)
113 (76.4)
35 (23.6)
163 226 136 71
(76.2) (74.3) (76.4) (75.5)
51 78 42 23
(23.8) (25.7) (23.6) (24.5)
0.35
0.95b
201 67 289 42
(77.0) (70.5) (76.5) (68.9)
60 28 89 19
(23.0) (29.5) (23.5) (31.1)
3.21
0.36b
Total numbers of patients varies between 764 and 795 due to missing educational level or Breslow data. a p-value from two-tailed t-test. b p-value from Pearson’s chi-squared test.
Vitamin A has been shown to have pro-differentiation and antiproliferative effects in vivo and in vitro in many cancers including melanoma.12,13 Moreover there is some evidence to suggest reduced susceptibility to melanoma with higher dietary vitamin A intake,14,15 and more recently a protective effect of retinol supplementation on melanoma risk.16 A randomised trial of oral vitamin A (1000 IU/day) versus observation in early stage (sentinel node negative) melanoma however showed no effect on disease-free survival or OS.17 This study of the Leeds Melanoma cohort was therefore designed to examine the association of vitamin A serum levels with melanoma thickness and survival from melanoma, and whether higher serum vitamin A levels modify the protective effect of serum vitamin D levels on survival.
2. Materials and methods Patients were recruited to the Leeds Melanoma Cohort as described previously and in accordance with the Declaration of Helsinki.1 Informed consent was obtained from all participants. 25hydroxyvitamin D2 and D3 at diagnosis were measured by liquid chromatography tandem spectrometry. D2 levels were almost uniformly undetectable, and D2 and D3 levels were therefore summed, which we shall refer to as serum vitamin D levels. Serum vitamin D levels vary seasonally, therefore adjusted means of serum vitamin D levels corrected for the season sampled were calculated using linear regression, and the seasonally adjusted serum vitamin D levels were used throughout. To reduce the skew of the frequency distribution, vitamin D level was categorized into six 20 nmol/l incremental groups and analysed as a continuum for modelling. All-trans-retinol levels (the predominant form of vitamin A in serum18) were measured on samples stored at 70 C by a highpressure liquid chromatography technique (Biolab, London, UK; normal range for this assay 1.05e2.80 mmol). We shall refer to these henceforth as serum vitamin A levels. The lower and upper limits of normal for the vitamin A assay used in this study were 1.05 and 2.80 mmol/l respectively. Vitamin A levels were significantly negatively correlated with duration of sample storage, therefore adjusted means of serum vitamin A levels corrected for sample storage time were calculated using linear regression (although we cannot exclude the possibility that storage time was a marker of an undefined environmental exposure over time e.g. dietary intake). To reduce the skew of the frequency distribution, serum vitamin A level was categorized into seven 0.5 mmol incremental groups and analysed as a continuum for modelling. To assess the effect of high vitamin A levels, a dichotomous variable was derived using the 75th centile of the frequency distribution (2.2 mmol) as the arbitrary cut-off value. ManneWhitney U tests and Pearson chi-squared tests were used to test for association between the dichotomous vitamin A level and: age at diagnosis, sex, body mass index (BMI) (kg/m2, grouped into three categories based on the World Health
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S. Field et al. / Clinical Nutrition 32 (2013) 1012e1016
Table 3 HRs and 95% confidence intervals from Cox proportional hazards models for the effects of vitamin A and D levels on overall and melanoma-specific survival.
Overall survival No. of observations, no. of eventsc Vitamin D per 20 nmol/l Vitamin A 2.2 mmol versus <2.2 mmol Melanoma-specific survival No. of observations, no. of eventsc Vitamin D per 20 nmol/l Vitamin A 2.2 mmol versus <2.2 mmol a b c
Unadjusted HR (95%CI, p-value)
Adjusteda HR (95%CI, p-value)
Vitamin A <2.2 mmol Adjustedb HR (95%CI, p-value)
Vitamin A 2.2 mmol Adjustedb HR (95%CI, p-value)
794, 166
753, 146
570, 109
183, 37
0.84 (0.73e0.98, 0.03)
0.82 (0.69e0.96, 0.02)
0.77 (0.64e0.93, 0.007)
0.99 (0.72e1.36, 0.93)
1.03 (0.72e1.45, 0.89)
0.95 (0.65e1.39, 0.79)
e
e
794, 137
753, 122
570, 88
183, 34
0.87 (0.74e1.03, 0.10) 1.14 (0.78e1.65, 0.51)
0.84 (0.70e1.00, 0.05) 1.11 (0.74e1.67, 0.60)
0.82 (0.67e1.01, 0.06) e
0.91 (0.64e1.29, 0.59) e
Model includes vitamin D, vitamin A (2.2 mmol versus <2.2 mmol), age, sex, BMI, Breslow thickness, tumour site and educational level. Models for the effect of Vitamin D stratified by Vitamin A level, adjusted for age, sex, BMI, Breslow thickness, tumour site and educational level. Number of observation in the models does not total 795 due to missing event data and missing demographic or Breslow data for some patients.
Organisation (WHO) classification (<25, 25 < 30, 30)), educational level as a measure of social status (Secondary level education, Sixth form/vocational, University education), Breslow thickness at diagnosis (categorized according to the AJCC staging system19; 1 mm, >1 2, >2 4, >4) and tumour site (trunk, head/neck, limbs, acral/rare). Vitamin A and vitamin D level were tested for association with vitamin A and/or vitamin D dietary supplement intake one year prior to diagnosis (categories: multivitamin only, cod liver oil only, both multivitamin and cod liver oil) using a nonparametric test for trend. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated from Cox proportional hazards models for overall survival (OS) and melanoma-specific survival (MSS). The effects of increasing vitamin D levels, increasing vitamin A levels and high vitamin A levels (2.2 mmol versus <2.2 mmol) were modelled separately in unadjusted analyses. A multiple regression model was then estimated including the following factors: vitamin D level, vitamin A level (2.2 mmol versus <2.2 mmol), age, sex, BMI, Breslow thickness, tumour site and educational level. The multiple regression model was then applied separately in patients with low (<2.2 mmol) and high (2.2 mmol) vitamin A levels to determine whether there was a differential effect and the difference between estimates was tested for by comparing the likelihoods of models with and without an interaction term. A nominal significance cutoff of 5% was used. Statistical analyses were performed using the statistical software, STATA (StataCorp. Stata Statistical Software: Release 10. College Station, TX: StataCorp LP 2007). 3. Results The median age at diagnosis of the 795 patients in this cohort was 54 (range 17e81) and 60% were female. The median seasonally adjusted vitamin D level was 49.5 nmol/l (range 7.2e121.5) and the median adjusted vitamin A level was 1.84 mmol/l (range 0.47e4.06). Dietary supplement data prior to diagnosis were available for 783 patients and 31% (240/783) used supplements containing vitamin A or D or both. The median adjusted vitamin A and seasonally adjusted vitamin D level in the 543 patients not taking vitamin A or D containing supplements were 1.79 mmol/l (range 0.47e3.75) and 45.4 nmol/l (range 7.2e102.8) respectively (data not shown). Table 1 shows the median vitamin A and vitamin D levels in patients who used supplements containing vitamin A and D; the median vitamin A and vitamin D levels were lowest in patients
taking multivitamin alone and were highest in patients taking both multivitamin and cod liver oil. Vitamin A and vitamin D levels were positively correlated overall (Pearson’s r ¼ 0.19, p < 0.001), in vitamin A and D supplement users (r ¼ 0.21, p ¼ 0.001) and non-users of vitamin A or D supplements (r ¼ 0.12, p ¼ 0.005) despite the majority of vitamin A being sourced from the diet and the majority of vitamin D usually being sourced from sunlight exposure. Supplement users were older than non-users (mean ages 55 and 52 years respectively, T-test p ¼ 0.002, data not shown). Females were no more likely to use supplements than males, however a higher proportion of females than males used multivitamins only (11% and 5% respectively), and a higher proportion of males than females used cod liver oil only (19% and 15% respectively), data not shown. Table 2 shows that patients with high vitamin A levels (2.2 mmol) were significantly older than patients with lower levels (58 and 53 years respectively), and a higher proportion of males than females had levels 2.2 mmol (30% and 21% respectively). Vitamin A level was not associated with BMI, educational level, Breslow thickness or tumour site (Table 2). Increasing levels of vitamin A (per 0.5 mmol) were not associated with MSS (unadjusted HR ¼ 1.04, 95%CI(0.90e1.20),p ¼ 0.59, data not shown); high vitamin A levels (2.2 mmol/l) conferred a nonsignificant increased risk of melanoma-specific death (adjusted HR ¼ 1.11, 95%CI(0.74e1.67),p ¼ 0.60) but not for death overall (adjusted HR ¼ 0.95, 95%CI(0.65e1.39), p ¼ 0.79)(Table 3). Increasing vitamin D levels (per 20 nmol/l) were significantly protective for death in unadjusted and adjusted OS models (adjusted HR ¼ 0.82, 95%CI(0.69e0.96),p ¼ 0.02)(Table 3). In a similar adjusted OS model stratifying by high/low vitamin A level (cut-off 2.2 mmol) vitamin D was significantly protective amongst patients with vitamin A levels <2.2 mmol (adjusted HR ¼ 0.77, 95%CI(0.64e 0.93), p ¼ 0.007). The protective effect of vitamin D was not seen in patients with vitamin A levels 2.2 mmol (HR ¼ 0.99, 95%CI(0.72e 1.36), p ¼ 0.93); however a likelihood ratio test for interaction did not reach statistical significance (p ¼ 0.26, data not shown). 4. Discussion In this study we did not find statistically significant evidence that vitamin A levels moderated the protective effect of vitamin D on OS. However, among patients with high vitamin A levels, the protective effect of vitamin D on OS was not apparent, suggesting that high vitamin A levels may be antagonizing the protective effect
S. Field et al. / Clinical Nutrition 32 (2013) 1012e1016
of vitamin D, consistent with our hypothesis. We also saw a modest increased risk for melanoma-specific death for high vitamin A levels overall, but again this was not statistically significant. In recent years there has been an increase in people supplementing their diet and concerns have been raised in the U.S. of subclinical toxicity with vitamin A as many Americans take a multivitamin and cod liver oil despite vitamin A being abundant in our everyday diet (eggs, milk and oily fish) and deficiency being rare in developed countries.20 It is noteworthy that the majority of study participants (94%, 744/795) had serum vitamin A levels below the upper level of normal (median 1.84 mmol/l, range 0.47e 4.06), and despite taking cod liver oil and multivitamin in combination 76% (22/29) of these individuals had vitamin A levels below the upper level of normal (median 2.03, range 1.11e4.06). The update on vitamin D by UK Scientific Advisory Committee on Nutrition 2007 recommended daily intake of vitamin D (10 mg/ day ¼ 400 IU/day) for adults at risk of deficiency such as those over 65 years of age, all pregnant and breastfeeding women and people not exposed to much sun. The latter category includes people confined indoors and those that cover the skin for cultural reasons; melanoma patients avoiding sun exposure following diagnosis would also fall into this category.21 Recommended daily intake of vitamin A in the UK for women is 600 mg and for men is 700 mg, noting that it is advised that population subgroups at risk of osteoporosis, such as postmenopausal women and older people, do not exceed retinol intake of 1500 mg/day.22 Recent guidance by the Institute of Medicine in the U.S. suggested an increased dosage of 600 IU/day or 15 mg of vitamin D as the recommended daily allowance for the majority. Most multivitamins contain 5 mg (400 IU) of vitamin D and 800 mg of vitamin A. Quantities of vitamin A and vitamin D in cod liver oil can vary (1 tablespoon ¼ 5e30 mg vitamin D, 1200e9000 mg of vitamin A). In contrast to vitamin D, vitamin A is much more abundant in our everyday diet. We demonstrated in our study that despite reporting taking multivitamin or cod liver oil, or cod liver oil and multivitamin in combination, the highest median vitamin D level was 62.2 nmol/l in those taking multivitamin and cod liver oil. It is likely that to reach a sufficient vitamin D level by these supplementation sources, recommended daily intake of vitamin A intake would be exceeded. The definition of sufficient or target serum vitamin D levels is much debated. Parathyroid hormone levels are thought to reach a plateau at 50e70 nmol/l.23 There are concerns that the dose response curves for vitamin D may have a J or U-shaped curve suggesting higher levels as well as low levels may be associated with an increased risk of death in breast cancer,24 increased cardiovascular risk25 and increased all-cause mortality in the general population26. Although the relationships reported above are not yet proven to be causal, the established effects of low vitamin D levels on bone health suggests that a vitamin D level in excess of 60 nmol/L would be advisable. The suggestion of J or U-shaped association curves guides us to suggest that a conservative approach for vitamin D serum target levels may be 60e85 nmol/l allowing for seasonal variation. To date there is no evidence available to support the hypothesis that supplementation with vitamin D to achieve sufficient serum levels has a benefit on outcome in patients with melanoma. However it seems reasonable to supplement melanoma patients who have sub-optimal levels of vitamin D to ensure sufficient levels as judged necessary for bone health. In this study we saw evidence of an increase in death from melanoma in patients with high versus low vitamin A levels. The protective effect of vitamin D was not apparent in patients with high levels of vitamin A. Although the differences in effect were not statistically significant, neither did we see any protective effects of vitamin A and, given the ubiquity of this vitamin in the diet, if
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supplementation is taken it seems sensible to use a source of vitamin D3 alone. Acknowledgements Statements of authorship: SF FE JNB had substantial contributions to conception and design, acquisition of data and analysis and interpretation of data, drafting the article. JRM KK had substantial contributions to conception and design, acquisition of data. JHB DTB had substantial contributions to analysis and interpretation of data. All authors revised the article critically and approved the final version for publication. Funding sources: British Skin Foundation 2009 Small Grant S501, Cancer Research United Kingdom (CR-UK) Project Grant C8216/A6129 and CR-UK Programme Grant C588/A10589. Our funding sources had no influence on the work. No authors have conflicts of interest related to this manuscript. References 1. Newton-Bishop JA, Beswick S, Randerson-Moor J, Chang YM, Affleck P, Elliott F, et al. Serum 25-hydroxyvitamin D3 levels are associated with breslow thickness at presentation and survival from melanoma. J Clin Oncol 2009;27:5439e44. 2. Buttigliero C, Monagheddu C, Petroni P, Saini A, Dogliotti L, Ciccone G, et al. Prognostic role of vitamin D status and efficacy of vitamin D supplementation in cancer patients: a systematic review. Oncologist 2011;16: 1215e27. 3. Al-Daghri NM, Alkharfy KM, Al-Saleh Y, Al-Attas OS, Alokail MS, Al-Othman A, et al. Modest reversal of metabolic syndrome manifestations with vitamin D status correction: a 12-month prospective study. Metabolism 2012;61(5): 661e6. 4. Idorn LW, Philipsen PA, Wulf HC. Sun exposure before and after a diagnosis of cutaneous malignant melanoma: estimated by developments in serum vitamin D, skin pigmentation and interviews. Br J Dermatol 2011;165:164e70. 5. Haussler MR, Jurutka PW, Hsieh JC, Thompson PD, Selznick SH, Haussler CA, et al. New understanding of the molecular mechanism of receptor-mediated genomic actions of the vitamin D hormone. Bone 1995;17:33Se8S. 6. Johansson S, Melhus H. Vitamin A antagonizes calcium response to vitamin D in man. J Bone Miner Res 2001;16:1899e905. 7. Rohde CM, Manatt M, Clagett-Dame M, DeLuca HF. Vitamin A antagonizes the action of vitamin D in rats. J Nutr 1999;129:2246e50. 8. Oh K, Willett WC, Wu K, Fuchs CS, Giovannucci EL. Calcium and vitamin D intakes in relation to risk of distal colorectal adenoma in women. Am J Epidemiol 2007;165:1178e86. 9. Bjelakovic G, Nikolova D, Gluud LL, Simonetti RG, Gluud C. Mortality in randomized trials of antioxidant supplements for primary and secondary prevention: systematic review and meta-analysis. JAMA 2007;297:842e57. 10. Druesne-Pecollo N, Latino-Martel P, Norat T, Barrandon E, Bertrais S, Galan P, et al. Beta-carotene supplementation and cancer risk: a systematic review and metaanalysis of randomized controlled trials. Int J Cancer 2010;127: 172e84. 11. Zhang X, Dai B, Zhang B, Wang Z. Vitamin A and risk of cervical cancer: a metaanalysis. Gynecol Oncol 2012;124:366e73. 12. Meyskens Jr FL, Fuller BB. Characterization of the effects of different retinoids on the growth and differentiation of a human melanoma cell line and selected subclones. Cancer Res 1980;40:2194e6. 13. Weinzweig J, Tattini C, Lynch S, Zienowicz R, Weinzweig N, Spangenberger A, et al. Investigation of the growth and metastasis of malignant melanoma in a murine model: the role of supplemental vitamin A. Plast Reconstr Surg 2003;112:152e8 [discussion 59e61]. 14. Feskanich D, Willett WC, Hunter DJ, Colditz GA. Dietary intakes of vitamins A, C, and E and risk of melanoma in two cohorts of women. Br J Cancer 2003;88: 1381e7. 15. Naldi L, Gallus S, Tavani A, Imberti GL, La Vecchia C. Risk of melanoma and vitamin A, coffee and alcohol: a case-control study from Italy. Eur J Cancer Prev 2004;13:503e8. 16. Asgari MM, Brasky TM, White E. Association of vitamin A and carotenoid intake with melanoma risk in a large prospective cohort. J Invest Dermatol 2012;132: 1573e82. 17. Meyskens Jr FL, Liu PY, Tuthill RJ, Sondak VK, Fletcher WS, Jewell WR, et al. Randomized trial of vitamin A versus observation as adjuvant therapy in highrisk primary malignant melanoma: a Southwest Oncology Group study. J Clin Oncol 1994;12:2060e5. 18. Furr HC. Analysis of retinoids and carotenoids: problems resolved and unsolved. J Nutr 2004;134:281Se5S.
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19. Balch CM, Gershenwald JE, Soong SJ, Thompson JF, Atkins MB, Byrd DR, et al. Final version of 2009 AJCC melanoma staging and classification. J Clin Oncol 2009;27:6199e206. 20. Ballew C, Bowman BA, Sowell AL, Gillespie C. Serum retinol distributions in residents of the United States: third National Health and Nutrition Examination Survey, 1988e1994. Am J Clin Nutr 2001;73:586e93. 21. Update on vitamin D, position statement. Scientific Advisory Committee on Nutrition. At: http://www.sacn.gov.uk/pdfs/sacn_position_vitamin_d_2007_ 05_07.pdf; 2007 [accessed 01.11.12]. 22. Review of dietary advice on vitamin A. Scientific Advisory Committee on Nutrition. At: http://www.sacn.gov.uk/pdfs/sacn_vita_report.pdf; 2005 [accessed 01.11.12].
23. Bjorkman M, Sorva A, Tilvis R. Responses of parathyroid hormone to vitamin D supplementation: a systematic review of clinical trials. Arch Gerontol Geriatr 2009;48:160e6. 24. Goodwin PJ, Ennis M, Pritchard KI, Koo J, Hood N. Prognostic effects of 25hydroxyvitamin D levels in early breast cancer. J Clin Oncol 2009;27: 3757e63. 25. Wang TJ, Pencina MJ, Booth SL, Jacques PF, Ingelsson E, Lanier K, et al. Vitamin D deficiency and risk of cardiovascular disease. Circulation 2008;117:503e11. 26. Durup D, Jorgensen HL, Christensen J, Schwarz P, Heegaard AM, Lind B. A reverse J-shaped association of all-cause mortality with serum 25-hydroxyvitamin D in general practice: the CopD study. J Clin Endocrinol Metab 2012;97:2644e52.
Contents lists available at SciVerse ScienceDirect
Clinical Nutrition journal homepage: http://www.elsevier.com/locate/clnu
Original article
Do vitamin A serum levels moderate outcome or the protective effect of vitamin D on outcome from malignant melanoma?q Sinead Field*, Faye Elliott, Juliette Randerson-Moor, Kairen Kukalizch, Jennifer H. Barrett, D. Timothy Bishop, Julia A. Newton-Bishop Section of Epidemiology & Biostatistics, Leeds Institute of Cancer Studies and Pathology, University of Leeds, Cancer Genetics Building, St. James’s University Hospital, Leeds LS9 7TF, United Kingdom
a r t i c l e i n f o
s u m m a r y
Article history: Received 28 November 2012 Accepted 8 April 2013
Background & aims: Low serum vitamin D levels (25-OH-vit D2/3) are reported to be associated with thicker melanomas and poorer outcome. Vitamin A metabolites and vitamin D bind to the same heterodimeric receptor. We report a study testing the hypothesis that high vitamin A levels may reduce the protective effect of vitamin D on outcome. Methods: Serum vitamin A levels were measured in 795 melanoma cases and assessed for association with Breslow thickness, overall (OS) and melanoma-specific survival (MSS), and modification of the effect of vitamin D levels on survival. Results: Higher vitamin A levels (2.2 mmol/l) conferred a non-significant increased risk of melanomaspecific death (adjusted HR ¼ 1.11, 95%CI(0.74e1.67), p ¼ 0.60) but not for death overall (adjusted HR ¼ 0.95, 95%CI(0.65e1.39), p ¼ 0.79). There was reduction in the protective effect of vitamin D on OS in patients with high vitamin A levels (2.2 mmol/l)(HR ¼ 0.99, 95%CI(0.72e1.36),p ¼ 0.93) compared to patients with low levels (<2.2 mmol)(HR ¼ 0.77, 95%CI(0.64e0.93),p ¼ 0.007), although the difference was not statistically significant (p ¼ 0.26). Conclusions: High vitamin A levels may reduce the protective effect of vitamin D. As sub-optimal levels of vitamin D are common in temperate climates, and are usually managed by dietary supplementation, we suggest vitamin D3 supplementation alone might be preferable for melanoma patients than preparations containing vitamin D and A. Ó 2013 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.
Keywords: Vitamin A Vitamin D Melanoma Survival Dietary supplements
1. Introduction Low serum levels of vitamin D have been reported to be associated with thicker tumours and poorer outcome for melanoma patients.1 Vitamin D has pleiotropic effects and there is strong evidence suggesting vitamin D has antiproliferative effects in cancer, therefore the role for vitamin D in primary and secondary cancer prevention in a number of cancers has been investigated. A recent meta-analysis showed that low vitamin D serum levels were associated with poorer outcome in prostate, breast and colon cancer.2 However, the beneficial effects of vitamin D in cancer
q Conference presentation: Presented as poster at the International Melanoma Congress, Tampa, Florida. * Corresponding author. Tel.: þ44 113206532; fax: þ44 1132340183. E-mail addresses: s.fi[email protected] (S. Field), [email protected] (F. Elliott), [email protected] (J. Randerson-Moor), [email protected] (K. Kukalizch), [email protected] (J.H. Barrett), [email protected] (D.T. Bishop), [email protected] (J.A. Newton-Bishop).
remain controversial. Vitamin D levels are higher in leaner fitter individuals, and although there are some data that lower levels are causally related to the metabolic syndrome,3 there is a concern that the association between higher vitamin D levels and survival in the healthy or the cancer population may not be a direct result of vitamin D but may be explained by confounding factors. Nonetheless many patients diagnosed with a melanoma are vitamin D insufficient at diagnosis,1 and avoidance of sunburn and excess sun exposure in these individuals can potentially lead to further subsequent reduction in vitamin D levels4 with likely adverse effects on overall health. Supplementation is therefore becoming more common; many sources of vitamin D (including cod-liver oil and multivitamins) also contain vitamin A (retinol). The transcriptional effects of vitamin D are mediated by binding to the vitamin D receptor (VDR), which forms a heterodimer with the retinoid receptor alpha (RXR-alpha). Vitamin A is the name for a group of fat-soluble retinoids. Structurally, retinoids are similar except for their polar end; a hydroxyl group in retinols, an aldehyde in retinals, and a carboxylic moiety in retinoic acids. Dietary
0261-5614/$ e see front matter Ó 2013 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved. http://dx.doi.org/10.1016/j.clnu.2013.04.006
S. Field et al. / Clinical Nutrition 32 (2013) 1012e1016
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Table 1 Vitamin A and D levels in melanoma patients taking single and multiple oral supplements.
Number of casesa (%) Vitamin A mmol/l median (range) Vitamin D nmol/l median (range)
Multivitamin alone
Cod liver oil alone
Multivitamin & cod liver oil
p-value for trend
65 (27.1) 1.79 (0.85e3.42) 51.9 (7.9e111.2)
132 (55.0) 1.94 (0.96e3.43) 59.1 (26.6e121.5)
29 (12.1) 2.03 (1.11e4.06) 62.2 (36.6e109.5)
e 0.02 0.01
a 14 patients (5.8%) were excluded; 4 who took pure vitamin D only, 2 who took pure vitamin D and cod liver oil, 5 who took pure vitamin D and multivitamin, 3 who took pure vitamin D, multivitamin and cod liver oil.
vitamin A is absorbed in the form of retinol (directly from animal source and metabolized from vegetable sourced carotenoids). Vitamin A metabolites bind to the RXR-alpha receptor. It has been hypothesised that high retinol levels may moderate the effect of vitamin D by metabolites competitively binding RXR-alpha rendering it unavailable to form a heterodimer with VDR.5 Despite uncertainty of the mechanism, evidence suggests high retinol levels can antagonise vitamin D induced calcium absorption in the human gut,6 and high levels have been associated with a higher risk of hip fractures and reduced bone mineralization in rats.7 These laboratory data have been supplemented by clinical studies. Oh et al. reported that high retinol intake (4800 IU/day) countered the beneficial effect of vitamin D on distal colorectal adenoma risk8 in humans. A Cochrane meta-analysis in 2007 showed an increase in allcause mortality with vitamin A supplementation,9 and a systematic review of betacarotene supplementation showed no preventive effect on melanoma risk and indeed an increased risk of stomach and lung cancer.10 A recent meta-analysis in cervical cancer suggests an inverse relationship with cervical cancer risk and vitamin A intake and blood levels.11 Overall, the data on the relationship between vitamin A and melanoma specifically are conflicting.
Table 2 Associations between vitamin A level, demographic characteristics and Breslow thickness. Statistic Age at diagnosis Mean (s.d) (years) Sex Female Number (%) Male BMI at diagnosis (kg/m2) <25 Number (%) 25 < 30 30 Educational level 2nd level Number (%) education 6th form/ vocational University education Breslow (mm) 1 Number (%) >1 2 >2 4 >4 Site of primary tumour Trunk Number (%) Head & neck Limbs Acral/rare
Vitamin A <2.2 mmol
Vitamin A 2.2 mmol
t or c2
p-value
52.5 (13.8)
55.6 (13.4)
2.75
0.006a
379 (78.8) 220 (70.1)
102 (21.2) 94 (29.9)
7.79
0.005b
236 (79.2) 226 (72.2) 129 (74.1)
62 (20.8) 87 (27.8) 45 (25.9)
4.17
0.12b
220 (75.6)
71 (24.4)
0.09
0.96b
244 (75.1)
81 (24.9)
113 (76.4)
35 (23.6)
163 226 136 71
(76.2) (74.3) (76.4) (75.5)
51 78 42 23
(23.8) (25.7) (23.6) (24.5)
0.35
0.95b
201 67 289 42
(77.0) (70.5) (76.5) (68.9)
60 28 89 19
(23.0) (29.5) (23.5) (31.1)
3.21
0.36b
Total numbers of patients varies between 764 and 795 due to missing educational level or Breslow data. a p-value from two-tailed t-test. b p-value from Pearson’s chi-squared test.
Vitamin A has been shown to have pro-differentiation and antiproliferative effects in vivo and in vitro in many cancers including melanoma.12,13 Moreover there is some evidence to suggest reduced susceptibility to melanoma with higher dietary vitamin A intake,14,15 and more recently a protective effect of retinol supplementation on melanoma risk.16 A randomised trial of oral vitamin A (1000 IU/day) versus observation in early stage (sentinel node negative) melanoma however showed no effect on disease-free survival or OS.17 This study of the Leeds Melanoma cohort was therefore designed to examine the association of vitamin A serum levels with melanoma thickness and survival from melanoma, and whether higher serum vitamin A levels modify the protective effect of serum vitamin D levels on survival.
2. Materials and methods Patients were recruited to the Leeds Melanoma Cohort as described previously and in accordance with the Declaration of Helsinki.1 Informed consent was obtained from all participants. 25hydroxyvitamin D2 and D3 at diagnosis were measured by liquid chromatography tandem spectrometry. D2 levels were almost uniformly undetectable, and D2 and D3 levels were therefore summed, which we shall refer to as serum vitamin D levels. Serum vitamin D levels vary seasonally, therefore adjusted means of serum vitamin D levels corrected for the season sampled were calculated using linear regression, and the seasonally adjusted serum vitamin D levels were used throughout. To reduce the skew of the frequency distribution, vitamin D level was categorized into six 20 nmol/l incremental groups and analysed as a continuum for modelling. All-trans-retinol levels (the predominant form of vitamin A in serum18) were measured on samples stored at 70 C by a highpressure liquid chromatography technique (Biolab, London, UK; normal range for this assay 1.05e2.80 mmol). We shall refer to these henceforth as serum vitamin A levels. The lower and upper limits of normal for the vitamin A assay used in this study were 1.05 and 2.80 mmol/l respectively. Vitamin A levels were significantly negatively correlated with duration of sample storage, therefore adjusted means of serum vitamin A levels corrected for sample storage time were calculated using linear regression (although we cannot exclude the possibility that storage time was a marker of an undefined environmental exposure over time e.g. dietary intake). To reduce the skew of the frequency distribution, serum vitamin A level was categorized into seven 0.5 mmol incremental groups and analysed as a continuum for modelling. To assess the effect of high vitamin A levels, a dichotomous variable was derived using the 75th centile of the frequency distribution (2.2 mmol) as the arbitrary cut-off value. ManneWhitney U tests and Pearson chi-squared tests were used to test for association between the dichotomous vitamin A level and: age at diagnosis, sex, body mass index (BMI) (kg/m2, grouped into three categories based on the World Health
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Table 3 HRs and 95% confidence intervals from Cox proportional hazards models for the effects of vitamin A and D levels on overall and melanoma-specific survival.
Overall survival No. of observations, no. of eventsc Vitamin D per 20 nmol/l Vitamin A 2.2 mmol versus <2.2 mmol Melanoma-specific survival No. of observations, no. of eventsc Vitamin D per 20 nmol/l Vitamin A 2.2 mmol versus <2.2 mmol a b c
Unadjusted HR (95%CI, p-value)
Adjusteda HR (95%CI, p-value)
Vitamin A <2.2 mmol Adjustedb HR (95%CI, p-value)
Vitamin A 2.2 mmol Adjustedb HR (95%CI, p-value)
794, 166
753, 146
570, 109
183, 37
0.84 (0.73e0.98, 0.03)
0.82 (0.69e0.96, 0.02)
0.77 (0.64e0.93, 0.007)
0.99 (0.72e1.36, 0.93)
1.03 (0.72e1.45, 0.89)
0.95 (0.65e1.39, 0.79)
e
e
794, 137
753, 122
570, 88
183, 34
0.87 (0.74e1.03, 0.10) 1.14 (0.78e1.65, 0.51)
0.84 (0.70e1.00, 0.05) 1.11 (0.74e1.67, 0.60)
0.82 (0.67e1.01, 0.06) e
0.91 (0.64e1.29, 0.59) e
Model includes vitamin D, vitamin A (2.2 mmol versus <2.2 mmol), age, sex, BMI, Breslow thickness, tumour site and educational level. Models for the effect of Vitamin D stratified by Vitamin A level, adjusted for age, sex, BMI, Breslow thickness, tumour site and educational level. Number of observation in the models does not total 795 due to missing event data and missing demographic or Breslow data for some patients.
Organisation (WHO) classification (<25, 25 < 30, 30)), educational level as a measure of social status (Secondary level education, Sixth form/vocational, University education), Breslow thickness at diagnosis (categorized according to the AJCC staging system19; 1 mm, >1 2, >2 4, >4) and tumour site (trunk, head/neck, limbs, acral/rare). Vitamin A and vitamin D level were tested for association with vitamin A and/or vitamin D dietary supplement intake one year prior to diagnosis (categories: multivitamin only, cod liver oil only, both multivitamin and cod liver oil) using a nonparametric test for trend. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated from Cox proportional hazards models for overall survival (OS) and melanoma-specific survival (MSS). The effects of increasing vitamin D levels, increasing vitamin A levels and high vitamin A levels (2.2 mmol versus <2.2 mmol) were modelled separately in unadjusted analyses. A multiple regression model was then estimated including the following factors: vitamin D level, vitamin A level (2.2 mmol versus <2.2 mmol), age, sex, BMI, Breslow thickness, tumour site and educational level. The multiple regression model was then applied separately in patients with low (<2.2 mmol) and high (2.2 mmol) vitamin A levels to determine whether there was a differential effect and the difference between estimates was tested for by comparing the likelihoods of models with and without an interaction term. A nominal significance cutoff of 5% was used. Statistical analyses were performed using the statistical software, STATA (StataCorp. Stata Statistical Software: Release 10. College Station, TX: StataCorp LP 2007). 3. Results The median age at diagnosis of the 795 patients in this cohort was 54 (range 17e81) and 60% were female. The median seasonally adjusted vitamin D level was 49.5 nmol/l (range 7.2e121.5) and the median adjusted vitamin A level was 1.84 mmol/l (range 0.47e4.06). Dietary supplement data prior to diagnosis were available for 783 patients and 31% (240/783) used supplements containing vitamin A or D or both. The median adjusted vitamin A and seasonally adjusted vitamin D level in the 543 patients not taking vitamin A or D containing supplements were 1.79 mmol/l (range 0.47e3.75) and 45.4 nmol/l (range 7.2e102.8) respectively (data not shown). Table 1 shows the median vitamin A and vitamin D levels in patients who used supplements containing vitamin A and D; the median vitamin A and vitamin D levels were lowest in patients
taking multivitamin alone and were highest in patients taking both multivitamin and cod liver oil. Vitamin A and vitamin D levels were positively correlated overall (Pearson’s r ¼ 0.19, p < 0.001), in vitamin A and D supplement users (r ¼ 0.21, p ¼ 0.001) and non-users of vitamin A or D supplements (r ¼ 0.12, p ¼ 0.005) despite the majority of vitamin A being sourced from the diet and the majority of vitamin D usually being sourced from sunlight exposure. Supplement users were older than non-users (mean ages 55 and 52 years respectively, T-test p ¼ 0.002, data not shown). Females were no more likely to use supplements than males, however a higher proportion of females than males used multivitamins only (11% and 5% respectively), and a higher proportion of males than females used cod liver oil only (19% and 15% respectively), data not shown. Table 2 shows that patients with high vitamin A levels (2.2 mmol) were significantly older than patients with lower levels (58 and 53 years respectively), and a higher proportion of males than females had levels 2.2 mmol (30% and 21% respectively). Vitamin A level was not associated with BMI, educational level, Breslow thickness or tumour site (Table 2). Increasing levels of vitamin A (per 0.5 mmol) were not associated with MSS (unadjusted HR ¼ 1.04, 95%CI(0.90e1.20),p ¼ 0.59, data not shown); high vitamin A levels (2.2 mmol/l) conferred a nonsignificant increased risk of melanoma-specific death (adjusted HR ¼ 1.11, 95%CI(0.74e1.67),p ¼ 0.60) but not for death overall (adjusted HR ¼ 0.95, 95%CI(0.65e1.39), p ¼ 0.79)(Table 3). Increasing vitamin D levels (per 20 nmol/l) were significantly protective for death in unadjusted and adjusted OS models (adjusted HR ¼ 0.82, 95%CI(0.69e0.96),p ¼ 0.02)(Table 3). In a similar adjusted OS model stratifying by high/low vitamin A level (cut-off 2.2 mmol) vitamin D was significantly protective amongst patients with vitamin A levels <2.2 mmol (adjusted HR ¼ 0.77, 95%CI(0.64e 0.93), p ¼ 0.007). The protective effect of vitamin D was not seen in patients with vitamin A levels 2.2 mmol (HR ¼ 0.99, 95%CI(0.72e 1.36), p ¼ 0.93); however a likelihood ratio test for interaction did not reach statistical significance (p ¼ 0.26, data not shown). 4. Discussion In this study we did not find statistically significant evidence that vitamin A levels moderated the protective effect of vitamin D on OS. However, among patients with high vitamin A levels, the protective effect of vitamin D on OS was not apparent, suggesting that high vitamin A levels may be antagonizing the protective effect
S. Field et al. / Clinical Nutrition 32 (2013) 1012e1016
of vitamin D, consistent with our hypothesis. We also saw a modest increased risk for melanoma-specific death for high vitamin A levels overall, but again this was not statistically significant. In recent years there has been an increase in people supplementing their diet and concerns have been raised in the U.S. of subclinical toxicity with vitamin A as many Americans take a multivitamin and cod liver oil despite vitamin A being abundant in our everyday diet (eggs, milk and oily fish) and deficiency being rare in developed countries.20 It is noteworthy that the majority of study participants (94%, 744/795) had serum vitamin A levels below the upper level of normal (median 1.84 mmol/l, range 0.47e 4.06), and despite taking cod liver oil and multivitamin in combination 76% (22/29) of these individuals had vitamin A levels below the upper level of normal (median 2.03, range 1.11e4.06). The update on vitamin D by UK Scientific Advisory Committee on Nutrition 2007 recommended daily intake of vitamin D (10 mg/ day ¼ 400 IU/day) for adults at risk of deficiency such as those over 65 years of age, all pregnant and breastfeeding women and people not exposed to much sun. The latter category includes people confined indoors and those that cover the skin for cultural reasons; melanoma patients avoiding sun exposure following diagnosis would also fall into this category.21 Recommended daily intake of vitamin A in the UK for women is 600 mg and for men is 700 mg, noting that it is advised that population subgroups at risk of osteoporosis, such as postmenopausal women and older people, do not exceed retinol intake of 1500 mg/day.22 Recent guidance by the Institute of Medicine in the U.S. suggested an increased dosage of 600 IU/day or 15 mg of vitamin D as the recommended daily allowance for the majority. Most multivitamins contain 5 mg (400 IU) of vitamin D and 800 mg of vitamin A. Quantities of vitamin A and vitamin D in cod liver oil can vary (1 tablespoon ¼ 5e30 mg vitamin D, 1200e9000 mg of vitamin A). In contrast to vitamin D, vitamin A is much more abundant in our everyday diet. We demonstrated in our study that despite reporting taking multivitamin or cod liver oil, or cod liver oil and multivitamin in combination, the highest median vitamin D level was 62.2 nmol/l in those taking multivitamin and cod liver oil. It is likely that to reach a sufficient vitamin D level by these supplementation sources, recommended daily intake of vitamin A intake would be exceeded. The definition of sufficient or target serum vitamin D levels is much debated. Parathyroid hormone levels are thought to reach a plateau at 50e70 nmol/l.23 There are concerns that the dose response curves for vitamin D may have a J or U-shaped curve suggesting higher levels as well as low levels may be associated with an increased risk of death in breast cancer,24 increased cardiovascular risk25 and increased all-cause mortality in the general population26. Although the relationships reported above are not yet proven to be causal, the established effects of low vitamin D levels on bone health suggests that a vitamin D level in excess of 60 nmol/L would be advisable. The suggestion of J or U-shaped association curves guides us to suggest that a conservative approach for vitamin D serum target levels may be 60e85 nmol/l allowing for seasonal variation. To date there is no evidence available to support the hypothesis that supplementation with vitamin D to achieve sufficient serum levels has a benefit on outcome in patients with melanoma. However it seems reasonable to supplement melanoma patients who have sub-optimal levels of vitamin D to ensure sufficient levels as judged necessary for bone health. In this study we saw evidence of an increase in death from melanoma in patients with high versus low vitamin A levels. The protective effect of vitamin D was not apparent in patients with high levels of vitamin A. Although the differences in effect were not statistically significant, neither did we see any protective effects of vitamin A and, given the ubiquity of this vitamin in the diet, if
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supplementation is taken it seems sensible to use a source of vitamin D3 alone. Acknowledgements Statements of authorship: SF FE JNB had substantial contributions to conception and design, acquisition of data and analysis and interpretation of data, drafting the article. JRM KK had substantial contributions to conception and design, acquisition of data. JHB DTB had substantial contributions to analysis and interpretation of data. All authors revised the article critically and approved the final version for publication. Funding sources: British Skin Foundation 2009 Small Grant S501, Cancer Research United Kingdom (CR-UK) Project Grant C8216/A6129 and CR-UK Programme Grant C588/A10589. Our funding sources had no influence on the work. No authors have conflicts of interest related to this manuscript. References 1. Newton-Bishop JA, Beswick S, Randerson-Moor J, Chang YM, Affleck P, Elliott F, et al. Serum 25-hydroxyvitamin D3 levels are associated with breslow thickness at presentation and survival from melanoma. J Clin Oncol 2009;27:5439e44. 2. Buttigliero C, Monagheddu C, Petroni P, Saini A, Dogliotti L, Ciccone G, et al. Prognostic role of vitamin D status and efficacy of vitamin D supplementation in cancer patients: a systematic review. Oncologist 2011;16: 1215e27. 3. Al-Daghri NM, Alkharfy KM, Al-Saleh Y, Al-Attas OS, Alokail MS, Al-Othman A, et al. Modest reversal of metabolic syndrome manifestations with vitamin D status correction: a 12-month prospective study. Metabolism 2012;61(5): 661e6. 4. Idorn LW, Philipsen PA, Wulf HC. Sun exposure before and after a diagnosis of cutaneous malignant melanoma: estimated by developments in serum vitamin D, skin pigmentation and interviews. Br J Dermatol 2011;165:164e70. 5. Haussler MR, Jurutka PW, Hsieh JC, Thompson PD, Selznick SH, Haussler CA, et al. New understanding of the molecular mechanism of receptor-mediated genomic actions of the vitamin D hormone. Bone 1995;17:33Se8S. 6. Johansson S, Melhus H. Vitamin A antagonizes calcium response to vitamin D in man. J Bone Miner Res 2001;16:1899e905. 7. Rohde CM, Manatt M, Clagett-Dame M, DeLuca HF. Vitamin A antagonizes the action of vitamin D in rats. J Nutr 1999;129:2246e50. 8. Oh K, Willett WC, Wu K, Fuchs CS, Giovannucci EL. Calcium and vitamin D intakes in relation to risk of distal colorectal adenoma in women. Am J Epidemiol 2007;165:1178e86. 9. Bjelakovic G, Nikolova D, Gluud LL, Simonetti RG, Gluud C. Mortality in randomized trials of antioxidant supplements for primary and secondary prevention: systematic review and meta-analysis. JAMA 2007;297:842e57. 10. Druesne-Pecollo N, Latino-Martel P, Norat T, Barrandon E, Bertrais S, Galan P, et al. Beta-carotene supplementation and cancer risk: a systematic review and metaanalysis of randomized controlled trials. Int J Cancer 2010;127: 172e84. 11. Zhang X, Dai B, Zhang B, Wang Z. Vitamin A and risk of cervical cancer: a metaanalysis. Gynecol Oncol 2012;124:366e73. 12. Meyskens Jr FL, Fuller BB. Characterization of the effects of different retinoids on the growth and differentiation of a human melanoma cell line and selected subclones. Cancer Res 1980;40:2194e6. 13. Weinzweig J, Tattini C, Lynch S, Zienowicz R, Weinzweig N, Spangenberger A, et al. Investigation of the growth and metastasis of malignant melanoma in a murine model: the role of supplemental vitamin A. Plast Reconstr Surg 2003;112:152e8 [discussion 59e61]. 14. Feskanich D, Willett WC, Hunter DJ, Colditz GA. Dietary intakes of vitamins A, C, and E and risk of melanoma in two cohorts of women. Br J Cancer 2003;88: 1381e7. 15. Naldi L, Gallus S, Tavani A, Imberti GL, La Vecchia C. Risk of melanoma and vitamin A, coffee and alcohol: a case-control study from Italy. Eur J Cancer Prev 2004;13:503e8. 16. Asgari MM, Brasky TM, White E. Association of vitamin A and carotenoid intake with melanoma risk in a large prospective cohort. J Invest Dermatol 2012;132: 1573e82. 17. Meyskens Jr FL, Liu PY, Tuthill RJ, Sondak VK, Fletcher WS, Jewell WR, et al. Randomized trial of vitamin A versus observation as adjuvant therapy in highrisk primary malignant melanoma: a Southwest Oncology Group study. J Clin Oncol 1994;12:2060e5. 18. Furr HC. Analysis of retinoids and carotenoids: problems resolved and unsolved. J Nutr 2004;134:281Se5S.
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S. Field et al. / Clinical Nutrition 32 (2013) 1012e1016
19. Balch CM, Gershenwald JE, Soong SJ, Thompson JF, Atkins MB, Byrd DR, et al. Final version of 2009 AJCC melanoma staging and classification. J Clin Oncol 2009;27:6199e206. 20. Ballew C, Bowman BA, Sowell AL, Gillespie C. Serum retinol distributions in residents of the United States: third National Health and Nutrition Examination Survey, 1988e1994. Am J Clin Nutr 2001;73:586e93. 21. Update on vitamin D, position statement. Scientific Advisory Committee on Nutrition. At: http://www.sacn.gov.uk/pdfs/sacn_position_vitamin_d_2007_ 05_07.pdf; 2007 [accessed 01.11.12]. 22. Review of dietary advice on vitamin A. Scientific Advisory Committee on Nutrition. At: http://www.sacn.gov.uk/pdfs/sacn_vita_report.pdf; 2005 [accessed 01.11.12].
23. Bjorkman M, Sorva A, Tilvis R. Responses of parathyroid hormone to vitamin D supplementation: a systematic review of clinical trials. Arch Gerontol Geriatr 2009;48:160e6. 24. Goodwin PJ, Ennis M, Pritchard KI, Koo J, Hood N. Prognostic effects of 25hydroxyvitamin D levels in early breast cancer. J Clin Oncol 2009;27: 3757e63. 25. Wang TJ, Pencina MJ, Booth SL, Jacques PF, Ingelsson E, Lanier K, et al. Vitamin D deficiency and risk of cardiovascular disease. Circulation 2008;117:503e11. 26. Durup D, Jorgensen HL, Christensen J, Schwarz P, Heegaard AM, Lind B. A reverse J-shaped association of all-cause mortality with serum 25-hydroxyvitamin D in general practice: the CopD study. J Clin Endocrinol Metab 2012;97:2644e52.