Vitamin D

Purported Benefits, Side Effects & More

Vitamin D

Purported Benefits, Side Effects & More
Vitamin D

Common Names

  • Vitamin D
  • Sunshine vitamin
  • D2; D3

For Patients & Caregivers

Tell your healthcare providers about any dietary supplements you’re taking, such as herbs, vitamins, minerals, and natural or home remedies. This will help them manage your care and keep you safe.

What is it?

Vitamin D is a vitamin your body needs to keep your bones healthy. Your bones need calcium to stay strong and your body needs vitamin D to absorb calcium. This is why it’s important to get vitamin D. You can get vitamin D from some foods like fortified milk and cereals, egg yolks, and fish. Your body can also make some vitamin D when you’re exposed to sunlight.

If you don’t get enough vitamin D, your healthcare provider may recommend you take vitamin D supplements, or take a multivitamin that has vitamin D.

What are the potential uses and benefits?

Vitamin D is used to:

  • Prevent osteoporosis (a condition in which bones become weak and brittle)
  • Prevent certain cancers
  • Treat a type of depression called seasonal affective disorder. This is related to the changes in season. It is seen mostly in people who live in climates where there is less sunlight during fall and winter.

Vitamin D also has other uses that haven’t been studied by doctors to see if they work.

It’s safe to eat foods with vitamin D. However, talk with your healthcare providers before taking supplements or higher amounts of vitamin D.

Supplements can interact with some medications and affect how they work. For more information, read the “What else do I need to know?” section below.

What are the side effects?

Vitamin D is generally safe. But it can sometimes cause side effects such as:

  • Vomiting (throwing up)
  • Abdominal (stomach) pain
  • High levels of calcium in the blood
  • High levels of calcium in urine (pee)
  • Kidney stones
What else do I need to know?
  • Talk to your healthcare provider if you have kidney stones, kidney disease, high blood calcium levels, heart disease, or liver disease. Vitamin D supplements may make these conditions worse.
  • Talk to your healthcare provider if you’re taking diuretics or water pills (medications that make you urinate more often) such as indapamide (Lozol), hydrochlorothiazide (Microzide®), or chlorthalidone (Thalitone®). Vitamin D may increase the calcium level in your blood. This can weaken your bones and create kidney stones.

For Healthcare Professionals

Scientific Name
Calciferol, ergocalciferol (D2), calcitriol, cholecalciferol (D3)
Clinical Summary

Vitamin D refers to several forms of fat-soluble vitamins found in fortified milk and cereals, egg yolks, and fish. The two forms utilized in humans are ergocalciferol (D2) and cholecalciferol (D3). Sunlight can promote the synthesis of D3 in the skin. Vitamin D maintains serum calcium and phosphorus levels by regulating their absorption and excretion, and is important for bone formation. Other biologic functions include its role as an antiproliferative agent (1), and as a pro-differentiation hormone (2) with anti-inflammatory and immunoregulatory properties (3). Low levels of vitamin D are associated with a greater risk of mortality (13), may affect cardiovascular health (14), and increase the risk for development of multiple sclerosis in women (74), but a large study found no association between lower levels and cognitive function (15). However, deficiency during pregnancy may affect neurocognitive development in newborns (75). Deficiency can also cause rickets or other bone disorders, and may be a risk factor for extraskeletal diseases (45). Lower D levels may occur due to time of year or living in northern climates (9); in non-Caucasian race (46) or obese individuals (47); with chronic use of steroids or anticonvulsants; or with diseases such as autoimmune disorders (3), cystic fibrosis (48), kidney disease, and cancer (46) (48) (49).

Although some studies suggest vitamin D improves bone mineral density and prevents fractures in the elderly (4) (5) and in postmenopausal women (6), it did not lower risk of fractures in midlife and older adults (108), in hemodialysis patients (121) or improve lower extremity function and was associated with an increased fall risk in older adults (64). Safety concerns also arose with doses of 1000 IU/d or higher in older persons who had elevated fall risk and low serum D levels (99) but conflicting findings do not support such concerns (113). Data are also conflicting for primary fracture prevention in other populations (7) (8) (9) and a meta-analysis did not find benefit for preventing fractures or falls, or for bone mineral density (100)

In healthy adults, D3 also does not appear to decrease fall risk (101) and high-dose supplementation did not benefit bone health (92), with 4000 or 10,000 IU compared with 400 IU resulting in greater bone mineral density loss in healthy vitamin D-sufficient women, but not men (93). Supplementation did not affect the rate of frailty change or incidence over time in healthy community-dwelling older adults (109), and US Preventive Services Task Force reports also found no associations between supplementation and reduced falls or fracture incidence in this subset (79) (80). Another study failed to find associations between vitamin D status and chronic pain (88).

Findings on whether vitamin D protects against cardiovascular (CV) risk factors have varied across populations and regimens. In a Women’s Health Initiative sub-study, calcium plus vitamin D and hormone therapy had a greater effect than either intervention alone or placebo (67), but vitamin D did not improve CV risk factors or physical function in large long-term trials of older adults (68) (110) or reduce all-cause mortality in older adults who are vitamin D-replete (111). Meta-analyses also found no effect on vascular function markers (81) nor reduction in CV disease endpoints (94). Yet in another placebo-controlled trial, supplementation benefited diabetic patients with coronary artery disease who were vitamin D-deficient (69). In addition, a single large dose of vitamin D2 improved endothelial function in type-2 diabetic patients (11). In non-dialysis patients with chronic kidney disease, D3 was more effective than D2 in raising serum D levels (70). Dietary vitamin D intake was shown to be inversely associated with mortality from stroke (76), but supplementation was not associated with reduced all-cause mortality in critically ill patients (102), and did not reduce risk of atrial fibrillation (103).

In other trials, vitamin D did not significantly reduce upper respiratory tract infections (URTIs) in healthy adults (16), or infections/antibiotic use in the elderly (17). However, it may protect against influenza (78) and reduce wheezing in some infants (82). Vitamin D was not helpful for mild psoriasis (83) or seasonal affective disorder (18) (19). Supplementation may reduce relapse risk in Crohn’s disease (12), and D3 plus calcium may have a small effect on postmenopausal weight gain (10). A single oral high-dose of D3 significantly improved fatigue in healthy persons who were vitamin D-deficient (72). Supplementation may also reduce the size of uterine fibroids (122) and improve sexual function in women with sexual dysfunction and vitamin D deficiency (89), but long-term supplementation did not prevent erectile dysfunction in older men (123) nor depression in healthy adults (96). In small studies, higher serum levels of vitamin D were associated with increased beneficial gut bacteria and decreased pathogenic bacteria (95) and supplementation improved liver fibrogenic factors in patients with metabolic dysfunction-associated steatotic liver disease  (124) and metabolic parameters in women with subclinical hypothyroidism (125) although a large trial did not find overall reduction in incidence of  hypothyroidism  (126).

In pediatric trials, vitamin D did not influence growth, body composition, or pubertal development (114), and did not prevent viral URTIs (71) or tuberculosis (115)

Vitamin D has also been examined for its anticancer potential. In animal models, dietary vitamin D3 exerted chemopreventive effects against breast cancer equivalent to those elicited by calcitriol without causing hypercalcemia (20). In humans, vitamin D from sunlight exposure and dietary intake may have protective effects against breast cancer (21) (22), and insufficiency among breast cancer patients is high (23). In postmenopausal women not on estrogen therapy, vitamin D and calcium supplementation may reduce colorectal cancer incidence (24) (25). In women with grade 1 cervical intraepithelial neoplasia, long-term supplementation resulted in regression and improved metabolic status (66). However, in a large trial of healthy postmenopausal women with mean vitamin D levels above those of the US population, taking vitamin D3 plus calcium did not lower cancer risk after 4 years of supplementation (73), and vitamin D supplementation did not prevent aromatase-induced arthralgia (97) or affect cognition when combined with calcium, protein and a multicomponent exercise training in men treated with ADT for prostate cancer (112). In addition, even though pooled analyses found associations between higher serum D levels and lower risks of breast and colon cancers (85) (86), other analyses have not found preventive effects against cancer with high-dose supplementation (87), and contributing factors such as better diet and lifestyle habits may also be at play.

In older patients with diffuse large B-cell lymphoma, supplementation normalized vitamin D levels and enhanced efficacy of rituximab (27). Active vitamin D compounds may also decrease incidence of post-transplant malignancy among kidney transplant recipients (28).

Other data reveal that vitamin D deficiency is highly prevalent in advanced pancreatic cancer (42) and colorectal cancer (CRC) patients (43), and that CRC patients with higher blood 25(OH)D concentrations have better survival (84). A meta-analysis of vitamin D supplementation on CRC survival outcomes also suggests clinically meaningful benefit (104). In patients with metastatic CRC, addition of high-dose vitamin D3 to chemotherapy resulted in statistically insignificant progression-free survival but improved supportive hazard ratio (90). Increased vitamin D intake reduced CRC risk (29) (31) (32) (33), but had no effect on colorectal adenomas (65). Data on benefits to reduce skin cancer risk (38) (105) and advanced cancers (106) are mixed. Vitamin D did not have a protective effect against non-Hodgkin lymphoma (34), ovarian (35), kidney (36), endometrial (37), esophageal or gastric (39) cancers, may significantly increase risk of pancreatic (40) or aggressive prostate cancer (41), and did not improve relapse-free survival in patients with digestive tract cancers (91) although conflicting findings in p53 immunoreactive subset (116) and in those with elevated serum levels of soluble CD40 ligand  (127) suggest otherwise. Data from meta-analyses, however, are conflicting on whether vitamin D supplementation can reduce cancer incidence or mortality (44) (77) (94).

In pediatric patients with solid tumors, findings showed a possible correlation between higher pretreatment serum vitamin D levels and improved overall and relapse-free survival (128).

Oral supplementation has been shown to be the safest way to increase vitamin D levels (51), although debate continues on how this may translate to optimizing vitamin D status (45). The Institute of Medicine recommends a Daily Dietary Allowance of vitamin D at 600 IU/day with the Upper Level Intake at 4,000 IU/day for bone health (50), although safety concerns have been noted with higher doses in some populations (99). Also, combined vitamin D and calcium supplementation has been associated with increased kidney stone incidence (7) (80). Therefore, patients should consult with their physicians if a deficiency is suspected to assess the amount of vitamin D needed for health maintenance and to avoid side effects.

Food Sources

Fatty fish, fish liver oils, egg yolks, fortified milk and cereals (5)

Purported Uses and Benefits
  • Osteoporosis
  • Cancer prevention
  • Seasonal affective disorder
Mechanism of Action

The most biologically active metabolite of vitamin D is calcitriol, which regulates calcium and phosphate homeostasis (52). In humans, the primary function of vitamin D is to maintain normal levels of serum calcium and phosphorus concentrations by enhancing small intestine dietary absorption efficiency of these minerals. 25-hydroxyvitamin D [25(OH)D] enhances the efficiency of calcium and phosphorus absorption along the entire small intestine, but primarily in the duodenum and jejunum (5). When dietary calcium intake is insufficient, 25(OH)D and parathyroid hormone (PTH) mobilize monocytic stem cells in the bone marrow to become mature osteoclasts. These osteoclasts mobilize calcium from the bones, thereby maintaining blood calcium levels (50). Vitamin D is thought to have physiological effects in other parts of the body as well because vitamin D receptors (VDRs) are found in the cells of other organs that include intestines, kidney, stomach, brain, prostate, breast, and white blood cells (2) (53).

The anticancer effect of vitamin D is thought to be due to induction of cell differentiation (1) (54) and antiproliferation (55). In lymphoma cells, interventional 25(OH)D3 to normalize levels (>30 ng/mL) resulted in significantly stronger antibody-dependent cell-mediated cytotoxicity, suggesting benefit in D-deficient individuals receiving rituximab (27). In xenograft models of breast cancer, dietary D3 elevated circulating D levels and increased CYP27B1 expression in both tumor and intestines, suggesting it stimulates local calcitriol synthesis in the tumor microenvironment and promotes the ensuing paracrine/autocrine actions that contribute to its anticancer activity (20). The upregulation of CYP27B1 expression by tumors was unique to D3 versus calcitriol in the same tissue (20). In other animal models, a positive feedback signaling loop between the serine-protein kinase ATM (ataxia telangiectasia mutated) and the VDR was identified as critical for cancer chemoprevention by vitamin D (56).

Calcitriol, the hormonally active form of vitamin D3, targets the vitamin D degrading enzyme CYP24A1, which is most abundant in the kidney, but also expressed in several other tissues (57). CYP24A1 overexpression in colon, ovary, breast, lung, and esophageal malignancies, likely leads to degradation of the locally available D3, impairing its antitumorigenic action in the tumor tissue (57).


Individuals with kidney stones, kidney disease, high blood calcium levels, gastrointestinal disease, heart disease, liver disease or other diseases associated with disorders of calcium metabolism should seek medical advice before taking supplemental vitamin D (9).

Adverse Reactions

Rare: Gastrointestinal symptoms, renal disease, nephrolithiasis, hypercalcemia, hypercalciuria (9) (44), hypervitaminosis in a breastfed infant (117).

Case Reports
Life-threatening hypercalcemia: In two women resulting from intake of over-the-counter vitamin-D concentrated supplements that were 100 — 1,000 times higher than stated on the label (58).
Severe hypercalcemia: In a 37-year-old man with previously undiagnosed sarcoidosis who was prescribed 50,000 units of weekly vitamin D 25 (OH) therapy for 4 weeks and presented after 2 weeks therapy with abdominal pain, nausea, and vomiting for 2 days (107).
Hypercalcemic crisis: In three cases after taking large quantities of vitamin D for an extended period of time (59) (118).
Post-prandial food vomiting and severe abdominal pain: In a 64-year-old woman after taking various vitamin complexes, including cholecalciferol, once daily for about 6 months (98). 
Acute renal failure and hypervitaminosis A: In a 51-year old woman after consuming an over-the-counter vitamin D supplement, which also caused vitamin A toxicity possibly due to renal failure related to the hypercalcemia induced by vitamin D toxicity (60).
Acute pancreatitis: In a 61-year-old man following vitamin D toxicity due to intake of large doses (119).  
Hypercalcemia and acute kidney injury: In a patient who was given high-dose vitamin D along with immunosuppressive therapy following autologous stem cell transplant for multiple sclerosis (120).

Herb-Drug Interactions
  • Aluminum hydroxide: May increase the absorption and blood level of aluminum (61).
  • Atorvastatin: Vitamin D reduces blood levels of atorvastatin but it also helps lower cholesterol concentrations (62) .
  • Thiazide diuretics: May increase serum calcium level (63).
Dosage (OneMSK Only)
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  6. Dipart Group. Patient level pooled analysis of 68 500 patients from seven major vitamin D fracture trials in US and Europe. BMJ. 2010;340:b5463. 
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  8. Moyer VA, Force* USPST. Vitamin D and calcium supplementation to prevent fractures in adults: U.S. Preventive Services Task Force recommendation statement. Ann Intern Med. May 7 2013;158(9):691-696. 
  9. Avenell A, Mak JC, O’Connell D. Vitamin D and vitamin D analogues for preventing fractures in post-menopausal women and older men. Cochrane Database Syst Rev. 2014;4:CD000227. 
  10. Caan B, Neuhouser M, Aragaki A, et al. Calcium plus vitamin D supplementation and the risk of postmenopausal weight gain. Arch Intern Med. May 14 2007;167(9):893-902.
  11. Sugden JA, Davies JI, Witham MD, et al. Vitamin D improves endothelial function in patients with Type 2 diabetes mellitus and low vitamin D levels. Diabet Med. Mar 2008;25(3):320-325. 
  12. Jorgensen SP, Agnholt J, Glerup H, et al. Clinical trial: vitamin D3 treatment in Crohn’s disease - a randomized double-blind placebo-controlled study. Aliment Pharmacol Ther. Aug 2010;32(3):377-383. 
  13. Gross C, Stamey T, Hancock S, et al. Treatment of early recurrent prostate cancer with 1,25-dihydroxyvitamin D3 (calcitriol). J Urol. Jun 1998;159(6):2035-2039; discussion 2039-2040.
  14. Tomaschitz A, Pilz S, Ritz E, et al. Independent association between 1,25-dihydroxyvitamin D, 25-hydroxyvitamin D and the renin-angiotensin system: The Ludwigshafen Risk and Cardiovascular Health (LURIC) study. Clin Chim Acta. Sep 6 2010;411(17-18):1354-1360. 
  15. Slinin Y, Paudel ML, Taylor BC, et al. 25-Hydroxyvitamin D levels and cognitive performance and decline in elderly men. Neurology. Jan 5 2010;74(1):33-41. 
  16. Murdoch DR, Slow S, Chambers ST, et al. Effect of vitamin D3 supplementation on upper respiratory tract infections in healthy adults: the VIDARIS randomized controlled trial. JAMA. Oct 3 2012;308(13):1333-1339. 
  17. Avenell A, Cook JA, Maclennan GS, et al. Vitamin D supplementation to prevent infections: a sub-study of a randomised placebo-controlled trial in older people (RECORD trial, ISRCTN 51647438). Age Ageing. Sep 2007;36(5):574-577.
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  19. Frandsen TB, Pareek M, Hansen JP, et al. Vitamin D supplementation for treatment of seasonal affective symptoms in healthcare professionals: a double-blind randomised placebo-controlled trial. BMC Res Notes. 2014;7:528. 
  20. Krishnan AV, Swami S, Feldman D. Equivalent anticancer activities of dietary vitamin D and calcitriol in an animal model of breast cancer: importance of mammary CYP27B1 for treatment and prevention. J Steroid Biochem Mol Biol. Jul 2013;136:289-295.
  21. Blackmore KM, Lesosky M, Barnett H, et al. Vitamin D from dietary intake and sunlight exposure and the risk of hormone-receptor-defined breast cancer. Am J Epidemiol. Oct 15 2008;168(8):915-924. 
  22. Robien K, Cutler GJ, Lazovich D. Vitamin D intake and breast cancer risk in postmenopausal women: the Iowa Women’s Health Study. Cancer Causes Control. Sep 2007;18(7):775-782. 
  23. Neuhouser ML, Sorensen B, Hollis BW, et al. Vitamin D insufficiency in a multiethnic cohort of breast cancer survivors. Am J Clin Nutr. Jul 2008;88(1):133-139.
  24. Ding EL, Mehta S, Fawzi WW, et al. Interaction of estrogen therapy with calcium and vitamin D supplementation on colorectal cancer risk: reanalysis of Women’s Health Initiative randomized trial. Int J Cancer. Apr 15 2008;122(8):1690-1694. 
  25. Wactawski-Wende J, Kotchen JM, Anderson GL, et al. Calcium plus vitamin D supplementation and the risk of colorectal cancer. N Engl J Med. Feb 16 2006;354(7):684-696. 
  26. Van Veldhuizen PJ, Taylor SA, Williamson S, et al. Treatment of vitamin D deficiency in patients with metastatic prostate cancer may improve bone pain and muscle strength. J Urol. Jan 2000;163(1):187-190.
  27. Bittenbring JT, Neumann F, Altmann B, et al. Vitamin D Deficiency Impairs Rituximab-Mediated Cellular Cytotoxicity and Outcome of Patients With Diffuse Large B-Cell Lymphoma Treated With but Not Without Rituximab. J Clin Oncol. 2014 Oct 10;32(29):3242-8.
  28. Obi Y, Ichimaru N, Hamano T, et al. Orally active vitamin D for potential chemoprevention of posttransplant malignancy. Cancer Prev Res (Phila). Oct 2012;5(10):1229-1235. 
  29. Garland C, Shekelle RB, Barrett-Connor E, et al. Dietary vitamin D and calcium and risk of colorectal cancer: a 19-year prospective study in men. Lancet. Feb 9 1985;1(8424):307-309.
  30. Garland CF, Garland FC, Gorham ED, et al. The role of vitamin D in cancer prevention. Am J Public Health. Feb 2006;96(2):252-261.
  31. Lappe JM, Travers-Gustafson D, Davies KM, et al. Vitamin D and calcium supplementation reduces cancer risk: results of a randomized trial. Am J Clin Nutr. Jun 2007;85(6):1586-1591.
  32. Ma Y, Zhang P, Wang F, et al. Association between vitamin D and risk of colorectal cancer: a systematic review of prospective studies. J Clin Oncol. Oct 1 2011;29(28):3775-3782. 
  33. Weinstein SJ, Purdue MP, Smith-Warner SA, et al. Serum 25-hydroxyvitamin D, vitamin D binding protein and risk of colorectal cancer in the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial. Int J Cancer. Mar 15 2015;136(6):E654-664. 
  34. Purdue MP, Freedman DM, Gapstur SM, et al. Circulating 25-hydroxyvitamin D and risk of non-hodgkin lymphoma: Cohort Consortium Vitamin D Pooling Project of Rarer Cancers. Am J Epidemiol. Jul 1 2010;172(1):58-69. 
  35. Zheng W, Danforth KN, Tworoger SS, et al. Circulating 25-hydroxyvitamin D and risk of epithelial ovarian cancer: Cohort Consortium Vitamin D Pooling Project of Rarer Cancers. Am J Epidemiol. Jul 1 2010;172(1):70-80.
  36. Gallicchio L, Moore LE, Stevens VL, et al. Circulating 25-hydroxyvitamin D and risk of kidney cancer: Cohort Consortium Vitamin D Pooling Project of Rarer Cancers. Am J Epidemiol. Jul 1 2010;172(1):47-57. 
  37. Zeleniuch-Jacquotte A, Gallicchio L, Hartmuller V, et al. Circulating 25-hydroxyvitamin D and risk of endometrial cancer: Cohort Consortium Vitamin D Pooling Project of Rarer Cancers. Am J Epidemiol. Jul 1 2010;172(1):36-46.
  38. Caini S, Boniol M, Tosti G, et al. Vitamin D and melanoma and non-melanoma skin cancer risk and prognosis: A comprehensive review and meta-analysis. Eur J Cancer. 2014 Oct;50(15):2649-58. 
  39. Abnet CC, Chen Y, Chow WH, et al. Circulating 25-hydroxyvitamin D and risk of esophageal and gastric cancer: Cohort Consortium Vitamin D Pooling Project of Rarer Cancers. Am J Epidemiol. Jul 1 2010;172(1):94-106. 
  40. Stolzenberg-Solomon RZ, Jacobs EJ, Arslan AA, et al. Circulating 25-hydroxyvitamin D and risk of pancreatic cancer: Cohort Consortium Vitamin D Pooling Project of Rarer Cancers. Am J Epidemiol. Jul 1 2010;172(1):81-93. 
  41. Ahn J, Peters U, Albanes D, et al. Serum vitamin D concentration and prostate cancer risk: a nested case-control study. J Natl Cancer Inst. Jun 4 2008;100(11):796-804.
  42. Van Loon K, Owzar K, Jiang C, et al. 25-Hydroxyvitamin D Levels and Survival in Advanced Pancreatic Cancer: Findings From CALGB 80303 (Alliance). J Natl Cancer Inst. Aug 2014;106(8). 
  43. Wesa KM, Segal NH, Cronin AM, et al. Serum 25-Hydroxy Vitamin D and Survival in Advanced Colorectal Cancer: A Retrospective Analysis. Nutr Cancer. Feb 3 2015:1-7.
  44. Bjelakovic G, Gluud LL, Nikolova D, et al. Vitamin D supplementation for prevention of cancer in adults. Cochrane Database Syst Rev. 2014;6:CD007469. 
  45. Aspray TJ, Bowring C, Fraser W, et al. National Osteoporosis Society Vitamin D Guideline Summary. Age Ageing. 2014 Sep;43(5):592-5.
  46. Hauser K, Walsh D, Shrotriya S, et al. Low 25-hydroxyvitamin D levels in people with a solid tumor cancer diagnosis: the tip of the iceberg? Support Care Cancer. Jul 2014;22(7):1931-1939. 
  47. Duerbeck NB, Dowling DD, Duerbeck JM. Vitamin D: hero or hype. Obstet Gynecol Surv. Dec 2013;68(12):799-810.
  48. Siwamogsatham O, Alvarez JA, Tangpricha V. Diagnosis and treatment of endocrine comorbidities in patients with cystic fibrosis. Curr Opin Endocrinol Diabetes Obes. 2014 Oct;21(5):422-9. 
  49. Skversky AL, Kumar J, Abramowitz MK, et al. Association of glucocorticoid use and low 25-hydroxyvitamin D levels: results from the National Health and Nutrition Examination Survey (NHANES): 2001-2006. J Clin Endocrinol Metab. Dec 2011;96(12):3838-3845. 
  50. Institute of Medicine. Dietary Reference Intakes for Calcium and Vitamin D. Available at: 2011 Accessed August 10, 2021.
  51. Terushkin V, Bender A, Psaty EL, et al. Estimated equivalency of vitamin D production from natural sun exposure versus oral vitamin D supplementation across seasons at two US latitudes. J Am Acad Dermatol. Jun 2010;62(6):929 e921-929. 
  52. Beer TM. ASCENT: the androgen-independent prostate cancer study of calcitriol enhancing taxotere. BJU Int. Sep 2005;96(4):508-513. 
  53. Stumpf WE, Sar M, Reid FA, et al. Target cells for 1,25-dihydroxyvitamin D3 in intestinal tract, stomach, kidney, skin, pituitary, and parathyroid. Science. Dec 7 1979;206(4423):1188-1190.
  54. Jamshidi F, Zhang J, Harrison JS, et al. Induction of differentiation of human leukemia cells by combinations of COX inhibitors and 1,25-dihydroxyvitamin D3 involves Raf1 but not Erk 1/2 signaling. Cell Cycle. Apr 1 2008;7(7):917-924.
  55. Popadic S, Ramic Z, Medenica L, et al. Antiproliferative effect of vitamin A and D analogues on adult human keratinocytes in vitro. Skin Pharmacol Physiol. 2008;21(4):227-234. 
  56. Ting HJ, Yasmin-Karim S, Yan SJ, et al. A positive feedback signaling loop between ATM and the vitamin D receptor is critical for cancer chemoprevention by vitamin D. Cancer Res. Feb 15 2012;72(4):958-968. 
  57. Hummel D, Aggarwal A, Borka K, et al. The vitamin D system is deregulated in pancreatic diseases. J Steroid Biochem Mol Biol. 2014 Oct;144 Pt B:402-9.
  58. Kaptein S, Risselada AJ, Boerma EC, et al. Life-threatening complications of vitamin D intoxication due to over-the-counter supplements. Clin Toxicol (Phila). Jun 2010;48(5):460-462. 
  59. Genzen JR. Hypercalcemic crisis due to vitamin D toxicity. Lab Med. Spring 2014;45(2):147-150.
  60. Granado-Lorencio F, Rubio E, Blanco-Navarro I, et al. Hypercalcemia, hypervitaminosis A and 3-epi-25-OH-D3 levels after consumption of an “over the counter” vitamin D remedy. a case report. Food Chem Toxicol. Jun 2012;50(6):2106-2108. 
  61. Demontis R, Leflon A, Fournier A, et al. 1 alpha(OH) vitamin D3 increases plasma aluminum in hemodialized patients taking AI(OH)3. Clin Nephrol. Sep 1986;26(3):146-149.
  62. Schwartz JB. Effects of vitamin D supplementation in atorvastatin-treated patients: a new drug interaction with an unexpected consequence. Clin Pharmacol Ther. Feb 2009;85(2):198-203. 
  63. Chandler PD, Scott JB, Drake BF, et al. Risk of hypercalcemia in blacks taking hydrochlorothiazide and vitamin D. Am J Med. Aug 2014;127(8):772-778. 
  64. Bischoff-Ferrari HA, Dawson-Hughes B, Orav EJ, et al. Monthly High-Dose Vitamin D Treatment for the Prevention of Functional Decline: A Randomized Clinical Trial. JAMA Intern Med. 2016 Jan 4:1-10.
  65. Baron JA, Barry EL, Mott LA, et al. A Trial of Calcium and Vitamin D for the Prevention of Colorectal Adenomas. N Engl J Med. 2015 Oct 15;373(16):1519-30.
  66. Vahedpoor Z, Jamilian M, Bahmani F, et al. Effects of Long-Term Vitamin D Supplementation on Regression and Metabolic Status of Cervical Intraepithelial Neoplasia: a Randomized, Double-Blind, Placebo-Controlled Trial. Horm Cancer. 2017 Feb;8(1):58-67.
  67. Schnatz PF, Jiang X, Aragaki AK, et al. Effects of Calcium, Vitamin D, and Hormone Therapy on Cardiovascular Disease Risk Factors in the Women’s Health Initiative: A Randomized Controlled Trial. Obstet Gynecol. Jan 2017;129(1):121-129.
  68. Hin H, Tomson J, Newman C, et al. Optimum dose of vitamin D for disease prevention in older people: BEST-D trial of vitamin D in primary care. Osteoporos Int. Mar 2017;28(3):841-851.
  69. Farrokhian A, Raygan F, Bahmani F, et al. Long-Term Vitamin D Supplementation Affects Metabolic Status in Vitamin D-Deficient Type 2 Diabetic Patients with Coronary Artery Disease. J Nutr. Mar 2017;147(3):384-389.
  70. Wetmore JB, Kimber C, Mahnken JD, et al. Cholecalciferol v. ergocalciferol for 25-hydroxyvitamin D (25(OH)D) repletion in chronic kidney disease: a randomised clinical trial. Br J Nutr. Dec 2016;116(12):2074-2081.
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