3 Little-Known Vitamin D Facts

We get our vitamin D mostly from the sun and it is important for maintaining bone health. Here are 3 lesser-known facts about vitamin D which you probably haven’t heard.

Vitamin D is a Hormone

Vitamin D is structured and functions much more like a hormone than a vitamin. In fact, vitamin D has more in common with hormones such as estrogen, testosterone and cortisol than it does with vitamins A, B12 or C1. A Vitamin D receptor has been identified on 229 different genes which are all strongly impacted by exposure to vitamin D2. This is an important finding because vitamins don’t act through binding to receptors but hormones do. Vitamins are also classified by a need to be obtained through the diet, whereas vitamin D can be obtained in sufficient quantities solely from skin exposure to sunlight.

Vitamin D Affects Cancer Risk

There has been encouraging evidence emerging over the past few years on the role vitamin D plays in cancer. The mechanism by which vitamin D helps cancer patients is thought to be through slowing spread, slowing differentiation and by directly killing cancer cells3. Vitamin D supplementation decreases the risk of developing skin cancer in people at high risk for skin cancer4, decreases the risk of developing breast cancer5,6, and also decreases the risk of developing colon cancer6,7,8,9. Research has also indicated that Vitamin D supplementation can help to control the spread of prostate cancer10.

More recent research has suggested that vitamin D supplementation also helps decrease adverse effects11 associated with some cancer treatments, including bone pain and bone mineral density depletion. Some of the positive effects of vitamin D supplementation in cancer patients have been attributed to the fact that many cancer patients are vitamin D deficient or become deficient during their cancer treatment12.

Vitamin D Affects Blood Pressure

It has been suggested that vitamin D may help to control blood pressure by interacting with blood-calcium levels and thereby affecting vascular smooth muscle “tightness”, which is indeed an important factor in blood pressure13. Over the past few years evidence has emerged showing that vitamin D supplementation can help to control blood pressure in healthy people14,15, in people with vitamin D deficiency16, in diabetics17 and in women with polycystic ovarian syndrome18. Considering the negative effects of high blood pressure on the cardiovascular system, this is an important finding.


Although vitamin D supplementation can have some significant benefits for certain groups of people it is not a magic bullet by any means. Vitamin D supplementation has the potential for adverse reactions in people with hyperparathyroidism, kidney disease, high blood-calcium levels, low blood pressure, immune disorders, certain cancers, in breastfeeding mothers and in infants. It is a good idea to consult your naturopathic doctor regarding whether you should take vitamin D and what dose is appropriate. To get a rough idea of how much vitamin D you can and should get from sun exposure daily check out this online calculator from the Norwegian Institute for Air Research.


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  2. Ramagopalan SV, Heger A, Berlanga AJ, Maugeri NJ, Lincoln MR, Burrell A, Handunnetthi L, Handel AE, Disanto G, Orton SM, Watson CT, Morahan JM, Giovannoni G, Ponting CP, Ebers GC, Knight JC. A ChIP-seq defined genome-wide map of vitamin D receptor binding: associations with disease and evolution. Genome Res. 2010 Oct;20(10):1352-60.
  3. Krishnan AV, Feldman D. Mechanisms of the anti-cancer and anti-inflammatory actions of vitamin D. Annu Rev Pharmacol Toxicol. 2011;51:311-36.
  4. Tang JY, Fu T, Leblanc E, Manson JE, Feldman D, Linos E, Vitolins MZ, Zeitouni NC, Larson J, Stefanick ML. J Clin Oncol. Calcium plus vitamin D supplementation and the risk of nonmelanoma and melanoma skin cancer: post hoc analyses of the women’s health initiative randomized controlled trial. 2011 Aug 1;29(22):3078-84.
  5. 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. 2007 Sep;18(7):775-82.
  6. Bolland MJ, Grey A, Gamble GD, Reid IR. Calcium and vitamin D supplements and health outcomes: a reanalysis of the Women’s Health Initiative (WHI) limited-access data set. Am J Clin Nutr. 2011 Oct;94(4):1144-9.
  7. Lappe JM, Travers-Gustafson D, Davies KM, Recker RR, Heaney RP. Vitamin D and calcium supplementation reduces cancer risk: results of a randomized trial. Am J Clin Nutr. 2007 Jun;85(6):1586-91.
  8. Hartman TJ, Albert PS, Snyder K, Slattery ML, Caan B, Paskett E, Iber F, Kikendall JW, Marshall J, Shike M, Weissfeld J, Brewer B, Schatzkin A, Lanza E; Polyp Prevention Study Group. The association of calcium and vitamin D with risk of colorectal adenomas. J Nutr. 2005 Feb;135(2):252-9.
  9. Grau MV, Baron JA, Sandler RS, Haile RW, Beach ML, Church TR, Heber D. Vitamin D, calcium supplementation, and colorectal adenomas: results of a randomized trial. J Natl Cancer Inst. 2003 Dec 3;95(23):1765-71.
  10. Marshall DT, Savage SJ, Garrett-Mayer E, Keane TE, Hollis BW, Horst RL, Ambrose LH, Kindy MS, Gattoni-Celli S. Vitamin D3 supplementation at 4000 international units per day for one year results in a decrease of positive cores at repeat biopsy in subjects with low-risk prostate cancer under active surveillance. J Clin Endocrinol Metab. 2012 Jul;97(7):2315-24.
  11. Van Veldhuizen PJ, Taylor SA, Williamson S, Drees BM. Treatment of vitamin D deficiency in patients with metastatic prostate cancer may improve bone pain and muscle strength. J Urol. 2000 Jan;163(1):187-90.
  12. Fakih MG, Andrews C, McMahon J, Muindi JR. A prospective clinical trial of cholecalciferol 2000 IU/day in colorectal cancer patients: evidence of a chemotherapy-response interaction. Anticancer Res. 2012 Apr;32(4):1333-8.
  13. Vaidya A, Forman JP. Vitamin D and hypertension: current evidence and future directions. Hypertension. 2010 Nov;56(5):774-9.
  14. Forman JP, Scott JB, Ng K, Drake BF, Suarez EG, Hayden DL, Bennett GG, Chandler PD, Hollis BW, Emmons KM, Giovannucci EL, Fuchs CS, Chan AT. Effect of vitamin D supplementation on blood pressure in blacks. Hypertension. 2013 Apr;61(4):779-85.
  15. Pfeifer M, Begerow B, Minne HW, Nachtigall D, Hansen C. Effects of a short-term vitamin D(3) and calcium supplementation on blood pressure and parathyroid hormone levels in elderly women. J Clin Endocrinol Metab. 2001 Apr;86(4):1633-7.
  16. Larsen T, Mose FH, Bech JN, Hansen AB, Pedersen EB. Effect of cholecalciferol supplementation during winter months in patients with hypertension: a randomized, placebo-controlled trial. Am J Hypertens. 2012 Nov;25(11):1215-22.
  17. Bonakdaran S, Hami M, Hatefi A. The effects of calcitriol on albuminuria in patients with type-2 diabetes mellitus. Saudi J Kidney Dis Transpl. 2012 Nov;23(6):1215-20.
  18. Pal L, Berry A, Coraluzzi L, Kustan E, Danton C, Shaw J, Taylor H. Therapeutic implications of vitamin D and calcium in overweight women with polycystic ovary syndrome. Gynecol Endocrinol.2012 Dec;28(12):965-8.