Brief and precise summary of Vitamin D
Note
6 minutes
difficulty level Easy
Matthew Messer

Matthew Messer

Editor-in-chief

Vitamin D might be the most important micronutrient everybody should be aware of. Vitamin D deficiency is widespread, and it is the main underlying cause of many chronic illnesses. (1) It’s quite different from other micronutrients: vitamin D is produced in the skin in response to sun exposure, but as a result of our modern lifestyle, sunlight is scarcely enough to maintain healthy levels of vitamin D. (2) Meals only contain a small amount of it, and it’s mostly found in food that’s not typically favored by the general population. (3) Thankfully, anybody can achieve ideal levels of vitamin D, the keystone of health, through vitamin D supplementation.

The types of vitamin D 

Vitamin D has two main types, vitamins D2 and D3. D3 is the vitamin we produce when sunbathing, and which has demonstrated positive results in most studies. 

Vitamin D2 can be found in mushrooms and some vegetables, but it’s much less effective than vitamin D3. Therefore it’s essential to focus on the supplementation of D3.

Why is it so hard to obtain enough vitamin D?  

Many micronutrients can be accessed through nutrition, but vitamin D3 is only present in very few foods. Only fish liver and fish liver oils contain a sufficient amount of vitamin D3, but they are rarely consumed. In addition, they contain nearly ten times more vitamin A than vitamin D3, therefore if one supplemented vitamin D3 solely from these, one would potentially overdose on vitamin A. This is particularly important, because ideally, the ratio of vitamins A and D3 should be 1:1. (6)

How much does sunbathing help? 

The majority of people cannot obtain enough vitamin D3 through sunbathing alone, as UV-B rays (which activate the production of the vitamin in the skin) are blocked by many factors. The further up North one lives, the less UV-B radiation they will be exposed to due to the sunbeams’ angle of incidence which means that for the most part of the year they don’t produce vitamin D. In today’s modern society most people work in buildings with little sun exposure, not to mention how clothing, clouds, urban air pollution and sunscreen all block UV-B rays. (4) 

Even if one spends plenty of time in the sun under the right circumstances, it cannot be guaranteed that their vitamin D3 levels will be optimal. A study conducted among Hawaiian surfers revealed that half of the participants suffered from vitamin D deficiency, even though they spent an average of 28 hours in the sun every week. (5) This is why it’s vital to get our vitamin D levels measured, since not even sunbathing can guarantee that we produce enough vitamin D. 

What is the optimal level of vitamin D? 

Opinions vary on the appropriate level. Official recommendations only regard extraordinarily low levels of vitamin D as a deficiency. 20 ng/ml (50 nml/l) is determined to be the threshold, and a 25-OH-D3 level below 10ng/ml (20 nml/l) is specified as severe deficiency. (2) However, several scientific studies have found that vitamin D levels below 30ng/ml (75 nmol/l) already significantly increase the risk of chronic illness, so many determined this as the limit value below which it should be considered as deficiency.  

The optimal amount is probably between 30 ng/ml (75 nmol/l) and 70 ng/ml (175 nmol/l), but we can safely assume that a higher vitamin D level doesn’t pose a risk either. (1) For a long time, the ridiculously low daily amount of 400 IUs of D3 was recommended, but this has been raised multiple times, since several studies warned that such a low amount is not even enough to prevent severe deficiency. (35,7) 

Can you overdose on vitamin D? 

While many caution against the risk of vitamin D overdose, such cases are incredibly rare. Even a study where 4700 participants took between 5000-50000 IUs of vitamin D daily for seven years reported only positive results. (8)

Interaction with other vitamins 

Vitamins A and K help protect against potential adverse effects and working together with vitamin D they help enhance its beneficial effects. (9,10,11,36)  

Unless one has a vitamin A rich diet, they should supplement the same amount of vitamin A as vitamin D3, in the ratio of 1:1. Previous research have concluded that their joint use can efficiently prevent the common cold, but taken separately, neither can be of help. (36,37) A recent study further confirmed the above: the combined use of 50000 IUs of vitamins A+D3 helped decrease the risk of stroke and increased vitamin D levels more than vitamin D3 taken on its own. (11)  

While many advise against the combined use of vitamins A and D3, this criticism is unwarranted, as vitamin A improves the absorption of vitamin D3 and helps prevent its possible side effects.  

How much vitamin D should we take? 

The first step is to determine our vitamin D level. This can be established from the 25-OH-D3 levels, which shows the exact amount of vitamin D in our bodies. (12) Unless one regularly supplements vitamin D3, they will almost certainly have a deficiency.  

The goal would be to raise the vitamin D level to between 30 ng/ml (75 nmol/l) and 70 ng/ml (175 nmol/l), since these levels minimize the risk of multiple illnesses. For adults, it means supplementing 2000 IUs-4000 IUs. For children, the recommended amount is 1000 IUs per 10 kilograms.  

Vitamin D supplements should be taken after breakfast or lunch, since fatty foods contribute to its absorption. (13) Once one reaches the ideal levels of vitamin D, they should get tested again to learn their personal ideal dosage.

What are the proven benefits of vitamin D?  

In the past decades the connection between vitamin D and various illnesses has been broadly discussed. It’s been common knowledge for long that vitamin D plays a role in keeping our bones healthy, as it’s necessary for the absorption of calcium. Combined with calcium and vitamin K, vitamin D can improve bone density and – although it’s more effective combined with vitamin K – it decreases the risk of bones fractures even on its own. (25,26,29)  

It’s a lesser known fact that vitamin D’s role goes beyond the protection of bones. Several studies have found that correcting vitamin D deficiency can significantly decrease the risk of certain cancers, cardiovascular diseases as well as type 1 and type 2 diabetes. (1,2,15, 16, 17, 18, 19,20,21,2,22,23)  

In addition, vitamin D improves blood sugar levels and insulin sensitivity, and it decreases the incidence of depression. (27,28,24) It has a key role in the proper functioning of the immune system, it reduces the risk of catching a cold or the flu, and in a recent study vitamin D supplementation almost completely put an end to severe courses of Covid-19. (30, 31) In the elderly, it improves muscle function and the nervous system, and thus lessens the risk of falling down. (32) In some experiments, vitamin D3 even advanced weight loss. (33,34)

Summary 

As a result of our modern lifestyle, most of us will need to supplement vitamin D3 to achieve a healthy level of vitamin D. This way, we can decrease the risk of chronic illness, and can improve our health and quality of life.  

Besides vitamin D3, it is advised to supplement fat-soluble vitamins and dietary minerals which are in synergy with it, such as vitamins A and K or magnesium. Supplemented jointly, vitamin D3 can be even more effective, and its rare side effects can be diminished. 

[The cover photo of the note shows sushi with tuna and salmon. 100 grams of tuna contains 227 IU, and 100 grams of salmon contains 685 IU of vitamin D, which in the case of tuna is a little more than one-twentieth of the required daily intake, while in the case of salmon it is enough for one-fifth.]

  1. Wang H, Chen W, Li D, Yin X, Zhang X, Olsen N, Zheng SG. Vitamin D and Chronic Diseases. Aging Dis. 2017 May 2;8(3):346-353. doi: 10.14336/AD.2016.1021. PMID: 28580189; PMCID: PMC5440113. 

  2. Palacios C, Gonzalez L. Is vitamin D deficiency a major global public health problem?. J Steroid Biochem Mol Biol. 2014;144 Pt A:138-145. doi:10.1016/j.jsbmb.2013.11.003 

  3. Lamberg-Allardt C. Vitamin D in foods and as supplements. Prog Biophys Mol Biol. 2006 Sep;92(1):33-8. doi: 10.1016/j.pbiomolbio.2006.02.017. Epub 2006 Feb 28. PMID: 16618499. 

  4. Matthias Wacker & Michael F. Holick (2013) Sunlight and Vitamin D, Dermato-Endocrinology, 5:1, 51-108, DOI: 10.4161/derm.24494 

  5. Binkley N, Novotny R, Krueger D, Kawahara T, Daida YG, Lensmeyer G, Hollis BW, Drezner MK. Low vitamin D status despite abundant sun exposure. J Clin Endocrinol Metab. 2007 Jun;92(6):2130-5. doi: 10.1210/jc.2006-2250. Epub 2007 Apr 10. PMID: 17426097. 

  6. https://www.westonaprice.org/health-topics/abcs-of-nutrition/vitamin-a-on-trial-does-vitamin-a-cause-osteoporosis/ 

  7. Holick MF, Binkley NC, Bischoff-Ferrari HA, Gordon CM, Hanley DA, Heaney RP, Murad MH, Weaver CM; Endocrine Society. Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2011 Jul;96(7):1911-30. doi: 10.1210/jc.2011-0385. Epub 2011 Jun 6. Erratum in: J Clin Endocrinol Metab. 2011 Dec;96(12):3908. PMID: 21646368. 

  8. McCullough PJ, Lehrer DS, Amend J. Daily oral dosing of vitamin D3 using 5000 TO 50,000 international units a day in long-term hospitalized patients: Insights from a seven year experience. J Steroid Biochem Mol Biol. 2019 May;189:228-239. doi: 10.1016/j.jsbmb.2018.12.010. Epub 2019 Jan 4. PMID: 30611908. 

  9. Fu X, Wang XD, Mernitz H, Wallin R, Shea MK, Booth SL. 9-Cis retinoic acid reduces 1alpha,25-dihydroxycholecalciferol-induced renal calcification by altering vitamin K-dependent gamma-carboxylation of matrix gamma-carboxyglutamic acid protein in A/J male mice. J Nutr. 2008 Dec;138(12):2337-41. doi: 10.3945/jn.108.093724. PMID: 19022954. 

  10. Kanellakis S, Moschonis G, Tenta R, Schaafsma A, van den Heuvel EG, Papaioannou N, Lyritis G, Manios Y. Changes in parameters of bone metabolism in postmenopausal women following a 12-month intervention period using dairy products enriched with calcium, vitamin D, and phylloquinone (vitamin K(1)) or menaquinone-7 (vitamin K (2)): the Postmenopausal Health Study II. Calcif Tissue Int. 2012 Apr;90(4):251-62. doi: 10.1007/s00223-012-9571-z. Epub 2012 Mar 4. PMID: 22392526. 

  11. Kadri A, Sjahrir H, Juwita Sembiring R, Ichwan M. Combination of vitamin A and D supplementation for ischemic stroke: effects on interleukin-1ß and clinical outcome. Med Glas (Zenica). 2020 Aug 1;17(2):425-432. doi: 10.17392/1137-20. PMID: 32567290. 

  12. Zerwekh JE. Blood biomarkers of vitamin D status. Am J Clin Nutr. 2008 Apr;87(4):1087S-91S. doi: 10.1093/ajcn/87.4.1087S. PMID: 18400739. 

  13. Mulligan GB, Licata A. Taking vitamin D with the largest meal improves absorption and results in higher serum levels of 25-hydroxyvitamin D. J Bone Miner Res. 2010 Apr;25(4):928-30. doi: 10.1002/jbmr.67. PMID: 20200983. 

  14. Gao Q, Kou T, Zhuang B, Ren Y, Dong X, Wang Q. The Association between Vitamin D Deficiency and Sleep Disorders: A Systematic Review and Meta-Analysis. Nutrients. 2018;10(10):1395. Published 2018 Oct 1. doi:10.3390/nu10101395 

  15. Skinner HG, Michaud DS, Giovannucci E, Willett WC, Colditz GA, Fuchs CS. Vitamin D intake and the risk for pancreatic cancer in two cohort studies. Cancer Epidemiol Biomarkers Prev. 2006 Sep;15(9):1688-95. doi: 10.1158/1055-9965.EPI-06-0206. PMID: 16985031. 

  16. Weinstein SJ, Purdue MP, Smith-Warner SA, Mondul AM, Black A, Ahn J, Huang WY, Horst RL, Kopp W, Rager H, Ziegler RG, Albanes D. 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. 2015 Mar 15;136(6):E654-64. doi: 10.1002/ijc.29157. Epub 2014 Sep 2. PMID: 25156182; PMCID: PMC4289432. 

  17. Garland CF, Gorham ED, Mohr SB, Grant WB, Giovannucci EL, Lipkin M, Newmark H, Holick MF, Garland FC. Vitamin D and prevention of breast cancer: pooled analysis. J Steroid Biochem Mol Biol. 2007 Mar;103(3-5):708-11. doi: 10.1016/j.jsbmb.2006.12.007. PMID: 17368188. 

  18. Gorham ED, Garland CF, Garland FC, Grant WB, Mohr SB, Lipkin M, Newmark HL, Giovannucci E, Wei M, Holick MF. Optimal vitamin D status for colorectal cancer prevention: a quantitative meta analysis. Am J Prev Med. 2007 Mar;32(3):210-6. doi: 10.1016/j.amepre.2006.11.004. PMID: 17296473. 

  19. Dobnig H, Pilz S, Scharnagl H, Renner W, Seelhorst U, Wellnitz B, Kinkeldei J, Boehm BO, Weihrauch G, Maerz W. Independent association of low serum 25-hydroxyvitamin d and 1,25-dihydroxyvitamin d levels with all-cause and cardiovascular mortality. Arch Intern Med. 2008 Jun 23;168(12):1340-9. doi: 10.1001/archinte.168.12.1340. PMID: 18574092. 

  20. Giovannucci E, Liu Y, Hollis BW, Rimm EB. 25-hydroxyvitamin D and risk of myocardial infarction in men: a prospective study. Arch Intern Med. 2008 Jun 9;168(11):1174-80. doi: 10.1001/archinte.168.11.1174. PMID: 18541825; PMCID: PMC3719391. 

  21. Brøndum-Jacobsen P, Benn M, Jensen GB, Nordestgaard BG. 25-hydroxyvitamin d levels and risk of ischemic heart disease, myocardial infarction, and early death: population-based study and meta-analyses of 18 and 17 studies. Arterioscler Thromb Vasc Biol. 2012 Nov;32(11):2794-802. doi: 10.1161/ATVBAHA.112.248039. Epub 2012 Aug 30. PMID: 22936341. 

  22. Pittas AG, Sun Q, Manson JE, Dawson-Hughes B, Hu FB. Plasma 25-hydroxyvitamin D concentration and risk of incident type 2 diabetes in women. Diabetes Care. 2010 Sep;33(9):2021-3. doi: 10.2337/dc10-0790. PMID: 20805275; PMCID: PMC2928356. 

  23. Borissova AM, Tankova T, Kirilov G, Dakovska L, Kovacheva R. The effect of vitamin D3 on insulin secretion and peripheral insulin sensitivity in type 2 diabetic patients. Int J Clin Pract. 2003 May;57(4):258-61. PMID: 12800453. 

  24. Sepehrmanesh Z, Kolahdooz F, Abedi F, Mazroii N, Assarian A, Asemi Z, Esmaillzadeh A. Vitamin D Supplementation Affects the Beck Depression Inventory, Insulin Resistance, and Biomarkers of Oxidative Stress in Patients with Major Depressive Disorder: A Randomized, Controlled Clinical Trial. J Nutr. 2016 Feb;146(2):243-8. doi: 10.3945/jn.115.218883. Epub 2015 Nov 25. PMID: 26609167. 

  25. Christakos S, Dhawan P, Porta A, Mady LJ, Seth T. Vitamin D and intestinal calcium absorption. Mol Cell Endocrinol. 2011;347(1-2):25-29. doi:10.1016/j.mce.2011.05.038 

  26. Kanellakis S, Moschonis G, Tenta R, Schaafsma A, van den Heuvel EG, Papaioannou N, Lyritis G, Manios Y. Changes in parameters of bone metabolism in postmenopausal women following a 12-month intervention period using dairy products enriched with calcium, vitamin D, and phylloquinone (vitamin K(1)) or menaquinone-7 (vitamin K (2)): the Postmenopausal Health Study II. Calcif Tissue Int. 2012 Apr;90(4):251-62. doi: 10.1007/s00223-012-9571-z. Epub 2012 2Mar 4. PMID: 22392526. 

  27. Zipitis CS, Akobeng AK. Vitamin D supplementation in early childhood and risk of type 1 diabetes: a systematic review and meta-analysis. Arch Dis Child. 2008 Jun;93(6):512-7. doi: 10.1136/adc.2007.128579. Epub 2008 Mar 13. PMID: 18339654. 

  28. Gregoriou E, Mamais I, Tzanetakou I, Lavranos G, Chrysostomou S. The Effects of Vitamin D Supplementation in Newly Diagnosed Type 1 Diabetes Patients: Systematic Review of Randomized Controlled Trials. Rev Diabet Stud. 2017;14(2-3):260-268. doi:10.1900/RDS.2017.14.260 

  29. Bischoff-Ferrari HA, Willett WC, Wong JB, Stuck AE, Staehelin HB, Orav EJ, Thoma A, Kiel DP, Henschkowski J. Prevention of nonvertebral fractures with oral vitamin D and dose dependency: a meta-analysis of randomized controlled trials. Arch Intern Med. 2009 Mar 23;169(6):551-61. doi: 10.1001/archinternmed.2008.600. PMID: 19307517. 

  30. Martineau A R, Jolliffe D A, Hooper R L, Greenberg L, Aloia J F, Bergman P et al. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data BMJ 2017; 356 :i6583 doi:10.1136/bmj.i6583 

  31. Entrenas Castillo M, Entrenas Costa LM, Vaquero Barrios JM, Alcalá Díaz JF, López Miranda J, Bouillon R, Quesada Gomez JM. "Effect of calcifediol treatment and best available therapy versus best available therapy on intensive care unit admission and mortality among patients hospitalized for COVID-19: A pilot randomized clinical study". J Steroid Biochem Mol Biol. 2020 Oct;203:105751. doi: 10.1016/j.jsbmb.2020.105751. Epub 2020 Aug 29. PMID: 32871238; PMCID: PMC7456194. 

  32. Mohammad Hassan Murad, Khalid B. Elamin, Nisrin O. Abu Elnour, Mohamed B. Elamin, Aziz A. Alkatib, Mitra M. Fatourechi, Jaime P. Almandoz, Rebecca J. Mullan, Melanie A. Lane, Hau Liu, Patricia J. Erwin, Donald D. Hensrud, Victor M. Montori, The Effect of Vitamin D on Falls: A Systematic Review and Meta-Analysis, The Journal of Clinical Endocrinology & Metabolism, Volume 96, Issue 10, 1 October 2011, Pages 2997–3006, https://doi.org/10.1210/jc.2011-1193 

  33. Salehpour A, Hosseinpanah F, Shidfar F, Vafa M, Razaghi M, Dehghani S, Hoshiarrad A, Gohari M. A 12-week double-blind randomized clinical trial of vitamin D₃ supplementation on body fat mass in healthy overweight and obese women. Nutr J. 2012 Sep 22;11:78. doi: 10.1186/1475-2891-11-78. PMID: 22998754; PMCID: PMC3514135. 

  34. Mason C, Xiao L, Imayama I, Duggan C, Wang CY, Korde L, McTiernan A. Vitamin D3 supplementation during weight loss: a double-blind randomized controlled trial. Am J Clin Nutr. 2014 May;99(5):1015-25. doi: 10.3945/ajcn.113.073734. Epub 2014 Mar 12. Erratum in: Am J Clin Nutr. 2014 Oct;100(4):1213. PMID: 24622804; PMCID: PMC3985208. 

  35. https://www.webmd.com/diet/news/20110606/new-guidelines-suggest-higher-doses-of-vitamin-d#1 

  36. SPIESMAN IG. MASSIVE DOSES OF VITAMINS A AND D IN THE PREVENTION OF THE COMMON COLD. Arch Otolaryngol. 1941;34(4):787–791. doi:10.1001/archotol.1941.00660040843010 

  37. Semba RD. Vitamin A as "anti-infective" therapy, 1920-1940. J Nutr. 1999 Apr;129(4):783-91. doi: 10.1093/jn/129.4.783. PMID: 10203551. 

Related contents:

The Interrelation of Vitamin D, Sunshine, and Menaloma

Note
3 minutes
difficulty level Easy
I want to read it

Century-Old Insights into the Dietary Aspects of Dental Health

Note
6 minutes
difficulty level Advanced
I want to read it