by Monica Mollica
If you’re following the health news, you know that vitamin D currently is in the media spotlight, and rightly so. Will Brink just did a great podcast “Vitamin D3 – scam or panacea?”, giving an overview on the importance of vitamin D. In this article I will expand upon some key points taken up in the podcast, and back up the case with a solid reference list of recent studies on the topic. I will also present some revealing prevalence stats on vitamin D insufficiency, in order to convince you to get your blood levels checked to find out your vitamin D status.
Vitamin D is interesting for several reasons:
1. The role of vitamin D for health promotion has undergone a paradigm shift. While traditionally thought to only be important for development and maintenance of strong bones, an impressive body of scientific research has accumulated over the past decade, showing that adequate vitamin D levels are necessary to prevent many diseases, especially cardiovascular disease, high blood pressure, endothelial dysfunction, diabetes (both type-1 and type-2), the metabolic syndrome, chronic inflammation, cancer, osteoporosis (including falls and fractures), muscle weakness, cognitive dysfunction and mental illness, autoimmune diseases (e.g. multiple sclerosis, rheumatoid arthritis), infectious diseases, as well as infertility and adverse pregnancy and birth outcomes [1-24].
Vitamin D deficiency/insufficiency is associated with all-cause mortality , and supplementation has been shown to decrease mortality rates [25, 26]. It has been estimated that doubling vitamin D levels in the general population (from 21 ng/mL to 44 ng/mL) would reduce vitamin D-related disease mortality rate by 20%, and increase life expectancy with about 2 years .
2. Insufficient levels of vitamin D also have direct implications for fitness enthusiasts and athletic performance, due to the importance of vitamin D for muscle function (I will cover this in much more dept in an upcoming article) [28-39].
3. In contrast to other vitamins, vitamin D deficiency/insufficiency is very common (more on that below).
4. The vitamin D requirement for health promotion and protection against the mentioned diseases and muscle dysfunction is much higher than the dietary recommendations (RDA) for bone health [4, 40-45].
Having heard about all the vitamin D benefits you might wonder what is the optimal vitamin D level? How low is too low and how high is too high? How much vitamin D does one have to consume to reap all the benefits? Let’s find out…
What are the blood level thresholds indicating vitamin D insufficiency?
The form of vitamin D that is measured in blood and used to indicate vitamin D status is called 25-hydroxy-vitamin D (abbreviated 25[OH]D) [9, 46]. So when I talk about blood vitamin D levels in this article, it is 25-hydroxy-vitamin D I am referring to (it’s easier for most people to think in terms of vitamin D levels than 25[OH]D or 25-hydroxy-vitamin D).
There is no official consensus about what is the optimal vitamin D level, and it is possible that different endpoints require different optimal vitamin D levels. However, based on the currently available data, prominent vitamin D researchers and authorities have presented the following guidelines:
Vitamin D status thresholds as defined by blood 25-hydroxy-vitamin D (25[OH]D) levels.
Vitamin D status
Risk for toxicity
[18, 22, 41, 47, 48, 50-58]
[4, 9, 22, 28]
[9, 46, 59]
* Severe deficiency that causes softening of the bones occurs with levels below 10 ng/mL (25 mmol/L) .
* Blood (serum) levels of 25(OH)D are reported in either nanograms per milliliter (ng/mL) and nanomoles per liter (nmol/L).
* 1 ng/mL = 2.5 nmol/L
Traditionally, government issued health guidelines have stated that vitamin D levels of 20 ng/mL are sufficient. However, in light of new data prominent vitamin D researchers now recommend vitamin D levels in the range of 50-60 ng/ml, for both health promotion and athletic/physical performance [4, 9, 28]. As indicated in the table, even though this new recommended level is 2-3 times the old recommendation, it is far below the risk for intoxication and is thus a safe target to aim for in order to achieve all the vitamin D related health benefits (which is will cover in dept in upcoming articles).
How common is vitamin D insufficiency?
Low vitamin D status, i.e. vitamin D deficiency or insufficiency, is far more common than previously thought.
When looking at stats, it’s important to distinguish vitamin D deficiency from insufficiency. While severe vitamin D deficiently isn’t as prevalent, vitamin D insufficiency is:
* 36% of the US population is deficient, with vitamin D levels below 20 ng/ml .
* In a study on subjects characteristic of the US white population, it was found that only 18% have a vitamin D level over 30 ng/ml . Thus, a whopping 82% are insufficient in vitamin D!
Similar results were found in the 2004 National Health and Nutrition Examination Survey (NHANES)  and in other analyses .
* To make things worse, data from (NHANES) showed that the number of persons with a vitamin D level below 30 ng/mL nearly doubled between the 1994 and 2004 .
Bearing in mind that the desired range as recommended by vitamin D research experts, is 50-60 ng/ml, these stats are alarming and underscore the fact that vitamin D insufficiency exists in epidemic proportions in the US. This vitamin D insufficiency epidemic spans across the globe .
How should I get my vitamin D?
The sources of vitamin D are sunlight exposure, food and supplements . However, only a few foods are naturally rich in vitamin D :
Salmon, fresh wild caught
Salmon, fresh farmed
600–1,000 IU/3.5 oz vitamin D3
100–250 IU/3.5 oz vitamin D3, vitamin D2
300–600 IU/3.5 oz vitamin D3
300 IU/3.5 oz vitamin D3
250 IU/3.5 oz vitamin D3
236 IU/3.5 oz vitamin D3
20 IU/yolk vitamin D3 or D2
100 IU/8 oz, usually vitamin D3
Thus, unless you eat oily fish every day, you cannot rely on your diet to cover your vitamin D needs.
Another source, the safety of which is controversial, is sunlight exposure. This is why vitamin D is called the “sunshine vitamin”. Because vitamin D can be produced by the skin upon sun exposure, it is actually not a vitamin in the traditional sense (per definition, vitamins are essential because they cannot be produced by the body). In fact, vitamin D is a pre-hormone to the hormone calcitriol (which is the active hormonal from of vitamin D that exerts effects on different tissues in the body). However, as said above, it is the vitamin D metabolite 25-hydroxy-vitamin D (25[OH]D) that is used to indicate vitamin D status and to guide supplementation needs.vitamin-d-sources
Even though sun exposure theoretically is an effective vitamin D source, it cannot safely be relied on. A recent study showed that vitamin D supplementation is actually more effective than advised sunlight exposure for treating vitamin D deficiency . The inferiority of sunlight exposure to improve and keep optimal vitamin D status is supported by findings of prevalent vitamin D insufficiency even in sunny Florida . This was also underlined in a study of tanned prototypic “surfer dudes” (mean age 24 years) who overall reported an average of 22.4 hours per week of unprotected sun exposure . Despite this abundant sunshine exposure, the mean blood vitamin D level was only 31 ng/mL (79 nmol/L), and 51% had a level below the recommended ideal 30 ng/mL (75 nmol/L) cutoff for sufficiency .
Also, the capacity to produce vitamin D in the skin is lower in dark skinned people, and diminishes as we get older [67, 68]. The darker skin types (III–VI) and the oldest people (>59 yr) are at the highest risk for not making enough vitamin D3 during the year from everyday outdoor exposures, even with a 2–3 week summer vacation . People living in northern latitudes are especially at risk of not getting enough vitamin D producing UVB radiation from the sun [68, 69].
Another issue with sun bathing is the consequence of skin aging and risk of skin cancer. Unfortunately, the UVB radiation that produces vitamin D in the skin, is also the culprit causing skin cancer and wrinkling [70, 71]. This is a legitimate reason to not attempt to cover your vitamin D requirements by sun exposure. And even if sun exposure was a safe and reliable way to cover vitamin D needs, in today’s society with hectic work schedules most people don’t have much time to be out in the sun. It has been established that most adult Americans do not go outside enough to meet their minimum vitamin D3 needs all year .
Vitamin D supplements come as either vitamin D2 (cholecalciferol) or vitamin D3 (ergocalciferol) [4, 72] and in over-the-counter dosages of up to 10,000 IU. In the past there was a scientific “D-bate” over the efficiency of D2 vs. D3. However, a recent systematic review and meta-analysis of all studies published to date concluded that vitamin D3 is more effective at raising blood levels of vitamin D (i.e. 25-hydroxy-vitamin D) . More specifically, vitamin D3 is approximately 87% more potent in raising and maintaining 25-hydroxy-vitamin D levels, and produces 2- to 3-fold greater body storage of vitamin D than does vitamin D2 . Given its greater potency and lower cost, the vitamin D3 form should be the preferred supplement choice to elevate and maintain health promoting vitamin D levels.
Now you know the importance of finding out your vitamin D level. Either ask your doctor to check it, or order a vitamin D blood test online without a doctor’s prescription if you don’t have health insurance. Life Extension offers great blood testing services, including vitamin D testing:
Vitamin D, 25-Hydroxy Blood Test
And it is very affordable: $30 for a Life Extension member, $62.67 for non-members. Talk about a great health investment!
In my store you find a link to Life Extension’s page explaining how the blood testing works.
If your blood level of 25-hydroxy-vitamin D shows that you are insufficient in vitamin D (which most folks are), you will need to get a vitamin D3 supplement to reap all the health and performance benefits from this multi-functional pre-hormone.
You also know why vitamin D supplementation is the way to go in order to safely get your vitamin D level to the optimal 50-60 ng/mL range. Adequate vitamin D supplementation and sensible sunlight exposure to reach optimal vitamin D status are among the front line factors of prophylaxis for a spectrum of commons diseases.
In the next article I will explain that there is no clear cut vitamin D dose-response relationship because of the considerable variation in how individuals respond to vitamin D supplementation. The response to treatment varies with baseline vitamin D levels, skin pigmentation (race), season and geographic location (latitude). This is why it is so important that you check your baseline level and also keep monitoring it every 6 months to see how you respond. The next article will cover supplemental vitamin D “loading” and maintenance dosages to raise your level fast and keep it there. I will also present studies that have investigated mega-dosages, to give you a perspective. Stay tuned!
About the Author:
Monica Mollica has a Bachelor’s and Master’s degree in Nutrition from the University of Stockholm, Sweden, and is an ISSA Certified Personal Trainer. She works a dietary consultant, health journalist and writer for www.BrinkZone.com, and is also a web designer and videographer.
Monica has admired and been fascinated by muscular and sculptured strong athletic bodies since childhood, and discovered bodybuilding as an young teenager. Realizing the importance of nutrition for maximal results in the gym, she went for a BSc and MSc with a major in Nutrition at the University.
During her years at the University she was a regular contributor to the Swedish bodybuilding magazine BODY, and she has published the book (in Swedish) “Functional Foods for Health and Energy Balance”, and authored several book chapters in Swedish publications.
It was her insatiable thirst for knowledge and scientific research in the area of bodybuilding and health that brought her to the US. She has completed one semester at the PhD-program “Exercise, Nutrition and Preventive Health” at Baylor University Texas, at the department of Health Human Performance and Recreation, and worked as an ISSA certified personal trainer. Today, Monica is sharing her solid experience by doing dietary consultations and writing about topics related to health, fitness, bodybuilding, anti-aging and longevity.
1. Pludowski, P., et al., Vitamin D effects on musculoskeletal health, immunity, autoimmunity, cardiovascular disease, cancer, fertility, pregnancy, dementia and mortality-A review of recent evidence. Autoimmun Rev, 2013.
2. Rosen, C.J., et al., The nonskeletal effects of vitamin D: an Endocrine Society scientific statement. Endocr Rev, 2012. 33(3): p. 456-92.
3. Zhang, R. and D.P. Naughton, Vitamin D in health and disease: current perspectives. Nutr J, 2010. 9: p. 65.
4. Wacker, M. and M.F. Holick, Vitamin D – effects on skeletal and extraskeletal health and the need for supplementation. Nutrients, 2013. 5(1): p. 111-48.
5. Milaneschi, Y., et al., The association between low vitamin D and depressive disorders. Mol Psychiatry, 2013.
6. Mezza, T., et al., Vitamin D deficiency: a new risk factor for type 2 diabetes? Ann Nutr Metab, 2012. 61(4): p. 337-48.
7. Mitri, J., M.D. Muraru, and A.G. Pittas, Vitamin D and type 2 diabetes: a systematic review. Eur J Clin Nutr, 2011. 65(9): p. 1005-15.
8. Vuolo, L., et al., Vitamin D and cancer. Front Endocrinol (Lausanne), 2012. 3: p. 58.
9. Holick, M.F., Vitamin D deficiency. N Engl J Med, 2007. 357(3): p. 266-81.
10. Bosomworth, N.J., Mitigating epidemic vitamin D deficiency: the agony of evidence. Can Fam Physician, 2011. 57(1): p. 16-20, e1-6.
11. Zittermann, A., Vitamin D in preventive medicine: are we ignoring the evidence? Br J Nutr, 2003. 89(5): p. 552-72.
12. Wang, C., Role of vitamin d in cardiometabolic diseases. J Diabetes Res, 2013. 2013: p. 243934.
13. Baz-Hecht, M. and A.B. Goldfine, The impact of vitamin D deficiency on diabetes and cardiovascular risk. Curr Opin Endocrinol Diabetes Obes, 2010. 17(2): p. 113-9.
14. Chagas, C.E., et al., Focus on vitamin D, inflammation and type 2 diabetes. Nutrients, 2012. 4(1): p. 52-67.
15. Rosenblum, J.L., et al., Calcium and vitamin D supplementation is associated with decreased abdominal visceral adipose tissue in overweight and obese adults. Am J Clin Nutr, 2012. 95(1): p. 101-8.
16. Martini, L.A. and R.J. Wood, Vitamin D status and the metabolic syndrome. Nutr Rev, 2006. 64(11): p. 479-86.
17. Bikle, D., Nonclassic actions of vitamin D. J Clin Endocrinol Metab, 2009. 94(1): p. 26-34.
18. Cavalier, E., et al., Vitamin D and type 2 diabetes mellitus: where do we stand? Diabetes Metab, 2011. 37(4): p. 265-72.
19. Muscogiuri, G., et al., Can vitamin D deficiency cause diabetes and cardiovascular diseases? Present evidence and future perspectives. Nutr Metab Cardiovasc Dis, 2012. 22(2): p. 81-7.
20. Oosterwerff, M.M., et al., Serum 25-hydroxyvitamin D levels and the metabolic syndrome in older persons: a population-based study. Clin Endocrinol (Oxf), 2011. 75(5): p. 608-13.
21. Nagpal, J., J.N. Pande, and A. Bhartia, A double-blind, randomized, placebo-controlled trial of the short-term effect of vitamin D3 supplementation on insulin sensitivity in apparently healthy, middle-aged, centrally obese men. Diabet Med, 2009. 26(1): p. 19-27.
22. von Hurst, P.R., W. Stonehouse, and J. Coad, Vitamin D supplementation reduces insulin resistance in South Asian women living in New Zealand who are insulin resistant and vitamin D deficient – a randomised, placebo-controlled trial. Br J Nutr, 2010. 103(4): p. 549-55.
23. Nazarian, S., et al., Vitamin D3 supplementation improves insulin sensitivity in subjects with impaired fasting glucose. Transl Res, 2011. 158(5): p. 276-81.
24. Mitri, J., et al., Effects of vitamin D and calcium supplementation on pancreatic beta cell function, insulin sensitivity, and glycemia in adults at high risk of diabetes: the Calcium and Vitamin D for Diabetes Mellitus (CaDDM) randomized controlled trial. Am J Clin Nutr, 2011. 94(2): p. 486-94.
25. Bjelakovic, G., et al., Vitamin D supplementation for prevention of mortality in adults. Cochrane Database Syst Rev, 2011(7): p. CD007470.
26. Autier, P. and S. Gandini, Vitamin D supplementation and total mortality: a meta-analysis of randomized controlled trials. Arch Intern Med, 2007. 167(16): p. 1730-7.
27. Grant, W.B., An estimate of the global reduction in mortality rates through doubling vitamin D levels. Eur J Clin Nutr, 2011. 65(9): p. 1016-26.
28. Cannell, J.J., et al., Athletic performance and vitamin D. Med Sci Sports Exerc, 2009. 41(5): p. 1102-10.
29. Hamilton, B., Vitamin d and athletic performance: the potential role of muscle. Asian J Sports Med, 2011. 2(4): p. 211-9.
30. Ceglia, L. and S.S. Harris, Vitamin d and its role in skeletal muscle. Calcif Tissue Int, 2013. 92(2): p. 151-62.
31. Ceglia, L., Vitamin D and skeletal muscle tissue and function. Mol Aspects Med, 2008. 29(6): p. 407-14.
32. Pfeifer, M., B. Begerow, and H.W. Minne, Vitamin D and muscle function. Osteoporos Int, 2002. 13(3): p. 187-94.
33. Boland, R.L., VDR activation of intracellular signaling pathways in skeletal muscle. Mol Cell Endocrinol, 2011. 347(1-2): p. 11-6.
34. Girgis, C.M., et al., The roles of vitamin D in skeletal muscle: form, function, and metabolism. Endocr Rev, 2013. 34(1): p. 33-83.
35. Birge, S.J. and J.G. Haddad, 25-hydroxycholecalciferol stimulation of muscle metabolism. J Clin Invest, 1975. 56(5): p. 1100-7.
36. Hamilton, B., Vitamin D and human skeletal muscle. Scand J Med Sci Sports, 2010. 20(2): p. 182-90.
37. Hazell, T.J., J.R. DeGuire, and H.A. Weiler, Vitamin D: an overview of its role in skeletal muscle physiology in children and adolescents. Nutr Rev, 2012. 70(9): p. 520-33.
38. Wassner, S.J., et al., Vitamin D Deficiency, hypocalcemia, and increased skeletal muscle degradation in rats. J Clin Invest, 1983. 72(1): p. 102-12.
39. Daly, R.M., Independent and combined effects of exercise and vitamin D on muscle morphology, function and falls in the elderly. Nutrients, 2010. 2(9): p. 1005-17.
40. Cashman, K.D., et al., Estimation of the dietary requirement for vitamin D in healthy adults. Am J Clin Nutr, 2008. 88(6): p. 1535-42.
41. Bischoff-Ferrari, H.A., et al., Estimation of optimal serum concentrations of 25-hydroxyvitamin D for multiple health outcomes. Am J Clin Nutr, 2006. 84(1): p. 18-28.
42. Aloia, J.F., et al., Vitamin D intake to attain a desired serum 25-hydroxyvitamin D concentration. Am J Clin Nutr, 2008. 87(6): p. 1952-8.
43. Vieth, R., et al., Randomized comparison of the effects of the vitamin D3 adequate intake versus 100 mcg (4000 IU) per day on biochemical responses and the wellbeing of patients. Nutr J, 2004. 3: p. 8.
44. Vieth, R., P.C. Chan, and G.D. MacFarlane, Efficacy and safety of vitamin D3 intake exceeding the lowest observed adverse effect level. Am J Clin Nutr, 2001. 73(2): p. 288-94.
45. Vieth, R., Experimentally observed vitamin D requirements are higher than extrapolated ones. Am J Clin Nutr, 2009. 90(4): p. 1114-5; author reply 1115-6.
46. Holick, M.F., et al., Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab, 2011. 96(7): p. 1911-30.
47. Holick, M.F., Vitamin D: a D-Lightful health perspective. Nutr Rev, 2008. 66(10 Suppl 2): p. S182-94.
48. Holick, M.F., Vitamin D status: measurement, interpretation, and clinical application. Ann Epidemiol, 2009. 19(2): p. 73-8.
49. Hollis, B.W., Circulating 25-hydroxyvitamin D levels indicative of vitamin D sufficiency: implications for establishing a new effective dietary intake recommendation for vitamin D. J Nutr, 2005. 135(2): p. 317-22.
50. Vieth, R., et al., The urgent need to recommend an intake of vitamin D that is effective. Am J Clin Nutr, 2007. 85(3): p. 649-50.
51. Heaney, R.P., The case for improving vitamin D status. J Steroid Biochem Mol Biol, 2007. 103(3-5): p. 635-41.
52. Vieth, R., Why the minimum desirable serum 25-hydroxyvitamin D level should be 75 nmol/L (30 ng/ml). Best Pract Res Clin Endocrinol Metab, 2011. 25(4): p. 681-91.
53. Mason, R.S., V.B. Sequeira, and C. Gordon-Thomson, Vitamin D: the light side of sunshine. Eur J Clin Nutr, 2011. 65(9): p. 986-93.
54. Souberbielle, J.C., et al., Vitamin D and musculoskeletal health, cardiovascular disease, autoimmunity and cancer: Recommendations for clinical practice. Autoimmun Rev, 2010. 9(11): p. 709-15.
55. Bischoff-Ferrari, H.A., et al., Benefit-risk assessment of vitamin D supplementation. Osteoporos Int, 2010. 21(7): p. 1121-32.
56. Hanley, D.A., et al., Vitamin D in adult health and disease: a review and guideline statement from Osteoporosis Canada. CMAJ, 2010. 182(12): p. E610-8.
57. Bischoff-Ferrari, H.A., The 25-hydroxyvitamin D threshold for better health. J Steroid Biochem Mol Biol, 2007. 103(3-5): p. 614-9.
58. Binkley, N., R. Ramamurthy, and D. Krueger, Low vitamin D status: definition, prevalence, consequences, and correction. Endocrinol Metab Clin North Am, 2010. 39(2): p. 287-301, table of contents.
59. Holick, M.F. and T.C. Chen, Vitamin D deficiency: a worldwide problem with health consequences. Am J Clin Nutr, 2008. 87(4): p. 1080S-6S.
60. Bikle, D.D., Vitamin D: newly discovered actions require reconsideration of physiologic requirements. Trends Endocrinol Metab, 2010. 21(6): p. 375-84.
61. Holick, M.F., et al., Guidelines for preventing and treating vitamin D deficiency and insufficiency revisited. J Clin Endocrinol Metab, 2012. 97(4): p. 1153-8.
62. Marantes, I., et al., Is vitamin D a determinant of muscle mass and strength? J Bone Miner Res, 2011. 26(12): p. 2860-71.
63. Ginde, A.A., M.C. Liu, and C.A. Camargo, Jr., Demographic differences and trends of vitamin D insufficiency in the US population, 1988-2004. Arch Intern Med, 2009. 169(6): p. 626-32.
64. Wicherts, I.S., et al., Sunlight exposure or vitamin D supplementation for vitamin D-deficient non-western immigrants: a randomized clinical trial. Osteoporos Int, 2011. 22(3): p. 873-82.
65. Levis, S., et al., Vitamin d deficiency and seasonal variation in an adult South Florida population. J Clin Endocrinol Metab, 2005. 90(3): p. 1557-62.
66. Binkley, N., et al., Low vitamin D status despite abundant sun exposure. J Clin Endocrinol Metab, 2007. 92(6): p. 2130-5.
67. The Australian and New Zealand Bone and Mineral Society, et al., Risks and benefits of sun exposure: Position Statement, 2007.
68. Godar, D.E., et al., Solar UV doses of adult Americans and vitamin D(3) production. Dermatoendocrinol, 2011. 3(4): p. 243-50.
69. Kimlin, M.G., Geographic location and vitamin D synthesis. Mol Aspects Med, 2008. 29(6): p. 453-61.
70. Wolpowitz, D. and B.A. Gilchrest, The vitamin D questions: how much do you need and how should you get it? J Am Acad Dermatol, 2006. 54(2): p. 301-17.
71. El Ghissassi, F., et al., A review of human carcinogens–part D: radiation. Lancet Oncol, 2009. 10(8): p. 751-2.
72. Thacher, T.D. and B.L. Clarke, Vitamin D insufficiency. Mayo Clin Proc, 2011. 86(1): p. 50-60.
73. Tripkovic, L., et al., Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis. Am J Clin Nutr, 2012. 95(6): p. 1357-64.
74. Heaney, R.P., et al., Vitamin D(3) is more potent than vitamin D(2) in humans. J Clin Endocrinol Metab, 2011. 96(3): p. E447-52.