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Recommended daily intake of Vitamin D for adults is around 5,000 IUs or 35,000-50,000 IU twice per week (recent research suggests that taking large doses is most effective). The following are the top 25 reasons to make sure your vitamin D levels measure up.

1. Bone Health

Low levels of vitamin D contribute to osteopenia, osteoporosis, and bone fractures. It is not news that low calcium intake and poor vitamin D status are key determinants of osteoporosis and fracture risk, but a 2010 study suggests that calcium and vitamin D supplementation is an essential component in maintaining bone health. Together these minerals can improve bone mineralization, and correct secondary hyperparathyroidism , thereby preventing falls.

Lips, P., Bouillon, R., Van Schoor, N., Vanderscheuren, D., Verscheuren, S., Kuchuk, N., Milisen, K., Boonen, S. Reducing fracture risk with calcium and vitamin D. Clinical Endocrinology. 2010. 73( 3), 277–285.

Fletcher, R., Fairfield, K. Vitamins for Chronic Disease Prevention in Adults. Journal of the American Medical Association. 2002. 287, 3127-3129.



2. Muscle Strength

Researchers have known for years that skeletal muscle is a target organ for vitamin D and that deficiencies lead to muscle weakness. Specifically, a lack of vitamin D leads to abnormalities in muscle contraction and relaxation, affecting muscle force production. There is also evidence that adequate levels of vitamin D reduce the degradation of protein in muscle.

Holick, M.F. Vitamin D deficiency. New England Journal of Medicine. 2007. 357(3), 266-281.
Boland, R. The role of vitamin D in skeletal muscle function. Endocrine Reviews. 1986. 7(4), 434-448.

3. Muscle Power

Optimal levels of vitamin D have been shown to improve muscle power development and jump height. Researchers found that the ability of the muscles to contract and produce force is affected by vitamin D status. Participants in a 2008 study with low concentrations of vitamin D generated less power than those with higher concentrations, leading to the conclusion that vitamin D is significantly associated with power and force Further, researchers suggest that sub-optimal force development has negative implications for long-term bone development.

Ward, K., Das, G., Berry, J., Roberts, S., Rawer, R., Adams, J., Mughal, A. Vitamin D status and muscle function in post-menarchal adolescent girls. The Journal of Clinical Endocrinology and Metabolism. 2009. 94(2), 559-563.

4. Lean Body Mass

Vitamin D is essential for the maintenance of muscle, lean body mass, and for avoiding the development of fat in muscle. A vitamin D deficiency can cause both muscle weakness and an increase in fat mass. A 2010 study found that vitamin D shortage is associated with increased fat infiltration in muscle. Vitamin D deficiency was identified as a serum concentration less than 29 ng/ml, a level that 59 percent of the subjects were below. The vitamin D-insufficient subjects had approximately 24 percent greater muscle fat infiltration than those with vitamin D levels above 29 ng/ml, leading researchers to conclude that vitamin D levels are significantly associated with the degree of fat in skeletal muscle.

Gilsanz, V., Kremer, A., Mo, A., Wren, T., Kremer, R. Vitamin D status and its relation to muscle mass and muscle fat in young women. Journal of Clinical Endocrinology and Metabolism. 2010. (95)4. 1595-1601.

5. Treatment of Psoriasis and Skin Disorders

Skin disorders such as psoriasis can be responsive to treatment with vitamin D because it lessens inflammation. Recent studies have shown that patients suffering from a variety of inflammatory conditions including psoriasis, dermatitis, dandruff, eczema, rosacea, and severe acne were often vitamin D-deficient. Vitamin D may actually help retard the abnormal growth and shedding rate of skin cells in conditions like psoriasis.

Holick, M. Vitamin D importance in the prevention of cancers, type 1 diabetes, heart disease, and osteoporosis. American Journal of Clinical Nutrition. 2004. 29 (3), 362-371.

Holick, MF. High prevalence of vitamin D inadequacy and implications for health. Mayo Clinic Proceedings. 2006. 81(3), 353-73.

Masuda, S., Jones, G. Promise of vitamin D analogues in the treatment of hyperproliferative conditions.Molecular Cancer Therapeutics. 2006. 5(4), 797-808.

6. Blood Sugar Regulation and Insulin Resistance

Supplementing with vitamin D has been shown to increase insulin sensitivity and decrease insulin resistance, indicating that it may be an effective way to offset the symptoms of diabetes. A 2010 study of South Asian women with insulin sensitivity (in a pre-diabetes state) found that taking 4,000 IUs of vitamin D a day resulted in significant decreases in insulin sensitivity, adding to data from a 2009 study that found that higher vitamin D levels lowered diabetes risk.

Von Hurst, P., Stonehouse, W., Coad, J. Vitamin D supplementation reduces insulin resistance in South Asian women living in New Zealand who are insulin resistant and vitamin D deficient – a randomized, placebo-controlled trial. British Journal of Nutrition. 2009. 4(103), 549 – 555.

Pittas, A., Lau, J., Hu, F., Dawson-Hughes, B. The role of vitamin D and calcium in type 2 diabetes. A systematic review and meta-analysis. Journal of Clinical Endocrinology and Metabolism. 2007. 92, 2017-2029.

Holick MF. Vitamin D deficiency. New England Journal of Medicine. 2007. 357(3), 266-81.

7. Preventing Multiple Sclerosis

Vitamin D deficiency is known to contribute to bone mineral loss and osteoporosis, but the good news is that adequate vitamin D levels have a protective effect on the risk of multiple sclerosis (MS). Researchers studied over 190,000 women in two studies called the Nurses’ Study I and II and found that women who used supplemental vitamin D, largely from multivitamins, had a 40 percent lower risk of MS than women who did not supplement. Findings from a second study of African Americans with MS published in 2011 supported the link between vitamin D deficiency and MS. Researchers reported that low vitamin D is a major risk factor for MS susceptibility and severity.

Interestingly, in national surveys, African Americans have a lower vitamin D status than non-Hispanic whites and Mexican Americans. The most likely explanation for this disparity is that melanin, the primary determinant of skin pigmentation, functions as an optical filter of ultraviolet (UV) light, limiting vitamin D synthesis. Darker pigmented individuals require longer UV exposure times than lighter pigmented individuals to synthesize equivalent amounts of vitamin D.

Munger, K., Zhang, S., O’Reilly, E., Hernán, M., Olek, M., Willett, W., Ascherio, A. Vitamin D intake and incidence of multiple sclerosis. Neurology. 2004. 62(1), 60-65.

Gelfand, J., Cree, B., McElroy, J., Oksenberg, J., Green, R., Mowry, E. Vitamin D in African Americans with multiple sclerosis. Neurology. 2011. (76)21, 1824-1830.

8. Cancer Prevention

Vitamin D has been linked with fighting numerous cancers including lung, breast, colon, and prostate. In the case of lung cancer, supplementing with Vitamin D may help offset elevated levels of an enzyme that is associated with the development of aggressive lung cancer tumors. In a 2011 study, lung cancer patients with high vitamin D levels had an 81 percent survival rate after five years compared to those with low levels (41percent survival rate). Scientists are investigating other anti-cancer benefits of taking vitamin D supplementation.

Chen, G., Kim, S., King, A., Zhao, L., Simpson, R., Christensen, P. CYP24A1 Is an independent prognostic marker of survival in patients with lung adenocarcinoma. Clinical Cancer Research. 2011. 17(4), 817-26.

9. Asthma Treatment

A study at the University of Colorado-Denver found that higher vitamin D levels are associated with improved lung function, reduced airway hyper-responsiveness, and improved in vitro glucocorticoids. The findings suggest that supplementation of vitamin D in patients with asthma may result in decreasing asthma severity and improved treatment response. This study also found that participants with lower vitamin D levels had more inflammation. Also, there was an inverse relationship between the participants’ Body Mass Index and their vitamin D levels, meaning that the fattest participants had the lowest vitamin D levels—more data to support what we already know about vitamin D supporting weight loss and an ideal lean body mass.

Sutherland, E., Goleva, E., Jackson, L., Stevens, A., Leung, D. Vitamin D levels, lung function, and steroid response in adult asthma. American Journal of Respiratory Critical Care Medicine. 2010. 181(7), 699-704.

Arunabh, S., Pollack, S., Yeh, J., Aloia, J. Body fat content and 25-hydroxyvitamin D levels in healthy women.Journal of Clinical Endocrinology and Metabolism. 2003. 88(1), 157-161.

Parikh, S., Edelman, M., Uwaifo, G., Freedman, R., Semega-Janneh, M., Reynolds, J., Yanovski. The relationship between obesity and serum 1,25-dihydroxy vitamin D concentrations in healthy adults. Journal of Clinical Endocrinology and Metabolism. 2010. 89(3), 1196-9.

10. Male Reproductive Health

New research from the University of Copenhagen found that vitamin D is associated with male reproductive health, specifically in regards to normal sperm count and sperm motility. Men with vitamin D deficiency had a lower proportion of mobile and morphologically normal sperm compared with men with high vitamin D levels. For maximal reproductive health and optimal sperm function, vitamin D supplementation is crucial in light of studies indicating that 51percent of men have low D levels.

Jensen, M., Bjerrum, P., Jessen, T., Nielsen, J., Joensen, U., Olesen, I., Petersen, J. Vitamin D is positively associated with sperm motility and increases intracellular calcium in human spermatozoa. European Journal of Human Reproduction and Embryology. 2011. 26(6), 1307-1317.

11. Cardiovascular Health

Vitamin D deficiency is linked with cardiovascular disease and high levels of vitamin D are associated with heart health. The Framingham Heart Study followed 1739 Caucasian individuals with a mean age of 59 years without prior cardiovascular disease. Participants’ vitamin D levels and cardiovascular health was assessed at the beginning of the study and 5 years later. The follow up study identified 120 individuals who had developed a first cardiovascular event. Additionally, for individuals with high blood pressure and low vitamin D levels there was a two-fold risk of cardiovascular incidence. The study indicates that maintaining optimal vitamin D levels is crucial in avoiding cardiovascular disease and that vitamin D supplementation could contribute to the prevention of cardiovascular disease.

Wang, T., Pencina, M., Booth, S., Jacques, P., Ingelsson, E., Lanier, K., Benjamin, E., D’Agostino, R., Wolf, M., Vasan, R. Vitamin D deficiency and risk of cardiovascular disease. Journal of the American Heart Association. 2008. 117, 503-511.

12. Brain Health

Low vitamin D levels are associated with cognitive impairment, specifically in individuals over age 75. A 2010 study of 752 women found that women with vitamin D deficiency had increased rates of significant cognitive impairment. Low levels of vitamin D have previously been associated with neurological concerns and disorders, but this new research indicates the importance of ample vitamin D for optimal brain health.

Annweiler, C., Schott, A., Allali, G., Bridenbaugh, S., Kressig, R., Allain, P., Herrmann, F., Beauchet, O. Association of vitamin D deficiency with cognitive impairment in older women. Neurology. 2010. 74(1), 27-32.

13. Fetal Brain Development

In light of the role of vitamin D on brain health, it is not surprising that it plays a role in fetal brain development. Scientists have concluded that pregnant mothers who are deficient in vitamin D have fetuses with developmental impairment in brain cells. Additionally, there is evidence that the offspring of vitamin D-deficient mothers are more susceptible to schizophrenia, bone disorders such as rickets, and the development of diabetes.

Cui, X., McGrath, J., Burne, T., Mackay-Sim, A., Eyles, D. Maternal vitamin D depletion alters neurogenesis in the developing rat brain. International Journal of Developmental Neuroscience. 2007. 25, 227–232.

McCann, J., Ames, B. Is there convincing biological or behavioral evidence linking vitamin D deficiency to brain dysfunction? Federation of American Societies of Experimental Biology Journal. 2008. 22, 982–1001.

Najada, A., Habashneh, M., Khader, M. The frequency of nutritional rickets among hospitalized infants and its relation to respiratory diseases. Journal of Tropical Pediatrics. 2004. 50, 364–368.

14. Female Reproductive and Maternal Health

Vitamin D plays a role in female fertility and rates of fetal implantation in the uterus. Additionally, vitamin D-deficient women are at risk for pre-eclampsia and gestational diabetes. Interestingly, due to the effect of vitamin D on muscle strength and function, women with low vitamin D levels appear to have a higher rate of cesarean sections due to sub-optimal muscle performance and strength during pregnancy.

Ozkan, S., Jindal, S., Greenseid, K. Replete vitamin D stores predict reproductive success following in vitro fertilization. Fertility and Sterility. E-Pub: July 8, 2009.

Merewood, A., Mehta, S., Chen, T., Bauchner, H., Holick, M. Association between vitamin D deficiency and primary cesarean section. Journal of Clinical Endocrinology and Metabolism. 2009. 94(3), 940–945.

Cror, D., Allen, L. Vitamin D inadequacy in pregnancy: biology, outcomes, and interventions. Nutrition Reviews. 2010. 68(8), 465-477.

15. Treatment of Depression and Brain Disorders

The likelihood of having depression and other brain disorders is significantly higher in vitamin D-deficient persons compared to those with adequate levels. Scientists are not entirely clear how vitamin D plays a role in mental health but they do know that vitamin D enhances the metabolic processes in brain neurons, promoting antioxidant activities that protect from oxidative degenerative processes. Additionally, vitamin D promotes nerve growth, and is an essential enzyme involved in the production of neurotransmitters that play a paramount role in mood regulation. Low levels are also linked to incidences of bipolar and schizophrenia.

Vijay, G., Milone, C., Cody, M., McCarty, F., Want, Y. Serum vitamin D concentrations are related to depression in young adult US population: the Third National Health and Nutrition Examination Survey.International Archives of Medicine. 3(1), 29.

16. Immune Function

Vitamin D is crucial to activating immune defenses and low serum levels inhibit the body’s T-cells ability to fight off serious infections. Specifically, inactive T-cells rely on vitamin D to activate them so that they can effectively fight off harmful pathogens that enter the body. Along with helping immune cells fight viruses such as the H1N1 flu, vitamin D helps increase the immune response by limiting inflammation, a major obstacle to healing and health. .

Von Essen, M., Kongsbak, M., Schjerling, P., Olgaard, K., Odum, N., Geisler, C. Vitamin D controls T cell antigen receptor signaling and activation of human T cells. Nature Immunology. 2010. 11, 344–349.

Holick, M. Vitamin D deficiency. New England Journal of Medicine. 2007. 357(3), 266-281.

17. Kidney Health

Vitamin D is vital for kidney health. Vitamin D is a key compound in treating chronic kidney disease and decreasing subsequent death rates. Understandably, individuals who are vitamin D deficient are at risk to develop kidney disease.

Williams, S., Malatesta, K., Norris, K. Vitamin D and Chronic Kidney Disease. Ethnicity and Disease. 2009. 19(4 Suppl 5), 8-11.

18. Treatment of Hypertension and Metabolic Diseases

Vitamin D deficiency is strongly associated with high blood pressure and associated metabolic diseases such as diabetes and obesity. Vitamin D supplementation is most effective at significantly reducing blood pressure when it is paired with taking calcium.

Kim, M., Kang, M., Oh, K., Kwon, H., Lee, J., Lee, W., Yoon, K., Son, H. The association of serum vitamin D level with presence of metabolic syndrome and hypertension in middle-aged Korean subjects. 2010. Clinical Endocrinology. 73(3), 330–338.

19. Prevention of Obesity

Low vitamin D levels may make you fat. Research shows that body fat mass is higher in individuals with vitamin D deficiency and that this shortage correlates with elevated levels of parathyroid hormone and intracellular calcium, considered to be major factors in determining obesity. The increased calcium levels trigger metabolic pathways that promote the accumulation of fat tissue and suppress fat burning. Previously it was thought that low vitamin D levels were consequences of obesity but a 2010 study suggests that reduced levels actually play a role in the development of obesity.

Valiña-Toth, A., Lai, Z., Yoo, W., Abou-Samra, A., Gadegbeku, C., Flack, J. Relationship of vitamin D and parathyroid hormone with obesity and body composition in African Americans. 2010. Clinical Endocrinology.72(5), 595–603.

20. Prevention of Parkinson’s Disease

Researchers have found a relationship between low Vitamin D levels and the early onset of Parkinson’s disease. Parkinson’s disease is an incurable disorder of the nervous system, with symptoms that include trembling hands, stiff muscles, digestive and urinary problems, and a decrease in dexterity and coordination. The average age of onset of the disease is 60, and when the disease appears before the age of 40 it is referred to as early-onset Parkinson’s disease. It is estimated that Parkinson’s affects approximately 5 million people worldwide, with 50,000 new Americans being diagnosed each year. Muhammad Ali, Michael J. Fox, and the Reverend Billy Graham are among the most famous people who have this disease.


Evatt, M., Delong, M., Kumari, M., Auinger, P., Mcdermott, M., Tangpricha, V. High prevalence of hypovitaminosis D status in patients with early Parkinson Disease. Archives of Neurology. 2011. 68, 314-319.

21. Prevention of Rickets and Osteomalacia

The development of rickets and osteomalacia is directly related to vitamin D deficiency. Rickets is a childhood disease that is characterized by the softening of bone, leading to bone fractures and skeletal deformities. For adults, osteomalacia is associated with osteoporosis but is a separate disease that starts with aches in the lumbar region and spreads to the arms and ribs. Bones become deformed, often fracturing, and sufferers typically complain of chronic fatigue.

Wagner CL, Greer FR. Prevention of Rickets and Vitamin D Deficiency in Infants, Children, and Adolescents.Pediatrics. 2008. 122(5), 1142-1152.

Plotnikoff, G., Quigley, J. Prevalence of Severe Hypovitaminosis D in Patients with Persistent, Nonspecific Musculoskeletal Pain. 2003. Mayo Clinic Proceedings.78(12 ), 1463-1470.

22. Chronic Obstructive Pulmonary Disease Prevention and Treatment

Chronic Obstructive Pulmonary Disease, also known as COPD, is characterized by respiratory weakness and the obstruction of the air pathways in the lungs. It typically manifests as emphysema and chronic bronchitis and can be treated by vitamin D supplementation. Considering the effect of vitamin D on increasing muscle strength and diminishing the symptoms of asthma, it is logical that it has positive effects on COPD. A 2011 study found that individuals supplementing with a monthly dose of 100,000 IU of vitamin D had significant improvements in all measures of COPD including oxygen consumption.

American Thoracic Society 2011 International Conference. 2011. American Journal of Respiratory Critical Care Medicine. 183, A2533.

23. Treatment of Autoimmune Conditions

Vitamin D deficiency affects immune function and is associated with an increased risk of AIDS progression and death from the disease. Conversely, in recent studies individuals with the highest levels of vitamin D have been seen to have a significantly lower risk of death than those with low levels. Vitamin D deficiency is seen as an important co-factor in HIV progression and supplementing with the vitamin may be an effective anti-viral therapy.

Viand, J., Souberbielle, J., Kirk, O., Reekie, J., Knysz, B., Losso, M., Gatell, J., Bogner,J., Lundgren, J., Mocroft, A. Vitamin D and clinical disease progression in HIV infection: results from the EuroSIDA study.Official Journal of the International AIDS Society. 2010. Published Ahead of Print.

24. Treatment of Childhood Anemia

Low vitamin D levels in children can cause anemia, a severe condition that leads to the damage of vital organs by depriving them of oxygen. Anemia occurs when the body has too few oxygen-carrying red blood cells and is diagnosed by measuring hemoglobin levels. Symptoms of mild anemia include fatigue, lightheadedness, and low energy.

Annual Meeting of the Pediatric Academic Societies. Low vitamin D levels linked to anemia in children. 2011.

25. Prevention of Infections

Adequate vitamin D plays a role in the prevention of infections and it may be used as a primary treatment for viral, bacterial, and fungal infections. In a recent review of the benefits of vitamin D on immune health and avoiding infections, researchers found that treatments of all of the following conditions benefit from optimal vitamin D levels: tuberculosis, psoriasis, eczema, Crohn's disease, chest infections, wound infections, influenza, urinary tract infections, eye infections, and wound healing.

Schwalfenberg, G. A review of the critical role of vitamin D in the functioning of the immune system and the clinical implications of vitamin D deficiency. 2011. Molecular Nutrition and Food Research. 55(1), 96–

Copyright ©2011 Charles Poliquin

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