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After reading this course, the participant should be able to:

1. Define the function of vitamin D.
2. Discuss which populations are at risk of vitamin D deficiency.
3. Explain how vitamin D is synthesized in the body.
4. List the negative side effects of vitamin D deficiency on oral and systemic health

Vitamin D deficiency is rampant across the globe regardless of age, gender, ethnicity, socioeconomic status, or level of health.1 

The prevalence of vitamin D deficiency among certain populations may be as high as one in two people. 1,2 Certain diseases substantially reduce circulating vitamin D levels including bone and muscle disorders, some cancers, chronic liver disease, fat malabsorption syndromes, Crohn's disease, cystic fibrosis, autoimmune disorders, multiple sclerosis, and rheumatoid arthritis. 3,4 The widespread deficiency of this important vitamin may have significant health consequences beyond even the traditional result of bone loss and insufficient bone development.

Geography and lifestyle factors affect people's vitamin D levels. Research shows that those who live north of 30° latitude, which in the United States is approximately north of Atlanta in the East and north of Los Angeles in the West, are at higher risk of vitamin D deficiency and face increased risk of developing certain cancers, such as colon, breast, prostate, pancreas, and leukemia. 5,6 Certain medications, alcohol consumption, and tobacco use may also have a negative impact on circulating vitamin D levels. Dietary vitamin D supplements are the most efficient, economical means of raising and maintaining circulating vitamin D blood levels because receiving enough through sunlight exposure or dietary intake is difficult. As preventive specialists, dental hygienists are perfectly poised to encourage their patients to have their vitamin D levels evaluated as part of the routine blood work conducted during an annual physical.


The primary function of vitamin D is to regulate calcium and phosphorus levels and bone metabolism. A unique fat-soluble nutrient, vitamin D occurs naturally in a limited number of foods and is produced in the skin after direct sun exposure. Fatty fish contain the highest amounts of vitamin D while other animal products contain low amounts (see Table 1). 7

Many foods are fortified with vitamin D2 or ergocalciferol, which is derived from plants. Sun exposure produces vitamin D3, or cholecalciferol, which is also found in vitamin supplements and is the form most easily absorbed by the body. Both forms are transported to the liver through vitamin D binding protein (DBP) where they are then metabolized by the kidneys (see Figure 1). In the liver, the enzyme 25-hydroxylase converts vitamin D to circulating serum 25(OH)D, which is what is measured when determining vitamin D levels in the body. Low serum calcium stimulates the parathyroid glands to produce and secrete parathyroid hormone (PTH). This hormone conserves available calcium by increasing its resorption by the kidneys.

The biologically active form of vitamin D helps protect the body against invading bacteria. Its most important function is to aid in the absorption of calcium from the intestines to help the body maintain adequate levels of calcium to support bone health. Vitamin D also reduces inflammation, facilitates neuromuscular function, and supports healthy gene activity.

Because most people no longer spend the majority of their time outside during the day, many are at risk of vitamin D deficiency. Plus, the form of vitamin D found in foods is more difficult to absorb than the type created via sun exposure. See Table 2 (page 48) for a list of populations at risk of vitamin D deficiency. People who are vitamin D deficient are at a higher risk of a myriad of chronic diseases including cancer and diabetes.


Studies suggest that the risk of some types of cancer, including colorectal cancer, is lower in people with high levels of calcium and vitamin D. 8,9 One study showed that women who were deficient in vitamin D had a 253% increased risk of developing colorectal cancer. 10 Another study found that women who consumed 1,100 international units (IUs) of vitamin D with calcium a day decreased the overall risk of developing cancer by almost 70%. 11

Vitamin D intake, serum blood levels of 25(OH)D, and increased sun exposure have all shown to reduce breast cancer risk in some epidemiologic studies. 12 In addition, certain vitamin D receptors may modify breast cancer susceptibility. 12 Estrogen deficiencies appear to reduce vitamin D levels, which may put post-menopausal women at an increased risk of breast cancer. 13 Highdose vitamin D supplementation may slightly reduce the risk of developing breast cancer. 10,14 Evidence supports vitamin D as a defender against prostate, colon, and breast cancer. 15 Additional study in this area is needed, however.


Osteoporosis is the most common metabolic bone disease, and vitamin D deficiency is an established risk factor. 10,16 Severe deficiency causes osteomalicia, the under-mineralization of skeletal tissues due to low intestinal absorption of calcium. Combining calcium and vitamin D supplements decreases fractures and increases bone min- eral density (BMD). 14,16 Osteoporosis is directly related to insufficient vitamin D intake because of suppressed calcium absorption in the intestines. Low serum 25(OH)D levels are associated with decreased calcium absorption rates and hyperparathyroidism, which leads to bone loss. 14 When circulating levels of 25(OH)D measure below 32 ng/mL, calcium absorption is impaired. Secondary hyperparathyroidism and poor calcium absorption due to vitamin D deficiency have harmful effects on skeletal integrity and are associated with lower BMD and increased risk of bone fractures. 17 Secondary hyperparathyroidism is the main characteristic of poor nutritional status in older adults. 17 


Chronic musculoskeletal pain occurs with a lack of circulating calcium (hypocalcemia) due to inadequate vitamin D, which then elevates the PTH that diminishes bone density (osteopenia) and affects bone architecture (osteoporosis). Osteomalicia, (bone metabolism dysfunction) causes persistent, generalized musculoskeletal pain and weakness. 18 Increased PTH levels impair proper bone mineralization, causing a spongy matrix to form under the periosteal membrane. This matrix is gelatin-like and can absorb fluid, expand, and cause outward pressure on periosteal tissues. These tissues are highly innervated with sensory pain fibers, which cause the sensation of musculoskeletal pain. Patients with chronic pain, muscle weakness or fatigue, fibromyalgia, and chronic fatigue syndrome may benefit from high doses of vitamin D after differential diagnosis has ruled out fractures, anatomical pain, neuropathic disorders, or injury-related causes. Vitamin D has shown to alleviate pain associated with migraine headaches in post-menopausal women. 19 


Low serum levels of vitamin D may be a contributing factor to diabetes. 20 Vitamin D insufficiency may also result in insulin resistance. 21 Men and women who ingest more than 800 IUs of vitamin D daily in conjunction with recommended doses of calcium reduce their risk of developing type 2 diabetes. 22 There may be an association between adequate vitamin D exposure in early childhood and a reduced risk of developing diabetes. 20-23 In addition, increased vitamin D may improve insulin sensitivity and promote beta-cell survival. 23,24 Zipitis and Akobeng found that infants given calcitriol during the first year of life were less likely to develop type 1 diabetes than infants fed lesser amounts of vitamin D. 25

Among people who have diabetes, 60% are vitamin D deficient. 26 The use of cod liver oil as a source of vitamin D to reduce the incidence of type 1 diabetes may be an option. 25 Chiu et al found that adults given vitamin D supplementation experienced improve insulin sensitivity. 27


Older adults are at a significant risk of vitamin D deficiency and subsequent bone fractures. 28 Muscle weakness is also a side effect of vitamin D deficiency and compounds the risk of fractures due to falls. Up to 99% of long-term care residents are deficient in vitamin D. 29 The older adult population exhibits vitamin D deficiency due to lack of exercise, reduced exposure to sunlight, and limited production/absorption of vitamin D through the skin, which deteriorates with age. Also contributing to vitamin D deficiency is poor consumption of adequate food sources containing vitamin D and calcium. One proposed solution is to supplement the diets of older adults with calcium and vitamin D, a combination that has reduced rates of nonvertebral fracture among elderly women living in retirement homes. 30 


Research shows a strong association between osteoporosis/BMD and alveolar bone and tooth loss. 31-34 This may indicate that inferior bone characteristics, due to age, smoking, and vitamin D deficiencies, are risk factors for periodontal diseases. 31-34 Calcium and vitamin D may benefit periodontal health, and calcium and vitamin D deficiencies may be risk factors for periodontal diseases. 35

A recent National Health and Nutrition Examination Survey (NHANES) found that low serum 25(OH)D concentrations were associated with periodontal diseases and loss of alveolar attachment in men and women over the age of 50. 36 In addition, research shows that vitamin D supplements decrease tooth loss significantly in those older than age 50. 37 Several risk factors are shared by periodontal diseases and osteoporosis; as such, they may be biologically linked. 38 Animal studies have shown that vitamin D's anti-inflammatory properties decrease pro-inflammatory cytokines (C-reactive proteins, interleukin 6 and 12) as well as increase anti-inflammatory cytokines (interleukin-10). 39-42 More research is needed to explore expanded uses of vitamin D in conjunction with traditional periodontal therapies.

With the risks of vitamin D deficiency so high and its prevalence so widespread, dental professionals should advise their patients to have their levels of vitamin D tested. Part two of this series will focus on the best way to measure vitamin D levels in the blood and supplementation recommendations.



Belmont Publications, Inc. is an ADA CERP Recognized Provider 

ADA CERP is a service of the American Dental Association to assist dental professionals in identifying quality providers of continuing dental education. ADA CERP does not approve or endorse individual courses or instructors, nor does it imply acceptance of credit hours by boards of dentistry. 


Margaret F. Lemaster, BSDH, MS, is an assistant professor in the School of Dental Hygiene at Old Dominion University (ODU), Norfolk, Va. She is also the junior theory and clinic coordinator. Her research interests include motivational interviewing in the dental setting and dental applications of cold plasma technology.   


Catherine S. Seifert, RDH, BS, has served as an adjunct clinical faculty member at ODU's School of Dental Hygiene for the past 10 years. Her private practice experience spans more than 40 years. Seifert also volunteers her time at the Western Tidewater Free Clinic in Suffolk, Va, and is active in her local and state dental hygienists' associations  


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From Dimensions of Dental Hygiene. December 2010; 8(12): 46-51.

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