Vitamin D and Health

Feature |
May 22, 2009

Vitamin D and Health

Do we have enough? How do we get more? What systems are affected?

Obtaining adequate levels of vitamin D is essential for health: What constitutes an adequate level and how best to obtain it have been the subject of many recent research reports. There are only three sources of vitamin D — sunlight, food, and supplements. Dermatologists have taken the position that exposure to sunlight is not a good solution for the prevention of vitamin D deficiency, because of concerns about skin cancer and other adverse effects of ultraviolet radiation. But can dietary sources and supplementation provide sufficient vitamin D for health and disease prevention? In this issue, we review three new research articles in depth and provide links to other coverage that explores the complexity of this issue.

Craig A. Elmets, MD, and Lowell A. Goldsmith, MD, MPH

First, a couple of large epidemiological studies provide some perspective on the prevalence of vitamin D deficiency.

Is the United States Vitamin D Deficient?

Data from the third National Health and Nutrition Examination Survey (NHANES III) suggest that a considerable vitamin D deficiency exists in the U.S. and that it has major public health implications.1

The investigators compared levels of serum 25-hydroxyvitamin D (25[OH] D) in 18,883 individuals in 1988–1994 with levels in another 13,369 in 2001–2004. Identical analytical techniques were used for all samples. As vitamin D levels vary with amounts of natural sunlight, samples were collected in the winter in southern latitudes and in the summer in northern latitudes during all survey periods.

In the earlier sampling period, 2% of participants had low 25(OH) D (<10 ng/mL). That percentage grew to 8% in the later period, and the proportion with low levels increased in all subgroups. Females had uniformly lower levels than males. Blacks and Latinos had lower vitamin D levels than whites in both periods. The percentage of non-Latino blacks with levels lower than 10 ng/mL increased from 9% to 29%, and the percentage of white women older than 40 with low levels increased from 4% to 11%. NHANES techniques oversample blacks, Mexican Americans, and those with low income.

Comment: These epidemiological data raise many questions about why vitamin D levels are falling. Are sources of vitamin D decreasing, or is vitamin D metabolism increasing? Few data or discussions of the latter possibility have been put forward. Have changes in eating patterns or food composition decreased vitamin D intake, and might such factors have greater impact on black and Mexican-American than on white populations?

Some answers may be obtained from another relatively large population survey in 1739 white adult children (average age, 59) of the original Framingham Heart Study participants.2 Serum vitamin D levels were collected between 1996 and 2001; no seasonal data were given. Vitamin D intake of both supplement and food sources was recorded. In these subjects, 28% had 25(OH) D levels lower than 15 ng/mL, and 9% had levels lower than 10 ng/mL. Those with levels above 15 ng/mL had significantly greater total vitamin D intake than those below that level (P<0.001). Participants with lower 25(OH) D levels had a multivariant-adjusted hazard ratio for cardiovascular disease of 1.62 (95% confidence interval, 1.30–3.48).

Sunlight is a major source of vitamin D. When ultraviolet rays strike the skin, vitamin D is synthesized in the epidermis from its precursor, 7-dehydrocholesterol, and distributed systemically. Decreased exposure to sunlight due to restricted outdoor activities and sunscreen use is often blamed for low vitamin D levels. If only patients were so compliant with their sunscreen use! Increased sunscreen use would not be a reasonable explanation for the growing decrease in blacks and Mexican Americans; sunscreen use is low in these populations. A current fact sheet from the National Institutes of Health includes current daily recommendations for vitamin D levels.

So, what is the best way to prevent vitamin D deficiency? Cutaneous production induced by exposure to sunlight is efficient but problematic because of melanoma risks. A review describes the complexity of this issue.

The Dilemma of Sunlight, Vitamin D, and Melanoma

The relation between sun exposure and melanoma is complicated. Substantial evidence demonstrates that sunlight is an etiologic factor for melanoma, but sunlight also fosters production of vitamin D, which may protect against the disease. A recent review examines these complexities.3

Evidence for vitamin D’s protective effect in melanoma comes from both experimental and epidemiological studies. Vitamin D receptors are present on primary melanomas, and the addition of calciferols to melanoma cells in culture inhibits their proliferation and induces differentiation. Vitamin D production also has immunomodulatory activity; its effects on innate and acquired immunity may play a role in the host defense against melanoma. Moreover, at least two polymorphisms in the vitamin D receptor have been implicated in melanoma risk: The f allele of the F/f polymorphism renders the receptor less active; subjects with this allele have a modestly increased melanoma risk. In a second variant, individuals homozygous for the BAt allele have higher vitamin D receptor mRNA levels and reduced melanoma risk. Vitamin D receptor polymorphisms have also been associated with increased disease aggression and metastases. However, the epidemiological evidence for a protective effect from vitamin D is less consistent. Although one study showed an association between high vitamin D intake and reduced melanoma development, few if any reports have shown an inverse correlation between serum vitamin D levels and melanoma incidence or prognosis.

Comment: Sunlight’s precise role in melanoma has been a subject of ongoing debate. Vitamin D’s contribution is the latest iteration in that question. The issue is important, because if vitamin D has a protective effect, dermatologists may need to modify their recommendations to patients with high melanoma risk. Evidence for a protective effect of vitamin D in melanoma is modest, resting on observations that patients with chronic sun exposure do not have the greatest risk, that sunscreens have not been definitively shown to protect against melanoma, and that heavy users of tanning beds that emit only small amounts of vitamin D–producing UVB have increased rates of disease. Dermatologists should keep an open mind, but, until more definitive data show otherwise, melanoma patients and those at risk should be counseled to stay out of the sun, wear sunscreen, and correct low vitamin D levels through diet and supplementation.

Another route proposed for providing adequate levels of vitamin D is through supplementation, but is this the best strategy?

Are Supplements Sufficient?

An adequate vitamin D level is required for bone health, and deficiency has been implicated as a risk factor for various malignancies. Epidemiological studies have associated reduced vitamin D levels with decreased survival in breast cancer patients, and the American Society of Clinical Oncology recommends that vitamin D–deficient breast cancer patients take 1200 mg of calcium and 400 IU of vitamin D daily.

Investigators in a recent study examined 103 premenopausal recipients of adjuvant chemotherapy for breast cancer to determine whether 400 IU of vitamin D3 daily adequately restored serum 25 (OH) D levels.4,5 At baseline, only 6% of patients had sufficient levels (≥30 ng/mL). The median level was 17 ng/mL; 74% were vitamin D deficient (<20 ng/mL), and 12% had levels lower than 12 ng/mL. After 1 year of supplementation, levels had improved only modestly: The median level had increased only to 19 ng/mL, only 11% of patients had sufficient levels, and the percentage of women that were vitamin D deficient had decreased only to 60%. Black (80%) and Latina women (84%) were more likely to be deficient than white women (66%), and black women were least likely to improve with supplementation.

Comment: We still don’t know the optimum vitamin D levels for preventing bone disease and reducing risks for malignancies and other diseases. We also don’t know how much supplementation is required to normalize vitamin D levels. It may be that in certain groups with high risk for deficiency (e.g., blacks, Latinos, and breast cancer patients), exposure to modest doses of ultraviolet light sufficient to correct vitamin D deficiency may be an appropriate strategy.

In recent years, researchers have examined the vitamin D story from a number of angles. To read more on this subject, see the following:

Sources, Prevalence, and Optimal Levels

Vitamin D Should Not Be Obtained Through Sunlight: American Academy of Dermatology Position Statement

Vitamin D Levels in Elders

Vitamin D Recommendations: They Change Again!

Vitamin D Deficiency Common Even in Southern U.S.

Vitamin D2 vs. Vitamin D3 Supplementation — Does It Matter?

Children and Adolescents

Vitamin D Deficiency in Young Children

Vitamin D Deficiency Prevalent in Infants, Toddlers

Vitamin D — It’s Not Just for Bones

Associations with Skin Diseases

Vitamin D and Actinic Keratoses

Lupus Patients Are at Risk for Vitamin D Deficiency

Associations with Systemic Diseases

Vitamin D and Risk for Breast Cancer According to Hormone-Receptor Status

Low Serum Vitamin D Linked to Increased Hip Fracture Risk in Postmenopausal Women

Vitamin D Deficiency Associated with Increased MI Risk in Men

Vitamin D and Death

Does the Vitamin D Emperor Have Clothes? Debate on Associations with Multiple Sclerosis

Are Low Vitamin D Levels Associated with Nonspecific Pain?

Vitamin D and Infections

Does Early Vitamin D Supplementation Prevent Type 1 Diabetes?

Study Links Low Serum Vitamin D with Increased Cardiovascular Risk


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Reader Comments (6)

"Jj" Other, Not applicable...

That was the best written summary, and informative article on the subject, at hand! Thanks...

B. Tetzlaff Other Healthcare Professional, Critical Care Medicine

I too experience a direutic effect when taking vitamin D. I too, was very deficient, with a strong family hx of autoimmune disorders (lupus, type one diabetes, mixed connective tissue dz, RA, and ITP. So, is it chicken or egg? A genetic vitamin D absorption or metabolism issue that then predisposes the family to autoimmune disruption, or is it the autoimmune or family hx that also causes low serum D levels?

V L Chan

I took 6-7000 units a ay for 12 months, felt GREAT, energy and reduced fibromyalgia pains. Eye blurs, floaters and sudden acceleration of epithelial growth on lens capsule ensued, even macular traction and pucker. The latter reduced quickly and dramaticaly when Vit D withdrawn, within 5 days. on restarting maintenance vit D3 at 1000 units, diuresis, reduction of fibromyalgia pains occurred within a few hours and eye blurring within 24 hours. Has anyone else had the eye blurring problem? 25-OH levels are now at 50, was at 20 when I started.

Competing interests: I am a doctor with no competing interests


vitamins a and d deplete each other. You need to take more vitamin A - butter, chicken skin, egg yolks, cod liver oil, etc, jersey cow milk has high levels of vitamin a - 8 ounces would do.


Dear friends, since many months now I take regularly Vitamin D, like 1000 to 2000 Units a day. Ever since I feel stronger and more balanced. No more fatigue or tiredness. I think seriously, that yes the US population is seriously depleted with Vit. D. I would start a National campaigne to promote more Vit. D use for very age, especially for our children and our elderly people. Thank you, with respect Csaba J. CSUKAS med. microbiologist P.O.Box 2182, West Sacramento, CA 95691

Competing interests: None declared

T.F. Miller

Over a six month trial 1000 Vitamin D3 has had a strong diuretic effect on me starting about three hours after ingestion and lasting about four hours. I am sure about this. No one else seems to think this is possible. I do not have the same effect with 1000 D2. I am a 70 year old Caucasian male with no other health problems except that I blood test low (25) for vitamin D

Competing interests: None declared

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