Vitamin D

NOTICE: This health information was not created by the University of Michigan Health System (UMHS) and may not necessarily reflect specific UMHS practices. For medical advice relating to your personal condition, please consult your doctor. Complete disclaimer

Vitamin D

Uses

Vitamin D

The fat-soluble vitamin D’s most important role is maintaining blood levels of calcium, which it accomplishes by increasing absorption of calcium from food and reducing urinary calcium loss. Both effects keep calcium in the body and therefore spare the calcium that is stored in bones. When necessary, vitamin D transfers calcium from the bone into the bloodstream, which does not benefit bones. Although the overall effect of vitamin D on the bones is complicated, some vitamin D is necessary for healthy bones and teeth.

When "D” is used without a subscript it refers to either D2 or D3, the two primary forms used as supplements.    

What Are "Star" Ratings?

a7_3star   Reliable and relatively consistent scientific data showing a substantial health benefit.

a7_2star   Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.

a7_1star   For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support.

Our proprietary “Star-Rating” system was developed to help you easily understand the amount of scientific support behind each supplement in relation to a specific health condition. While there is no way to predict whether a vitamin, mineral, or herb will successfully treat or prevent associated health conditions, our unique ratings tell you how well these supplements are understood by the medical community, and whether studies have found them to be effective for other people.

For over a decade, our team has combed through thousands of research articles published in reputable journals. To help you make educated decisions, and to better understand controversial or confusing supplements, our medical experts have digested the science into these three easy-to-follow ratings. We hope this provides you with a helpful resource to make informed decisions towards your health and well-being.

This supplement has been used in connection with the following health conditions:


Used for Amount Why
Crohn’s Disease
 1,000 to 1,200 IU daily under medical supervision 3 stars   Vitamin D malabsorption is common in Crohn’s and can lead to a deficiency of the vitamin. Supplementation can help prevent bone loss in cases of deficiency.

3 stars  Crohn’s Disease

1,000 to 1,200 IU daily under medical supervision

Vitamin D malabsorption is common in Crohn’s1 and can lead to a deficiency of the vitamin.2 Successful treatment with vitamin D for osteomalacia (bone brittleness caused by vitamin D deficiency) triggered by Crohn’s disease has been reported.3 Another study found 1,000 IU per day of vitamin D prevented bone loss in people with Crohn’s, while an unsupplemented group experienced significant bone loss.4 In addition, in a double-blind trial, vitamin D supplementation (1,200 IU per day for 12 months) prevented relapses in patients with Crohn's disease in remission. The patients in that study had normal vitamin D status prior to receiving vitamin D supplementation.5 A doctor should be consulted to determine the right level of vitamin D for supplementation.


Used for Amount Why
Cystic Fibrosis
 1,000 to 2,000 IU daily 3 stars   The fat malabsorption associated with cystic fibrosis often leads to a deficiency of fat-soluble vitamins, such as vitamin D. Supplementation can help counteract the deficiency.

3 stars  Cystic Fibrosis

1,000 to 2,000 IU daily

The fat malabsorption associated with CF often leads to a deficiency of fat-soluble vitamins. Oral supplementation of these nutrients is considered crucial to maintaining good nutritional status.6 Current recommendations for supplementation are as follows: vitamin A, 5,000 to 10,000 IU/day; vitamin D, 1,000 to 2,000 IU/day; vitamin E, 100 to 300 IU/day; and vitamin K, 5 mg every three days. Of the water-soluble vitamins, only vitamin B12 is poorly absorbed in cystic fibrosis,7 and taking pancreatic enzymes helps prevent B12 deficiencies.8

Used for Amount Why
Osteoporosis
 400 to 800 IU daily depending on age, sun exposure, and dietary sources 3 stars   Vitamin D increases calcium absorption and helps make bones stronger. Vitamin D supplementation has reduced bone loss in women who don’t get enough of the vitamin from food and slowed bone loss in people with osteoporosis. It also works with calcium to prevent some musculoskeletal causes of falls and subsequent fractures.

3 stars  Osteoporosis

400 to 800 IU daily depending on age, sun exposure, and dietary sources

Vitamin D increases calcium absorption, and blood levels of vitamin D are directly related to the strength of bones.9 Mild deficiency of vitamin D is common in the fit, active elderly population and leads to an acceleration of age-related loss of bone mass and an increased risk of fracture.10 In double-blind research, vitamin D supplementation has reduced bone loss in women who consume insufficient vitamin D from food and slowed bone loss in people with osteoporosis.11 , 12 However, the effect of vitamin D supplementation on osteoporosis risk remains surprisingly unclear,13 , 14 with some trials reporting little if any benefit.15 Moreover, trials reporting reduced risk of fracture have usually combined vitamin D with calcium supplementation,16 making it difficult to assess how much benefit is caused by supplementation with vitamin D alone.17

Impaired balance and increased body sway are important causes of falls in elderly people with osteoporosis.18 Vitamin D works with calcium to prevent some musculoskeletal causes of falls.19 In a double-blind trial, elderly women who were given 800 IU per day of vitamin D and 1,200 mg per day of calcium had a significantly lower rate of falls and subsequent fractures than did women given the same amount of calcium alone.20 Vitamin D in the amount of 800 IU per day effectively prevented falls in a double-blind study of elderly nursing home residents, but lower amounts were ineffective.21

Despite inconsistency in the research, many doctors recommend 400 to 800 IU per day of supplemental vitamin D, depending upon dietary intake and exposure to sunlight.

One trial studying postmenopausal women combined hormone replacement therapy with magnesium (600 mg per day), calcium (500 mg per day), vitamin C, B vitamins, vitamin D, zinc, copper, manganese, boron, and other nutrients for an eight- to nine-month period.22 In addition, participants were told to avoid processed foods, limit protein intake, emphasize vegetable over animal protein, and limit consumption of salt, sugar, alcohol, coffee, tea, chocolate, and tobacco. Bone density increased a remarkable 11%, compared to only 0.7% in women receiving hormone replacement alone.


Used for Amount Why
Rickets
 Consult a qualified healthcare practitioner 3 stars   Vitamin D supplements may be helpful in preventing and treating rickets.

3 stars  Rickets

Consult a qualified healthcare practitioner

Vitamin D and calcium supplements should be used to treat rickets only if a medical professional has diagnosed rickets and has also determined the cause is a nutritional deficiency. Amounts needed to treat rickets should be determined by a doctor and will depend on the age, weight, and condition of the child. For prevention of rickets, 400 IU of vitamin D per day is considered reasonable. Doctors often suggest 1,600 IU per day for treating rickets caused by a lack of dietary vitamin D.

Used for Amount Why
Asthma and Children
 1,200 IU per day for 15 to 17 weeks 2 stars   A study of Japanese children found that daily supplementation with vitamin D during the winter months significantly reduced the amount of times the children experienced asthma attacks.

2 stars  Asthma and Children

1,200 IU per day for 15 to 17 weeks

In a double-blind study of Japanese children (average age, ten years), supplementation with 1,200 IU per day of vitamin D for 15 to 17 weeks during the winter significantly reduced the incidence of asthma attacks compared with a placebo.23

Used for Amount Why
Burns
 200 to 600 IU day in cases of extensive burns 2 stars   People with a history of an extensive burn might benefit from vitamin D supplementation, since the skin may not be as effective at manufacturing vitamin D from sunlight.

2 stars  Burns

200 to 600 IU day in cases of extensive burns

Burns affecting a large proportion of the body may result in vitamin D deficiency24, potentially increasing the risk of osteoporosis, which is a frequent long-term consequence of severe burns.25 Vitamin D deficiency may result from the inability of previously burned skin to manufacture vitamin D after exposure to sunlight. People with a history of an extensive burn might benefit from vitamin D supplementation.

Used for Amount Why
Celiac Disease and Vitamin D Deficiency
 Consult a qualified healthcare practitioner 2 stars   Malabsorption-induced vitamin D deficiency can lead to bone weakening in people with celiac disease. Supplementing with vitamin D may help increase bone density.

2 stars  Celiac Disease and Vitamin D Deficiency

Consult a qualified healthcare practitioner

The malabsorption that occurs in celiac disease can lead to multiple nutritional deficiencies. The most common nutritional problems in people with celiac disease include deficiencies of essential fatty acids, iron, vitamin D, vitamin K, calcium, magnesium, and folic acid.26 Zinc malabsorption also occurs frequently in celiac disease27 and may result in zinc deficiency, even in people who are otherwise in remission.28 People with newly diagnosed celiac disease should be assessed for nutritional deficiencies by a doctor. Celiac patients who have not yet completely recovered should supplement with a high-potency multivitamin-mineral. Some patients may require even higher amounts of some of these vitamins and minerals—an issue that should be discussed with their healthcare practitioner. Evidence of a nutrient deficiency in a celiac patient is a clear indication for supplementation with that nutrient.

After commencement of a gluten-free diet, overall nutritional status gradually improves. However, deficiencies of some nutrients may persist, even in people who are strictly avoiding gluten. For example, magnesium deficiency was found in 8 of 23 adults with celiac disease who had been following a gluten-free diet and were symptom-free. When these adults were supplemented with magnesium for two years, their bone mineral density increased significantly.29

Malabsorption-induced depletion of vitamin D can lead to osteomalacia (defective bone mineralization) in people with celiac disease.30 Although supplementation with vitamin D appears to increase bone density, the excess risk of bone fracture may not be entirely eliminated.

Used for Amount Why
Depression
 400 to 800 IU daily 2 stars   Some studies have shown that supplementing with vitamin D leads to improved mood.

2 stars  Depression

400 to 800 IU daily

Blood levels of vitamin D (measured as 25-hydroxyvitamin D) have been found to be significantly lower in people with depression than in healthy people.31 Vitamin D supplementation may be associated with elevations in mood. In a double-blind trial, healthy people were given 400–800 IU per day of vitamin D3, or no vitamin D3, for five days during late winter. Results showed that vitamin D3 significantly enhanced positive mood and there was some evidence of a reduction in negative mood compared to a placebo.32 In another double-blind trial, people without depression took 600 IU of vitamin D along with 1,000 mg of calcium, or a placebo, twice daily for four weeks.33 Compared to the placebo, combined vitamin D and calcium supplementation produced significant elevations in mood that persisted at least one week after supplementation was discontinued.


Used for Amount Why
Hypertension and Vitamin D Deficiency
 800 IU daily 2 stars   In one trial, women with low blood levels of vitamin D who were given calcium supplement plus vitamin D experienced significantly reduced systolic blood pressure.

2 stars  Hypertension and Vitamin D Deficiency

800 IU daily

In a double-blind trial, women with low blood levels of vitamin D (measured as 25-hydroxyvitamin D3) were given a calcium supplement, plus either 800 IU of vitamin D per day or a placebo for eight weeks. Compared with the placebo, vitamin D significantly reduced systolic blood pressure by an average of 9.3%, but did not affect diastolic blood pressure.34

Used for Amount Why
Influenza
 800 IU per day for two years; then 2,000 IU per day after that 2 stars   In one study, long-term vitamin D supplementation for three years significantly reduced flu and cold symptoms.

2 stars  Influenza

800 IU per day for two years; then 2,000 IU per day after that

In a double-blind study, African Americans who received vitamin D supplements for three years had significantly fewer symptoms of influenza or colds, when compared with women who received a placebo. The amount of vitamin D was 800 IU per day for the first two years, followed by 2,000 IU per day for one year.35

Used for Amount Why
Influenza and Children
 1,200 IU per day for 15 to 17 weeks 2 stars   A study of Japanese children found that daily supplementation with vitamin D during the winter months significantly reduced the amount of times the children developed the flu.

2 stars  Influenza and Children

1,200 IU per day for 15 to 17 weeks

In a double-blind study of Japanese children (average age, ten years), supplementation with 1,200 IU per day of vitamin D for 15 to 17 weeks during the winter significantly reduced the incidence of influenza infections by 42%, compared with a placebo.36

Used for Amount Why
Low Back Pain and Vitamin D Deficiency
 Refer to label instructions 2 stars   In people with muscle pain associated with vitamin D deficiency, supplementing with the vitamin may improve pain.

2 stars  Low Back Pain and Vitamin D Deficiency

Some studies have found that vitamin D levels are lower in people with back pain than in healthy people.37 , 38 In patients with muscle pain associated with vitamin D deficiency, vitamin D supplementation has resulted in improvement in the pain.39

Used for Amount Why
Seasonal Affective Disorder and Low Blood Levels
 Refer to label instructions 2 stars   Supplementing with vitamin D may improve mood and well-being, especially among people with low levels of the vitamin.

2 stars  Seasonal Affective Disorder and Low Blood Levels

Vitamin D is well known for its effects on helping to maintain normal calcium levels, but it also exerts influence on the brain, spinal cord, and hormone-producing tissues of the body that may be important in the regulation of mood.40 A double-blind study found that mood improved in healthy people without SAD who received 400 or 800 IU per day of vitamin D for five days in late winter.41

In another study, people with SAD were randomly assigned to receive either 100,000 IU of vitamin D one time only or two hours of bright-light therapy every day for one month. After one month, researchers observed a significant improvement in depression in the group that received vitamin D, but not in the group given light therapy.42 However, a one-year study of healthy postmenopausal women found that supplementation with 400 IU of vitamin D per day did not prevent the mood decline that often occurs in the winter.43 Certain differences in these studies might account for the different results: In the study in which vitamin D was beneficial, the participants suffered from SAD and their pretreatment vitamin D blood levels tended to be low. In the negative study, the participants did not have SAD, and their pretreatment vitamin D blood levels were higher. Although additional research needs to be done, the available evidence suggests that people with SAD who have marginal or deficient vitamin D levels might benefit from supplementation. This treatment should be supervised by a doctor to assure that the amount of vitamin D used is high enough to be effective, but not so high as to cause adverse effects.


Used for Amount Why
Tension Headache
 Refer to label instructions 2 stars    
Type 1 Diabetes
 Consult a qualified healthcare practitioner 2 stars   Vitamin D is needed to maintain adequate insulin levels, and supplementing with it may reduce the risk of developing type 1 diabetes.

2 stars  Type 1 Diabetes

Consult a qualified healthcare practitioner

Vitamin D is needed to maintain adequate blood levels of insulin.44 Vitamin D receptors have been found in the pancreas where insulin is made and preliminary evidence suggests that supplementation might reduce the risk of developing type 1 diabetes.45 Not enough is known about optimal amounts of vitamin D for people with diabetes, and high amounts of vitamin D can be toxic. Therefore, people with diabetes considering vitamin D supplementation should talk with a doctor and have their vitamin D status assessed.

Used for Amount Why
Type 2 Diabetes
 1,332 IU daily 2 stars   Vitamin D is needed to maintain adequate insulin levels, and supplementing with it may improve blood sugar control in people with type 2 diabetes.

2 stars  Type 2 Diabetes

1,332 IU daily

Vitamin D is needed to maintain adequate blood levels of insulin.46 Vitamin D receptors have been found in the pancreas where insulin is made, and preliminary evidence suggests that supplementation can improve some measures of blood sugar control in people with type 2 diabetes.47 , 48 In addition, in a preliminary trial supplementation with about 2,000 IU of vitamin D per day for three months significantly improved pain by almost 50% in patients with diabetic neuropathy.49 Not enough is known about optimal amounts of vitamin D for people with diabetes, and high amounts of vitamin D can be toxic; therefore, people with diabetes considering vitamin D supplementation should talk with a doctor and have their vitamin D status assessed.

Used for Amount Why
Alcohol Withdrawal
 Refer to label instructions 1 star   If deficient, supplementing with this vitamin may help prevent bone loss and muscle weakness.

1 star  Alcohol Withdrawal

Although the incidence of B-complex deficiencies is known to be high in alcoholics, the incidence of other vitamin deficiencies remains less clear.51 Nonetheless, deficiencies of vitamin A, vitamin D, vitamin E, and vitamin C are seen in many alcoholics. While some reports have suggested it may be safer for alcoholics to supplement with beta-carotene instead of vitamin A,52 potential problems accompany the use of either vitamin A or beta-carotene in correcting the deficiency induced by alcoholism.53 These problems result in part because the combinations of alcohol and vitamin A or alcohol and beta-carotene appear to increase potential damage to the liver. Thus, vitamin A-depleted alcoholics require a doctor’s intervention, including supplementation with vitamin A and beta-carotene accompanied by assessment of liver function. Supplementing with vitamin C, on the other hand, appears to help the body rid itself of alcohol.54 Some doctors recommend 1 to 3 grams per day of vitamin C.

Used for Amount Why
Amenorrhea and Osteoporosis
(Calcium)
 Refer to label instructions 1 star   Despite the lack of evidence that calcium and vitamin D supplements alone are helpful to amenorrheic women, they are still generally recommended to prevent the added burden of calcium and vitamin D deficiency from further contributing to bone loss.

1 star  Amenorrhea and Osteoporosis

A preliminary trial showed that bone loss occurred over a one-year period in amenorrheic exercising women despite daily supplementation with 1,200 mg of calcium and 400 IU of vitamin D.55 In a controlled study of amenorrheic nursing women, who ordinarily experience brief bone loss that reverses when menstruation returns, bone loss was not prevented by a multivitamin supplement providing 400 IU of vitamin D along with 500 mg twice daily of calcium or placebo.56 Despite the lack of evidence that calcium and vitamin D supplements alone are helpful to amenorrheic women, they are still generally recommended to prevent the added burden of calcium and vitamin D deficiency from further contributing to bone loss.57 Amounts typically recommended are 1,200 to 1,500 mg calcium and 400 to 800 IU vitamin D daily.

Used for Amount Why
Breast Cancer
 Refer to label instructions 1 star   Vitamin D from supplements and from exposure to the sun both appear to protect against breast cancer.

1 star  Breast Cancer

Breast cancer rates have been reported to be relatively high in areas of low exposure to sunlight.58 Sunlight triggers the formation of vitamin D in the skin, which can be activated in the liver and kidneys into a hormone with great activity. This activated form of vitamin D causes “cellular differentiation”—essentially the opposite of cancer.

The following evidence indicates that vitamin D might have a protective role against breast cancer:

  • Synthetic vitamin D-like molecules have prevented the equivalent of breast cancer in animals.59
  • Activated vitamin D appears to have antiestrogenic activity.60
  • Both sunlight and dietary exposure to vitamin D have correlated with a reduced risk of breast cancer.61 , 62

Activated vitamin D comes in several forms. One of them—1,25 dihydroxycholecalciferol—is an exact duplicate of the hormone made in the human body.

The following preliminary, non-clinical evidence supports the idea that activated vitamin D may be of help to some breast cancer patients:

  • In combination with tamoxifen, a synthetic, activated-vitamin D-like molecule has inhibited the growth of breast cancer cells in test tube research.63
  • Synthetic vitamin D-like molecules induce tumor cell death in breast cancer cells.64
  • Activated vitamin D suppresses the growth of human cancer cells transplanted into animals.65
  • In test tube research, activated vitamin D has increased the anticancer action of chemotherapy.66

In a preliminary trial, activated vitamin D was applied topically to the breast, once per day for six weeks, in 19 patients with breast cancer.67 Of the 14 patients who completed the trial, three showed a large reduction in tumor size, and one showed a minor improvement. Those who responded had tumors that contained receptors for activated vitamin D. However, other preliminary reports have not found that high levels of these receptors consistently correlate with a better outcome.68 , 69 , 70

With a doctor’s prescription, compounding pharmacists can put activated vitamin D, a hormone, into a topical ointment. Due to potential toxicity, use of this hormone, even topically, requires careful monitoring by a physician. Standard vitamin D supplements are unlikely to duplicate the effects of activated vitamin D in women with breast cancer. The patients in the breast cancer trial all had locally advanced disease.


Used for Amount Why
Cardiac Arrhythmia
 Refer to label instructions 1 star   One case report described relief from a type of arrhythmia after supplementing with vitamin D.

1 star  Cardiac Arrhythmia

One case of long-standing sick-sinus syndrome (another type of arrhythmia) was reported to resolve upon supplementation with 800 IU per day of vitamin D prescribed for an unrelated condition. However, it was not clear from that report whether the improvement was due to the vitamin D.71 More research is needed.

Used for Amount Why
Colon Cancer
 Refer to label instructions 1 star   People who take vitamin D supplements have been shown to be at low risk for colon cancer.

1 star  Colon Cancer

Ultraviolet light from sun exposure increases the risk of skin cancers and melanoma. Nonetheless, where sun exposure is low, rates of several cancers have been reported to be high.72 , 73 , 74 An association between greater sun exposure and a reduced risk of colon cancer has appeared in some,75 but not all, studies.76

In preliminary reports, people who take vitamin D supplements have been reported to be at low risk for colon cancer, though the differences between supplement takers and others might have been due to chance.77 , 78 More research is needed to determine whether vitamin D supplements may be useful in connection with the prevention of colon cancer.


Used for Amount Why
Migraine Headache
 Refer to label instructions 1 star   Taking large amounts of the combination of calcium and vitamin D has been reported to produce a marked reduction in the incidence of migraines in several women.

1 star  Migraine Headache

Taking large amounts of the combination of calcium (1,000 to 2,000 mg per day) and vitamin D has been reported to produce a marked reduction in the incidence of migraines in several women.79 , 80 However, the amount of vitamin D given to these women (usually 50,000 IU once a week), can cause adverse reactions, particularly when used in combination with calcium. This amount of vitamin D should be used only under medical supervision. Doctors often recommend that people take 800 to 1,200 mg of calcium and 400 IU of vitamin D per day. However, it is not known whether theses amounts would have an effect on migraines.

Used for Amount Why
Multiple Sclerosis
 Refer to label instructions 1 star   Studies suggest that vitamin D may help reduce the number of MS attacks and may protect against the development of the disease.

1 star  Multiple Sclerosis

Animal studies have demonstrated that vitamin D can prevent an experimental form of multiple sclerosis. In humans, striking geographical differences in the prevalence of multiple sclerosis suggest that sun exposure (which promotes the synthesis of vitamin D) may protect against the development of the disease. In addition, higher blood levels of vitamin D are associated with a lower risk of developing MS.81 However, no clinical trials have been done to determine whether increasing vitamin D intake or sunlight exposure would prevent MS.

Used for Amount Why
Parkinson’s Disease
 Refer to label instructions 1 star   Vitamin D deficiency is common in Parkinson’s disease and may increase the risk of hip fracture due to osteoporosis. This risk may be reduced by taking vitamin D.

1 star  Parkinson’s Disease

Vitamin D deficiency is common in Parkinson’s disease. People with Parkinson’s often get insufficient sun exposure and have reduced levels of activity that adversely affect calcium metabolism.82 Low vitamin D levels in Parkinson’s disease have been reported to increase the risk of hip fracture due to osteoporosis.83 This risk has been significantly reduced with the use of synthetic, activated vitamin D—a prescription drug.84 Whether the same effect could be achieved with supplemental vitamin D remains unknown, though some doctors recommend 400–1,000 IU vitamin D per day. People with Parkinson’s disease may wish to discuss the use of synthetic activated vitamin D with a healthcare professional.

Used for Amount Why
Urinary Incontinence
 Refer to label instructions 1 star   Higher blood levels of vitamin D are associated with lower risk of urinary incontinence in women.

1 star  Urinary Incontinence

Vitamin D may be important for normal muscle function, including muscles that help control urinary continence.85 , 86 Higher blood levels of vitamin D are associated with lower risk of urinary incontinence in women, according to one preliminary study.87 Controlled trials are needed to determine whether vitamin D supplements can help prevent or treat urinary incontinence.

Used for Amount Why
Vitiligo
 Refer to label instructions 1 star   When used in combination with sun exposure, a form of vitamin D called calcipotriol may be effective in stimulating repigmentation in children with vitiligo.

1 star  Vitiligo

When used topically in combination with sun exposure, a pharmaceutical form of vitamin D, called calcipotriol, may be effective in stimulating repigmentation in children with vitiligo. In a preliminary study, children applied a cream containing calcipotriol daily and exposed themselves to sunlight for 10–15 minutes the following morning.88 After 11 months, marked to complete repigmentation occurred in 55% of the children, moderate repigmentation occurred in 22%, and little or no improvement was seen in 22%. None of the children developed new areas of vitiligo. The first evidence of repigmentation occurred within 6 to 12 weeks in the majority of the children. All participants tolerated the cream well, with approximately 17% complaining of mild, transient skin irritation. Calcipotriol is a prescription medication to be used only under the supervision of a doctor. It is not known whether vitamin D as a dietary supplement has any effect on vitiligo.

Used for Amount Why
Sunburn
(Vitamin A)
 Refer to label instructions  

Sunburn

Antioxidants may protect the skin from sunburn due to free radical–producing ultraviolet rays.89 Combinations of 1,000 to 2,000 IU per day of vitamin E and 2,000 to 3,000 mg per day of vitamin C, but neither given alone, have a significant protective effect against ultraviolet rays, according to double-blind studies.90 , 91 , 92

Oral synthetic beta-carotene alone was not found to provide effective protection when given in amounts of 15 mg per day or for only a few weeks’ time in larger amounts of 60 to 90 mg per day, but it has been effective either in very large (180 mg per day) amounts or in smaller amounts (30 mg per day) in combination with topical sunscreen.93 , 94 , 95 , 96 , 97

Natural sources of beta-carotene or other carotenoids have been more consistently shown to protect against sunburn. One controlled study found that taking a supplement of natural carotenoids (almost all of which was beta-carotene) in daily amounts of 30 mg, 60 mg, and 90 mg gave progressively more protection against ultraviolet rays.98 In another controlled study, either 24 mg per day of natural beta-carotene or 24 mg per day of a carotenoid combination of equal amounts beta-carotene, lutein, and lycopene helped protect skin from ultraviolet rays.99 A preliminary study compared synthetic lycopene (10.1 mg per day), a natural tomato extract containing 9.8 mg of lycopene per day plus additional amounts of other carotenoids, and a solubilized tomato drink (designed to increase lycopene absorption) containing 8.2 mg of lycopene plus additional amounts of other carotenoids. After 12 weeks, only the two tomato-based products were shown to give significant protection against burning by ultraviolet light.100

Still other trials have tested combinations of several antioxidants. One preliminary study found that a daily combination of beta-carotene (6 mg), lycopene (6 mg), vitamin E (15 IU), and selenium for seven weeks protected against ultraviolet light.101 However, a double-blind trial of a combination of smaller amounts of several carotenoids, vitamins C and E, selenium, and proanthocyanidins did not find significant UV protection compared with placebo.102 Similarly, in a controlled trial, a combination of selenium, copper, and vitamins was found to be ineffective.103

It should be noted that while oral protection from sunburn has been demonstrated with several types of antioxidants, the degree of protection (typically less than an SPF of 2) is much less than that provided by currently available topical sunscreens. On the other hand, these modest effects will provide some added protection to skin areas where sunscreen is also used and will give a small amount of protection to sun-exposed areas where sunscreen is not applied. However, oral protection from sunburn is not instantaneous; maximum effects are not reached until these antioxidants have been used for about eight to ten weeks.104 , 105

How It Works

How to Use It

People who get plenty of sun exposure do not require supplemental vitamin D, since sunlight increases vitamin D synthesis when it strikes bare skin. Although the recommended dietary allowance for vitamin D is 200 IU per day for adults, there is some evidence that elderly people need 800 to 1,000 IU per day for maximum effects on preserving bone density and preventing fractures.106 , 107 , 108 , 109 Sun-deprived people should take no less than 600 IU per day and ideally around 1,000 IU per day.110 , 111

Where to Find It

Cod liver oil is an excellent dietary source of vitamin D, as are vitamin D-fortified foods. Traces of vitamin D are found in egg yolks and butter. However, the majority of vitamin D in the body is created during a chemical reaction that starts with sunlight exposure to the skin. Cholecalciferol (vitamin D3) is the animal form of this vitamin.

Possible Deficiencies

In adults, vitamin D deficiency may result in a softening of the bones known as osteomalacia. This condition is treated with vitamin D, sometimes in combination with calcium supplements. Osteomalacia should be diagnosed, and its treatment monitored, by a doctor. In people of any age, vitamin D deficiency causes abnormal bone formation. In addition, vitamin D deficiency can cause muscle weakness, which improves with vitamin D supplementation.112 Vitamin D deficiency occurs more commonly following winter, owing to restricted sunlight exposure during that season. Living in an area with a lot of atmospheric pollution, which can block the sun's ultraviolet rays, also appears to increase the risk of vitamin D deficiency.113 114

Vitamin D deficiency is more common in strict vegetarians (who avoid vitamin D-fortified dairy foods), dark-skinned people,115 alcoholics, and people with liver or kidney disease. People with liver and kidney disease can make vitamin D but cannot activate it.

Vitamin D deficiency is more common in people suffering from intestinal malabsorption, which may have occurred following previous intestinal surgeries, or from celiac disease.116 People with insufficient pancreatic function (e.g., those with pancreatitis or cystic fibrosis) tend to be deficient in vitamin D. Vitamin D deficiency is also common in individuals with hyperthyroidism (Graves' disease), particularly women.117

In children, vitamin D deficiency is called rickets and causes a bowing of bones not seen in adults with vitamin D deficiency. Vitamin D deficiency is common among people with hyperparathyroidism, a condition in which the parathyroid gland is overactive. In a study of 124 people with mild hyperparathyroidism, vitamin D levels were below normal in 7% of them and suboptimal in 53% of them.118 Vitamin D deficiency is also common in men with advanced prostate cancer. In one study, 44% of 16 men with advanced prostate cancer had decreased blood levels of vitamin D.119

One in seven adults has been reported to be deficient in vitamin D.120 In one study, 42% of hospitalized patients under age 65 were reported to be vitamin D deficient.121 In this same study, 37% of the people were found to be deficient in vitamin D, despite the fact they were eating the currently recommended amount of this nutrient. Vitamin D deficiency is particularly common among the elderly. Age-related decline in vitamin D status may be due to reduced absorption, transport, or liver metabolism of vitamin D.122

Interactions

Interactions with Supplements, Foods, & Other Compounds

Vitamin D increases both calcium and phosphorus absorption and has also been reported to increase aluminum absorption.123

Interactions with Medicines

Certain medicines interact with this supplement.

May Be Beneficial: Some medicines may increase the need for this supplement.
Avoid: Some medicines interact with this supplement, so they should not be taken together.
Check: Some interactions between this supplement and certain medicines require more explanation. Click the link to see details.

Note: The following list only includes the generic or class name of a medicine. To find a specific brand name, use the Medicines Index.

May Be Beneficial: Carbamazepine
May Be Beneficial: Carbamazepine
May Be Beneficial: Cholestyramine
May Be Beneficial: Cimetidine
May Be Beneficial: Colesevelam
May Be Beneficial: Colestipol
May Be Beneficial: Cortisone
May Be Beneficial: Dexamethasone
May Be Beneficial: Felbamate
May Be Beneficial: Felbamate
May Be Beneficial: Flurbiprofen
May Be Beneficial: Heparin
May Be Beneficial: Hydroxychloroquine
May Be Beneficial: Isoniazid
May Be Beneficial: Levetiracetam
May Be Beneficial: Levetiracetam
May Be Beneficial: Methylprednisolone
May Be Beneficial: Mineral Oil
May Be Beneficial: Neomycin
May Be Beneficial: Orlistat
May Be Beneficial: Oxcarbazepine
May Be Beneficial: Oxcarbazepine
May Be Beneficial: Phenytoin
May Be Beneficial: Prednisolone
May Be Beneficial: Prednisone
May Be Beneficial: Primidone
May Be Beneficial: Primidone
May Be Beneficial: Sodium Fluoride
May Be Beneficial: Topiramate
May Be Beneficial: Topiramate
May Be Beneficial: Zonisamide
May Be Beneficial: Zonisamide
Avoid: Verapamil
Avoid: Warfarin
Check: Allopurinol
Check: Bendroflumethiazide
Check: Chlorothiazide
Check: Chlorthalidone
Check: Estradiol
Check: Gabapentin
Check: Hydrochlorothiazide
Check: Hydroflumethiazide
Check: Indapamide
Check: Medroxyprogesterone
Check: Methyclothiazide
Check: Metolazone
Check: Phenobarbital
Check: Polythiazide
Check: Risedronate
Check: Trichlormethiazide
Check: Valproate

Side Effects

Side Effects

People with hyperparathyroidism should not take vitamin D without consulting a physician. People with sarcoidosis should not supplement with vitamin D, unless a doctor has determined that their calcium levels are not elevated. Too much vitamin D taken for long periods of time may lead to headaches, weight loss, and kidney stones. Rarely, excessive vitamin D may even lead to deafness, blindness, increased thirst, increased urination, diarrhea, irritability, children’s failure to gain weight, or death.

Most people take 400 IU per day, a safe amount for adults. Some researchers believe that amounts up to 10,000 IU per day are safe for the average healthy adult, although adverse effects may occur even at lower levels among people with hypersensitivity to vitamin D (e.g. hyperparathyroidism).124 In fact, of all published cases of vitamin D toxicity for which a vitamin D amount is known, only one occurred at a level of intake under 40,000 IU per day.125 Nevertheless, people wishing to take more than 1,000 IU per day for long periods of time should consult a physician. People should remember the total daily intake of vitamin D includes vitamin D from fortified milk and other fortified foods, cod liver oil, supplements that contain vitamin D, and sunlight. People who receive adequate sunlight exposure do not need as much vitamin D in their diet as do people who receive minimal sunlight exposure.

Some,126 but not all,127 research suggests that vitamin D may slightly raise blood levels of cholesterol in humans.

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