Burns affecting a large proportion of the body may result in vitamin D deficiency⁶, potentially increasing the risk of osteoporosis, which is a frequent long-term consequence of severe burns.⁷ 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.

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.^8,9 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.

Vitamin D increases calcium absorption, and blood levels of vitamin D are directly related to the strength of bones.¹⁰ 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.¹¹ 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^12,13 and in postmenopausal women.¹⁴ However, the effect of vitamin D supplementation on osteoporosis risk remains surprisingly unclear,^15,16 with some trials reporting little if any benefit.¹⁷ Moreover, trials reporting reduced risk of fracture have usually combined vitamin D with calcium supplementation,¹⁸ making it difficult to assess how much benefit is caused by supplementation with vitamin D alone.¹⁹

Impaired balance and increased body sway are important causes of falls in elderly people with osteoporosis.²⁰ Vitamin D works with calcium to prevent some musculoskeletal causes of falls.²¹ 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.²² 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.²³

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.²⁴ 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.

Vitamin D is needed to regulate immune activity and research has shown it has an important role in preventing autoimmune diseases, including type 1 diabetes.³⁰ Vitamin D receptors have been found in the pancreas where insulin is made and some, but not all, preliminary evidence suggests that supplementation might reduce the risk of developing type 1 diabetes.^31,32 Case reports even suggest a combination of high-dose vitamin D and omega-3 fatty acids may completely reverse the onset of type 1 diabetes.^33,34

Vitamin D deficiency is common in people with type 1 diabetes and associated with poor glucose control. Supplementation with cholecalciferol (vitamin D3), in doses ranging from 2,000 IU per day to about 6,000 IU per day, has been shown in randomized controlled trials to slow the decline of pancreatic function in people with newly diagnosed type 1 diabetes who have not yet suffered an extensive loss of pancreatic function.³⁵ Furthermore, the majority of the research shows vitamin D3, in doses ranging from 2,000–10,000 IU per day, improves short and long term glycemic control in people with type 1 diabetes, particularly in those with low vitamin D status, possibly by preserving beta cell function and increasing insulin production.^{36,37,38,39,40,41}

Vitamin D is now recognized as necessary for healthy immune function, regulation of inflammatory processes, insulin production, and cellular responsiveness to insulin.^42,43 Vitamin D deficiency has been linked to high blood glucose levels, insulin resistance, type 2 diabetes, and diabetes complications.^44,45 Numerous studies have examined the effect of vitamin D supplementation on blood glucose control in people with type 2 diabetes, and meta-analyses of randomized controlled trials have found evidence of benefits, particularly in those with vitamin D deficiency.^46,47,48 One meta-analysis found a minimum dose of 4,000 IU of vitamin D per day is needed to improve blood glucose management and insulin sensitivity in people with type 2 diabetes.⁴⁹

Vitamin D is vital for both large and small blood vessel health, and deficiency has been associated with cardiovascular and microvascular diabetes complications. More research is needed to clearly establish a role for vitamin D supplementation in prevention and treatment of diabetes complications.⁵⁰

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.⁵⁶

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.⁷⁴ More research is needed.

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.⁷⁵Vitamin 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.⁷⁶ 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.⁷⁷ 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. In still another double-blind trial, the combination of 1,500 IU per day of vitamin D and the antidepressant drug fluoxetine was more effective than fluoxetine alone in the treatment of major depression.⁷⁸

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.⁷⁹

In one 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.⁸⁰ However, another double-blind study found that supplementation with 2,800 IU per day of vitamin D during the winter was not beneficial for people with SAD.⁸¹ Most of the participants in the study in which vitamin D was beneficial were deficient in vitamin D, whereas most of the participants in the negative study were not deficient. While additional research needs to be done, current evidence suggests that vitamin D supplementation may improve SAD in people with vitamin D deficiency but not in people without vitamin D deficiency.

Burns affecting a large proportion of the body may result in vitamin D deficiency⁸⁵, potentially increasing the risk of osteoporosis, which is a frequent long-term consequence of severe burns.⁸⁶ 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.

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.⁸⁷ 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.

Breast cancer rates have been reported to be relatively high in areas of low exposure to sunlight.⁹⁰ 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.⁹¹
• Activated vitamin D appears to have antiestrogenic activity.⁹²
• Both sunlight and dietary exposure to vitamin D have correlated with a reduced risk of breast cancer.^93,94

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.⁹⁵
• Synthetic vitamin D-like molecules induce tumor cell death in breast cancer cells.⁹⁶
• Activated vitamin D suppresses the growth of human cancer cells transplanted into animals.⁹⁷
• In test tube research, activated vitamin D has increased the anticancer action of chemotherapy.⁹⁸

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.⁹⁹ 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.^100,101,102

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.

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.¹⁰³ 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.¹⁰⁴ 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.¹⁰⁵ Amounts typically recommended are 1,200 to 1,500 mg calcium and 400 to 800 IU vitamin D daily.

Vitamin D malabsorption is common in Crohn’s¹⁰⁹ and can lead to a deficiency of the vitamin.¹¹⁰ Successful treatment with vitamin D for osteomalacia (bone brittleness caused by vitamin D deficiency) triggered by Crohn’s disease has been reported.¹¹¹ 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.¹¹² 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.¹¹³ In a preliminary study of patients with mild-to-moderate Crohn's disease, vitamin D supplementation for 24 weeks was associated with an improvement in disease activity. The amount used in that study was 1,000 to 5,000 IU per day, based on blood levels of the vitamin.¹¹⁴ A doctor should be consulted to determine the right level of vitamin D for supplementation.

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.¹¹⁵Zinc malabsorption also occurs frequently in celiac disease¹¹⁶ and may result in zinc deficiency, even in people who are otherwise in remission.¹¹⁷ 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.¹¹⁸

Malabsorption-induced depletion of vitamin D can lead to osteomalacia (defective bone mineralization) in people with celiac disease.¹¹⁹ Although supplementation with vitamin D appears to increase bone density, the excess risk of bone fracture may not be entirely eliminated.

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.¹²⁴ 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.¹²⁵ 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.¹²⁶ Amounts typically recommended are 1,200 to 1,500 mg calcium and 400 to 800 IU vitamin D daily.