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 A doctor should evaluate vitamin D status and suggest the right level of vitamin D supplements.

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.⁵ 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,⁶ and taking pancreatic enzymes helps prevent B12 deficiencies.⁷

Vitamin D increases calcium absorption, and blood levels of vitamin D are directly related to the strength of bones.⁸ 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.⁹ 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.^{10, 11} However, the effect of vitamin D supplementation on osteoporosis risk remains surprisingly unclear,^{12, 13} with some trials reporting little if any benefit.¹⁴ Moreover, trials reporting reduced risk of fracture have usually combined vitamin D with calcium supplementation,¹⁵ making it difficult to assess how much benefit is caused by supplementation with vitamin D alone.¹⁶

Impaired balance and increased body sway are important causes of falls in elderly people with osteoporosis.¹⁷ Vitamin D works with calcium to prevent some musculoskeletal causes of falls.¹⁸ 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.¹⁹ 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.²⁰

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.²¹ 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 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.

Burns affecting a large proportion of the body may result in vitamin D deficiency²², potentially increasing the risk of osteoporosis, which is a frequent long-term consequence of severe burns.²³ 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.

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.²⁴ Zinc malabsorption also occurs frequently in celiac disease²⁵ and may result in zinc deficiency, even in people who are otherwise in remission.²⁶ 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.²⁷

Malabsorption-induced depletion of vitamin D can lead to osteomalacia (defective bone mineralization) in people with celiac disease.²⁸ Although supplementation with vitamin D appears to increase bone density, the excess risk of bone fracture may not be entirely eliminated.

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.²⁹ 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.³⁰ 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.³¹ 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 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.³²

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.³⁶ 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.³⁷

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.³⁸ 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.³⁹ 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.

Although the incidence of B-complex deficiencies is known to be high in alcoholics, the incidence of other vitamin deficiencies remains less clear.⁴⁷ 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,⁴⁸ potential problems accompany the use of either vitamin A or beta-carotene in correcting the deficiency induced by alcoholism.⁴⁹ 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.⁵⁰ Some doctors recommend 1 to 3 grams per day of vitamin C.

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.⁵¹ 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.⁵² 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.⁵³ Amounts typically recommended are 1,200 to 1,500 mg calcium and 400 to 800 IU vitamin D daily.

Breast cancer rates have been reported to be relatively high in areas of low exposure to sunlight.⁵⁴ 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.⁵⁵
• Activated vitamin D appears to have antiestrogenic activity.⁵⁶
• Both sunlight and dietary exposure to vitamin D have correlated with a reduced risk of breast cancer.^{57 , 58}

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.⁵⁹
• Synthetic vitamin D-like molecules induce tumor cell death in breast cancer cells.⁶⁰
• Activated vitamin D suppresses the growth of human cancer cells transplanted into animals.⁶¹
• In test tube research, activated vitamin D has increased the anticancer action of chemotherapy.⁶²

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.⁶³ 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.^{64 , 65 , 66}

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.

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.⁶⁷ More research is needed.

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.^{68 , 69 , 70} An association between greater sun exposure and a reduced risk of colon cancer has appeared in some,⁷¹ but not all, studies.⁷²

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.^{73 , 74} More research is needed to determine whether vitamin D supplements may be useful in connection with the prevention of colon cancer.

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.^{75 , 76} 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.

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.⁷⁷ However, no clinical trials have been done to determine whether increasing vitamin D intake or sunlight exposure would prevent MS.

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.⁷⁸ Low vitamin D levels in Parkinson’s disease have been reported to increase the risk of hip fracture due to osteoporosis.⁷⁹ This risk has been significantly reduced with the use of synthetic, activated vitamin D—a prescription drug.⁸⁰ 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.

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.⁸⁴ 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.

Antioxidants may protect the skin from sunburn due to free radical–producing ultraviolet rays.⁸⁵ 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.^{86, 87, 88}

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.^{89 , 90 , 91 , 92 , 93}

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.⁹⁴ 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.⁹⁵ 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.⁹⁶

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.⁹⁷ 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.⁹⁸ Similarly, in a controlled trial, a combination of selenium, copper, and vitamins was found to be ineffective.⁹⁹

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.^{100 , 101}