encyclopedia

Vitamin D

Natural Sources:
Cod liver oil, fish (salmon, mackerel, sardines, eel), liver, egg yolk

Forms:
Standardized vitamin D capsules, tablets and liquid supplements; multivitamin pills containing vitamin D.

Therapeutic Uses:
Aging Disorders

Back Pain

Bone Health

Cellular Regeneration

Dental Health

Immune System Health

Lower Back Pain

Multiple Sclerosis Prevention

Muscle Spasms

Nervous System Health

Osteomalacia Prevention

Osteoporosis

Psoriasis

Rickets Prevention

Skin Disorders

Vitamin D Deficiency (RDA=200-600 IU/day)

Overview:

Vitamin D, a fat-soluble vitamin otherwise known as calciferol, is most well known for its benefits for the bones. It is found in food but can also be made by the human body by skin cells after exposure to ultraviolet rays from the sun. Vitamin D helps the body to maintain normal blood levels of calcium and phosphorus and is important for the prevention of rickets in children and osteomalacia and osteoporosis in adults. Vitamin D is also important for immune system health, normal muscle contractions, nerve function, blood cell formation and cancer prevention. The main function of vitamin D is to aid the body in the absorption of calcium, helping to form and maintain strong bones and teeth. It promotes bone mineralization in concert with a number of other vitamins, minerals, and hormones. Vitamin D (activated creams) can also be used topically for treating psoriasis and other skin diseases. Vitamin D exists in several forms, some more active than others. The liver and kidney help convert vitamin D to its active hormone form. Fortified foods are the major dietary sources of vitamin D. Prior to the fortification of milk in the 1930s, rickets (a bone disease seen in children) was a major public health problem in the developed world. Milk is fortified with 10 micrograms (400 IU) of vitamin D per quart, and rickets is now uncommon. One cup of vitamin D fortified milk supplies about one-fourth of the estimated daily need for this vitamin for adults. However, a study of 333 postmenopausal women found that women need about twice as much vitamin D to prevent calcium loss as they typically get in their diets. Most women get only 112 IUs when they need at least 220 IUs. Without vitamin D, bones can become thin, brittle, soft, or misshapen.

Chemistry:
Vitamin D, also known as calciferol, is chemically referred to as a steroid, more specifically a seco-steroid. The chemical structures of the D vitamins were determined in the 1930s in the laboratory of Professor A. Windaus at the University of Gφttingen in Germany. Vitamin D2 can be produced by ultraviolet irradiation of ergosterol and Vitamin D3 results from the ultraviolet irradiation of 7-dehydrocholesterol. Vitamin D3 is the anti-rickets component of cod liver oil and other fish oils. Between 1968 and 1971, researchers made great progress in understanding the metabolic processing of vitamin D and its physiological activity. It is now clear that the liver changes vitamin D3 to 25-hydroxyvitamin D3, the major circulating form of the vitamin. The kidneys then convert 25-hydroxyvitamin D3 to 1,25-dihydroxyvitamin D3, the active form of the vitamin. [Reference: WholeHealthMD.com Website; and University of California, Riverside, Vitamin D Workshop http://www.beyonddiscovery.org].

Suggested Amount:

The recommended daily allowance for vitamin D is between 200-600 IUs daily, depending upon your age and health condition as follows:

For men and women ages 19 to 50: 200 IU a day.

For men and women ages 51 to 70: 400 IU a day.

For men and women ages 71 and older: 600 IU a day.

For back pain: Take 400 IU daily.

For preventing and treating osteoporosis: Take 200-300 IU of vitamin D in combination with 600 mg calcium twice a day.

For osteoarthritis: Take 400 IU daily.

For Crohn’s Disease: Take 400 IU daily.

For Psoriasis: Take 400 IU twice daily until condition is under control, then continue with 400 IU daily. Use vitamin D activated cream as directed by physician.

Note: Although milk is fortified with vitamin D, dairy products made from milk such as cheese, yogurt, and ice cream are generally not fortified with vitamin D. Only a few foods naturally contain significant amounts of vitamin D including fatty fish and fish oils. Three and a half ounces of salmon has 500 IUs, canned sardines have 300 IUs and eel has an astounding 6,400 IUs.

Drug Interactions:
Vitamin D supplements should not be combined with antacids containing magnesium. Together, they can cause high blood levels of magnesium. When taken with thiazide diuretics, such as hydrochlorothiazide, vitamin D can cause excessive–and possibly toxic–levels of calcium in the body, which can cause the kidneys to fail. There is evidence that the use of steroid-type drugs may impair vitamin D metabolism and contribute to the loss of bone and development of osteoporosis associated with steroid medications. Corticosteroid medications are often prescribed to reduce inflammation from a variety of medical problems. These medicines may be essential for a person’s medical treatment, but they have potential side effects, including decreased calcium absorption. For these reasons, individuals on chronic steroid therapy should consult with their physician or registered dietitian about the need to increase vitamin D intake through diet and/or dietary supplements.

Contraindications:
Pregnant and lactating women should not take more than 800 IU of vitamin D daily. Higher doses during pregnancy may cause birth abnormalities. Additionally, vitamin D supplements should not be combined with antacids containing magnesium. Together, they can cause high blood levels of magnesium.

Side Effects:
There are no side effects known when vitamin D is taken at normal dosages. However, doses greater than 1,000 IU a day are not recommended. The body efficiently eliminates any extra vitamin D it makes from sunlight. However, toxic reactions can occur if you get more than 1,000 IU a day from supplements and vitamin D-fortified foods. Symptoms of a toxic reaction include loss of appetite, headache, nausea, vomiting, diarrhea and excessive thirst and urination. Taking 10,000 to 15,000 IU a day regularly can cause weight loss, paleness, constipation, fever, and a number of serious complications. Long-term over-consumption of vitamin D at any dose greater than 1,000 IU daily may cause high blood pressure, premature hardening of the arteries and kidney damage. Bones may weaken and a calcium buildup in muscles and other soft tissues may occur.

References:

Carper, J. 1991. The Food Pharmacy Guide to Good Eating. Bantam Books, 666 Fifth Avenue, New York, New York 10103. Pp. 290.

Holm EA, Jemec GB. 2002. The therapeutic potential of calcipotriol in diseases other than psoriasis. Int J Dermatol. 2002 Jan; 41(1): 38-43.

Marcus R, Wong M, Heath H 3rd, Stock JL. 2002. Antiresorptive treatment of postmenopausal osteoporosis: comparison of study designs and outcomes in large clinical trials with fracture as an endpoint. Endocr Rev. 2002 Feb; 23(1): 16-37. Review.

PMID: 11844743 [PubMed – indexed for MEDLINE]

Mason J, Mason AR, Cork MJ. 2002. Topical preparations for the treatment of psoriasis: a systematic review. Br J Dermatol. 2002 Mar; 146(3): 351-64. Review.

Pfeifer M, Lehmann R, Minne HW. Related Articles 2001. [Therapy of osteoporosis from the viewpoint of evidence-based medicine] Med Klin. 2001 May 15; 96(5): 270-80. Review. German.

Additional Information:

Vitamin D Deficiency:

Insufficient amounts of vitamin D can lead to the development of rickets in children and osteomalacia and osteoporosis in adults. Other signs of a deficiency are nervousness, muscle twitches, insomnia, and diarrhea. Rickets is rare in developed countries today because milk is fortified with vitamin D. Additionally, most children get enough exposure to sunlight for their bodies to manufacture all the vitamin D that they need. Just 10 to 15 minutes in the summer sun a few days a week supplies adequate amounts of vitamin D, although those who don’t get out in the sun may still need a supplement. It is wise to take a vitamin D supplement during the winter months to avoid deficiency, particularly in northern regions. Unfortunately, the body’s ability to manufacture vitamin D appears to decline with age, so older adults may need to get more vitamin D through diet or supplements, whether they’re exposed to sunlight or not. Young adults may also have inadequate stores of this nutrient. One study involving almost 300 patients of varying ages (hospitalized for different types of ailments) found that 57% were low in levels of vitamin D. This insufficiency occurred in a full one-third of the people who were getting the recommended amounts of vitamin D from their diet or supplements.

Positive Clinical Results for Osteoporosis:

In a study of 176 men and 213 women over age 65 done at Tufts University, those who took 500 mg of calcium and 700 IU of vitamin D daily for three years experienced a decrease in bone density loss. Moreover, the incidence of fractures was cut in half. In another study, of 3,270 healthy elderly French women, a daily dietary supplement of 1,200 mg calcium plus 800 IU of vitamin D lowered the incidence of hip fractures by 43% in just two years.

Positive Clinical Results for Cancer Prevention:

In a clinical trial of 438 men, researchers reported that participants with colon cancer had lower blood levels of vitamin D than those who did not have the disease. In addition, the men with the highest intake of vitamin D were the least likely to get colon cancer. Other studies indicate that vitamin D may be useful in preventing cancer of the breast and prostate.

Positive Clinical Results for Arthritic Joint Damage:

One recent study showed that taking 400 IU or more of vitamin D daily was effective in delaying or stopping the progression of osteoarthritis of the knees. It did not, however, prevent the disease from developing.

Possible Protection against Multiple Sclerosis:

Preliminary animal research suggests a possible connection between high vitamin D levels and immunity to the disabling nerve disorder, Multiple Sclerosis. It also happens that MS is rare both in the tropics (where there is ample sun to boost vitamin D levels) and in coastal Norway (where sun is scarce, but fatty fish rich in vitamin D abound and are commonly eaten by the local population). Human studies are needed to confirm the possible role of this vitamin in MS prevention.

Positive Results for the Treatment of Psoriasis:

Studies have shown that individuals with psoriasis have low levels of vitamin D. Vitamin D plays a role in skin cell replication and growth and appears to be helpful in treating the itching and flaking associated with psoriasis, possibly through normalizing cell replication. Studies show that a vitamin D3 derivative (1,25 dihydroxycholecalciferol), or activated vitamin D (available only by prescription in cream and supplement form), may be useful for psoriasis. Non-activated creams have little effect on psoriasis.