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Vitamin D

"One of the top 10 medical breakthroughs of 2007" Time Magazine

On this page: About | Bone Health | Heart Disease | Cancer | Autoimmune Disease | Deficiency | Toxicity | Sources of Vit D

Vitamin D is important in chronic disease prevention yet vitamin D deficiency is widespread

Vitamin D supplementation appears to protect against diabetes, gum disease, multiple sclerosis, peripheral neuropathy, osteoporosis, and possibly cancer, stroke, and heart disease. New research on the benefits of vitamin D has been recognized in the December 2007 issue of Time magazine as "one of the top 10 medical breakthroughs of 2007".(13)

The new National Osteoporosis Foundation guidelines for adults 50 years and older is 800–1,000 IU of vitamin D3/day (along with 1,200 mg of calcium/day). Currently, the recommended daily intake of Vitamin D in adults ages 51-70 is 400 IUs (with 200 IUs or less for younger ages), which, according to the researchers, leaves circulating blood levels of the the vitamin too low to have a positive effect on certain chronic diseases. *The National Academy of Sciences' Institute of Medicine (IOM) has set the Upper Limits (UL) for vitamin D at 1,000 IU for infants up to 12 months of age and 2,000 IU for children, adults, pregnant, and lactating women.

A simple blood test can measure the circulating Vitamin D levels in your blood. Many doctors are now drawing blood levels of Vitamin D to to make sure patients are getting enough vitamin D to optimize good bone health and prevent chronic disease. Ask your doctor about this.

The Many Roles of Vitamin D

RicketsThe functions of Vitamin D: Calcium works in concert with Vitamin D to form and maintain strong bones. Without vitamin D, bones will become thin, brittle, or misshapen. A deficiency in Vitamin D can result in rickets in children and osteomalacia in adults, two forms of skeletal diseases that weaken bones. Note the bowed legs in the photo. Nutritional Rickets is a condition in which children's bones are too soft, and do not develop properly due to a deficiency of vitamin D. Photo Courtesy of the Center for Disease Control

Vitamin D has many important roles in promoting good health In addition to helping calcium build strong bones. It helps regulate the immune system and the neuromuscular system, and also plays a major role in the life cycle of human cells.

Calcium and vitamin D deficiency is widespread in the United States and worldwide.

In the 1930s, Vitamin D deficiency resulting in rickets was a major public health problem in the United States. A milk fortification program was implemented to combat rickets, and it nearly eliminated this disorder in the U.S., yet a vitamin D deficiency commonly persists in both children and adults but especially in people over 50. Recent studies have found that:
  • More than 50% of younger and older women are not consuming recommended amounts of vitamin D. The deficiency is also found in men, but twice as many women as men are found to have low blood levels of the vitamin.(8)
  • Many healthy children have inadequate blood levels of Vitamin D. In a recent Harvard study of 365 healthy children eight months to two years old, 12% had a vitamin D deficiency, while 40% had suboptimal levels of the nutrient.

Low Vitamin D levels are linked with many serious, chronic diseases, such as weak bones and muscles, mental decline in elderly, diabetes, gum disease, multiple sclerosis, peripheral neuropathy, osteoporosis, and possibly cancer, stroke, and heart disease.

  • Hip fractures and muscle weakness, in people over 50, linked with a deficiency in Vitamin D. It has been estimated that as many as 30% to 40% of older adults with hip fractures are vitamin D deficient. In another study of hospitalized women with hip fractures due to osteoporosis, 50 percent were found to also have signs of vitamin D deficiency. Supplementation with calcium plus 800 IU of vitamin D per day was associated with a significantly reduced incidence of hip fractures in this population.

  • Vitamin D deficiency has been implicated in muscle weakness and frequent falls in those 65 and older. In a recent study, handgrip strength and physical performance tests were significantly worse in elderly with low blood levels of Vitamin D compared to same-aged people with normal vitamin D levels. Researchers emphasize that people over 65 have a high rate of vitamin D deficiency.(8)

  • Lack of Vitamin D may increase heart disease A recent finding from the Framingham Heart Study revealed a link between moderate vitamin D deficiency and a nearly doubled risk of myocardial infarction, stroke, and heart failure in people who also have high blood pressure. The authors in the study point out that up to half of middle-age and older adults in the U.S. have low levels of circulating vitamin D.

  • Vitamin D appears to reduce the risk of many types of cancer.

  • Lack of Vitamin D is linked with mental decline in the elderly A growing body of research is finding that those with the lowest levels of Vitamin D in their blood are significantly more likely to have a higher incidence of cognitive impairment. More studies are needed to determine whether Vitamin D supplementation is a cost-effective means of reducing the incidence of cognitive impairment in the elderly.

  • Vitamin D may help prevent type 1 diabetes. Findings of a recent study supported the use of vitamin D supplements in infants to help prevent type 1 diabetes. Researchers from Manchester Children's University Hospitals found that infants given extra vitamin D were 29% less likely to develop type 1 diabetes than those not given the supplement.(15)

  • Adequate levels of Vitamin D have been linked to protection against multiple sclerosis and other autoimmune disease

Those at increased risk for vitamin D deficiency

  • Americans age 50 and older are believed to be at increased risk of developing vitamin D deficiency. As people age, skin cannot synthesize vitamin D as efficiently, also the kidney is less able to convert vitamin D to its active hormone form.
  • Breastfed Infants In infants, vitamin D requirements cannot be met by human (breast) milk alone. Sunlight is a potential source of vitamin D for infants, but the American Academy of Pediatrics recommends that infants be kept out of direct sunlight. The American Academy of Pediatrics (AAP) recommends a daily supplement of 200 IU vitamin D for breastfed infants beginning within the first 2 months of life unless they are weaned to receive at least 500 ml (about 2 cups) per day of vitamin D-fortified formula.
  • Children and adolescents who are not routinely exposed to sunlight and do not consume at least 2, 8-fluid ounce servings of vitamin D-fortified milk per day are also at higher risk of vitamin D deficiency and may need a dietary supplement containing 200 IU vitamin D.
  • People with little or no sun exposure should consume recommended amounts of vitamin D in their diets or consider vitamin D supplementation.
  • Persons with greater skin melanin content Melanin is the pigment that gives skin its color. The high melanin content in darker skin limits the skin's ability to produce vitamin D from sunlight. It is very important for those with dark-pigmented skin to consume recommended amounts of vitamin D and may benefit from a vitamin D supplement.
  • Persons with fat malabsorption conditions As a fat soluble vitamin, vitamin D requires some dietary fat for absorption. Individuals who have a reduced ability to absorb dietary fat may require vitamin D supplements. Symptoms of fat malabsorption include diarrhea and oily stools. Fat malabsorption is associated with a variety of medical conditions such as: Pancreatic enzyme deficiency, Crohn's Disease, Cystic Fibrosis, Sprue, (also known as Celiac Disease), Liver disease, and surgical removal of part or all of the stomach or intestines can impair digestion and absorption of many nutrients, including fat malabsorption.

You can get too much of Vitamin D

Vitamin D is a fat soluble vitamin, thus toxicity can occur from high intakes of vitamin D. Overdosage can occur from large amounts of supplements or cod liver oil, but it is unlikely to result from sun exposure or diet. Parents should consult with their pediatrician before giving any child vitamin D supplements. Excess vitamin D can reach toxic levels and be harmful.

Regular excess intake of vitamin D may lead to hypercalcemia and excess bone loss. Individuals at particular risk include those with hyperparathyroidism, kidney disease, sarcoidosis, tuberculosis, or histoplasmosis. Chronic hypercalcemia may lead to serious or even life-threatening complications, and should be managed by a physician. Early symptoms of hypercalcemia may include nausea, vomiting, and anorexia (appetite/weight loss), followed by polyuria (excess urination), polydipsia (excess thirst), weakness, fatigue, somnolence, headache, anorexia, dry mouth, metallic taste, vertigo, tinnitus (ear ringing), and ataxia (unsteadiness). Kidney function may become impaired, and metastatic calcifications (calcium deposition in organs throughout the body) may occur, particularly affecting the kidneys. Treatment involves stopping intake of vitamin D or calcium, and lowering the calcium levels under strict medical supervision, with frequent monitoring of calcium levels.

Vitamin D should be used with caution in patients taking herbs with similar properties on the heart as digoxin, because hypercalcemia (which may result with excess vitamin D use) may precipitate abnormal heart rhythms.(16)


Diagnosis of Vitamin D Deficiency

A simple blood test can measure the circulating Vitamin D levels in your blood. Many doctors measure vitamin D levels to make sure patients are getting enough vitamin D to optimize good bone health. You might want to ask your doctor about this.

Sources of Vitamin D

You can get vitamin D in three ways:

  1. Sun--Through the skin from exposure to sunlight.

  2. Foods

    • Fortified foods are the best and most common food sources of vitamin D. Since the 1930s when the milk fortification program was implemented to combat rickets, about 98% to 99% of the milk supply in the U.S. is fortified with 400 International Units (or IU) of vitamin D per quart.(9) Although milk is fortified with vitamin D, dairy products made from milk, such as cheese and ice creams, are generally not fortified with vitamin D and contain only small amounts. Some ready-to-eat breakfast cereals may be fortified with vitamin D, often at a level of 10% to 15% of the Daily Value. There are only a few commonly consumed foods that are good sources of vitamin D such as cod liver oil, egg yolks, and certain fish such as salmon.

  3. Supplements

    • Calcium supplements: Most often calcium supplements with Vitamin D are recommended by health care professionals. Read more about calcium and vitamin D supplements.

    • Multivitamins: Vitamin D is included in most multivitamins, usually in strengths from 50 IU to 1,000 IU.

    • Vitamin D 1,000 IU is available over-the-counter

    • More from the National Institute of Health

References:

1) Osteoporosis Overview from the National Institute of Health
2) Osteoporosis: A debilitating disease that can be prevented and treated from the National Osteoporosis Foundation
3) Milk intake and bone mineral acquisition in adolescent girls: British Medical Journal, 315, 1997
4) Effect of Calcium Carbonate on the Absorption of Levothyroxine JAMA. 2000;283:2822-2825 5) Vitamins and Minerals, Nurse Practitioner Prescribing Reference, Winter 2006-2007
6) Dietary Supplement Fact Sheet: Vitamin D from the Office of Dietary Supplements, National Institute of Health

7) National Osteoporosis Foundation’s Updated Recommendations for Calcium and Vitamin D3 Intake. from the National Osteoporosis Foundation.
8) Vitamin D Deficiency Associated with Weakness in Older Patients from MedPage Today/J Gerontol A Biol Sci Med Sci 2007
9) Vitamin D Fact Sheet from the Office of Dietary Supplements, National Institute of Health
10) Vitamin D Benefits from Sun Exposure Outshine Cancer Risk from MedPage Today
11) Cancer Meta analyses Shine on Vitamin D from MedPage Today
12) Vitamin D from Medline Plus
13) "
Should the Sunshine Vitamin be taken with a grain of salt?" MerckMedicus, April 2008
14)
Low Vitamin D Plus Hypertension May Worsen Cardiovascular Risks, MedPage Today/Circulation, January 2008
15)
Vitamin D Boost in Infancy May Prevent Type 1 Diabetes, MedPage Today/Archives of Disease in Childhood, March 2008

16) Vitamin D from Medline Plus

Written by N Thompson, ARNP, MSN and M Thompson MD, last updated January 2009

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