| Vitamin :: Vitamin D |
| Other Terms: | Calciferol | Ergocalciferol (Vitamin D2) | Cholecalciferol (Vitamin D3) |
| Solubility: | Fat-soluble, which means it needs to be taken with fats to be absorbed in the digestive system. It is stored by the body in the liver. |
| On this Page: | What is Vitamin D · Benefits · Deficiency Signs · Foods · Supplements · RDA · Toxicity | Overdose |
What is Vitamin D ?
Vitamin D, an essential nutrient, is also known as calciferol for the part it plays in the deposition of calcium in bones and building of bone density.
There are several forms of vitamin D. The two most important to humans are ergocalciferol or vitamin D2 from plants, and cholecalciferol or vitamin D3 that is made from a type of cholesterol in skin, when sunlight acts on it. Both types need further metabolism in our liver and kidneys before they can become the active forms (ercalcitriol and calcitriol respectively) that the body uses.
Vitamin D is typically measured in micrograms (shown as µg or mcg), or in International Units (IU). One µg cholecalciferol = 40 IU vitamin D.
Vitamin D in food is stable and not much depleted by cooking or storage.
What is vitamin D good for? There is increasing evidence that vitamin D benefits our health in many more ways than previously thought.
Aside from its importance to bone health and prevention of osteoporosis, vitamin D is now known to also help a number of diseases such as heart disease, diabetes, hypertension, autoimmune diseases, and cancers of the breast, ovary, prostate and colon.
Recent research shows that higher intake of vitamin D cuts cancer risk by half. According to the Orthomolecular Medicine News Service, October 2 2008 report, “ample intake of vitamin D, about 2,000 IU per day, can cut breast cancer incidence by half“, and “inadequate Vitamin D is associated with high incidence rates of colorectal cancer and specifically urges that prompt public health action is needed to increase intake of Vitamin D-3 to 1000 IU/day“.
The report noted that “Vitamin D’s anticancer properties are so evident, and so important, that the Canadian Cancer Society now recommends supplementation with 1,000 IU of Vitamin D per day for all adults in winter, and year-round for persons at risk.”
This list sets out the main ways that vitamin D benefits our health.
| :: | Vitamin D Benefits & Functions |
| 1. | main role of vitamin D is to maintain the right level of calcium in blood by promoting calcium absorption in the intestines, and stimulating bones to release calcium when blood calcium is low (known as hypocalcemia), and reversing this process when blood calcium is high |
| 2. | promotes adequate levels and use of calcium and phosphorus, which is especially vital for development of bones and teeth, and for ensuring normal bone mineralization, growth and remodeling |
| 3. | increases calcium deposition into bones and builds bone density to prevent osteoporosis and bone fractures |
| 4. | prevents and treats rickets and osteomalacia |
| 5. | may be needed for normal cell growth (especially those of the brain and immune system) |
| 6. | may reduce age-related decline in mental agility (according to a study by the University of Manchester reported in the Journal of Neurology, Neurosurgery and Psychiatry) |
| 7. | stimulates production of insulin which is needed to handle blood sugars |
| 8. | protects against hypertension (high blood pressure) |
| 9. | recent research suggests vitamin D may protect against diseases like cancer (particularly breast, prostate, colon cancers) and heart disease |
| 10. | may also help regulate immune system function to control inflammatory response, which is important for preventing auto-immune diseases such as type 1 diabetes, rheumatoid arthritis, psoriaris, and irritable bowel diseases such as ulcerative colitis and Crohn’s disease |
| 11. | preliminary studies suggest that long-term supplementation decreases the risk of multiple sclerosis (an autoimmune disease) |
Vitamin D Deficiency Symptoms and Causes
What causes vitamin D deficiency? There are a few possible reasons why vitamin D deficiency symptoms might arise.
Vitamin D2 and D3 requires conversion by the liver and kidney before it can become active. People with liver or kidney disorders are therefore at higher risk of deficiency and osteoporosis.
Low vitamin D levels could also be due to poor absorption of the nutrient. People with inflammatory bowel diseases that result in malabsorption such as Crohn’s disease, or a fat-deficient diet (fat being needed for vitamin D absorption), or fat malabsorption syndromes such as cystic fibrosis, are at risk. So are those with intestinal or gallbladder disorders, or who have had gastric or intestinal surgery.
Antacids, steroid hormones, and certain cholesterol-lowering drugs also hinder vitamin D absorption. Mineral oil, alcohol, and anti-convulsant drugs interfere with action of vitamin D.
Infants fed only breast milk are also at risk of deficiency and may develop rickets. High doses of vitamin D given to breastfeeding mothers in clinical trials have been shown to improve levels of it in both mother and child.
People with limited exposure to sunlight, or who are obese, tend to have low vitamin D levels and need higher intake from their diet or supplements. Darker skinned people need much more exposure to sunlight to make the same amount of vitamin D in their skin as lighter skinned people.
People aged 50 and over are at greater risk of vitamin D insufficiency too. That’s because with age, the skin synthesizes vitamin D less efficiently, and kidneys are less able to convert it to its active form.
A lack of vitamin D results in poor absorption of calcium, that gives rise to classic calcium and vitamin D deficiency symptoms.
| :: | Vitamin D Deficiency Symptoms |
| 1. | rickets in children, where bones soften and become so pliable that they bend, resulting in skeletal problems such as knock-knees, bow legs, spinal curvature, contracted pelvis, abnormally enlarged head, soft skull bones and increased joint space; the breastbone may be misshapened, causing the chest to be sunken and leading to breathing difficulties |
| 2. | osteomalacia (adult rickets) due to inadequate calcium in bones, and characterized by weak soft bones, muscular weakness, even bow legs |
| 3. | muscle or bone pain (including low back pain) |
| 4. | frequent bone fractures |
| 5. | osteoporosis where bones become porous, weak and brittle |
| 6. | higher risk in those aged 50 and over of periodontal disease (a chronic inflammatory gum disease) |
| 7. | rheumatoid arthritis |
| 8. | increased risk of diabetes due to insufficient insulin produced |
| 9. | increased risk of high blood pressure (hypertension) |
| 10. | hypocalcemia (low blood calcium level) characterized by muscle cramps, twitching nerves or muscles, numbness and tingling of fingers and toes, irregular heart contractions, and irritability |
Vitamin D Foods
Sunlight is one of the best sources of vitamin D, which is made in the skin when exposed to ultraviolet radiation from the sun. As little as 10 or 15 minutes a day of bright sunlight might be enough. Avoid over-exposure, as it raises the risk of skin cancer. Most of ultraviolet radiation does not penetrate glass, so you generate little vitamin D when sitting in a car.
Not many foods naturally contain vitamin D. Some foods are fortified with it, i.e. they have vitamin D added.
Rich vitamin D foods
· fish liver oils · mackerel · salmon, especially sockeye salmon · sardine · shrimp.
Other foods with vitamin D
· alfalfa · animal liver · egg yolk · milk fortified with vitamin D · oatmeal · fatty salt-water fish like cod, halibut, tuna · sweet potatoes.
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Vitamin D Supplements
Taking vitamins and minerals in their correct balance is vital to the proper functioning of all vitamins. They work synergistically, which means that the effectiveness of any one nutrient requires or is enhanced, sometimes dramatically, by the presence of certain other nutrients.
For this reason, if you are looking to take supplements for maintenance of optimal health, the recommended approach is to take a multi-vitamin that has the proper balance of all the necessary nutrients your body needs.
For a list of reputable top ranked vitamin and mineral supplements chosen in an independent supplement review, see Best Multivitamin Supplements. Many of these are manufactured to pharmaceutical or nutraceutical GMP compliance, which is the highest multivitamin standard possible.
Keep in mind, however, that while vitamin supplements are useful to plug nutritional gaps that are almost inevitable in modern diets, and to ensure we get optimal doses ofnutrients, they are no substitute for a good diet. Instead, use them to complement a healthy diet and lifestyle.
Vitamin D RDA (Recommended Dietary Allowance)
The Food & Nutrition Board of the Institute of Medicine, National Academy of Sciences, in their 1997-2001 collaboration between the US and Canada, set the daily Adequate Intake (AI) of Vitamin D as follows.
| Life Stage | Gender | Vitamin D Dosage | Day |
| Infants 0-6 mths | 5* µg |
| Infants 7-12 mths | 5* µg |
| Children 1-3 yrs | 5* µg |
| Children 4-8 yrs | 5* µg |
| Girls 9-13 Yrs | 5* µg |
| Boys 9-13 Yrs | 5* µg |
| Females 14-18 Yrs | 5* µg |
| Males 14-18 Yrs | 5* µg |
| Females 19-50 Yrs | 5* µg |
| Males 19-50 Yrs | 5* µg |
| Females 50-70 Yrs | 10* µg |
| Males 50-70 Yrs | 10* µg |
| Adults older than 70 Yrs | 15* µg |
| Pregnant Women 14-18 Yrs | 5* µg |
| Pregnant Women 19-50 Yrs | 5* µg |
| Lactating Mothers 14-18 Yrs | 5* µg |
| Lactating Mothers 19-50 Yrs | 5* µg |
These dosages are the minimum required per day to ward off deficiency. In therapeutic use of this nutrient, dosage is increased as necessary for the ailment, keeping in mind Vitamin D toxicity levels.
Legend
1 µg = 1 mcg = 1 microgram = 1/1,000,000 of a gram
1 mg = 1 milligram = 1/1,000 of a gram
* Indicates AI figures based on Dietary Reference Intake (DRI) figures
Vitamin D Overdose Symptoms, Toxicity Level & Side Effects
Vitamin D toxicity symptoms include loss of appetite, unusual thirst, itchy skin, sore eyes, nausea, vomiting, diarrhea, kidney damage, and over time, calcium deposits in the lungs and blood vessels.
The Food and Nutrition Board of the Institute of Medicine has set Tolerable Upper Intake Levels (ULs) for vitamin D. These are the highest average daily intake levels above which there is risk of vitamin D overdose.
| Life Stage | Tolerable Upper Intake Levels (UL) per Day |
| 0 to 12 months | 25 µg (1,000 IU) |
| 1 year & above | 50 µg (2,000 IU) |
| Pregnant Women | 50 µg (2,000 IU) |
| Lactating Mothers | 50 µg (2,000 IU) |
The ULs do not apply to the therapeutic use of vitamin D for treatment, which should be under the supervision of a healthcare professional.
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References
| 1. | Institute of Medicine, Food and Nutrition Board. Dietary reference intakes for calcium, phosphorous, magnesium, vitamin D, and fluoride. Washington DC: National Academy Press; 1997. |
| 2. | U.S. National Libary of Medicine [NLM] & National Institutes of Health [NIH]: MedlinePlus. NLM-NIH home page. <http://www.nlm.nih.gov/medlineplus>. Use the built-in search function to find specific data. Accessed 2009 March – June. |
| 3. | National Institutes of Health, NIH Clinical Center: Office of Dietary Supplements [ODS]. ODS home page. <http://ods.od.nih.gov>. Use the built-in search function to find specific data. Accessed 2009 Mar – Jun. |
| 4. | The George Mateljan Foundation: The world’s healthiest foods [WHFoods]. WHFoods home page. <http://www.whfoods.com>. Accessed 2009 March – June. |
| 5. | Mayo Foundation for Medical Education and Research. Mayo Clinic book of alternative medicine: The new approach to using the best of natural therapies and conventional medicine. New York, NY: Time Inc; 2007. p 67-75. |
| 6. | Balch JF, Balch PA. Prescription for nutritional healing: A practical A-Z reference to drug-free remedies using vitamins, minerals, herbs & food supplements. Garden City Park, New York: Avery Publishing; 1990. |
| 7. | Ulene A. Dr. Art Ulene’s complete guide to vitamins, minerals and herbs. New York, NY: Avery Publishing; 2000. |
| 8. | Journal of Neurology, Neurosurgery and Psychiatry: Association between 25-hydroxyvitamin D levels and cognitive performance in middle-aged and older European men. <http://jnnp.bmj.com/cgi/content/abstract/jnnp.2008.165720v1>. Accessed 2009 Jun 26. |
