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Vitamin D

(cholecalciferol and ergocalciferol)

Vitamin D is a fat-soluble vitamin that is well-known for promoting calcium absorption thereby playing a role in bone and joint health. This vitamin also has strong anti-cancer benefits as those with lower intakes have higher rates of colon and breast cancer.

Major functions of Vitamin D:

- Required for absorption and utilization of calcium and phosphorus
- Important in prevention and treatment of osteoporosis
- Protects against muscle weakness and involved in regulation of the heartbeat
- Regulation of immune function especially autoimmune diseases (rheumatoid arthritis, multiple sclerosis)
- Regulation of blood pressure and cardiovascular health
- Regulation of insulin and blood sugar (vitamin D deficiency is a risk factor for type II diabetes)

Vitamin D is synthesized in the skin through the action of sunlight. Enzymatic reactions in the liver and kidneys convert D3 into a more potent form of this vitamin (calcidiol and calcitriol, respectively). Vitamin D is available in a number of forms but the two most common include D2 (plant based ergocalciferol) and D3 (animal based cholecalciferol). D2 which is derived from by irradiating yeast with UV light is generally used in fortified foods. Most nutritional supplements use D3 as this form is considered to be three times more effective than D2.

Researchers have investigated a number of diseases which are related to vitamin D deficiency Interestingly, individuals with certain autoimmune diseases have more flare ups in the winter months when exposure levels to sunlight levels are lower. Additionally, the prevalence of multiple sclerosis and Crohn’s disease are more prevalent in the Northern vs. Southern hemisphere.

Individuals most likely to be deficient in vitamin D are those not regularly exposed to sunlight due to where they live (more Northerly latitudes receive less sunlight during the winter months). The elderly (indoors more frequently; less able to synthesize the more active form of vitamin D), children (due more indoor games and increased sun screen use) and the obese (greater amounts of body fat alter the release of vitamin D into the bloodstream) are also at risk. National health statistics taken in 2001-2004 indicates that the majority of children and adults, and almost all African Americans and Mexican Americans, are deficient in this vitamin. This is most likely due to changes in body mass, lower milk consumption and increased sunscreen use. Vitamin D deficiency in adults results in osteomalacia which is characterized by a lack of bone strength and density; muscle and joint pain.

Food Sources

Vitamin D is not naturally present in many foods. It is concentrated in fish liver oils (e.g., cod liver oil) and the skin of cold water fish (salmon, mackerel, herring and sardines). The majority of vitamin D intake comes from fortified foods such as orange juice, milk, cereal, yogurt and margarine. Lower levels of vitamin D can also be found in liver, egg yolks, butter and dark green leafy vegetables.

You may start noticing a brand called Monterey Mushrooms that provide 400 IUs of vitamin D in a 3-ounce serving of their white, brown and portabella mushrooms. In a collaborative effort with the USDA’s Agricultural Research Service, Monterey Mushrooms discovered that mushrooms have a natural level of vitamin D and when exposed to ultraviolet light they synthesize vitamin D that is stable, maintaining its nutritional value even after cooking or freezing.

Recommended Dietary Allowance

The Recommended Dietary Allowance (RDA) for vitamin D increases with age. In women under 50 years, the RDA is 200 IUs. In women 50 to 70 years, the RDA is 400 IUs. And, in women over 70, the RDA is 600 IUs. The Tolerable Upper Intake Level for vitamin D is 2,000 IUs in men and women of all ages.

If you look on a nutritional supplement facts panel, you'll notice the Amount Per Serving for vitamin D and the % Daily Values is at located at the top of the panel. The Amount Per Serving is based on the Reference Daily Intake (RDI) for this nutrient which is considered to be sufficient to meet the requirements of nearly all (97–98%) healthy individuals in each life-stage and sex group. The Reference Daily Intake for vitamin D is 400 IUs which represents 100% of the Daily Values.

Substantial published studies justify a reevaluation of the RDA in healthy populations. Researchers recommend increasing the RDA for adults from 400 to 800 IU and increasing the Upper Intake Level from 2,000 to 10,000 IU. Medical organizations like the American Academy of Pediatrics also recommend increasing the RDA in children from 200 to 400 IU.

To address this issue, the Food and Nutrition Board (FNB) established an expert committee to review the Dietary Reference Intakes (DRIs) for vitamin D (and calcium). The current DRIs for this nutrient were established in 1997. The FNB is expected to issue its report in November 2010.


Corticosteroid medications such as prednisone, bile acid sequestrants (cholesterol lowering drugs), heparin (an anticoagulant) and fat blocking weight loss drugs can interfere with vitamin D metabolism, absorption or activation. Conversely, hormone replacement therapy (HRT) may increase blood levels of vitamin D.

Vitamin D may interfere with the effectiveness of calcium channel blockers; a class of drugs used for high blood pressure, to control heart rate and angina pain.

VitaMedica Products

In our Recovery Product line, the Recovery Support Program and Clinical Support Program are formulated with 375 IUs of vitamin D3. Our Anti-Aging Products are formulated with a higher level of vitamin D3 to ensure adequate intake of this nutrient on a daily basis. Energy Support and Bone Support each contain 450 IUs of vitamin D3. Combined, these two products comprise our Multi-Vitamin & Mineral, providing 900 IUs of vitamin D3 daily. Anti-Aging Formula is formulated with slightly less vitamin D3 (600 IUs).

Last updated July 1, 2018

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