Vitamin D: Facts & Figures

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For the last 80 years, scientists have focused on the link between vitamin D and calcium—the vitamin is necessary for calcium absorption and its deficiency leads to rickets. But this is just the visible tip of the iceberg.

Beyond calcium absorption, vitamin D plays a role in cell-cycle and immune regulation, because it is involved in gene-expression processes. This lesser-known role actually accounts for about 85 percent of the metabolism of vitamin D everyday in the human body. This means that, depending on which type of cells it affects, vitamin D inadequacy can be involved in many other dysfunctions, including cardiovascular diseases and cancer.

Cardiovascular Diseases: A study of 1,739 participants, showed that vitamin D deficiency at less than 15 ng/mL and less than 10 ng/mL is associated with a 50-percent and 80-percent increase in the risk of developing cardiovascular disease, respectively.

Hypertension: Further evidence shows that vitamin D deficiency leads to a three-fold increased risk of developing hypertension.

Cancer: Additionally, vitamin D has been shown to reduce cancer risks for a number of cancers including colon, breast, prostate, lung cancers and lymphoma.

The two major forms of vitamin D are D2 (or ergocalciferol) and D3 (or cholecalciferol). Vitamin D3 is produced physiologically and is more effective at increasing the levels of circulating vitamin D hormone, but, at appropriate levels, both vitamin D2 and vitamin D3 are efficient. There is no difference in terms of availability between vitamin D in fortified food or in supplement form.

Vitamin D intake has been shown to be safe up to at least 10, 000 IUs a day, and no case of intoxication has been reported below 30,000 IUs. Evidence shows all functions improve when serum levels of vitamin D are at 80 to 100 nmol/L (achieved with 4,000 IUs to 5,000 IUs a day). This is much higher than current recommendations, which call for 400 IUs to 800 IUs a day for adults under 50 years old.

Groups at greater risk of deficiency include:

  • Elderly: A 70-year-old person has 25 percent of the capacity to produce cholecalciferol compared with a healthy young adult.
  • Infants: While infant formula is generally fortified with vitamin D, breast milk does not contain significant levels of vitamin D. Infants who are exclusively breastfed are likely to require vitamin D supplementation beyond early infancy, especially at northern latitudes.
  • Obese Individuals: Obesity may result in lower levels of the circulating form of vitamin D, probably because of reduced bioavailability, as the cholecalciferol is sequestered deep in the body fat.
  • Sunscreen users: The use of sunscreen with a sun protection factor (SPF) of 8 inhibits more than 95 percent of vitamin D production in the skin. To avoid vitamin D deficiency, it is recommended that people consider supplementation along with sunscreen use.
  • Dark-skinned Individuals: Dark-skinned people may require extra vitamin D to avoid deficiency at higher latitudes, particularly during the winter months.
  • People With Renal/Hepatic Disorders: Conditions such as hepatic or renal disorders, or, rarely, a number of hereditary disorders can impair conversion of vitamin D into active metabolites.

Source: Irish Medical Times

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