The Vitamin D Story

How much vitamin D is enough, and why is it important?

It is estimated that >50% of postmenopausal women treated for osteoporosis have inadequate vitamin D levels¹

Sun exposure is a major source of vitamin D and levels are affected by sun exposure potential within populations. Some key considerations affecting vitamin D levels are:

• Reduced sun exposure (higher latitudes, limited outdoor activity, winter season, etc) can significantly impact vitamin D levels^2,3

• Wearing sunscreen (SPF 8 or more) reduces the skin's ability to produce vitamin D by 95%⁴

• Women with darker skin may need as much as 5 to 10 times longer skin exposure^2,3

• Older individuals are less efficient in making vitamin D²

"...vitamin D deficiency is highly prevalent in the US and worldwide, affecting as many as one third to one half of otherwise healthy middle-aged to elderly adults..."
Medscape. Vitamin D Deficiency: A Risk Factor for Heart Disease? January 7, 2008⁵

Fracture risk reduction, calcium, and the role of vitamin D₃

The major physiologic function of vitamin D is to maintain the serum calcium at a physiologically acceptable level.⁶ As such, vitamin D plays a major role in calcium absorption and bone health.⁷ It is essential for ensuring adequate absorption of calcium from the GI tract.³

• A low serum vitamin D concentration leads to decrease in calcium absorption³

• Gross vitamin D deficiency in women can reduce dietary calcium absorption by half³

Vitamin D supplementation has also been shown to help reduce the likelihood of falling, in a certain population, by more than 20%⁸, which is important for patients with already compromised bone health. Adequate vitamin D intake must also be considered when prescribing osteoporosis drug therapy.

• Most of the pivotal efficacy studies done with bisphosphonates required calcium + vitamin D supplementation.⁹

• The NIH Women's Health Initiative study¹⁰ used supplementation that provided 400 IU of vitamin D₃ per day, along with 1000 mg of calcium, an OS-CAL formulation. [In addition to baseline mean total intake of 1148 mg/day vs 1154 mg/day calcium and 365 IU/day vs 368 IU/day of vitamin D for the active and placebo groups respectively]

  • At these levels, this formulation achieved a 29% reduction in hip fracture risk when > 80% of study medication was taken

Vitamin D benefits beyond osteoporosis have being cited¹¹

Vitamin D has a broad range of activities beyond its role in calcium homeostasis. Research has identified the following physiologic areas where vitamin D may play a role:

• Cancer
• Rheumatoid arthritis
• Multiple sclerosis
• Type 1 diabetes
• Hypertension

NOF vitamin D₃ recommendations have changed⁷

New vitamin D₃ recommendations for adults 50+ are 800 to 1000 IU per day from all sources.

"NOF revised its recommendations after careful consideration and review of a growing body of evidence that calcium and vitamin D₃ deficiency is widespread throughout the world as well as in the U.S., particularly in adults 50 and older."
National Osteoporosis Foundation Website