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 levels2,3
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 exposure2,3
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
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]
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:
- Rheumatoid arthritis
- Multiple sclerosis
- Type 1 diabetes
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