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About
Vitamin D is a hormone that is produced when sunlight is absorbed by the skin. Vitamin D insufficiency has been recognized as a problem in areas where sun exposure is limited, especially in the wintertime. In addition, the more pigmented the skin is, the less capable it is of utilizing sunlight to make vitamin D. Vitamin D plays an important role in helping the body absorb calcium and in building strong bones. It has also been shown to improve muscle function in the elderly. As we get older, our vitamin D levels in the blood go down and this may increase the risk for falls and fractures. If we can improve vitamin D status as we age, we may be able to improve muscle strength and decrease the risk of falls and fractures.
Full description
The long-term goal of this project is to develop strategies for the prevention of osteoporotic fractures in African Americans. Most intervention studies have excluded African Americans because of the erroneous belief that osteoporosis is not a major health problem in this population. In fact, the incidence rate of hip fracture in blacks is 50% of the rate in whites. Since longevity is increasing in the black population, osteoporotic fractures will become an even greater problem for this ethnic minority in the future. Furthermore, morbidity and mortality from osteoporotic fractures is greater in blacks. The elderly require higher intake of vitamin D to prevent bone loss resulting from secondary hyperparathyroidism. Calcium with sufficient vitamin D supplementation may decrease fractures in elderly white populations as a result of reduction in bone loss and falls (improved physical performance). The only fracture intervention study to include African Americans-the Women's Health Initiative-used an inadequate dose of vitamin D (400 IU), a dose unlikely to achieve the vitamin D status proposed by U.S. experts: serum 25 hydroxyvitamin D [25(OH)D] concentration above 75 nmol/L. No calcium/vitamin D intervention studies on fall prevention or physical performance have included African Americans.
As a result of increased skin pigmentation, blacks synthesize less vitamin D from sun exposure. As a result, serum 25(OH)D levels are often in the "insufficient" range. This is accompanied by secondary hyperparathyroidism, but adult blacks have a relative skeletal resistance to PTH, so that they have lower bone turnover. They also have more efficient renal conservation of calcium starting in childhood. Addition of vitamin D3 to a calcium-sufficient African American postmenopausal population does not prevent bone loss. The calcium/vitamin D requirements of black adults may be lower than white adults through midlife. However, the elderly require more vitamin D to produce the higher 25(OH)D levels required to overcome the hyperparathyroidism associated with aging. The skeleton of elderly African Americans appears to be susceptible to the increasing parathyroid hormone levels of old age. Bone loss accelerates and bone turnover markers increase in elderly African Americans just as in whites. The specific aims of this project are to determine if dietary supplementation with calcium/vitamin D will safely reduce bone loss and bone turnover and improve physical performance in elderly African Americans. We will enroll 250 African American women in a four-year vitamin D3 intervention trial where serum 25(OH)D will be maintained at an optimum level above 75 nmol/L. Adequate calcium intake will be ensured. Functional markers of vitamin D including bone density, serum PTH, and bone turnover will be measured. The NIH Conference on Vitamin D and Health in the 21st Century, September 5-6, 2007 concluded that research in this population is a high priority.
Enrollment
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Inclusion criteria
Exclusion criteria
Serum 25(OH)D levels ≤ 20 nmol/L or ≥ 65 nmol/L.
BMD total hip below - 2.5 standard deviation (using NHANES III adult young white men and women as the point of reference) or history of osteoporotic fracture.
Moderate to severe fracture in one or more vertebrae by Instant Vertebral Assessment on DXA.
Treatment with HRT, SERMS, calcitonin, PTH, androgens, bisphosphonates, phosphate or anabolic steroids during 6 months prior to entry.
Use of systemic corticosteroids (oral or IV) within the last year at an average dose of greater than 5 mg per day of oral prednisone or equivalent for a period of three months or more prior to screening.
Hypercalcemia (serum calcium > 10.6 mg (dl) or history of primary hyperparathyroidism.
History of chronic liver disease, chronic renal insufficiency, Parkinson's, metabolic bone disease, hematologic tumors, rheumatologic disease requiring steroids, malabsorption or new diagnosis or active treat-ment of cancer 12 months prior to inclusion.
Use of medications that influence bone metabolism (e.g. anticonvulsants).
Significant deviation from normal in either: history, physical examination or laboratory tests as evaluated by the Principle Investigator. Participants with a history of hypercalciuria, nephrolithiasis and active sarcoidosis will also be excluded.
Participation in another investigational trial 30 days prior to screening.
Spinal disease that affects interpretation of bone densitometry like scoliosis with a Cobb angle greater than 15o, history of surgery at lumbosacral spine.
Bilateral hip replacement.
Currently smoking more than 10 cigarettes daily.
Body width on DXA > 25 cm.
Patients who are deemed unsafe to perform muscular function testing as evaluated by the investigator.
---------- Study participants should live close to the study site, as this study requires multiple visits over a four year period.
Primary purpose
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Interventional model
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260 participants in 2 patient groups, including a placebo group
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Data sourced from clinicaltrials.gov
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