Treatment of Vitamin D Insufficiency
Treatment of Vitamin D Insufficiency
The purpose of this study is to answer the following questions: Does vitamin D increase
 calcium absorption, bone mass and muscle mass and function in women past menopause who have
 mildly low vitamin D levels? Do these benefits require prescription-strength vitamin D, or is
 an over the counter vitamin D dose enough?
Osteoporosis is a major health problem in postmenopausal women. At age 50, half of women will
 suffer an osteoporotic fracture in their remaining lifetime, causing increased disability and
 mortality. Vitamin D deficiency, defined as a serum 25(OH)D <15 ng/mL, contributes to
 osteoporosis via decreased calcium absorption (Ca·Ab), secondary hyperparathyroidism (HPT),
 increased bone resorption and decreased bone mineral density (BMD). Thus, experts agree that
 patients with vitamin D deficiency should receive vitamin D therapy.

 Vitamin D insufficiency (VDI) is a milder form of hypovitaminosis D defined as a 25(OH)D
 level between 15 and 30 ng/mL regardless of parathyroid hormone (PTH) status. Experts
 disagree on whether to treat VDI, as the clinical benefits of therapy are uncertain. Some
 experts insist the optimal 25(OH)D level is ≥30 ng/mL. By contrast, both the Food and
 Nutrition Board and NIH Evidence Report No. 158 state that insufficient evidence exists to
 declare the optimal serum 25(OH)D for bone health, despite review of ~170 studies.
 Consequently, the Food and Nutrition Board cannot determine a recommended daily allowance for
 vitamin D. Confusion over the optimal 25(OH)D level results, in part, because previous trials
 failed to recruit subjects based on initial 25(OH)D levels and/or failed to target or achieve
 25(OH)D levels ≥30 ng/mL. Moreover, secondary HPT, the proposed mechanism by which VDI causes
 bone loss, occurs in only 10% to 33% of people with VDI. As such, people with VDI and normal
 PTH might not experience clinical benefits from vitamin D therapy. VDI is widespread,
 affecting 26% to 39% of postmenopausal American women with and without osteoporosis.
 Therefore, determining the ideal 25(OH)D level for optimal calcium homeostasis and bone
 health is of utmost clinical and public health importance. Our overall goal, congruent with
 Healthy People 2010 objective 2-9, is to evaluate the effect of vitamin D therapy on the risk
 of osteoporosis in postmenopausal women with VDI, as reflected by changes in Ca·Ab, BMD and
 muscle fitness. Our second goal is to evaluate whether a high-dose vitamin D regimen, chosen
 to achieve and maintain a 25(OH)D level ≥30 ng/mL, is superior in its effects on study
 outcomes compared to a low-dose vitamin D regimen that can permit continued VDI.

 We will conduct a randomized, placebo-controlled double-blind trial of low-dose and high-dose
 vitamin D in postmenopausal women with vitamin D insufficiency in order to investigate the
 following aims:

 1. To evaluate the effect of vitamin D3 therapy on Ca·Ab in postmenopausal women less than
 or equal to 75 years old with VDI. Sub-aims include the investigation of subject
 variables influencing Ca·Ab and 25(OH)D levels at baseline and one month, the accuracy
 of oral isotope plasma levels for Ca·Ab measurement and the ability of a questionnaire
 to identify patients with low vitamin D status.

 2. To evaluate the effects of vitamin D3 therapy on the 12-month change in BMD and bone
 turnover in the same trial conducted for Aim 1. Sub-aims include the identification of
 subject variables significantly influencing change in BMD and an evaluation of the
 relationship between changes in Ca·Ab and changes in BMD.

 3. To evaluate the effect of vitamin D therapy on muscle mass and functional capacity in
 the same trial conducted for Aim 1. We will measure muscle mass by whole body bone
 densitometry and assess muscle function using the Timed Up and Go (TUG) Test and the
 modified Stanford Health Assessment Questionnaire (HAQ) score. Sub-aims include the
 identification of subject variables significantly influencing muscle outcomes.
Inclusion Criteria:

 -  Vitamin D insufficiency, defined as a serum 25(OH)D 16 to 25 ng/mL by high performance
 liquid chromotography assay

 -  Women ≥ 5 years past the date of last menses or bilateral oophorectomy, or ≥ 60 years
 old if they had prior hysterectomy without bilateral oophorectomy

 -  Total dietary and supplemental calcium intake < 600 mg daily but ≤ 1,400 mg daily,
 based on a food frequency questionnaire

 Exclusion Criteria:

 -  Women > 75 years old

 -  Hypercalcemia (serum calcium corrected for albumin > 10.4 mg/dL)

 -  Nephrolithiasis by medical record or patient report

 -  Inflammatory bowel disease, malabsorption or chronic diarrhea

 -  Stage 3, 4 or 5 Chronic Kidney Disease based on the Modification of Renal Diet (MDRD)
 formula

 -  Use of bone-active medications within the past 6 months including bisphosphonates,
 estrogen compounds, calcitonin, teriparatide, oral corticosteroids and anticonvulsants

 -  Allergy or intolerance to orange juice

 -  Allergy or intolerance to sunscreen

 -  Prior adult clinical fragility fracture of the hip, spine or wrist or a T-score below
 -2.5 at the lumbar spine or femur