desirable levels of vitamin D and supplementation
21 December, 2015:
In a recent article in JAMA, Hansen and colleagues presented a randomized clinical trial of treatment of vitamin D insufficiency in postmenopausal women . The trial compared the effects of placebo, low-dose cholecalciferol, and high-dose cholecalciferol on 1-year changes in total fractional calcium absorption, bone mineral density (BMD), timed-up-and-go and five sit-to-stand tests, and muscle mass in postmenopausal women with vitamin D insufficiency. This randomized, double-blind, placebo-controlled trial studied a total of 230 postmenopausal women 75 years or younger with baseline levels of 25-hydroxyvitamin D or 25(OH)D of 14–27 ng/ml and no osteoporosis. Outcome measures were 1-year change in total fractional calcium absorption using two stable isotopes, BMD and muscle mass, using dual-energy X-ray absorptiometry. After baseline absorption was controlled for, calcium absorption increased by 1% (10 mg/day) in the high-dose arm but decreased by 2% in the low-dose arm (p = 0.005 vs. high-dose arm) and 1.3% in the placebo arm (p = 0.03 vs. high-dose arm). We found no between-arm changes in spine, mean total hip, mean femoral neck, or total body BMD, trabecular bone score, muscle mass, and timed-up-and-go or five sit-to-stand test scores. Likewise, we found no between-arm differences for number of falls, number of fallers, physical activity, or functional status.
High-dose cholecalciferol therapy increased calcium absorption, but the effect was small and did not translate into beneficial effects on BMD, muscle function, muscle mass, or falls. We found no data to support experts’ recommendations to maintain serum 25(OH)D levels of 30 ng/ml or higher in postmenopausal women. Instead, we found that low- and high-dose cholecalciferol were equivalent to placebo in their effects on bone and muscle outcomes in this cohort of postmenopausal women with 25(OH)D levels less than 30 ng/ml.
In the US National Library of Medicine , we can read that vitamin D includes both cholecalciferol and ergocalciferol. Vitamin D is a hormone since it is formed in the skin by action of ultraviolet rays upon the precursors, 7-dehydrocholesterol and ergosterol, and acts on vitamin D receptors to regulate calcium in opposition to parathyroid hormone (PTH). But, because in our times, exposure to sunlight is so difficult, vitamin D is really a vitamin, as we need take vitamin D with meals; however, we have another problem: a diet does not usually contain a sufficient amount of vitamin D, as it is present in very few foods.