Postmenopausal bone loss can be limited by high doses of Vitamin D
Postmenopause: bone loss can be limited with vitamin D
Daily intake of 1000 IU of Vitamin D, corresponding to 25 µg, can slow down bone density loss, a condition that is very common among women in old age. For lower doses, on the other hand, such as 400 IU daily, the vitamin is unable to perform this protective action.
This is according to a study conducted by researchers at the University of Aberdeen, Scotland, and published in the pages of the Journal ofBoneand Mineral Research. The finding supports the decision of the Institute of Medicine (Scotland) to raise the recommended daily dose of vitamin D from 400 IU to 600 IU, for children and adults aged 1 to 70 years.
Vitamin D and its functions
Vitamin D is a fat-soluble vitamin that can be introduced into the body through food, or synthesized in the human body from a precursor, by the action of sunlight. It exists in several forms, the most common being ergocalciferol (D2) of plant origin, and cholecalciferol (D3) of animal origin. The roles of vitamin D in the human body are varied: it intervenes in the absorption of calcium and phosphorus in the intestines, modulates the functioning of the immune system, and most importantly regulates bone growth, development, and mineralization. Vitamin D requirements vary according to age and health conditions. In postmenopausal women for example, vitamin D is very important because the lack of estrogen, which helps regulate the absorption and deposition of calcium in bone, can promote loss of bone mineral tissue and thus osteoporosis. Vitamin D concentration in the body is detected by measuring one of its metabolites, 25(OH)D (25-hydroxycholecalciferol). Recent studies have shown that the concentration of 25(OH)D in the blood should be at least 75 nmol/L
High doses to maintain the optimum of 25(OH)D
During the study, 265 women between the ages of 60 and 70 were recruited for a one-year trial. One randomly formed group of them received a 400 IU supplement of Vitamin D3 each day, another 1000 IU, and one received a placebo. Analyzing after 12 months the 25(OH)D concentration of each, it was found that in the women who had taken 1000 IU of Vitamin D, the metabolite had increased by an average of 42.6 nmol/L. In those who had taken only 400 IU it had increased by 31.6 nmol/L, while it had even decreased by 4.1 nmol/L in the placebo-treated women. In addition, there had been a loss of bone mineral density, in the hip, of 0.05% in the group that had received 1000 IU vitamin D and 0.6% in those that had received the lower dose and placebo Blood tests at one month after the end of treatment revealed that all subjects given the supplement had a 25(OH)D concentration of 25(OH)D at or above 25 nmol/L. In contrast, 40% of women treated with placebo did not reach this value. The 50 nmol/L concentration of 25(OH)D was not reached by 16% and 50% of those who had received 1000 IU and 400 IU of supplement, respectively, and by 94% of women who had taken placebo. The percentage of subjects treated with 1000 IU vitamin D3 that did not reach the threshold value of 75 nmol/L increased from 48% to 83%, 30 days after stopping treatment.
Long-term positive effects?
Based on the results, the researchers identified that a daily dose of 1,000 IU of vitamin D is needed to raise 25(OH)D to a protective concentration of 76 nmol/L, which is useful for maintaining bone health and reducing mineral density loss. To maintain this circulating 25(OH)D value, however, treatment should not be interrupted. It remains to be understood whether prolonged supplementation can actually maintain the positive effects over the long term in a way that preserves the population from the risk of Vitamin D deficiency.
Source: Helen M Macdonald, Adrian D Wood, Lorna S Aucott, Alison J Black, William DFraser,Alexandra Mavroeidi, David M Reid, Karen R Secombes, William G Simpson, Frank Thies. "Hip bone loss is attenuated with 1000 IU but not 400 IU daily vitamin D3: A 1-year double-blind RCT in postmenopausal women " Journal of Bone and Mineral Research.
