The Effect of Season and Vitamin D Supplementation on Bone Mineral Density in Healthy Women: A Double-Masked Crossover Study

Abstract

Vitamin D status is known to be an important determinant of bone mineral density (BMD). There is a significant seasonal variation in serum vitamin D, and some studies have reported an associated seasonal variation in BMD. The present study was devised to investigate whether a seasonal variation in BMD could be detected in healthy normal subjects, along with associated variations in serum parathyroid hormone (PTH), intestinal calcium absorption and biochemical markers of bone turnover. A second aim was to investigate whether, if such variations were identified, they could be suppressed by vitamin D supplementation. The subjects were 70 healthy female volunteers (mean age 47.2 years, range 24-70 years) recruited into a double-masked crossover study and followed over 2 years. During the first year 35 subjects received a daily oral supplement containing 800 IU (20 micrograms) cholecalciferol (group 1) and 35 subjects received a placebo preparation (group 2). During the second year the treatment each group received was reversed. Lumbar spine (L1-L4), left proximal femur and total body BMD were measured by DXA at 3-month intervals. Serum 25-hydroxyvitamin D (25-OHD), serum PTH, bone markers (bone-specific ALP (BSAP) and urinary crosslinks (DYPD/creatinine)) and calcium absorption were also measured at each visit. Cholecalciferol treatment increased serum 25-OHD by 25.4 nmol/l (p < 0.001), while a reciprocal decrease in serum PTH of 6.6 ng/l (p = 0.011) was seen in subjects in the lowest quartile of baseline serum 25-OHD. The treatment had no significant effect on spine, femur or total body BMD, calcium absorption or bone markers. When Fourier analysis was used to analyze the data for seasonal effect (defined as twice the amplitude of the 1-year period variation) a highly significant effect for 25-OHD of 18 nmol/l (p < 0.001) was found. However, no effect was found for BMD, PTH, calcium absorption or bone markers. The analysis set a 95% confidence limit to the seasonal effect of less than 0.6% for spine, total hip and total body BMD. It was concluded that in the population of healthy women studied there was no evidence of seasonal variation in spine, femur or total body BMD, serum PTH, calcium absorption or bone markers. Vitamin D supplementation was found to have no effect on BMD.

How Much Vitamin D3Do the Elderly Need?

“…Our results are consistent with those of Patel et al [23], Harris & Dawson-Hughes [8], who marked similar changes in S-25-OHD concentrations in groups receiving 10 g and 20 g vitamin D 3 /d. Yet, some studies [24 -27] have reported greater increments which refer to stronger response to supplementation.…”

Physical performance and life quality in postmenopausal women supplemented with vitamin D: a two-year prospective study

“…In the present study, no changes were detected in serum PTH levels in subjects who were treated with 600 mg/d elemental calcium and 800 IU/d cholecalciferol. Patel et al [24] examined the effect of cholecalciferol on bone metabolism in healthy adult women who ranged in age from 23 to 70 years (mean age 45.3 years). The results revealed that supplementation with 800 IU/d cholecalciferol for 12 months increased serum 25(OH)D levels, whereas no effects on serum PTH or bone turnover marker levels were detected.…”

Bone Mineral Density and Metabolism at an Early Stage of Menopause When Estrogen and Calcium Supplement Are Not Used and without the Interference of Major Confounding Variables

“…The best clinical indicator of this vitamin status is the serum 25(OH)D 3 level which varies inversely with PTH (parathyroid hormone) levels [7]. Patel et al [8] demonstrated a highly significant seasonal effect on 25(OH) 2 D 3 concentrations but not on BMD and PTH. To our knowledge, only one study has been reported on the vitamin D status in the phase of early postmenopausal bone loss [9].…”