Maintaining Adequate Vitamin D Levels is Positively Correlated with Bone Health in Postmenopausal Women

by | May 23, 2023 | 2023, Bone Health, Vitamin D - Recommended Levels, Women's Health - Bone Health

Written by Taylor Woosley, Staff Writer. When vitamin D intake was raised by 1 µg/1000 kcal, there was an increase of 0.226 ng/mL and 0.314 ng/mL in the serum 25(OH)D levels during the summertime and wintertime, respectively (p < 0.01, p < 0.001, respectively). 

woman doing yogaVitamin D is a fat-soluble prohormone that plays an essential role in bone mineral metabolism, being involved in calcium and phosphorus metabolism and skeletal homeostasis1. The active form of vitamin D (1,25(OH)2D), not only stimulates osteoclastic bone resorption, and osteoblast function and decreases parathyroid hormone secretion but also has extra skeletal functions such as enhancing muscular function and the immune system2. Over the past two decades, epidemiological studies have suggested that low vitamin D status may be associated with a variety of health risks such as osteoporosis and cardiovascular disease3.

Postmenopausal women are at a risk of vitamin D deficiency as increased age, increased adiposity, and inadequate sun exposure lead to decreased blood vitamin D levels4. Postmenopausal women are prone to develop serious complications such as osteoporosis and consequent catastrophic fractures5. With the recognition of widespread vitamin D deficiency and its impact on the health of postmenopausal women, the importance of a thorough understanding of the determinants of vitamin D supplementation in this population is becoming more widely recognized6.

Shin et al. conducted a study to identify the factors affecting bone mineral density (BMD) and the 25(OH)D levels in Korean postmenopausal women by assessing their dietary status during four seasons in a year, measuring BMD measurements twice, and analyzing biochemical indices and their results. Inclusion criteria consisted of postmenopausal women aged 45-69 years who had undergone menopause over 1 year ago, who were neither underweight nor obese based on the body mass index (BMI) status (18.5 ≤ BMI < 30 kg/m2), women who had at least two regular meals per day, and women who did light exercise for at least two or three times a week for a minimum of 10 minutes. 96 subjects completed the study.

Outdoor time was self-reported by participants every season and included the total duration of outdoor activities during a day on weekdays and weekends in every season. Physical activity was evaluated using the short form of the International Physical Activity Questionnaire (IPAQ) and divided into three physical activity stages. Subjects completed self-reported dietary records for 3 days, including 1 day on the weekend and 2 weekdays. Blood samples were obtained during a fasted state to measure calcium, intact parathyroid hormone (iPTH), serum 25(OH)D, and bone alkaline phosphatase (BAP) levels.

Subjects’ general characteristics and lifestyle, sun exposure, biochemistry, BMD, and nutrient intake were expressed as frequencies or means ± standard errors. The paired t-test and Wilcoxon signed-rank test were utilized for regularly normalized variables and nonparametric variables, respectively. Participants were categorized into either a group below the criteria or a group above the criteria of the Institute of Medicine vitamin D deficiency cut-off (20 ng/mL) to investigate the associations between the annual average serum 25(OH)D levels and BMD. Significant findings of the study are as follows:

  • Serum calcium levels were significantly higher in the summertime than in the wintertime (8.99 ±24 vs. 8.88 ± 0.28 mg/dL, p < 0.01). In contrast, wintertime values of iPTH (40.72 ± 12.02 vs. 35.97 ± 10.36 pg/mL, p < 0.001) and BAP (14.66 ± 4.11 vs. 14.12 ± 4.39 µg/L, p < 0.05) were significantly higher than those in the summertime.
  • In the summertime, no biochemical indices showed a significant correlation with the BMD. In the wintertime, the BMI was positively correlated with the BMDs of all the skeletal sites (L-spine, p < 0.05; femoral neck, p <0.01; total hip, p < 0.001).
  • When vitamin D intake was raised by 1 µg/1000 kcal, there was an increase of 0.226 ng/mL and 0.314 ng/mL in the serum 25(OH)D levels during the summertime and wintertime, respectively (p < 0.01, p < 0.001, respectively).

Results show that the average levels of serum 25(OH)D in postmenopausal women were approximately 1.9-fold higher in the annual average data and 1.7-fold higher in the summertime data. This data suggests that increased sun exposure in postmenopausal women is a major factor in increasing serum 25(OH)D levels, along with the increased intake of vitamin D supplementation. Study limitations include the potential affect of COVID-19 on participants’ lifestyle factors and dietary intake.

Source: Shin, Hye Ran, Ye Jin Lee, and Sun Yung Ly. “Optimal Serum 25 (OH) D Levels and Vitamin D Intake in Korean Postmenopausal Women.” Nutrients 15, no. 8 (2023): 1856.

© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

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Posted May 23, 2023.

Taylor Woosley studied biology at Purdue University before becoming a 2016 graduate of Columbia College Chicago with a major in Writing. She currently resides in Glen Ellyn, IL.

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