Highly prevalent among postmenopausal women, vitamin D deficiency is linked to numerous conditions such as osteoporosis, cardiovascular diseases, metabolic syndrome, autoimmune disorders, and cancer.
To study the factors that affect vitamin D status in postmenopausal women and responses to vitamin D supplementation, a systematic review was conducted by researchers from Malaysia and the UAE.
The review analysed 19 studies that were published on several platforms up until October 2022, including MEDLINE, Embase, Web of Science, Scopus, and clinical trial registries.
A total of 4,677 postmenopausal women from 13 countries, aged between 51 and 78, were included. The duration of the studies ranged from eight weeks to three years.
The different trials investigated the effects of various forms and dosages of vitamin D supplementation on overall vitamin D status.
Six trials administered vitamin D as a dietary supplement (fortified milk, yogurt or cheese), while other trials provided vitamin D in the form of oral supplements of vitamin D2, vitamin D3, and calcidiol.
Vitamin D metabolites called 25-hydroxyvitamin D (25(OH)D) in blood serum were measured to determine one’s vitamin D status. Vitamin D deficiency was defined as a 25(OH)D level of less than 12 ng/mL, while 25(OH)D concentrations between 12 to 20 ng/mL were identified as vitamin D insufficiency.
It was found that a single oral dose of 250,000 to 300,000 IU of vitamin D per day increased 25(OH)D significantly more than the usual daily recommended intake of 800 IU.
“With the administration of high doses, 25(OH)D returned to baseline after three months. This highlighted that a maintenance dose with regular intervals would be reasonable for those undergoing single-, large-dose vitamin D supplementation.
“Although there was no agreement on the optimal doses or concentrations, clinical practice can benefit from the fact that higher doses were shown to be safe and effective in specific groups,” said the authors.
In addition, the review also discovered that participants who had vitamin D deficiency showed a better response to vitamin D supplementation.
“The lower the 25(OH)D baseline level, the bigger the response to vitamin D supplementation,” the authors added.
Other notable findings
It was also found that while vitamin D2 was effective at raising serum 25(OH)D levels, a higher dosage is required than vitamin D3, making the latter a more effective option.
The effect of sun exposure and seasons on the response to vitamin D supplementation was noted by different studies.
One of them indicated that sunlight exposure had lower efficacy compared to vitamin D supplementation. Similarly, a meta-analysis of seven trials also suggested that vitamin D3 intake significantly increased 25(OH)D levels, compared to sun exposure alone.
Furthermore, one study observed a pronounced peak in 25(OH)D levels from June to September, the summer season in the Northern Hemisphere. This underlined the importance of vitamin D supplementation during the winter season.
According to the findings, Vitamin D-fortified foods could be a valuable source of elevating 25(OH)D levels, especially when sun exposure is limited.
“Fortified milk with vitamin D was demonstrated to be beneficial in boosting vitamin D status in postmenopausal women who are at increased risk due to insufficient sun exposure and calcium consumption,” said the authors.
Despite consistency in the findings, it should be noted that this review’s ability to provide conclusive recommendations was limited by the diverse assessment and intervention methods used across all studies.
“Determinants and Effects of Vitamin D Supplementation in Postmenopausal Women: A Systematic Review”
Authors: Mohammed M. Hassanein, et al