Vitamin D in the Different Stages of Women’s Lives

Posted May 26, 2020

Vitamin D deficiency is highly prevalent worldwide and is considered a public health problem. Despite its name, vitamin D is considered a hormone, being essential for the maintenance of calcium levels [U1] and of bone health. Recent studies also point out to a possible association with arterial hypertension, diabetes, metabolic syndrome, some types of cancer, autoimmune and infectious diseases.

Once in circulation, 85 of 90% of circulating vitamin D are bound to a carrier protein produced by the liver and called vitamin D-binding protein (DBP). The synthesis of this protein is regulated by estrogens, and its concentration is positively correlated with total vitamin D levels. The occurrence of genetic variations, or polymorphisms, in the DNA sequence of this protein may lead to qualitative and/or quantitative changes associated with a higher risk of vitamin D deficiency in the population.

The Survey

The objective of the study, developed by the INTC team, was to assess what the scenario would be in a female population with no established clinical diseases.

According to the biologist Betânia Rodrigues Santos*, “it was necessary to evaluate the behavior of vitamin D and some genetic variants, related to its metabolism, among apparently healthy women, because the presence of diseases could confound information”.

The survey was conducted with almost 450 women, aged from 20 to 72 years old, in a wide universe that included different stages of women’s reproductive life. “Our research studied the frequency of vitamin D deficiency in women with no specific clinical conditions, assessed DBP, and, based on these data, calculated free and bioavailable vitamin D”, explained the biologist.

The participants were divided according to their current life period: reproductive, menopausal transition, and postmenopause. “We observed that nearly 40% of participants had vitamin D deficiency, and that women at menopausal transition or at postmenopause showed lower DBP levels. This possibly resulted from a decrease in estrogen levels in this life stage. However, total, free and bioavailable vitamin D remained stable, regardless of participants’ life stage”, said the researcher.

Research Challenges

The study found that circulating vitamin D levels were equal in the study groups; likewise, the proportion of women with vitamin D deficiency was also similar in the different life stages. In addition to revealing this adaptive mechanism, responsible for maintaining vitamin D levels stable in older women despite the significant decrease in DBP, the study corroborates that the measurement of total 25 (OH) vitamin D is a reliable method to investigate vitamin D deficiency in this population.

Genetic Evaluations

Considering the influence of carrier globulin on total vitamin D, three DBP polymorphisms (rs2282679, rs4588 and rs7041) were assessed. The combination of two polymorphisms assessed simultaneously (rs4588 and rs7041) is the genetic basis for the three main circulating forms of DBP, known as GC1f, GC1s and GC2. The rs2282679 polymorphism and the GC2 form were associated with a greater risk for vitamin D deficiency. These results suggest that the presence of a given DNA sequence may contribute to vitamin D deficiency, although it is not a determining factor for this condition.

The results of this study were recently published on Plos One:

Santos BR, Costa NC, Silva TR, Oppermann K, Magalhães JA, Casanova G, Spritzer PM. Prevalence of vitamin D deficiency in women from southern Brazil and association with vitamin D-binding protein levels and GC-DBP gene polymorphisms. PLoS One. 2019 Dec 12;14(12):e0226215. doi: 10.1371/journal.pone.0226215.

* Dr. Betânia Rodrigues Santos has a master’s and a PhD degree in physiology from UFRGS and is currently a postdoctoral student affiliated with the INCT Hormona.