Vitamin D in human reproduction: the more, the better? An evidence-based critical appraisal.

OBJECTIVE: Vitamin D is a fat-soluble secosteroid hormone that regulates calcium, magnesium, and phosphate homeostasis and plays a pivotal role as antiproliferative and immunomodulatory mediator. Considering the different sources of synthesis and dietary intake as well as the pleiotropic actions in extremely diverse (micro)environments of the body, the supplementation of this Vitamin should be carefully evaluated taking into account the several pathways that it regulates. In the current brief review, we aimed to summarize the available evidence about the topic, in order to suggest the best evidence-based supplementation strategy for human reproduction, avoiding the unuseful (and sometimes hazardous) empiric supplementation. MATERIALS AND METHODS: Narrative overview, synthesizing the findings of literature retrieved from searches of computerized databases. RESULTS: Accumulating evidence from in vitro fertilization (IVF) trials suggests that fertilization rate decreases significantly with increasing levels of 25OH-D in follicular fluid; in addition, Vitamin D levels in the follicular fluid are negatively correlated to the quality of embryos and the higher values of Vitamin D are associated with lower possibility to achieve pregnancy. Both low and high Vitamin D serum concentrations decrease not only spermatozoa count, but their progressive motility as well as increase morphological abnormalities. Finally, studies in animal models found that severe hypervitaminosis D can reduce the total skeletal calcium store in embryos and may compromise the postnatal survival. CONCLUSIONS: Based on the retrieved data, we solicit to be extremely selective in deciding for Vitamin D supplementation, since its excess may play a detrimental role in fertility.

Soy isoflavones, inulin, calcium, and vitamin D3 in post-menopausal hot flushes: an observational study.

PURPOSE OF INVESTIGATION: To evaluate the effect of soy isoflavones and inulin (SII) on hot flushes (HF) and quality of life in a clinical setting, the authors conducted an observational study. MATERIALS AND METHODS: The authors performed an observational, prospective, multicentric study on women in peri-/post-menopause treated or untreated with a product present on the Italian market, consisting in a mixture of calcium (500 mg), vitamin D3 (300 IU), inulin (3 g) and soy isoflavones (40 mg). RESULTS: A total of 135 patients, 75 (55.6%) in the SII group and 60 (44.4%) in the untreated group entered the study. After three months, the mean number of HF declined of 2.8 (SD 3.7) in the SII group and 0.0 in the untreated one. The corresponding values after six months were -3.7 (SD 2.7) in the SII group and -0.9 (SD 5.3) in the control group (p = 0.02). CONCLUSION: This observational trial suggests a possible beneficial effect of a dietary soy supplement containing 40 mg of isoflavone/day plus inulin in the management of menopausal symptoms such as hot flashes.