An epidemic of vitamin D deficiency has been emerging over the last decade among all racial groups in the world. In fact, the prevalence of vitamin D insufficiency nearly doubled from 1994 to 2004. Among women of reproductive age, more than 40 percent are insufficient in vitamin D. Majority of our population lives in areas receiving ample sunlight throughout the year and hence there was a disbelief that Vitamin D deficiency is uncommon in India.However from the data available in the published literature, Vit D deficiency is very common in India in all the age groups and both sexes across the country.
Vit D deficiency is a common problem in India due to several factors: Changing food fads and food habits contribute to low dietary calcium and Vit D intake. High fibre diet containing phosphates and phytates which can deplete Vit D stores and increase calcium requirement.Genetic factors like having increased 25(OH)D-24- hydroxylase which degrades 25(OH)D to inactive metabolites.10 It has been shown that increment in serum 25(OH)D in response to treatment depends on the heritability of Vit D binding protein. With modernization, the number of hours spent indoor have increased thereby preventing adequate sun exposure. This is particularly true in the urban Indians. Increased pollution can hamper the ultraviolet rays to adequately synthesize Vit D in the skin. Cultural and traditional habits prevalent in certain religions like “Burqa” and the “pardah” system in Muslims have been well known. . Repeated and unplanned, unspaced pregnancies in dietary deficient patients can aggrevate Vit D deficiency in the mother and the foetus.
Vitamin D’s most important role in the human body is to keep bones healthy and strong by helping the body absorb calcium. However, recent research has pointed to additional ways that vitamin D deficiency factors into our overall health, including its role in chronic diseases like diabetes, obesity, autoimmune disease, cardiovascular disease and cancer, as well as an association with a higher risk of both overall and cancer mortality.Instead of only affecting cells that live in the bone, we now understand that Vitamin D is able to affect many different types of cells in different organs in the body. The way it does this is by turning genes within that cell, “on and off.” In other words, vitamin D affects the way a cell carries out its function, and it can control the growth or the death of that cell. Vitamin D metabolic enzymes are described in the human testis, the ejaculatory tract, mature spermatozoa and in the Leydig cells.
In the world of reproduction, the importance of vitamin D was initially shown in experiments with mice. Mice who are either deficient in vitamin D, or who lack the vitamin D receptor, can demonstrate underdevelopment of the uterus and inability to form normal mature eggs, resulting in infertility.If pregnancy is achieved, the fetuses of these mice show impaired growth.Reproduction is normalized in mice with vitamin D supplementation, but not with calcium alone, suggesting that vitamin D’s role in female reproduction is not related to helping the body absorb calcium.
In humans, the vitamin D receptor is present in many female organs, including the ovary, uterus, and placenta. The active form of vitamin D (calcitriol) has many roles in female reproduction. Bound to its receptor, calcitriol is able to control the genes involved in making estrogen. The uterine lining produces calcitriol in response to the embryo as it enters the uterine cavity, shortly before implantation.Calcitriol controls several genes involved in embryo implantation.Once a woman becomes pregnant, the uterus and placenta continue to make calcitriol, which helps organize immune cells in the uterus, so that infections can be fought without harming the pregnancy. Poor vitamin D status has been associated with certain pregnancy complications such as gestational hypertension and diabetes.
Women about to undergo in vitro fertilization (IVF) can provide valuable insight into the role of vitamin D, since it is possible to examine each aspect of reproduction, from egg development to implantation of the embryo. A recent study found that women with higher vitamin D levels were significantly more likely to achieve pregnancy from IVF compared to women with lower levels of vitamin D.This study was repeated in another IVF center, which confirmed a four-fold difference in pregnancy rates between vitamin D replete and deficient women. In another study looking at the recipients of donor eggs, vitamin D levels in the recipients were associated with clinical pregnancy, emphasizing that the critical role of vitamin D in pregnancy may be within the uterus. Though more research is needed, it appears that vitamin D levels are associated with IVF success, and that its most important role in reproduction may be at the uterine lining. No studies have yet evaluated whether giving vitamin D improves IVF outcomes. But the data that does exist at this point suggests that a role for vitamin D supplementation may exist as a means of improving one’s natural fertility both among the fertile and infertile.
As the researchers reported in the European Journal of Endocrinology: Among women, vitamin D appears to impact in vitro fertilization (IVF) outcomes, endometriosis, polycystic ovary syndrome (PCOS), the most common female endocrine disorder, as well as boost levels of progesterone and estrogen, which regulate menstrual cycles and improve the likelihood of successful conception. Vitamin D have direct effect on AMH production, and thus increase longer maintenance of ovarian reserve in the patients with its higher concentration. The occurrence of uterine myomas in the group with vitamin D deficiency was evaluated as much higher comparing to controls. On the other hand it is supposed that high concentration of calciferol may be related to an impaired elimination of endometrial cells passing to peritoneal cavity via ovarian reflux causing endometriosis.
In men, vitamin D is essential for the healthy development of the nucleus of the sperm cell, and helps maintain semen quality and sperm count. Vitamin D also increases levels of testosterone, which may boost libido. Interestingly, another study published in November 2009 confirmed that human sperm does in fact have a vitamin D receptor. In male infertility both low (<20 ng/ml) and high (>50 ng/ml) concentration of vitamin D in serum negatively affects spermatozoa number per ml of semen, their progressive movement and morphology.
25(OH)D is the better marker of overall D status. It is this marker that is most strongly associated with overall health. A few years back, the recommended level was between 40 to 60 nanograms per milliliter (ng/ml), but more recently the optimal vitamin D level has been raised to 50-70 ng/ml. The Endocrine Practice Guidelines Committee(132) suggests a daily intake of 1500–2000?IU vitamin D3 daily for adults >18 years up to 70 years in order to raise the blood level of 25(OH)D consistently above 30?ng/ml; the UL was defined as 10?000?IU/day. The same daily intake and UL were suggested for adult pregnant and lactating women. Importantly, vitamin D intoxication resulting in hypercalcemia, renal damage, and vascular calcification is not observed until 25(OH)D levels >150?ng/ml .
Infertility can be a challenging condition with multiple contributing factors, but you have nothing to lose and everything to gain by optimizing your vitamin D levels. It is free if you do it via sun exposure, and inexpensive if you use a safe tanning bed or vitamin D3 supplement. It’s a simple step that can have a profound impact on your health, even if trying to conceive naturally is not your primary goal.Regardless of potential fertility benefits, patients should be counseled regarding appropriate vitamin D supplementation for overall health benefits, including bone health, pregnancy health, and chronic disease risk reduction.
References
- Michaelsson, K; Baron, JA; Snellman, G; Gedeborg, R; Byberg, L; Sundstrom, J; Berglund, L; Arnlov, J et al. Plasma vitamin D and mortality in older men, a community-based prospective cohort study. The American Journal of Clinical Nutrition, 2010;92(4):841-8.
- Kinuta K, Tanaka H, Moriwake T, Aya K, Kato S, Seino Y. Vitamin D is an important factor in estrogen biosynthesis of both female and male gonads. Endocrinology, 2000;141:1317–24.
- Ozkan S, Jindal S, Greenseid K, Shu J, Zeitlian G, Hickmon C, Pal L. Replete vitamin D stores predict reproductive success following in vitro fertilization. Fertility and Sterility, 2010;94(4):1314-9.
- Rudick B, Ingles SA, Stanczyk F, Chung K, Paulson R, Bendikson K. The role of vitamin D levels on IVF outcomes in donor-recipient cycles. O-9, Annual Meeting of the Pacific Coast Reproductive Society,2011.
- Johnson LE, DeLuca HF. Vitamin D receptor null mutant mice fed high levels of calcium are fertile. J Nutr 2001;131:1787–91.
- January 24, 2012, doi: 10.1530/EJE-11-0984Eur J Endocrinol January 24, 2012EJE-11-0984.
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