Medical contribution by Eric A. Widra, M.D.
Eric A. Widra, M.D., is the medical director of Shady Grove Fertility in Metropolitan Washington, D.C.; Baltimore; and Philadelphia, and the associate director of the Combined Federal Fellowship in Reproductive Endocrinology and Infertility—a post-graduate training program for future leaders in this subspecialty, operated through the National Institutes of Health, Walter Reed National Military Medical Center, and Shady Grove Fertility.
Most people have at least heard of vitamin D, as it has been widely discussed the last several years. Vitamin D is also known as the “sunshine vitamin.” It is produced in the skin in response to sunlight exposure, and can also be consumed through food and supplements.
What most people may not know, however, is that a person’s vitamin D status may affect their fertility. We recently interviewed SGF’s Chief Medical Officer, Dr. Eric Widra, from SGF’s K Street office, to discuss how vitamin D may impact female fertility.
What is vitamin D?
Vitamin D3 (cholecalciferol) is the main form of vitamin D in the skin. It is the form produced in the skin, and it can be found in some food and nutritional supplements. Prescription vitamin D is vitamin D2 (ergocalciferol). In general, research shows that we metabolize vitamin D3 more efficiently than vitamin D2.1
Given enough time in the sun, most of us can make all the vitamin D we need. However, many women do not get enough sun exposure to maintain a normal vitamin D level throughout the year. Few foods are naturally rich in vitamin D, so it is also difficult to get enough vitamin D from your diet.
Other factors also affect vitamin D status. For instance, if you are overweight or have dark skin, you may be at risk for vitamin D deficiency. For these and other reasons, many women trying to conceive are likely to be low in vitamin D.
How is vitamin D linked to fertility?
Vitamin D has been linked to a variety of health benefits. For women trying to conceive, it appears to be linked to better fertility, as well as a healthy pregnancy. Because of these potential benefits, SGF screens all female patients for vitamin D deficiency as part of their initial screening process.
According to Dr. Widra, “The data on vitamin D and natural fertility as well as success during fertility treatment is mixed. There are some studies showing that being vitamin D replete improves success rates in both in vitro fertilization (IVF) as well as transfer of frozen donor egg embryos. Other studies have not demonstrated that connection.”
Although the data for vitamin D and fertility is not conclusive, several studies have found that vitamin D blood levels of 30 ng/mL or higher are associated with higher pregnancy rates.2-5 Two studies found that among populations of mostly Caucasian and non-Hispanic white women, those with a normal vitamin D level were four times more likely to get pregnant through IVF compared to those who had a low vitamin D level.3-4 Another study found that donor egg recipients with a normal vitamin D level had higher pregnancy rates than those with a low vitamin D level.6
A recent meta-analysis investigated whether vitamin D blood levels are associated with live birth rates in women undergoing fertility treatments. It found that women with a level greater than 30 ng/mL had higher live birth rates than women with lower vitamin D levels.7
How much vitamin D do I need?
As explained by Dr. Widra, “During a couple’s initial screening, we check the woman’s vitamin D level in addition to certain hormone levels, and screen for common infectious diseases. If a patient’s vitamin D level is low, we follow the usual vitamin D replacement protocol using Theralogix vitamin D products.”
Per this protocol, SGF recommends that women with a vitamin D level less than 24 ng/mL take 4,000 IU per day. For those with a vitamin D level of 24-30 ng/mL, SGF recommends taking 2,000 IU per day.
“Our goal is to have someone in the normal vitamin D range, which is typically over 30 ng/mL. We do not know the exact blood level range that vitamin D has an impact on fertility. We feel that a reasonable threshold is the accepted normal range of approximately 30 ng/mL and above,” states Dr. Widra.
Once the goal of 30 ng/mL is achieved, taking 2,000 IU of vitamin D per day is appropriate to maintain a normal level.
Is vitamin D also important during pregnancy?
Not only does achieving a normal vitamin D level seem to positively impact fertility, it may also improve the odds of having a healthy pregnancy. Studies have linked vitamin D deficiency during pregnancy with an increased risk of preterm birth, gestational diabetes, preeclampsia (very high blood pressure during pregnancy), and bacterial vaginosis.8-11
So, continuing a vitamin D supplement once pregnant is good for both mom and baby. Research has shown that taking 2,000 – 4,000 IU of vitamin D is safe and effective in achieving a normal vitamin D level for pregnant women and preventing vitamin D deficiency in newborns.12-13
“Our opinion is that given the simplicity of testing and treatment with vitamin D, the low cost associated with it, as well as the absence of real risk, we should err on the side of having patients be vitamin D replete as they go through fertility treatment and enter pregnancy. For any medical intervention, you need to weigh the potential benefits against the risks and costs. The risks and costs are so low for vitamin D that any potential benefit is worth considering,” explains Dr. Widra.
Which vitamin D products do you recommend?
Shady Grove Fertility recommends Theralogix, a line of evidence-based, independently tested and certified fertility products for men and women. All Theralogix products are NSF tested for content accuracy, purity, freedom from contaminants, and proper disintegration.
Nutritional supplements can be an important complement to your fertility treatment but they do not replace fertility evaluation and care. You should have your fertility evaluated if you are under 35 years old and have been having unprotected intercourse without conception for 1 year, after 6 months if you are between the ages of 35-39, and after 3 months if you are 40 and over. Women should consult their reproductive endocrinologist before beginning any vitamin regimen.
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All Things Prenatal Vitamins with Dr. Anate Brauer
- Houghton and Vieth. Am J Clin Nutr. 2006; 84(4):694-7.
- Paffoni et al. J Clin Endocrinol Metab. 2014; 99(11):E2372-6.
- Ozkan et al. Fertil Steril. 2010; 94:1314-19
- Rudick et al. Hum Reprod. 2012; 27(11):3321-7.
- Garbedian et al. CMAJ. 2013;1(2):E77-82.
- Rudick et al. Fertil Steril. 2014; 101(2):447-52.
- Chu et al. Hum Reprod. 2018; 33(1):65-80.
- Bodnar et al. Obstet Gynecol. 2015; 125(2):439-47.
- Zhang et al. Nutrients. 2015; 7(10):8366-75.
- Baca et al. Ann Epidemiol. 2016; 26(12):853-857.
- Bodnar et al. J Nutr. 2009; 139:1157-61.
- Hollis et al. J Bone Miner Res. 2011; 26(10):2341-57.
- Rodda et al. Clin Endocrinol (Oxf). 2015; 83(3):363-8.