What You Should Know About Vitamin D

RISE and get that sunSHINE everyone!

And when I say sunshine, what I’m actually referring to Vitamin D.

Vitamin D is so important. It’s most well known function is absorption and regulation of calcium and phosphorus to utilize for bone mineralization. Adequate Vitamin D status has also been associated with decreased risk for many chronic diseases.

Over 1 billion people (and 50% of US adults) are deficient in Vitamin D. The current RDA is 600 IU per day unless there’s adequate sunlight exposure but many resources suggest this is not enough to maintain optimal blood levels. The optimal level of circulating Vitamin D (25(OH)D) is between 30-80 ng/mL.

Vitamin D receptors are also found in reproductive organs including the ovary, uterus, placenta, hypothalamus, and pituitary glands so it is hypothesized to play a huge role in reproductive health. With such a large portion of the population deficient, it could play a factor in fecundability and pregnancy.

There are vast amounts of research studies analyzing Vitamin D status in regards to reproductive health. Research topics include it’s relationship with positive pregnancy tests, pre-eclampsia risk, live birth rates, miscarriage rates, and the list goes on and on. However, even after multiple studies, there are discrepancies between findings. There is still no definitive answer regarding if or how much Vitamin D status affects fertility and pregnancy. But we can conclude that it is still an important vitamin to consider when addressing reproductive health. 


When planning on conceiving, preparing your hormones and body should start 3-6 months prior to conception. It takes about 3 months for complete egg maturity so you need to be nourishing your body months before trying to conceive. In regards to Vitamin D status,  one study found that women with previous pregnancy losses were more likely to achieve pregnancy and live birth if their serum Vitamin D status >30 ng/mL compared to those with inadequate status. This same study noted that Vitamin D status before pregnancy was associated with reduced risk of pregnancy loss but at 8 weeks of pregnancy, it had no effect. Only a couple studies have found these results and some studies have found no association so we cannot confirm findings. But if your serum Vitamin D status is low, there’s no risk in taking supplements and getting enough sunlight to potentially boost fertility.


We know that the fetus is entirely dependent on the mother’s Vitamin D status. But in the womb, their levels (via cord blood) are only about 50-80% of the mother’s, making it very important for the mother’s status to be sufficient. Low status has been found to be associated with not only pregnancy loss but also increased risk of small for gestational age and preterm birth. Once again, studies have also found no correlations between Vitamin D status in perinatal risk so no firm conclusions are set in place. The current guidelines recommend 400 to 800 IU per day for pregnant women so we do know it’s serving some benefit. But is this dose enough? It may not be. The only way to truly know is to have your Vitamin D status (specifically measuring circulating 25(OH)D) checked before pregnancy, and during each trimester. Aim to have levels between 30-80ng/mL.

Male Fertility

There have been numerous studies hypothesizing that Vitamin D status has an affect on male fertility as well. Findings have found positive correlations between Vitamin D concentrations and the motility and normal morphology of sperm in infertile men. Severe deficiency has been found to be associated with a lower proportion of motile and normal sperm when compared to those with Vitamin D sufficiency. However, a U-shaped correlation has also been found where not only low, but high concentrations are associated with impaired sperm quality. Another interesting study found that there were a higher number of spontaneous pregnancies when men were receiving 1400 IU with 500mg calcium per day in compared to men receiving a placebo. The research has concluded that Vitamin D supplementation may improve sperm quality leading to an increase in spontaneous pregnancies.  However, there can be no definitive recommendations because, once again, numerous studies have not found links in the relationship with Vitamin D. Further studies are needed but supplementation should definitely be a consideration if levels are low. 

Sources of Vitamin D

The best way to ensure sufficient Vitamin D levels is to get sunlight exposure on a daily basis. 80-90% of Vitamin D is derived from the skin. Getting 15-30 minutes of sunlight (ideally midday) daily is all you need. Darker skin tones may need increased exposure to reach adequate levels. Food sources of Vitamin D include fatty fish like salmon, cod liver oil, egg yolk, mushrooms, yeast, or fortified foods. But do not rely on food sources exclusively. During winter months, it may be more difficult to reach adequate sun exposure so supplements may be required. The only way to know for sure is to get your serum Vitamin D checked regularly. 

Overall Take Away Message..

Although research has not shown definitive answers to whether Vitamin D will have an impact on fertility and pregnancy, we can conclude that it is still an important micronutrient. Get your levels checked and supplement if needed to reach at least 30ng/mL of serum Vitamin D. 

Shoot me a message for any further questions!

Your Dietitian,


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