Vitamin D and Embryo Health in IVF
By Dr. Harsimranjeet Singh Bhatia, ND
The quick summary: A new IVF study found that women with higher vitamin D levels tended to have more chromosomally normal embryos. It does not prove that vitamin D causes better embryos, but it adds to a growing body of research linking healthy vitamin D levels with better fertility outcomes. Since correcting a deficiency is worthwhile for your overall health anyway, it makes sense to know your level and work toward a healthy range with guidance.
If you are preparing for IVF, you have probably been asked to think about a long list of things at once. Vitamin D is one of the few that is simple to measure, inexpensive to address, and can be good for your health regardless of what happens in your cycle. A study published this month gives us another reason to pay attention to it.
What did the new study find about vitamin D and embryos?
Researchers at a fertility centre in Romania looked back at 42 women who each completed one IVF cycle with genetic testing of their embryos. That testing tells us which embryos have the balanced number of chromosomes, called euploid embryos. These are the embryos with the best chance of implanting and becoming a healthy pregnancy, which is why the number a of chromosomes per cell of the embryo gets so much attention.
The team measured vitamin D in each woman's blood before her cycle began. Women with higher vitamin D levels tended to have more euploid embryos, and a higher share of their tested embryos came back chromosomally normal. What makes this finding stand out is how well it held up. The researchers tested it several different ways, including accounting for egg reserve and for how many embryos each woman had tested, and vitamin D remained the most consistent factor every time.
It is also worth knowing that every woman in this study had vitamin D levels below what is generally considered sufficient. In other words, the pattern was seen in people who were low to begin with, which is exactly the group most likely to benefit from paying attention to it.
This was a small study from a single clinic, and it looked back at records rather than testing a treatment, so it shows a link rather than cause and effect. Even so, it fits with earlier research. A 2018 review of eleven studies and about 2,700 women undergoing fertility treatment found that women with sufficient vitamin D had higher live birth rates than those who were low, and a separate study found that vitamin D levels in the fluid surrounding the egg were associated with whether the resulting blastocysts were chromosomally normal.
Why might vitamin D impact quality of eggs and embryos?
Vitamin D is often thought of as a bone nutrient, but it behaves more like a hormone. Receptors for vitamin D are found throughout the reproductive system, including the ovaries and the lining of the uterus.
Lab research suggests vitamin D helps regulate the cells that surround and nourish a developing egg. It appears to influence how the ovary produces hormones, how follicles mature, and how inflammation is kept in balance in the tiny environment where each egg grows. An egg spends months developing before it is retrieved, so the conditions it grows in during that time may matter. These mechanisms make the link with embryo quality biologically plausible, even though they have not yet been proven to change outcomes in people with substantial evidence.
Is the vitamin D in my prenatal enough?
For some people it is, and for many it is not. The only way to know is to measure.
Most prenatal vitamins contain a modest amount of vitamin D, designed to help maintain a healthy level in someone who is already there. It is often not enough to bring a person up from a real deficiency, particularly here in Ottawa, where the winter sun is too weak for the skin to make meaningful vitamin D for several months of the year.
I regularly meet patients who are doing everything right. They take their prenatal faithfully, they have been told it covers their vitamin D, and yet their blood work still shows a significant deficiency. In my clinical experience, a prenatal alone rarely corrects a true deficiency through an Ottawa winter. This is not anyone's fault. It is simply a gap between a general recommendation and what an individual body actually needs.
Vitamin D testing in Ontario is usually not covered by OHIP for routine purposes, so many people pay for it out of pocket. For anyone preparing for fertility treatment, it is one of the more useful and affordable tests you can ask about.
Why do some people need more vitamin D than others, and why not just take a lot?
Two people can take the same supplement for the same length of time and end up with very different blood levels. There are a few reasons for this.
Genetics plays a role. A 2022 review of eight studies found that common variations in the vitamin D receptor gene changed how much a person's blood level rose with supplementation. The form of the supplement matters too. A review of controlled trials found that vitamin D3 generally raises blood levels more effectively than vitamin D2. Because vitamin D is fat soluble, what you take it with also has an impact on absorption, and one trial found it was absorbed noticeably better alongside a meal containing some fat than with a fat free meal. Digestive health is another piece. Conditions such as celiac disease and inflammatory bowel disease are commonly linked with low vitamin D, partly because they reduce how well it is absorbed in the first place. Sun exposure, skin tone, and time spent indoors all shape the picture as well.
The result is that the amount needed to reach a healthy level can vary a great deal from one person to the next, and some people need considerably more than what is in a standard prenatal.
That does not mean more is always better. Vitamin D is stored in the body, so it can build up over time. Health Canada sets a safe upper limit for daily intake, and in Canada, higher strength vitamin D products require a prescription. Taking too much for long periods without supervision raises the risk of too much calcium in the blood, which can lead to problems such as kidney stones and, in more serious cases, can affect the heart and kidneys. This is why correcting a deficiency is best guided by a clinician who tests your level before and after, rather than guessed at.
The approach that makes the most sense is a simple one: test, correct with guidance and retest to confirm nutrient level sufficiency. That way you reach a healthy level without guessing in either direction.
Where we go from here with this information
This new study adds to the case that vitamin D deserves a place in fertility preparation. We do not yet know for certain that raising vitamin D will improve embryo quality from this research alone, and larger studies are needed to answer that. What we do know is that deficiency is common, that it is easy to measure, and that correcting it supports your health in many ways beyond fertility. That makes it a sensible thing to address before treatment, not as a guarantee, but as one reasonable piece of looking after yourself.
If you would like help understanding your own levels, a naturopathic doctor who focuses on fertility can guide testing vitamin D, look at the factors that may be affecting your absorption, guide an approach that fits you, and follow up to make sure it is working. It is a conversation worth having before your next cycle, and our team is always happy to talk it through with our patients.
Disclaimer
This article is for educational purposes only and is not medical advice. It is not intended to diagnose, treat, or prevent any condition. Individual circumstances vary, and decisions about your care should be made with your own healthcare team. If you are trying to conceive or are currently in treatment, please speak with your physician or a licensed naturopathic doctor before making changes, including starting or changing a vitamin D supplement.
References
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Arnanz A, De Munck N, El Khatib I, et al. Vitamin D in follicular fluid correlates with the euploid status of blastocysts in a vitamin D deficient population. Frontiers in Endocrinology. 2021;11:609524. https://doi.org/10.3389/fendo.2020.609524
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