Shining Light on Fertility: The Integral Role of Vitamin D
Welcome, to an in-depth exploration of a nutrient that’s proving to be a beacon of hope in the world of fertility. I’m talking about Vitamin D, otherwise known as the 'sunshine vitamin', whose role in our overall wellbeing has been extensively studied, but its specific impact on fertility is gaining increasing attention. In this blog I aim to shed light on the link between Vitamin D and fertility.
It might come as a surprise that Vitamin D, which we usually associate with strong bones and a robust immune system, can also influence our fertility. However, recent research is suggesting that this nutrient, which our body can generate when our skin soaks up sunlight, has significant implications for reproductive health in both women and men.
In this blog, I'll delve into the nuances of this connection, drawing upon the latest scientific findings to understand how Vitamin D can affect fertility. We'll explore the vitamin's function, its sources, and the vital role it may play in your fertility journey. Whether you're currently trying to conceive, planning for a baby in the future, or simply keen to know more about your body's workings, keep reading…
Understanding Vitamin D: The 'Sunshine Vitamin'
Vitamin D, often referred to as the "sunshine vitamin," is a fat-soluble nutrient that plays a multitude of critical roles in our body. This vitamin is unique because it can be synthesised by our body when our skin is exposed to sunlight, specifically ultraviolet B (UVB) rays. Aside from sunlight, Vitamin D can also be obtained from certain foods such as fatty fish, cheese, and egg yolks, as well as from dietary supplements. Vitamin D is biologically inactive in its original form and undergoes two processes in the body - first in the liver and then in the kidney - to be transformed into its active form, calcitriol (1,25-dihydroxyvitamin D) (1). Once activated, Vitamin D carries out a host of functions. It is instrumental in maintaining the health of our bones and teeth, as it aids in the absorption of calcium and phosphorus, key minerals for bone health (2). Moreover, Vitamin D has also been linked with improved immune function, with deficiency associated with increased susceptibility to infection (3). Emerging research suggests a vital role for Vitamin D in reproductive health as well. Recent studies suggest that Vitamin D could have a positive influence on fertility in both men and women (4).
Vitamin D and Reproductive Health
You may be wondering why Vitamin D holds such importance for fertility? The answer lies in its wide-ranging impact on various bodily functions. We already know it aids in calcium absorption, crucial for bone health, but what about its connection with fertility? Well, Vitamin D receptors have been found in the ovaries and uterus, indicating its potential role in reproductive processes! Here, I look into what the studies tell us about vitamin D and reproductive health.
Vitamin D Status & Women’s Health
In women, vitamin D is involved in hormone production and regulation. Several studies have shown a connection between adequate vitamin D levels and the production of sex hormones such as progesterone and oestrogen, which are essential for regular menstrual cycles and successful implantation of an embryo (5). Moreover, Vitamin D receptors have been identified in the ovaries and endometrial lining, suggesting a direct role in female reproduction (6). A number of studies have also suggested a link between vitamin D and egg quality. For example, one study found that women undergoing IVF had higher pregnancy rates when their vitamin D levels were adequate, indicating a possible role in egg maturation and embryo quality (7). More recently, a link between vitamin D deficiency and miscarriage has been highlighted. Women with low vitamin D levels are at significantly increased risk of miscarriage, a new study reveals (8).
Vitamin D Status & Men’s Health
For men, Vitamin D appears to have a significant impact on sperm health. The vitamin is thought to be involved in the production of testosterone and the development and motility of sperm. One study showed that men with adequate vitamin D levels had higher sperm motility compared to those with a deficiency (9). Additionally, Vitamin D is believed to improve sperm's ability to fertilise an egg, contributing to overall male fertility (10).
However, while there is growing evidence of the importance of Vitamin D in reproductive health, more research is needed to fully understand its role and potential benefits. It's always recommended to seek advice from a healthcare professional or fertility specialist before starting any new supplement regimen.
Vitamin D Deficiency: Causes, Symptoms, and Risks
A deficiency in vitamin D can often be subtle and many people may not be aware they have low levels of this essential nutrient. It's even been referred to as the "invisible deficiency" due to its asymptomatic nature in the early stages. However, as the deficiency progresses, it may lead to noticeable symptoms such as bone pain, muscle weakness, increased susceptibility to infections due to weakened immune function, and fatigue (11). Mood changes, particularly a propensity toward depression, have also been linked with low vitamin D levels (12). Certain groups are more susceptible to vitamin D deficiency, including those with limited sun exposure, people with darker skin, individuals who are overweight or obese, and those with gastrointestinal disorders that impair fat absorption, such as Crohn's disease and celiac disease (13).
Specifically in terms of fertility and pregnancy, a vitamin D deficiency may pose additional risks. In women, there is evidence that low vitamin D levels may be associated with polycystic ovary syndrome (PCOS) and endometriosis, two conditions that can impair fertility (14). During pregnancy, inadequate vitamin D levels have been linked to an increased risk of gestational diabetes, pre-eclampsia, and preterm birth (15). In men, a deficiency in vitamin D has been associated with reduced semen quality and testosterone levels, impacting male fertility potential (16). So, maintaining optimal vitamin D levels is vital, not just for overall health, but particularly for those trying to conceive or who are already pregnant.
Vitamin D and IVF Outcomes
A growing body of research suggests a connection between vitamin D levels and the success rates of in vitro fertilisation (IVF). Multiple studies have indicated that women with sufficient vitamin D levels are more likely to achieve a higher rate of successful pregnancies following IVF, as compared to those who are vitamin D deficient. In a recent study, researchers examined vitamin D levels in the follicular fluid (fluid surrounding the egg) of women undergoing IVF. They found that women with sufficient levels of vitamin D were more likely to have a higher quality of embryos and a higher pregnancy rate compared to those with vitamin D deficiency (17). Similarly, another study showed that women with sufficient vitamin D levels had higher rates of clinical pregnancy following IVF when compared to women with vitamin D deficiency or insufficiency (18). Moreover, a meta-analysis reviewing 11 studies with a total of 2700 IVF patients, found that women with sufficient vitamin D levels had a significantly higher live birth rate compared to those who were vitamin D deficient or insufficient (19). These findings suggest that optimal vitamin D levels might improve the chances of pregnancy in women undergoing IVF.
The exact mechanisms of how vitamin D influences IVF outcomes are not entirely clear and further research is needed to substantiate these observations and to establish guidelines for vitamin D supplementation in the context of fertility treatments.
This is why vitamin D is one of the first things we look at in clinic to optimise ahead of pregnancy or fertility treatments. Whilst your GP may have given you the ok in terms of vitamin D status, adequate levels are not optimal for fertility, and often men are overlooked in this scenario. In this case, we start with a loading dose to raise vitamin D levels before moving on to a maintenance dosage. Dosages are individual on a case-by-case basis and so I highly recommend booking in your FREE 20-minute chat to find out more about how I might help you.
Supporting Vitamin D Levels for Fertility
Optimising vitamin D levels can be achieved through various ways, including safe sun exposure, dietary changes, and appropriate supplementation, keep reading for my top tips:
1. Sun Exposure - Vitamin D is often referred to as the 'sunshine vitamin' because our skin can synthesise it when exposed to the sun's ultraviolet B (UVB) rays. However, the amount of sun exposure you need can depend on several factors, including your geographic location, skin type, time of year, and time of day. A general recommendation is to expose your face, arms, legs, or back without sunscreen for about 10 to 30 minutes between 10 AM and 3 PM at least twice a week. However, excessive sun exposure can increase the risk of skin cancer, so it's important to balance these recommendations with sun safety measures.
2. Dietary Changes - Incorporating vitamin D-rich foods into your diet is another effective way to support your levels. Some of these foods include fatty fish like salmon and mackerel, fortified dairy products, egg yolks, and beef liver. However, it's difficult to get enough vitamin D through diet alone, especially if you're deficient or at risk of deficiency (20).
3. Supplementation - Vitamin D supplements can be an effective way to ensure you're getting enough, especially for those with limited sun exposure or difficulty absorbing the vitamin. The amount you need can depend on many factors, so it's essential to consult with a healthcare provider before starting a new supplement regimen.
A final note on testing…
Regular testing can help monitor vitamin D levels and adjust intake as needed. I recommend that you test your levels every 6 months, even in the summer so that you can adjust your supplementation accordingly. If you're struggling to increase your levels, are at high risk of deficiency, or are experiencing symptoms of deficiency, it's essential to seek medical advice. Remember, maintaining adequate vitamin D levels can be an important aspect of fertility and overall health.
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3. Aranow, C. (2011). Vitamin D and the immune system. Journal of investigative medicine, 59(6), 881–886.
4. Lerchbaum, E., & Rabe, T. (2014). Vitamin D and female fertility. Current opinion in obstetrics & gynecology, 26(3), 145-150.
5. Lerchbaum, E. and Rabe, T., (2014). Vitamin D and female fertility. Current Opinion in Obstetrics & Gynecology, 26(3), pp.145-150.
6. Irani, M. and Merhi, Z., (2014). Role of vitamin D in ovarian physiology and its implication in reproduction: a systematic review. Fertility and Sterility, 102(2), pp.460-468.e3.
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8. Jennifer A. Tamblyn et al. (2022). Vitamin D and miscarriage: a systematic review and meta-analysis, Fertility and Sterility.
9. Blomberg Jensen, M., Bjerrum, P.J., Jessen, T.E., Nielsen, J.E., Joensen, U.N., Olesen, I.A., Petersen, J.H., Juul, A., Dissing, S. and Jørgensen, N., (2011). Vitamin D is positively associated with sperm motility and increases intracellular calcium in human spermatozoa. Human Reproduction, 26(6), pp.1307-1317.
10. Ramlau-Hansen, C.H., Moeller, U.K., Bonde, J.P., Olsen, J. and Thulstrup, A.M., (2011). Are serum levels of vitamin D associated with semen quality? Results from a cross-sectional study in young healthy men. Fertility and Sterility, 95(3), pp.1000-1004.
12. Holick, M.F., (2007). Vitamin D deficiency. New England Journal of Medicine, 357(3), pp.266-281.
12. Anglin, R.E., Samaan, Z., Walter, S.D. and Sarah, M., (2013). Vitamin D deficiency and depression in adults: systematic review and meta-analysis. The British Journal of Psychiatry, 202, pp.100-107.
13. Holick, M.F., (2007). Vitamin D deficiency. New England Journal of Medicine, 357(3), pp.266-281.
14. Krul-Poel, Y.H.M., Snackey, C., Louwers, Y., Lips, P., Lambalk, C.B., Laven, J.S.E., Simsek, S., (2018). The role of vitamin D in metabolic disturbances in polycystic ovary syndrome: A systematic review. European Journal of Endocrinology, 179(6), pp. 489-499.
15. Aghajafari, F., Nagulesapillai, T., Ronksley, P.E., Tough, S.C., O’Beirne, M., Rabi, D.M., (2013). Association between maternal serum 25-hydroxyvitamin D level and pregnancy and neonatal outcomes: systematic review and meta-analysis of observational studies. British Medical Journal, 346, f1169.
16. Blomberg Jensen, M., Bjerrum, P.J., Jessen, T.E., Nielsen, J.E., Joensen, U.N., Olesen, I.A., Petersen, J.H., Juul, A., Dissing, S. and Jørgensen, N., (2011). Vitamin D is positively associated with sperm motility and increases intracellular calcium in human spermatozoa. Human Reproduction, 26(6), pp.1307-1317.
17. Anifandis, G., Koutselini, E., Louridas, K., Liakopoulos, V., Leivaditis, K., Mantzavinos, T., & Vamvakopoulos, N. (2020). Association of follicular fluid volume and oocyte maturity in different follicle sizes among infertile patients treated with intracytoplasmic sperm injection cycles. Archives of gynecology and obstetrics, 282(4), pp. 409-413.
18. Ozkan, S., Jindal, S., Greenseid, K., Shu, J., Zeitlian, G., Hickmon, C., & Pal, L. (2010). Replete vitamin D stores predict reproductive success following in vitro fertilization. Fertility and sterility, 94(4), pp. 1314-1319.
19. Chu, J., Gallos, I., Tobias, A., Tan, B., Eapen, A., & Coomarasamy, A. (2018). Vitamin D and assisted reproductive treatment outcome: a systematic review and meta-analysis. Human Reproduction, 33(1), pp. 65-80.
20. Nair, R., & Maseeh, A. (2012). Vitamin D: The “sunshine” vitamin. Journal of pharmacology & pharmacotherapeutics, 3(2), pp. 118–126.