Few vitamins are discussed as extensively and controversially as vitamin D. It is a fascinating vitamin because it can be obtained through diet on the one hand, and on the other hand, a large portion is produced by the body itself in the skin through sun exposure (UVB light). Vitamin D is found in only a few foods (e.g., fatty sea fish, organ meats, and to a lesser extent in egg yolk and margarine), so only a small amount, approximately 10–20%, can be obtained through diet, while a much larger portion must be produced by the body itself through sun exposure. Unfortunately, in our latitudes, this is only possible from approximately March to October, and vitamin D deficiency is quite common. For women or couples trying to conceive, the question often arises as to what role vitamin D plays in fertility.
- Why is vitamin D important for health?
- How can vitamin D levels be determined?
- What are the recommendations for supplementation?
- What influence does vitamin D have on fertility and the chance of becoming pregnant?
- Frequently asked questions about vitamin D and fertility
Why is vitamin D important for health?
Vitamin D is involved in many metabolic processes and in the regulation of a multitude of genes. There are numerous studies showing a correlation between vitamin D levels and the occurrence of chronic diseases, autoimmune diseases, cancer, and cardiovascular diseases. However, a causal relationship has not yet been demonstrated.
How can vitamin D levels be determined?
Vitamin D levels can be measured in the blood. According to international criteria, a value 12 ng/ml indicates vitamin D deficiency, and a value 20 ng/ml indicates suboptimal supply.
What are the recommendations for supplementation?
The German Nutrition Society recommends that adults take 20 µg of vitamin D per day. In many supplements, the dosage is given in units, which corresponds to 800 I.U. However, this only applies under the condition that the body does not produce its own vitamin D.
What influence does vitamin D have on fertility and the chance of becoming pregnant?
Interestingly, pregnancy rates in our northern hemisphere fluctuate depending on the seasons. Pregnancy rates are highest in summer and autumn, the seasons with the highest vitamin D concentrations (Muscogiuri et al. 2017).
A number of studies in high-ranking journals describe a positive correlation between pregnancy and birth rates and vitamin D levels. A large review that examined 11 studies with a total of over 2,700 women showed that in IVF/ICSI treatment, the chances of pregnancy and live birth rates are lower in women with low vitamin D levels than in women with adequate vitamin D supply (Chu et al. 2018).
Another study in England examined vitamin D levels and live birth rates after assisted reproduction in 500 women. 50% of the women had vitamin D deficiency, 30% had low vitamin D levels between 20–29 µg/l, and only 16% had sufficiently high vitamin D levels of > 30 µg/l. The results showed that 24% of women with low, 27% of women with medium vitamin D, and 34% of women with a value > 30 µg/l had a live birth (Chue et al. 2019).
Additional studies show a positive correlation between AMH levels, ovarian reserve, and vitamin D levels.
Common conditions associated with fertility, such as PCOS and endometriosis, are also linked to low vitamin D levels.
Frequently Asked Questions About Vitamin D and Fertility
What symptoms occur with vitamin D deficiency?
Those affected frequently report fatigue, exhaustion, muscle or bone pain, and increased susceptibility to infections. Since these symptoms are nonspecific, a blood test provides the most clarity.
Can vitamin D deficiency prevent pregnancy?
Vitamin D deficiency is usually not the sole reason for failure to conceive, but it can indirectly affect fertility. It is therefore advisable to determine the level (25-OH-vitamin D) in the blood rather than taking high doses without confirmation.
How much vitamin D should one take for fertility?
The German Nutrition Society recommends that adults take 20 µg of vitamin D per day (equivalent to 800 I.U.) when the body does not produce its own vitamin D. The dosage that is appropriate for you when trying to conceive should first be determined medically through blood testing.
Why is it sometimes said “no vitamin D” during pregnancy?
Vitamin D is not fundamentally prohibited during pregnancy, but uncontrolled high doses can adversely affect calcium metabolism. Therefore, supplementation should be dosed and ideally coordinated with your physician or midwife.
Muscogiuri G., Altieri B., de Angelis C., Palomba S., Pivonello R., Colao A., Orio F. Shedding new light on female fertility: The role of vitamin D. Rev. Endocr. Metab. Disord. 2017;18:273–283
Chu J., Gallos I., Tobias A., Tan B., Eapen A., Coomarasamy A. Vitamin D and assisted reproductive treatment outcome: A systematic review and meta-analysis. Hum. Reprod. 2018;33:65–80.
