Why vitamin D is vital for immunity and fertility
Vitamin D for fertility – what to know
We get so many questions from readers about which supplements to consider when trying to conceive or supporting fertility treatment. With growing interest in how to best prepare our bodies for both immunity and fertility, we turned to Bristol-based expert nutritionist Kirsten Oddy, to explore the role of vitamin D for fertility.
Why is vitamin D important?
Vitamin D is widely recognised for supporting immune health, but there’s increasing evidence that it also plays a significant role in reproductive processes for both men and women. Around one in five people have low levels of vitamin D, making now the ideal time to ensure this essential nutrient is part of your fertility support plan.
Vitamin D’s biological actions are mediated through receptors found throughout the body – not only in immune cells but also in reproductive tissues. In women, vitamin D receptors are present in the ovaries, placenta and endometrium. And in men, they’re found in the smooth muscles of the genital tract, testicular tissue and sperm.
This distribution suggests that vitamin D is involved in the regulation of reproductive functions across both sexes.
Fertility specifics – the vitamin D impact
Ovarian reserve
Vitamin D may positively influence anti-Müllerian hormone (AMH), a hormone produced by ovarian cells that’s often used as a marker of ovarian reserve and fertility potential.
Embryo implantation
High concentrations of vitamin D found in the endometrium during the first trimester of pregnancy suggest a role in supporting embryo implantation. Additionally, a key gene for implantation is upregulated by vitamin D receptors – potentially improving pregnancy outcomes and reducing the risk of complications like preeclampsia and gestational diabetes.
Polycystic Ovarian Syndrome (PCOS)
Vitamin D deficiency in women with PCOS has been linked to obesity, insulin resistance, and hormonal imbalances. Supplementing with vitamin D may improve menstrual regularity and ovulation, enhancing fertility outcomes.
Recent trials also showed that women with PCOS receiving vitamin D during intrauterine insemination had increased endometrial thickness.
Reproductive immunology
Vitamin D’s immune-modulating benefits are well documented. It can reduce the toxicity of natural killer (NK) cells – key players in the immune system – and lower levels of antiphospholipid antibodies, which are associated with poor reproductive outcomes.
IVF outcomes
For women undergoing in-vitro fertilisation (IVF), maintaining sufficient vitamin D levels is important. Adequate levels have been linked to higher chances of achieving clinical pregnancy, likely due to vitamin D’s effects on the endometrium – although genetics may also contribute to this relationship.
Sperm health
Low vitamin D levels have been associated with poor semen quality, including abnormal motility and morphology. Deficiency is also linked to reduced testosterone levels, which can impact fertility by lowering sperm production and indirectly affecting libido and erectile function.
How to increase vitamin D levels for fertility
When it comes to supporting your reproductive health, ensuring adequate levels of vitamin D for fertility is essential. While it’s known as the “Sunshine Vitamin,” vitamin D is also found naturally in small amounts in a few key foods:
- Oily fish – such as salmon, sardines, herring and mackerel
- Red meat
- Liver
- Eggs
- Fortified foods – including some dairy-free milks and cereals
Vitamin D is produced in the body when our skin is exposed to UVB light from the sun. During the spring and summer months, most people can get enough vitamin D through sunlight alone. However, in autumn and winter – or anytime sun exposure is limited – it’s important to increase dietary intake and consider supplementation.
Supplementing with vitamin D may be a helpful and low-cost addition to other fertility treatments and therapies, especially in women experiencing infertility. However, it’s important to be mindful: long-term or excessive supplementation can lead to negative health effects.
Regular testing of your vitamin D levels and guidance from a qualified nutritionist can help you stay in the safe and effective range.
