Vitamin D was once a very unassuming micronutrient, known mainly for its role in in bone health, but fast forward a few years and vitamin D has established itself as a key player in immune and metabolic health, with a starring role in fertility.
Photo Credit: Nichola Solerieu
How does vitamin D work?
Vitamin D is formed in the body when the sun is exposed to our skin. It is converted into its active form via the liver and kidneys, which is then taken to the cells to be used (1). Cloudy skies and rain, and a distinct fondness for complaining about this, are a common feature in the UK! This means vitamin D is not easily absorbed and deficiencies can easily occur during autumn and winter. But it’s not just the UK that has this problem, vitamin D deficiency is common throughout the world, even in sunnier climates. There are many reasons for this, including; skin colour, latitude, disease, increasing time spent indoors, sun screen, and an array of other factors.
What role vitamin D play in fertility?
Vitamin D plays a role in hormonal function, and in terms of fertility, it regulates sex hormones via the pituitary gland (2), as well as playing a role in oestrogen production (3). Hormonal balance is essential in the menstrual cycle and consequentially for fertility levels.
Vitamin D deficiency may also play a role in disorders such, as PCOS and endometriosis. These disorders are known to affect fertility, as well as causing a range of unpleasant symptoms. For those with PCOS, low levels of vitamin D can contribute to hormonal and insulin imbalance (2), and for those with endometriosis, low levels of vitamin D may trigger an immune inflammatory response (2).
When trying for a baby, higher levels of vitamin D may improve the chances of conceiving. In IVF studies, those with higher vitamin D levels were more likely to conceive than those with lower levels (4). Some studies indicate that vitamin D may also help in the process of the embryo being implanted in the uterus (5). The good news is, the benefits of vitamin D are not restricted to fertility in women, studies have also found that vitamin D can be beneficial for sperm motility in males too (6).
What foods can I find vitamin D in?
Unlike most vitamins and minerals, which are found in numerous foods, vitamin D is limited to a few select food sources. This is because, like humans, animals, and also mushrooms, absorb the vitamin D through direct sunlight through their skin.
Mushrooms can be a very good source, but this is very dependent upon their growing conditions. Wild mushrooms, effectively the sunbathers of the mushroom world, contain high amounts of vitamin D2, however, they’re commercially grown friends tend to be grown in the dark, so are deplete. Some commercially grown mushrooms are treated with UV light to synthesise the D2 (7), so it’s best to check on the packaging if you’re unsure. Other sources of vitamin D include oily fish and eggs. Again, the levels of vitamin D will vary greatly depending on the environment. Vitamin D can also be found in some fortified products, such as cereal products, although not all. Talks are ongoing about wide spread fortification of foods with vitamin D, just like some other key micronutrients.
Should I be supplementing?
In the UK, from October to March, when the weather is dreary and the UV rays aren’t at their peak, it is recommended that adults, including pregnant and breastfeeding mothers, should take a 10 microgram (400IU) supplement of vitamin D3 per day. For those that have darker skin, and those with very minimal sun exposure, even in spring and summer it may be beneficial to supplement throughout the year (8).
However, if you have LOW levels, you will need MORE than this to get your levels up to an optimal level. (Though make sure you do this under the supervision of a health practitioner!)
You may not get enough Vitamin D if: ✅ You don’t get enough sunlight (especially during winter!) ✅ You don’t take supplements (it’s hard to get enough Vitamin D from the foods you eat alone) ✅ You have naturally darker skin. The darker your skin is the more sun you need to get the same amount of vitamin D as a fair-skinned person. ✅ You are overweight
How do I get the most out of vitamin D?
Vitamin D, does it best work with a little help from its friends. Vitamin D and calcium are an important pair. Vitamin D is required to absorb calcium, which is extremely important for bone health (9), particularly for us ladies to prevent osteoporosis. Make sure you’re getting enough calcium in your diet by adding lots of green leafy vegetables, sesame seeds, pulses, some dried fruit and fortified foods.
Magnesium is also part of the dream team, alongside vitamin D and calcium. It allows vitamin D to be converted into its active form, calcitriol (10). This allows vitamin D to work its magic across the cells in the body. Magnesium rich foods include; leafy green veg, nuts, seeds, bananas, sweet potatoes, legumes and 70% cocoa dark chocolate.
1) Wintermeyer, E., et al., 2016. Crucial Role of Vitamin D in the Musculoskeletal System, Nutrients, 8 (6).
2) Muscogiuri , 2017. Shedding new light on female fertility: The role of vitamin D, Reviews in endocrine and Metabolic Disorders, 18, 273-283.
3) Kinuta, K., Tanaka, H., Moriwake, T., Aya, K., Kato S and Seino, Y., 2000. Vitamin D is an important factor in estrogen biosynthesis of both female and male gonads. Endocrinology, 141, 1317–1324.
4) Paffoni, A., et al., 2014. Vitamin D Deficiency and Infertility: Insights From in vitro Fertilization Cycles, The Journal of Endocrinology and Metabolism, 99 (11), 2372-2376.
5) Cermisoni et al., 2018. Vitamin D and Endometrium: A Systematic Review of a Neglected Area of Research, International Journal of Molecular Science, 19 (8).
6) Cito, G., et al., 2020. Vitamin D and Male Fertility: An Updated Review, The World Journal of Men’s Health, 38 (2), 164-177.
7) Simon, R. R., et al 2013. Safety assessment of the post-harvest treatment of button mushrooms (Agaricus bisporus) using ultraviolet light, Food and Chemical Toxicology, 56, 278-289.
9) Cashman, K.D., 2007. Calcium and vitamin d, Novartis Found Symp, 123-138.
10) Rosanoff, A., Dai, Q. and Shapses, S.A., 2016.Essential Nutrient Interactions: Does Low or Suboptimal Magnesium Status Interact with Vitamin D and/or Calcium Status?, Advances in Nutrition, 7 (1), 25-43.