We hear a lot about this nutrient, however you may not realise the significant impact it has on fertility.  In fact, this nutrient is even referred to as a pro-hormone due to its widespread activity in the body, yet I find almost all my patients are deficient.

It’s vitamin D.

You have likely heard of the importance of vitamin D in bone health, where it helps to transport calcium to our bones to support the maintenance of optimal bone strength.

However, Vitamin D also plays a vital role in fertility.  This is largely due to its role in hormone production and regulation.

Vitamin D deficiency is extremely common, especially in women struggling with fertility.  In a study from Yale University School of Medicine it was found that 93% of infertile women, had low levels of vitamin D.

A recent review of current data relating to the impact of vitamin D deficiency on fertility showed that healthy vitamin D levels improve fertility and ability to fall pregnant and have a healthy pregnancy.

Healthy vitamin D levels are associated with higher rates of successful pregnancy in women undergoing IVF treatment, whether this be using their own eggs or via egg donation.  Researchers suggest that this may be due to the role of vitamin D in immune regulation, improving implantation and immune balance to support acceptance of the embryo.


Vitamin D supplementation has also been found to be effective in improving fertility issues associated with Polycystic Ovarian Syndrome (PCOS) and the related blood sugar imbalance, insulin resistance, cravings and weight gain.  Vitamin D may also play a role in endometriosis.

So it is clear that vitamin D has a much greater role in the body than just calcium absorption.

Vitamin D is also a unique prenatal nutrient during pregnancy.  It is unique in that deficiency can be passed on to your baby.  For most other nutrients, the baby will take everything it needs from the mother, even leaching nutrition from Mum’s bones where necessary, leaving the mother deplete but keeping baby healthy.  This is not the case with vitamin D.

The unfortunate reality is that deficiency is much harder to treat in the infant after birth than it is prior to birth.  So having healthy vitamin D levels going into pregnancy not only supports your ability to conceive but also helps pass on those healthy levels to your baby.

Deficiency in the infant can impact the child’s short and long-term health, including growth retardation, low birth weight, premature labour and reduced health of bones and teeth.

Studies also link vitamin D deficiency in the infant, to a range of disorders in the child, including diabetes and neurological disorders, both short term and later in life.

So it is very important to ensure healthy vitamin D levels, not only to improve fertility and support a healthy conception and pregnancy, but for the long term health of your future baby.

Personally, I like to check Vitamin D levels as early as possible, because deficiency can take some time to rectify.  Many nutrients, like vitamin C and the B vitamins are water soluble meaning levels can be very quickly boosted.  Vitamin D is a fat soluble nutrient, which means increasing levels can take much longer.

For water soluble nutrients, levels increase almost immediately post supplementation or increased intake, however, improving vitamin D levels can take months.

The good news is that getting your vitamin D levels checked is a simple as requesting a blood test from your GP.

Once you have your report it is best to work with someone like myself or your Naturopath to be advised on the best dose and supplement for you.

As a general guide, around 1000IU is what I recommend for people with relatively healthy levels.  Around 4000IU has been frequently used in studies to support fertility, with much success.  However, some studies are using up to 60,000IU.  So professional guidance on the best dose for you is recommended.

Of course, we all know that vitamin D is the sunshine nutrient.  The best natural source of vitamin D is getting outdoors into the sunshine.

You would think we would be getting plenty of that here in Australia.  (Or maybe not so much here in Melbourne!)

However, it is very hard to quantify how much vitamin D we get from sunshine.  We are all metabolically different and we all metabolise vitamin D from sunshine differently.  For some people 15 minutes on their lunch break will be sufficient.  For others this will be no where near enough.  Studies show that some people absorb no vitamin D from sunlight at all in the winter months.

Our use of protective sunscreens also impairs our ability to metabolise vitamin D.  Yet the risk of cancer from too much sun exposure is real so slip, slop, slap is of course a valid message.

Therefore the current Australian and New Zealand guidelines recommend supplementation over sun exposure, especially in the important preconception and pregnancy period.

Now, I would normally talk about dietary sources, which are so important.  But vitamin D is one of the few nutrients where very little is available through food sources.

Cod or cod liver oil is a good source of vitamin D.  (My my brother and I used to be given a tablespoon of cod liver oil every morning over the winter months to support our immune system.  Strangely enough we used to love it!)  However, if you are pregnant, cod liver oil is also high in vitamin A, which needs to be cautioned during pregnancy.  So I don’t recommend using this a your primary source of vitamin D.

Salmon and dairy are other good sources however there are other factors such as endometriosis, when dairy may not be recommended.

The other issue with food sources is that metabolism of vitamin D from our diet is relatively poor.  For this reason, correct supplementation is important if your levels are low.

So the important thing to remember about vitamin D is that it is not just for bone health, low levels can have a significant impact your ability to conceive and carry a healthy baby.  Low levels during pregnancy can also have a significant impact on the long term health of your baby.

The best way to improve vitamin D levels is by getting outdoors and getting a healthy (and safe) dose of sunshine, which can offer many other positive benefits on mood and stress levels as well.  And by having your levels checked by your GP and using supplementation where indicated.

I hope this has given you a greater understanding of the role of vitamin D in fertility as well as ways you can start addressing any potential issues today!