Vitamin D deficiency is blamed for most things these days (!) but what does the science say about its role in male fertility? More specifically the growing sperm crisis.

What crisis you may ask? The fact that sperm counts (on average) have fallen over 50% in the last 40 years.  Click here for much more. 

Let’s take a look at the latest science which is starting to suggest that Vitamin D could play a positive role:

We know two interesting things when it comes to Vitamin D:

Firstly, many of us, particularly in the Northern Hemisphere are deficient. With some data in the US for example showing deficiency in as many as 40% of the population. Obviously with wide variations within that. (9) 

Secondly, we know that Vitamin D now has a much greater role to play in keeping the body in optimal function than we had previously thought. We are learning it plays a role in almost everything. From hormone production and regulation, to even the immune system. Research has even demonstrated links between adequate vitamin D levels in pregnancy and development of autoimmunity or infection risk in children. Click here for more. 

So what about for men and their fertility?! 

We know that sperm has been under fire over the last few decades. Data suggests sperm counts have fallen over 50% in the last 40 years. Click here for more. As always, there is rarely a single, ‘silver bullet’ reason. The reality is that there are many potential reasons often in combination behind why this may be happening. 

Is Vitamin D deficiency one of them?

We have known for a while that Vitamin D is important in some way for male reproduction. How do we know this? Well we know that Vitamin D receptors and metabolising enzymes are present in the testis and spermatozoa (which in English is the reproductive cell within semen) (3, 4). This has led to further investigation…. 

The question is how (and how much) does this matter when it comes to trying to have a healthy baby? 

The reality is, despite quite a bit of investigation (in both animal and human studies) the data is pretty murky with quite a bit of contradiction. Sigh. If only it were so simple! 

However, here is what we do know:

Although there is less conclusive evidence around its role in testosterone production for example, experimental studies have shown a beneficial effect of Vitamin D on male fertility. Largely related to semen quality. In fact the most consistent supporting evidence lies around its impact on sperm motility (3).  An important part of the picture. 

We also know that it may play a crucial role in protection of sperm. There is in fact evidence to suggest that having enough Vitamin D may be protective against something we know is at the heart of many issues when it comes to sperm. This is DNA damage (or fragmentation) resulting from oxidative stress. Something that sperm cells are particularly vulnerable to. Click here for a lot more on this.

How does it provide protection? 

Some studies have shown Vitamin D plays a role in producing FOXO3 which is an ‘important molecule in the prevention of oxidative stress’ (4). Once again, oxidative stress is something that research is suggesting lies at the heart of damage to sperm. Moreover, it has been shown that DNA fragmentation increases significantly in the spermatozoa of animals with vitamin D deficient diet.’ (4)

Other areas like regulation of key hormones like testosterone have been examined but as of now the results are inconclusive. 

So: what to do?

Well as with most things, keeping a healthy and balanced body is always the way to go. Particularly when it comes to trying to have a healthy child. Vitamin D plays a significant role in many of our body’s functionality. It seems healthy sperm is another avenue. 

How to get enough?

We firmly believe that getting your own individual picture is always the best way to go. A simple blood test that you can ask your doctor to do will tell you very quickly your own internal picture. 

Deficiency is defined as a level of less than 37.5nmol/l (10,11).

The most effective way to get enough Vitamin D is of course via the sun. Half an hour of sunlight delivers 50,000 iu of Vitamin D with Caucasian skin (5). It is worth bearing in mind that skin pigmentation lowers the amount of Vitamin D synthesis that you get from UV exposure, so, the darker your skin the less you get (6) 

What does 50,000 iu mean in ‘real life’?!

These numbers can be super confusing. Here is some context. 10 micrograms is the amount recommended by NICE guides for pregnant and breastfeeding mothers. This is equivalent to 400 iu. So as you can see 50,000 from the sun is a lot! (7,8) 

The main risk factors for a low level are:

• You live in an area with less sunlight or you spend a lot of time indoors.
• During the winter months when the days are shorter
• If you always cover your skin and always use high factor sunblock
• If you have darker skin
• If you are obese (BMI +30)
• If you are a Vegan: eggs, oily fish are rich in Vitamin D
• Genetics: some people have genetic abnormalities which impact how Vitamin D is metabolised and transported around the body.

How do you get more?

Of course sun exposure is a tricky thing as we are all now more aware of the dangers of too much sun! (Never easy is it?!). Everyone is different but the good news is that you don’t need to sunbathe. Typically just 15 minutes a day in the sun, two or three times a week, should be enough in sunny weather, and you only need to expose your arms and face. Of course everyone is different and it depends on your skin type, the time of day and the time of year. If in doubt, get your levels tested and avoid too much exposure particularly during the midday heat. Sun Safety is equally important.

What about supplements? What (if anything) should I take?

Once again speaking to your doctor and checking your levels is always good before supplementing with anything. That being said, it is important to ensure you are getting enough. If sun exposure isn’t for you and you did want to take a supplement, taking D3 with a fat to help absorption (click here for much more) is the way to go. Remember though. Always speak to your doctor before starting any supplement.

Footnotes:

(1) Vitamin D and Testosterone in Healthy Men: A randomised Controlled Trial: The Journal of Clinical Endocrinology & Metabolism: Vol 102, Issue 11,  Nov 4292-4302

(2) Effect of Vitamin D supplementation on testosterone levels in men: Hormone Metabolic Research: 2011: Mar; 43(3): 223-5 

(3) The Role of Vitamin D in male fertility: A focus on the testis: Review Endocrinology & Metabolic Disorders: 2017: Sep: 18(3): 285-305

(4) Vitamin D and Male Fertility: An updated Review: World Journal of Mens Health: 2019;37 

(5) Yu CK, Sykes L, Sethi M, Teoh TG, Robinson S. Vitamin D deficiency and supplementation during pregnancy. Clin Endocrinol (Oxf) 2009;70:685–90.

(6) Moukarzel S, Ozias M, Carlson S: Maternal Vitamin D Status and Infant Infection: MDPI Nutrients: 2018: Feb: 10(2): 111

(7) Chief Medical Officers for the United Kingdom. Vitamin D – advice on supplements for at risk groups. Cardiff, Belfast, Edinburgh, London: Welsh Government, Department of Health, Social Services and Public Safety, The Scottish Government, Department of Health; 2012 [http://www.scotland.gov.uk/Resource/0038/00386921.pdf].

(8) National Institute for Health and Clinical Excellence. Antenatal care. NICE clinical guideline Manchester: NICE; 2008.

(9) Parva NR, Tadepalli S, Cheriyath P: Prevalence of Vitamin D Deficiency and Associated Risk Factors in the US Population: Cureus: 2018 Jun; 10(6)  

(10) Merewood A, Mehta SD, Chen TC, Bauchner H, Holick MF. Association between vitamin D deficiency and primary cesarean section. J Clin Endocrinol Metab 2009;94:940–5.

(11) Bodnar LM, Krohn MA, Simhan HN. Maternal vitamin D deficiency is associated with bacterial vaginosis in the first trimester of pregnancy. J Nutr 2009;139:1157–61.

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