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How to Improve your Vitamin D levels to Support Fertility by Sarah Trimble

By May 6, 2022May 10th, 2022No Comments
Vitamin D

Making improvements to our lifestyle and eating better is an essential step in preparation for trying to conceive. However, there is one specific fertility enhancing nutrient that we can’t get enough of from our diet, vitamin D. While certain foods contain small amounts of vitamin D, it is impossible to meet our requirements for vitamin D from diet alone and, as a result, deficiency is very common. Testing for and then treating vitamin D deficiency is a relatively straightforward way to improve both male and female fertility and improve the chances of conceiving. 

Vitamin D: why it’s difficult to get enough 

Vitamin D is essential for healthy reproductive function for both men and women. It acts more like a hormone in our bodies because it controls several important bodily functions – some of which are key reproductive functions. It is almost impossible to know if you are getting enough vitamin D because our main source is sunlight. When UVB rays hit our skin they stimulate a chemical reaction in the body that results in vitamin D production and we rely on the action of sunlight for around 80-90% of our vitamin D stores. As mentioned above, you can find small amounts of vitamin D in foods such as eggs, liver, oily fish, and mushrooms, however, we can’t get adequate vitamin D levels from diet alone.

Because we rely on sunlight to produce vitamin D, it is estimated that around 50% of the UK population is vitamin D deficient. In the UK we don’t get enough strong sunshine throughout the year, in fact from October to March the sun’s rays are not strong enough to stimulate vitamin D production. Spending time in the sun during the spring and summer months can build vitamin D stores, however, the body can quickly use up these stores over the autumn and winter months. 

Because we don’t know how much vitamin D our body is producing from sunlight exposure, it can be difficult to predict vitamin D levels and there are many risk factors for developing a vitamin D deficiency. 

Risk factors for vitamin D deficiency

  • Inadequate sunlight exposure: we should be exposing our skin to sunlight between 12-3 pm when most of us are at work. 
  • Dark skin colour: individuals with darker skin need more sunlight to stimulate vitamin D production and can find it difficult to get enough in the UK climate. 
  • Obesity: fat tissue absorbs and retains vitamin D, making it inactive
  • Poor absorption: digestive issues that affect the absorption of dietary vitamin D include gallbladder removal and coeliac disease

 Vitamin D and Female Fertility

Having optimal vitamin D levels can have a real positive impact on female fertility. In some studies, women with better vitamin D levels were 3 times more likely to get pregnant than those women who were vitamin D deficient, and having healthy vitamin D levels improves the chances of having a healthy pregnancy. Vitamin D deficiency is considered a risk factor for miscarriage. Having higher blood levels of vitamin D can also improve symptoms of PCOS and endometriosis – the two most common conditions that reduce women’s chances of conceiving. 

Immune system imbalances can negatively impact a woman’s chances of conceiving and increase the risk of miscarriage. Improving vitamin D stores is an important and straightforward way to rebalance the immune system. Vitamin D acts as an immune system modulator, balancing an immune system that might be underactive or overactive. The research shows that women with better vitamin D levels in the pre-conceptual period have a reduced risk of miscarriage and better rates of conception during IVF. It is recommended that all women who are trying to conceive, either naturally or through IVF should test their vitamin D status so that appropriate steps can be taken to achieve and maintain healthy vitamin D stores. 

Vitamin D and Male Fertility

Vitamin D can help to improve sperm health and the research shows a very clear and direct relationship between better blood levels of vitamin D and better semen quality. Men who had good levels of vitamin D had better sperm, quality, concentration, and motility compared to men who were vitamin D deficient. Vitamin D is linked to testosterone production and men with low testosterone levels saw these levels improve after spending more time in the summer sun and naturally increasing their vitamin D. In one study infertile men who were treated for vitamin D deficiency saw their testosterone levels and sperm quality improve in line with improved vitamin D levels. 

How to optimise vitamin D levels to support fertility

An important first step is to test vitamin D levels either with your GP or using a private testing kit. When preparing the body for conception and pregnancy achieving vitamin D levels of 100nmol/L (or 45ng/ml) is recommended. If your vitamin D levels are well below this it is recommended to supplement with vitamin D for a few months to increase vitamin D stores. 

Experts use the following equation to determine the dosage of vitamin D required to increase vitamin D levels over 2 months: 

(Target level – Current vitamin D level in ng/ml) x (Bodyweight in kg/70) x 10,000 

An example for someone aiming for levels of 45ng/ml: 

Target level = 45ng/ml Current vitamin D level = 25ng/ml Body weight = 75kg

(45-25) x (75/70) x 10,000 = 214,285 

A dosage of around 3,500 i.u. daily is required to reach vitamin D levels of 45ng/ml over 60 days.

Nuabiome For Women and Men provides 400 i.u. of vitamin D, which will maintain an already healthy vitamin D status, and can safely be used together with an additional vitamin D supplement for a few months if vitamin D deficiency is discovered. 

Always seek the advice of your GP, a qualified medical or nutritional professional before introducing any nutritional supplementation. 


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Andersen LB, Jørgensen JS, Jensen TK, Dalgård C, Barington T, Nielsen J, Beck-Nielsen SS, Husby S, Abrahamsen B, Lamont RF, Christesen HT. Vitamin D insufficiency is associated with an increased risk of first-trimester miscarriage in the Odense Child Cohort. Am J Clin Nutr. 2015 Sep;102(3):633-8. 

Mumford SL, Garbose RA, Kim K, Kissell K, Kuhr DL, Omosigho UR, Perkins NJ, Galai N, Silver RM, Sjaarda LA, Plowden TC, Schisterman EF. Association of preconception serum 25-hydroxyvitamin D concentrations with live birth and pregnancy loss: a prospective cohort study. Lancet Diabetes Endocrinol. 2018 Sep;6(9):725-732. 

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Cito G, Cocci A, Micelli E, Gabutti A, Russo GI, Coccia ME, Franco G, Serni S, Carini M, Natali A. Vitamin D and Male Fertility: An Updated Review. World J Mens Health. 2020 Apr;38(2):164-177. 

Kumari S, Singh K, Kumari S, Nishat H, Tiwary B. Association of Vitamin D and Reproductive Hormones With Semen Parameters in Infertile Men. Cureus. 2021 Apr 15;13(4):e14511.

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Pilz S, Frisch S, Koertke H, Kuhn J, Dreier J, Obermayer-Pietsch B, Wehr E, Zittermann A. Effect of vitamin D supplementation on testosterone levels in men. Horm Metab Res. 2011 Mar;43(3):223-5. 


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