by Sue Bedford Nutritional Therapist)
There is growing support and evidence of the important role that Vitamin D plays in fertility as well as other health conditions and this article will explore some of the latest findings on this.
First things first! What is Vitamin D?
Vitamin D is a fat-soluble vitamin (often known as Calciferol) which is only found naturally in small amounts in a few foods. Vitamin D performs a number of important roles in the body including: contributing to the maintenance of normal absorption and utilization of calcium and phosphorus levels in the body, for the maintenance of normal bones, teeth and muscle function and contributes to the normal functioning of the immune system. It also plays a vital role in the reproductive system as a vitamin D deficiency has been linked to a variety of issues such as an increased risk of preeclampsia, gestational diabetes, lower birthweight and more recently there have been studies conducted to investigate the effects of vitamin D levels and outcomes of fertility treatment.
Vitamin D is frequently referred to as the ‘Sunshine Vitamin’ as sunlight is necessary for the synthesis of this vitamin (which is produced underneath the skin following exposure to sunlight). Vitamin D occurs in two forms: vitamin D2, which is present in a small number of foods, and vitamin D3, which is formed in the skin when exposed to sunlight. Both D2 and D3 are converted into a form that the body can use in the liver and the kidneys. People need varying degrees of vitamin D depending on where they live and their diets.
In the UK (and people living in the northern hemisphere) we don’t get enough of the kind of sunlight that causes our bodies to manufacture vitamin D under the skin. Only one kind of solar radiation does this: UVB sunlight. Vitamin D is produced only when we’re exposed to UVB rays – and unless UVB rays are present it doesn’t matter how warm it is, or in fact how brightly the sun is shining: your skin cannot produce vitamin D. Therefore, individuals who live in darker or colder environments are more susceptible to lower vitamin D levels, as are those with darker skin, those who rarely go outside and those who wear clothing that covers most of their skin. In the UK we are exposed to UVB in reality from April to October.
It is the opinion of Harvard Medical School that ‘Except during the summer months, the skin makes little if any vitamin D from the sun at latitudes above 37 degrees north or below 37 degrees south of the equator. People who live in these areas are at relatively greater risk for vitamin D deficiency’.
To ensure that we are obtaining enough vitamin D many people take a supplement during the winter months – the Department of Health suggest that from October to March it is advisable to take a daily supplement of vitamin D (10 micrograms). Everyone is different so it is advisable to contact your GP or health provider if you have an existing health condition or are unsure.
Which foods contain vitamin D?
To make vitamin D more available to us, it is added to dairy products, juices, and cereals that are then said to be ‘fortified with vitamin D’. But most vitamin D – 80% to 90% of what the body gets – is obtained through exposure to sunlight. Here are some food sources of vitamin D:
- Egg yolk
- Red meat
- Oily fish such as Sardines, Mackerel, Salmon and Herring
- Tuna
- Liver
- Mushrooms
How is Vitamin D linked to fertility?
Vitamin D has been linked to a variety of health benefits. For women trying to conceive, it appears to be linked to better fertility, as well as a healthy pregnancy.
In humans, there are vitamin D receptors present in many female organs including the uterus, ovary and placenta.
The results from studies which looked at the effect of vitamin D on fertility are not conclusive, but several studies have found that vitamin D blood levels of 30 ng/mL or higher are associated with higher pregnancy rates.
The active form of vitamin D (D3) has various important roles in human reproduction and fertilisation. It is thought to help control the genes involved in making oestrogen. It also controls several genes involved in the implantation of the embryo. Once a woman is pregnant vitamin D3 is involved in the organisation of the immune cells in the uterus. During pregnancy, if a woman is deficient in vitamin D it has been linked to some complications such as diabetes and hypertension.
In men, vitamin D status has been associated with semen quality and sperm count, motility and morphology. There is evidence to suggest that if a man is not deficient in vitamin D then there is a positive effect to be seen on semen quality, testosterone concentrations and fertility outcomes. Further studies are required in this area.
IVF and vitamin D
IVF helps in the study of the role of vitamin D during preconception from egg development to the implantation of the embryo. In a recent study it was discovered that women with higher vitamin D levels were significantly more likely to achieve a pregnancy from IVF compared to women with lower levels of vitamin D.
The study was repeated in a different IVF unit and it was found that there was a fourfold difference in pregnancy achievement between these with sufficient vitamin D levels in comparison those women who were deficient.
Another study found that donor egg recipients with a normal vitamin D level had higher pregnancy rates than those with a low vitamin D level. Further research is needed into this emerging evidence that vitamin D levels may be linked to IVF success.
Vitamin D and health
In addition, Vitamin D is used in the treatment of conditions of the heart and blood vessels, including high blood pressure and high cholesterol. It is also used for diabetes, obesity, muscle weakness, multiple sclerosis, rheumatoid arthritis, chronic obstructive pulmonary disease (COPD), asthma, bronchitis, premenstrual syndrome (PMS), and tooth and gum disease. Some people use vitamin D for skin conditions including psoriasis, actinic keratosis, and lupus vulgaris.
Although the recommended daily dose of vitamin D is 400 international units (IU), or 10 micrograms per day (mcg) new research suggests taking at least 1,700 IU of vitamin D daily to get its health benefits. And while sunshine is the best source of vitamin D, you can still load up on the vitamin by adding vitamin D-rich foods to your diet.
Vitamin D rich recipe – Mushroom soup
Shiitake mushrooms are low in calories, a good source of fibre, contain important amino acids, B vitamins and many important minerals. They also contain sterols and lipids linked to boosting the immune system and lowering cholesterol. These very tasty mushrooms also provide a great vitamin D boost as they contain D2, D3 and D4 forms. Pak Choi are an excellent source of vitamin A and C and are a good source of manganese and zinc… and then we’ve got the ginger too.
Ingredients (3 portions – double up and freeze as appropriate)
- 8 shiitake mushrooms, cleaned, stems removed and thinly cut
- 4 Pak choy, washed and cut vertically in half
- 1.5 tbsp rice vinegar
- 3 garlic, grated
- 2 thumb-sized ginger, peeled and grated
- Pinch of Sea salt
- 200 g noodles
- 700 ml of vegetable stock
- 1 tbsp of Olive oil
How to make:
- In a saucepan, cook the noodles according to their instructions, drain and set aside.
- Use the same saucepan to bring the vegetable stock to the boil and place aside.
- In a wok over a medium heat, heat the Olive oil and add the garlic and ginger, cook for roughly about 1-2 mins.
- Add the shiitake mushrooms and cook until soft.
- Next, add the Pak Choi and cook until soft, but still crunchy.
- Add rice vinegar and a sprinkle of salt and continuously to stir for another 1-2 mins. Adjust the seasoning, if needed.
- Into serving bowls, first add the noodles, then the vegetable stock. Finally top the bowl with Pak Choi and Shiitake mushrooms. Enjoy!
Further reading:
Anagnostis P, Karras S, Goulis DG (2013). Vitamin D in human reproduction: a narrative review. Int J Clin Pract;6 7(3):225-35.
Ozkan S, Jindal S, Greenseid K, Shu J, Zeitlian G, Hickmon C, Pal L (2010) Replete vitamin D stores predict reproductive success following in vitro fertilization. Fertility and Sterility; 94(4):1314-9.
Rudick B, Ingles SA, Stanczyk F, Chung K, Paulson R, Bendikson K (2010) Characterizing the role of vitamin D levels on IVF outcomes: stimulation, embryo, or endometrium? O-245, Annual Meeting of the American Society for Reproductive Medicine.
Rudick et al. Fertil Steril. 2014; 101(2):447-52.