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Vitamin D deficiency is one of the leading dietary deficiencies worldwide.

It is especially prevalent among women and children. Vitamin D deficiency affects every 1 out of  3 women in the reproductive years of 19 to 45. Depending on your skin color, amount of time you spend outdoors and the latitude of the place you live in, chances that you are vitamin D deficient could be even higher.

Statistics have shown that 93% of the women with infertility issues suffer from vitamin D deficiency. And just today I’ve read an interesting study published in 2014 in Human Reproduction: 368  women were treated over a period of 15 months prior to IVF cycle. Following the single embryo transfer on the day 5 , it turned out that pregnancy rates were lower in women with vitamin D deficiency compared to those who had normal vitamin D levels.

In other words, findings suggest that women with sufficient levels of vitamin D are more likely to achieve pregnancy following IVF or ICSI treatment. Therefore, vitamin D supplementation (with supplements like this one for example) could provide an easy way to improve pregnancy chances.

The biosynthesis of vitamin D is quite complex, even if you are a biochemist and in love with vitamin D like I am. It means that multiple organs orchestrate together to produce the final, bioactive form of vitamin D. That substance is called 1, 25-dihydroxyvitamin D3 (vitamin D is just a short name to describe it) and it is best known for maintaining calcium and phosphate balance in the body, among other things.

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Vitamin D is of special importance in women of reproductive age and in pregnant ladies. A healthy vitamin D status is imperative for a healthy pregnancy and for normal development of the fetus. And there are many more other processes which just don’t function well without a proper vitamin D, for example:

• Muscle activity
• Maintenance of bone density
• Contractility muscle fibers in the heart
• Neuronal activity (i can’t count how many brain-derived cell lines I’ve seen functioning better with vitamin D)
• Cellular growth and proliferation
• Immune response

Besides, studies from recent years have shown that vitamin D deficiency plays a role in onset of several disorders in mothers, such as:

• Preeclampsia
• Insulin resistance
• Gestational diabetes
• Increased the risk of C-sectional delivery
• Depressive disorders including postnatal depression
• Increased risk of infections due to depressed immune system
• Hormonal irregularities as a result of impaired hormone synthesis

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So how vitamin D increases fertility?

Vitamin D receptors have been found in all fertility-related organs and cells, including sperm, ovaries and placenta. Vitamin D receptors are proteins which actually do the real work in the cell, but need vitamin D molecules to dock onto them first, so they can change their shape and convert to the active form. This sounds weird I know, but that is actually a common way how protein receptors work. To come back to how vitamin D increases fertility:

Vitamin D was found to affect sperm motility as well as several other parameters associated with sperm quality.

Vitamin D was found to improve embryo quality and positively affect endometrial receptiveness, both are currently really hot research areas. Vitamin D seems to improve egg quality  and this may have to do with the last complex meyotic step which takes place in the ovulating egg, but many details still need to be worked out. Also in IVF patients, vitamin D status proved to be a better predictor of success then any other conventionally used clinical parameter.

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By strengthening the immune system, vitamin D works against unexplained infertility. And just recently I’ve come across the study which reported that naturally increased levels of vitamin D over 20 weeks of seasonal change,  improved fertility in overweight as well as in Polycystic Ovarian Syndrome (PCOS) patients.

Some more protective effects of vitamin D include:

• Vitamin D protects against the breast cancer by downregulating several genes involved in carcinogenesis. It can trigger apoptosis (kind of cellular suicide) of cancerous cells.
• By strengthening the bones and letting calcium and phosphates take their places, vitamin D significantly lowers the risk of bone fractures. This is especially true for older women but applies to women of all ages.
• Vitamin D boosts the immunity and thus, protects against infections and chronic inflammatory disorders.

A dietary intake of at least 2000 IU daily protects against the adverse effects of vitamin D deficiency, but whether that dose is enough to achieve and maintain a healthy vitamin D level is something you can only find out by making a simple blood test for vitamin D. Have you even done that? It is really simple and the last time I did it, it cost me about $30. Not a huge investment for such an important information, I would say.

My favorite vitamin D supplements (5000IU, 2000IU) and books

(the first is about a self-experiment with high doses of vitamin D, the second is written by the world’s leading vitamin D-expert):