Vitamin D and Fertility

What is Vitamin D?

• Vitamin D is a name for a group of steroid compounds, soluble in fats, which exert powerful effects on the human body, and whose receptors are found in various organs.
  
• Approximately 80–90% derives from sunlight-induced production in the skin.
  
• A small amount of the body’s total vitamin D is also derived from diet (plants, fungi, fatty fish or cod-liver oil) and/or supplements.

The vitamin comes in two main forms

Vitamin D2 (ergocalciferol): from plant sources and fortified foods.
Sources of Vitamin D2: Mushrooms (grown in UV light); Fortified foods; Dietary supplements.

Vitamin D3 (cholecalciferol): found in animal-sourced foods; produced by skin when it’s exposed to sunlight.
Sources of Vitamin D3: Oily fish and fish oil; Liver; Egg yolk; Butter; Dietary supplements.

What We Know

Vitamin D2 is cheaper to produce, it’s the most common form in fortified foods.
Vitamin D2 and D3 are not equal when it comes to raising your vitamin D status.
Both are effectively absorbed into the bloodstream. However, the liver metabolizes them differently.
Most studies show that vitamin D3 is more effective than vitamin D2 at raising blood levels.

Up to 80% of the population have low vitamin D levels. This is particularly common amongst people who lead unhealthy, sedentary lifestyles or are obese.
There is consensus that levels below 25nmol/L (10ng/ml) qualify as ‘deficient’.
There is currently no standard definition of ‘optimal’ 25(OH)D levels. Some sources suggest that levels above 50nmol/L (30ng/ml) are ‘sufficient’, while 70–80nmol/L (28-32ng/ml) is ‘optimal’.

Vitamin D and PCOS

There is some evidence suggesting that vitamin D deficiency might be involved in the pathogenesis of insulin resistance and the metabolic syndrome in PCOS.
The supplementation with vitamin D should be applied in PCOS treatment both due to an improved insulin resistance and the results of infertility treatment.

Vitamin D and Endometriosis

The pathogenesis of endometriosis is related to an impairment of immunologic mechanisms and inflammatory responses.
Evidence on the association of endometriosis with vitamin D metabolism is sparse. But we know that the endometrium is an extrarenal site of vitamin D synthesis and vitamin D action. And that vitamin D is involved in the regulation of the immune system.

Vitamin D, Fibroids & Myomas

Vitamin D deficiency is believed to be a major risk factor in the development of fibroids and myomas.
In many studies vitamin D appears to be a powerful factor against fibroids and myomas, resulting in inhibition of tumour cell division and a significant reduction in its size.

Vitamin D and POI

It has been previously established that the risk of POI increases when autoimmune conditions are present. For the immune system to function efficiently, there must be an adequate intake of vitamin D.
Vitamin D deficiency is common in women with primary ovarian insufficiency (POI).
Vitamin D has a direct effect on AMH production, and thus increases longer maintenance of ovarian reserve in the patients with its higher concentration.

Vitamin D and Male Factor

In male infertility both low (<20 ng/ml) and high (>50 ng/ml) concentration of vitamin D in serum negatively affects spermatozoa number per ml of semen, their progressive movement and morphology.
Vitamin D supplementation can improve semen quality, fertility outcomes and testosterone concentrations.

Vitamin D and Live Birth

Women diagnosed with infertility during the vitamin D exposed period had an 87% higher chance of having a live birth in the 12 months following their diagnosis, compared to women diagnosed later, during the non-exposed period.

Vitamin D and IVF

Studies investigating the association of vitamin D status with IVF outcome revealed inconsistent results.
Several observational studies reported a better in-vitro fertilization outcome in women with sufficient vitamin D levels (≥30 ng/ml), which was mainly attributed to vitamin D effects on the endometrium.
Women with correct levels of vitamin D were:

• 34% more likely to have a positive pregnancy test.
• 46% more likely to achieve a clinical pregnancy.
• third more likely to have a live birth.