Many women take vitamin D while trying to conceive and in preparation for IVF knowing that having stellar vitamin D levels may improve their chances of conceiving considerably. What they may not know, is that taking vitamin D at the optimal time of day can dramatically improve absorption of this vital fertility vitamin.

Vitamin D is a fat-soluble vitamin, this means that you will absorb it far better with food, not just any food, it really needs to be taken with a meal that contains other fats or oils to trigger the digestive enzymes and processes that break down and assimilate fats. Taking vitamin D with a piece of fruit, a glass or water or a light, low fat meal may be akin to taking very little vitamin D at all. Not so great for your fertility.

A Cleveland clinic study (1) sought to examine the effect of consuming vitamin D with different types of meals and discovered that vitamin D absorption may increased by an astonishing 56.7% simply by taking the vitamin with a main meal. The researchers concluded that:

"...it is concluded that taking vitamin D with the largest meal improves absorption and results in about a 50% increase in serum levels of 25(OH)D levels achieved. Similar increases were observed in a wide range of vitamin D doses taken for a variety of medical conditions."

This is very important information to take note of if you are taking vitamin D to improve your fertility, this is also good to remember during pregnancy when good vitamin D levels are also vital to maintain.

A 2011 review (2) from the Medical University of South Carolina has shed light on the controversial topic of vitamin D requirements in pregnancy. Although the RDA for vitamin D has been increased from 400 IU a day to 600 IU - the level in many prenatal vitamins is still 400 IUs, a level considered by many experts to be wholly inadequate especially during pregnancy.

The topic of vitamin D supplementation is rarely addressed pre-conceptually or at the twelve week ante-natal visit leaving many women in the dark about new recommendations. The 2011 review concludes that ten times the usual amount of vitamin D may be needed:

"Current evidence supports the concept that circulating 25-hydroxyvitamin D should be 40-60 ng/ml (100-150 nmol) during pregnancy and a daily intake of 4000 IU vitamin D3 is required to attain that circulating level."

If you are trying to conceive or are pregnant ask your physician for a 25-hydroxy vitamin D test to check your levels. If they are low ask about beginning a supplement program and re-testing to make sure that your levels are adequate to conceive, and to have a healthy pregnancy.

Vitamin D3 is considered to be the safest form of vitamin D to supplement. Studies have shown that having good vitamin D levels can have a protective effect upon your pregnancy reducing the incidence of premature birth so it is important that your levels are good.

This article is for informational purposes only and is NOT intended as a substitute for medical or nutritional advice for which you should consult a medical physician or dietitian.

1. J Bone Mineral Res. 2010 Apr;25(4):928-30.
Taking vitamin D with the largest meal improves absorption and results in higher serum levels of 25-hydroxyvitamin D.
Mulligan GB, Licata A.


2. Curr Opin Endocrinol Diabetes Obes. 2011 Aug 17. [Epub ahead of print] Hollis BW, Wagner CL. Vitamin D requirements and supplementation during pregnancy.