What causes vitamin d deficiency other then lack of sun? and does it hurt fertility if you are deficient?

Mostly low sun, YES!: Sun is our main source of Vit D; one can get some from cod liver oil, salmon & other foods but food can't provide enough D. Except in the deep south we can not produce any D from the sun in fall & winter months so everyone should take 5-8000 iu of D3/day in those months! There is strong evidence that low D can cause infertility. See http://natural-fertility-info.com/fertility-vitamin-d.html

Primarily sun: The sun is the primary source of vitamin D. We are doing a good job of preventing skin cancer with our sunscreens and spending more time indoors but it has caused an epidemic of vit. D deficiency. Vitamin D is now considered a "pro-hormone" so healthy levels are important for all kinds of things. Don't throw away your sun screen (skin cancer is still bad). Take a supplement but be careful how much

Here you go.: Vitamin D is made in the skin in response to sunlight. Vitamin D3 can also be taken in supplement form. Most physicians under-dose vitamin D. Vitamin D is essentially a hormone, and is crucial in many bodily processes. Being deficient can have many negative health consequences and is very common. See a forward-thinking physician and get your vitamin D up to the optimal range for best health.