I go on a two hour bike ride almost daily, so I get a lot of sun, but I decided recently to start taking D3 after reading so much about it. I started talking 2,000 IU/day (for almost three weeks) and got massive constipation to the point that I could only go once a week, and had painful stomach cramps. I quit talking the D3 and quickly returned to normal within a couple days, and haven’t taken it since.

I did some research and read that it’s a common side effect. One article said that suffering constipation from Vit D is a sign that you’re low on magnesium… So now I’m thoroughly confused.