Also, I have taken it internally
When I was very sick with CF, one of the first things I learned, was my saliva PH was very acidic. When I was 4.5PH, I stunk stunk stunk! My hubby told me I smelt like my dad, an old dying man! My breath also wreaked!
So I tried every supplement (calcium, magnesium, potassium and sodium) out there to try raise my alkalinity. They all made me constipated.
Then I tried a common magnesium product you add to water, called 'calm'. I really helped me sleep. The problem with it is it helps you go to the washroom, which should be a good thing. However, the days I didn't use it, I would be constipated. I think it was bad for me for 2 reasons. Firstly, your colon is supposed to work on it's own stregngth. Anything that helps you go eventually becomes habitual.
Secondly, when using it, I found that I was losing good bacteria because it was more like diarrhea.
Sorry this all sounds gross, but having a healthy bowel is the key to feeling great, smelling lovely, and looking young!