I do not think eating prior to taking the collagen makes a difference to the efficacy, which we are interested in, i.e., stronger bones. I use a brand sold by NutriKey. There is nothing on the label about taking it with or without food. It seems to me they would specify that if it's important.

I'm not sure but many supplements recommend taking with food though food-based supplements usually do not and citrate forms of calcium say you can take anytime. Perhaps it's the same with magnesium citrate as well. Might be a good idea to try it with some food to see if it helps or perhaps switch to the forms that don't cause stomach upset.