I take it occasionally. It works for me. You could also take a daily fiber supplement. My guilty pleasure is a 90-calorie treat from FiberOne. They have lots of delicious (but potentially triggering) 90-calorie options -- brownies, mint brownies, coffee cake, etc. And it deliciously resolves my constipation issues.
My protein bars actually are really good, but like you I am affected by my diet. I actually usually take something over here called Senokot, not sure if it is available in the states. It is just a herbal pill that you can take before bed to aid bowel movement. If you try the milk of magnesia then let me know
Maybe this is obvious, but I find that eating a lot of high fiber vegetables helps, as does drinking a ton of water. But if those are difficult for you, then yeah, taking a laxative might help (although not regularly, since that could make the problem worse).
Fiber and fluid are both important, but may not be enough. People trimming calories often don't each much fat. Try to make sure you get enough healthy fat in your diet. A little olive oil (for example) can really help with this problem.
Milk of Magnesia??/
