what are the best and most cost effective? whenever i eat i get full for a long time and can't eat every few hours like i want to. I had 2 scoops of optimum whey in skim milk this morning for breakfast and an apple and i felt like crap. the only thing that helps is taking enzymes. are these good to take all the time? and is there a reason i would need digestive enzymes? like a medical issue or do some people just have less than others?