any time you drastically alter your dietary intake the digestion will change. most likley this is due to the digestion being shocked. there are different enzymes needed to digest different kinds of food. so your husband has been producing certain kinds of enzymes for a long time to digest the food he normlally eats, now all of a sudden he eats differently and the body needs to produce different enzymes to digest the food, but can't just switch up instantly. he may just want to go back to his regular diet. if he wants to improve his diet then start introducing a healthier diet over a period of days or weeks. constipation is not good. i have read a lot of posts in this forum from people who have digestion problems from altering their diet completely overnight, the body has a hard time with it.