For mine, at that age, I blamed the rice cereal. I switched to oatmeal (Earth's Best, to be precise) and life was good again for a while. Mine was still breastfed (it is supposed to help with constipation), but it still happened, I'd say at least once a month. I bought dried organic, unsulphured prunes from Wholefoods (could not find fresh and organic anywhere), boiled them in a little water, then pureed them, and frozen them in the ice cube tray. Whenever I got worried about her being constipated, I'd pop one in her food, and she'd go by the next meal... When I finished those I figured that they actually carry prune stuff at BabiesRUs, and I bought a couple from there. To be onest, the one I made was the most efficient, but the one from the shelf works too - might need to have two meals of it before it works, though.
I never gave her rice cereal again, and I go easy on the bananas - half a banana every other day is the max my 14 months gets. The other thing is to offer them water often - they don't know they are thirsty yet...
To answer your question, the foods that cause constipation are:
- High In Fat foods Like animal fats
- Low in Fiber Foods
- Foods with high cholesterol content
- Foods with high contents of margarine and flour
- Processed foods
- dairy and wheat Foods
- Refined Sugars
- Prepared proteinous food
- Supplementary iron Foods
- Supplementary calcium Foods