If you suffer from digestive problems, allergies, nutrient deficiencies or unexplained changes in moods, then perhaps something in your diet is a contributing factor.
From the same author of the original 2011 Foods and Moods application for OS X, Foods and Moods for mobile allows you to track what you eat and how you feel while you're on the go. The mobile version has the same summary view to help find commonalities, in addition to a new correlation view, which graphs out your moods and meals in one-week slices.
For each meal entry you can track:
* Date and time of meal
* Type of meal
For each mood entry, you can track:
* Date and time of mood
* Rating of how you feel from 1 to 10
Unfortunately, the OS X version is currently not iCloud compatible to sync with the mobile version, due to a more efficient data structure for mobile. The OS X version may be updated in the future.