Do you have a smart, creative, loving child who is also cranky, inattentive, and sometimes downright obnoxious? If you've written off this negative behavior as "typical" for your child's age--whether toddler or teen--stop and think: Does your child have a taste for soda, sugary breakfast cereals, and treats like candy and cookies? Does she eat regularly scheduled meals or skip them? What, exactly, does he drink and snack on throughout the day?

Your child's behavior may be linked to diet--specifically to the sugar in obvious sources like sweets and soda and to hidden...