Cup soups are not exactly what nutritionists would recommend as food for babies and toddlers. MSG or monosodium glutamate is a flavor enhancer of many processed food items. Though MSG is considered generally safe and approved for use, some people have shown side effects such as dizziness or have developed allergic reactions.
About three decades ago, some baby food manufacturers tried to lessen the food additives (not only MSG) in their products after some reports of brain damage or mental retardation that could have been caused by food additives were discovered.
Offer your babies a variety of food and go natural by making fresh broth more often. In minute amounts, these additives should be safe. There should be nothing wrong if you give instant cup soups sparingly.