The "Sugar" in Ingredients Lists Not Lactose

Here's a recent question emailed to me that been asked often enough to warrant a feature here:

I have had the typical symptoms of L.I. after consuming canned peas that were labeled "peas, salt and sugar". I am wondering if the sugar in these peas is milk sugar. Do the labeling directives require that it be indicated if the disaccharide is lactose? I am a label reader and I often wonder if the list of ingredients has been changed to indicate any recent changes in the contents?

The answer to this is simple. The only ingredient that can be called just plain "sugar" on a food label in the United States is sucrose, ordinary table sugar.

Lactose must be referred to as lactose. Any other sweetener, from glucose to honey to corn syrup to aspartame to any and all of the hundreds of others, must be called by its proper name. Never just "sugar."

Lactose can be hidden in other milk products, of course. Whey is mostly lactose, to take the most important example.

But sugar is always sugar and lactose is always lactose and never the twain shall meet.