Answers to Questions from Readers, part 10

Q. What is whey? I heard it was the byproduct or waste water from cottage cheese. I've noticed that cookies or items with whey seem to bother me more than others.

Milk separates into lactose (milk sugar), whey proteins, casein proteins, water, fat, and a few vitamins and minerals. Most cheeses, not just cottage and other soft cheeses, are predominantly hardened casein. The remaining liquid is known as whey. It has some of the milk's proteins and almost all of the sugar. Commercial bakers love whey because it is indeed a cheap waste product, but one that gives a product many of the same nutritional and taste benefits of whole milk. Most commercial whey is dried, meaning that it is roughly 50-75% pure lactose and the rest mostly whey protein. If you are lactose intolerant, whey is one of the worst ingredients to encounter on a label. Most allergies seem to be to casein, but many people are allergic to the whey proteins as well. And of course, since the majority of the world's population is LI, by sheer chance many of them have protein allergies as well. It's not clear which is your problem, but you should avoid whey on a package label. See my SuperGuide to Dairy Products for more info on dairy.

Q. Do eggs contain lactose?

For some reason, probably since eggs are so often found in the "dairy" case in supermarkets, many people believe that eggs are dairy products and need to be avoided. This is completely false. Eggs come from chickens, not cows. They contain absolutely no lactose. (This is true of most mayonnaise as well.)

Q. Why does the lactase that is in me when I am born, decrease when I grow older?

Here's what one researcher had to say:

"Speculation as to why the lactose gene 'turns off' is a fascinating topic. One theory suggests that lactase deficiency evolved early in mammalian history, perhaps 75 million years ago, as a means to facilitate weaning and shorten the dependence of the child on the parent for lactation. The gas and diarrhea produced by lactose malabsorption would stimulate the child to become weaned. One competing theory suggests that lactose malabsorption in adults prevents competition of adults with infants for food (who can only digest milk early in life), and another theory proposes that lactose intolerance evolved as a defense mechanism against intestinal infections."

In other words, nobody knows for sure.

Q. My 80-year-old mother has been diagnosed as being LI. I've heard that it was unusual to have this happen so late in life. What do you know about this?

It is unusual, but hardly unknown. Different people are genetically programmed to lose their ability to make lactase at different ages, that's all. (Unless she had some sort of intestinal disease or surgery that might have damaged her intestines. That can cause LI at any age.)