Living Gluten-Free
by Tricia Thompson, MS, RD, The Gluten-Free Dietitian

When they are newly diagnosed with celiac disease, many people also discover that they are lactose intolerant and have difficulty digesting milk and products containing milk.

This type of lactose intolerance is called "secondary lactose intolerance." It is a temporary form that develops as a result of celiac disease and resolves (in most cases) as the intestine heals.

Lactose is a sugar found in milk. It is a "disaccharide" meaning it is made up of two units of sugars. "Di" means two and "saccharide" means sugar. Specifically, lactose is made up of one unit of glucose and one unit of galactose.

Disaccharides -- including lactose -- cannot be absorbed intact from the small intestine. Instead they must be separated into single units of sugar (monosaccharides). Enzymes that help do this are found in the small intestine.

When someone has lactose intolerance, lactose passes undigested through the intestinal tract where it causes symptoms familiar to anyone who suffers from this condition — diarrhea, gas and bloating.

But why does lactose intolerance develop in the first place?

The lining of the small intestine contains hair-like projections called villi. These villi are lined by cells called enterocytes, and each one of them has smaller hair-like projections called microvilli. These microvilli also are called the "brush border." Enzymes that help digest sugars (as well as break down products of protein) are found in the brush border and are called "brush border enzymes."

When you have celiac disease, the mucosa (or lining) of your small intestine is damaged. Specifically, the villi become shortened or even completely flattened. This results in a decrease in brush border enzymes.

Brush border enzymes include lactase which helps digest the sugar lactose found in milk; sucrase which helps digest the sugar sucrose found in varying amounts in all plant foods, including fruits, vegetables, and sugar cane; and maltase which helps digest the sugar maltose found in cereal grains.

Should you also be concerned about sucrose and maltose intolerance?

Because the enzymes sucrase and maltase needed to digest sucrose and maltose also are found in the brush border you may be wondering if you might have secondary intolerances to these sugars.

I asked Dr. Stefano Guandalini, Director of the University of Chicago Celiac Disease Center, to explain why this probably is not the case.
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