Answers to Questions from Readers, part 7

Q. Is vomiting sometimes a symptom of lactose intolerance?

Normally, no. Vomiting is only associated with LI in extremely young children. Unfortunately, it's impossible to say anything about a single instance of vomiting. It could be caused by almost anything.

Q. Am I wrong but isn't lactose not listed as an ingredient on food packages? Do soft drinks such as Coke, Pepsi etc contain lactose?

Fortunately, you are wrong. If lactose is an ingredient it must be listed. "Sugar" as an ingredient means sucrose and sucrose only. Every other sugar must be listed by name. So Coke and Pepsi do not contain any lactose.

Q. How does Imodium A-D work inside your body?

According to the Physician's Desk Reference, Imodium (whose active ingredient is loperamide hydrochloride) acts by slowing intestinal motility and by affecting water and electrolyte movement through the bowel. It inhibits peristaltic activity by a direct effect on the circular and longitudinal muscles in the intestinal wall, prolonging the transit time of the intestinal contents. It reduces the daily fecal content, increases the viscosity and bulk density, and diminishes the loss of fluid and electrolytes.

Translated, Imodium calms the muscles so that they stop spasming. So instead of your feeling a slurry of water and fecal material straining to get out, your insides have a chance to do their jobs properly. The result is that the material has time to bulk up into a single proper bowel movement instead of lots of little watery ones.

Q. Is lactose intolerance caused by a gene or chromosome? If so, which one? Is lactose intolerance dominant or recessive? Can this be diagnosed through genetic screening or other mechanism?

Production of Lactase (the enzyme that digests lactose) appears to be controlled by a single gene on chromosome 2. It either stops lactase production with aging or it doesn't, depending upon which version of the gene a person has. The gene that allows a person to continue producing lactase forever is dominant. I would assume that genetic screening could test which version of the gene a person has; I don't know if anyone has ever done so.

Q. Are bananas considered dairy? I have some of the same symptoms as with milk with them.

No, nothing that doesn't come from a cow should be considered dairy. But you can have a reaction to almost anything; being LI doesn't make you immune from any of that.