Cancer is characterized by the rapid division of cells that have lost many of the traits that normally limit cellular growth and differentiate one cell type from another. Malignant cells also tend to violate boundaries that demarcate different tissues, allowing tumors to spread to distant sites. Chemotherapy is designed to interfere with some aspect of metabolism in such rapidly dividing cells, which accounts for both its clinical effectiveness and its various side effects, including "induced" lactose intolerance.
Side Effects
Since chemotherapy can impinge on the growth of all rapidly dividing cells in your body, even healthy tissues that turn over relatively rapidly are adversely affected during treatment for cancer. This accounts for the hair loss, diarrhea, oral ulcerations, bone marrow suppression and skin breakdown that frequently accompany chemotherapy. These adverse effects are the reason many chemotherapeutic protocols are "pulsed," allowing your normal tissues to recover between treatments.
Lactose Intolerance
Most infants are equipped with an intestinal enzyme called lactase that allows them to quickly digest lactose, or "milk sugar." As children grow, many of them naturally lose the ability to produce lactase, leading to a condition called lactose intolerance. When such persons consume lactose they typically develop bloating, cramping, flatulence and diarrhea. According to scientists at the University of Kansas School of Medicine, humans lose 90 to 95 percent of their birth lactase levels on a global basis. However, some demographic groups -- particularly people of northern European descent -- tend to retain lactase throughout life. Lactase levels may be impacted by chemotherapy in some individuals.
Chemotherapy-Induced Lactose Intolerance
The cells lining your gastrointestinal tract are normally subjected to mechanical and chemical forces that cause them to turn over relatively quickly. Due to their rapid rate of division, intestinal cells are adversely affected by many forms of chemotherapy. In 1994, researchers at the University of Maryland Cancer Center demonstrated that chemotherapy patients often develop lactase deficiency during treatment, as demonstrated by hydrogen breath tests. However, a minority of such patients -- around 10 percent -- actually develop symptoms of lactose intolerance.
Considerations
Chemotherapy-induced lactose intolerance is uncommon overall among cancer patients, but your personal risk for developing a transient lactase deficiency depends on your individual chemotherapeutic protocol. Some types of chemotherapy are inherently more toxic to your intestinal lining. The duration of your treatment also plays a role in how severely your gastrointestinal tract will be impacted and how quickly it will recover. Talk to your doctor about other patients' experiences with the type of chemotherapy you are receiving. If you do develop symptoms of lactose intolerance following consumption of dairy products, talk to your physician about your options.
