As I was sitting in my new favorite bar which just happens to have a delicious all-you-can-eat wing special on Monday nights, the bartender and I got to talking about life, drinking, the meaning of functional alcoholism and (oddly) her chemotherapy treatments. Being of medical science background, I became interested when she declared that her taste for things, especially spicy food, had completely changed after her treatments has concluded. I was fascinated and asked about as many probing questions as possible without being downright rude.

Chemotherapy generally targets rapidly dividing cells in an effort to poison malignancies that exhibit unrestrained cell growth. These drugs are rarely specific so tend to attack the metabolism of all rapidly diving cells, resulting in the common hair loss, GI difficulty, nausea, ect. As olfactory cells (odor chemoreceptors in the sinus) and gustatory cells (receptors in taste buds) must be replenished regularly, they are on this list of rapidly diving cells and both become sickly and decrease in number. So, it's easy to understand why someone would lose their acute sense of taste and smell. But it does not explain why totally different tastes/preferences would take over later.

Which brings me to my question. Is there a CNS (central nervous system) reason behind this? It is widely accepted that the great majority of cells in our brains do not divide beyond early childhood. In fact, many cognitive psychology experimenters consider "general cognitive decline" to occur after age 21 in males. Our brain cells will only decrease in number over time. However, there are cells in the hippocampus near a place called the dentate gyrus that seem to continuously divide into adulthood. These are generally thought to have a role in memory formation, emotional processing, and experiential learning, although there is some uncertainty. If these cells are affected by chemotherapy drugs and connected to memories whose shared storage includes odor references, it might explain a partial or total loss of taste/odor preferences. This is my speculation.

How many people have studied this? Zero. There are a few clinical studies examining taste changes in chemotherapy patients and they have basically found that yes, chemotherapy drugs do seem to harm your ability to taste foods as well. But then they stop! Why? The clinician's primary concern is to ensure health and safety of the patient, i.e. getting them to eat a nutritious diet. They don't particularly care why it happens, so long as the patient is aware and can either move through it or find a preferred flavor enhancer. I want to know why, mechanistically, this happens. Maybe the hippocampus has absolutely nothing to do with it, but I am bothered that clinical research often falls short of actually probing for a conclusion. Retrospectives are great, but do not challenge the medical science community to move beyond treating a symptom. If we instead examine a mechanism, the least we will do is learn more about the root cause; we can hope to elucidate an effective treatment to mitigate the negative consequences for future patients.