Behind your tongue, just a few inches down the back of your throat, lies a dangerous precipice: over one edge it's a straight shot down your trachea and bronchi and into the lungs, and over the other edge is the esophagus, leading to the acid-filled stomach. 

If you or anyone you know has ever had difficulty swallowing, this anatomy is where the trouble begins. An estimated 9 million Americans suffer from difficulty swallowing, otherwise known as "dysphagia." Dysphagia becomes more prevalent with age, affecting up to 1 in 5 older adults, and up to 40 percent in institutionalized settings. Among those with advanced dementia, the problem is even more staggering: More than 80 percent will suffer from eating difficulties, and 50 percent of those patients will die within six months. 

Many of those suffering from dysphagia will end up aspirating, which means that food — along with digestive enzymes and millions of bacteria — veers into the lungs. We have all experienced the hacking cough when you swallow and it goes down the "wrong pipe." 

If enough food, destructive enzymes and bacteria deviate to the lungs, the results can be deadly, including pneumonia and respiratory failure. All that protects us is a thin, cartilaginous flap of tissue called the epiglottis. Like all tissues in our body, it weakens with aging and illness.You may have never heard of dysphagia, but it is one of the biggest killers in America. 

The treatment for aspiration is to spoil the experience of eating. Thickened liquids are a concoction of unflavored, powdered starch. Imagine industrial-strength Kool-Aid powder with no flavor and a tendency to solidify. A group of geriatricians at the University of California at San Francisco challenged themselves to subsist on thickened liquids for a mere 12 hours; few made it through.

Solid foods can be pureed into mush. If that's not enough to stop aspiration, doctors make a patient "NPO" ("Nil per os," which is Latin for "nothing by mouth"), where no food or drink can be swallowed. 

A 2009 study of thickened liquids found that people drank far less when put on thickened liquids, causing dehydration and higher rates of urinary tract infections. Even worse, it is unclear whether thickened liquids prevent pneumonia and death.

There are only a few situations where making a patient NPO clearly helps, and in many situations it does not. The human mouth is a constant factory of bacteria and enzyme-saturated saliva, which continuously drips down the back of the throat.

In the short term, we doctors can thread a plastic tube through the nose down to the stomach and pump sustenance into the body. And for the dementia patients who are never expected to recover, permanent feeding tubes are inserted through the abdominal wall. Dinner at a nursing home may look like a dystopian fast-food stop: A hallway of humans with bags of graham-cracker-colored nutrition dripping from plastic bags hung above their heads.

The American Geriatrics Society flatly recommends against placing feeding tubes in patients with advanced dementia, and endorses hand-feeding by caregivers as a safer and more humane approach. Rather than preventing suffering in those with advanced dementia, feeding tubes can cause it.

It's time to rethink the way we as a society address dysphagia. For doctors like us, this means initiating a conversation about the value that each patient places on eating. We must become comfortable with simply saying no, if the downsides of tubes and forgoing the taste of apple pie are too great.

Eating food and the surprisingly complex act of swallowing may just be what makes life worth living. 

Douglas Jacobs and Joshua Lang are physicians at Brigham and Women's Hospital in Boston.