Behind your tongue, and slightly down the back of your throat, lies a dangerous precipice: over one edge it is a straight shot down your trachea and bronchi and into the lungs, and over the other edge is the oesophagus, leading to the acid-filled stomach.
For those who have ever had difficulty swallowing, or dysphagia, this anatomy is where the trouble begins. Dysphagia becomes more prevalent with age, affecting up to one in five older adults, and up to 40 per cent in institutionalised settings such as nursing homes.
Among those with dementia, the problem is worse: More than 80 per cent of individuals with advanced dementia will suffer from eating difficulties.
Many of those suffering from dysphagia will end up aspirating, which means that food - along with digestive enzymes and millions of bacteria - veers down the wrong path and 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 from the oesophagus to the lungs, the results can be deadly, including pneumonia and respiratory failure.
All that protects us from aspirating is a thin, cartilaginous flap of tissue called the epiglottis. Like all of the other muscles and tissues in our body, it weakens with age and illness, putting people at risk.
What can doctors do to stop dysphagia? Not much. There are a few simple tests to diagnose the severity of dysphagia. It begins with sips of water at the bedside, and if needed, more complex tests such as video swallow studies that quantify the amounts of liquid being aspirated.
The treatment for aspiration is to spoil the experience of eating. For a small amount of aspiration, doctors may thicken your liquid drinks.
Percentage of individuals with advanced dementia who will suffer from eating difficulties.
1 in 5
Proportion of older adults affected by dysphagia.
Thickened liquids are a concoction of unflavoured, powdered starch, which can be made to the thickness of "nectar" or "honey".
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, and all of them were disgusted during the process, suffering from a combination of thirst, dry mouth and premature fullness.
A recent study comparing thickened liquids to strategies where patients with dementia were encouraged to drink in a chin-tucked position found that the two were equivalent in preventing pneumonia.
Solid foods can be pureed and processed into mush. If that is 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 is allowed to be swallowed.
There are only a few situations where making a patient NPO clearly helps. Yet the fear of massive aspiration events keeps doctors from allowing foods and liquids near these patients.
And then the real trouble begins: A couple of days without food may be torture, but more than that means starvation.
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 their ability to swallow, surgeons place permanent feeding tubes that are inserted through the abdominal wall into the stomach.
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.
Placing feeding tubes in these patients does not reduce the likelihood of death or pneumonia, and is instead associated with agitation, pressure ulcers and a bevy of other tube-related complications.
It is time to rethink the way healthcare professionals and we as a society address dysphagia. To be clear, there are instances where dysphagia diets, NPO and even feeding tubes make sense, such as when a patient is recovering from a stroke.
However, for most cases, thickened liquids and feeding tubes have questionable benefits at best.
For doctors like us, this means initiating a conversation on the value each patient places on eating, before evaluating how food passes over the epiglottis. It also means being forthcoming on the lack of efficacy of thickened liquids and feeding tubes, and the risks of these approaches.
Patients, friends and family members of those affected should feel empowered to ask physicians about the risks of thickening fruit juice to more of a fruit paste.
For our loved ones with advanced dementia, our goals for them may simply be to savour the food at the dinner table. Eating food and the surprisingly complex act of swallowing, while not a uniquely human endeavour, may just be what makes life worth living.
• The writers are physicians at Brigham and Women's Hospital in Boston.