Alibi V.23 No.51 • Dec 18-24, 2014 

Flash in the Pan

Fat is Flavor

Science reveals new truths about how our body reacts to fats

CoralBrowne via Wikimedia Commons, CC by SA 4.0

The holidays and the accompanying onslaught of rich feasts present a timely opportunity to think about fat, and there is much to consider these days. It's beginning to look like some deeply-held beliefs about fat might be wrong.

One such aspect is the science of how fat is perceived by the body.

A friend of mine who went to cooking school was fond of saying, "fat is flavor." But according to traditional scientific understanding of flavor perception, fat doesn't have any flavor. This isn't to say that anyone ever claimed fatty foods aren't delicious. But it was thought that other qualities of fat made this so; the creamy, viscous, lubricating qualities that it imparts are what make the food to which it is added taste better.

But flavor is a specific metric, a combination of what is perceived by the tongue and smell. And fat, until recently, was thought to contain neither taste nor smell. But thanks to some new research, it looks like the cooks might have been right all along.

Earlier this year researchers at the Monell Chemical Senses Center, a nonprofit institute, reported evidence that humans can smell fat. And in the last few years, fat receptors on the human tongue have been discovered and confirmed by other research teams, which indicates humans can taste fat.

But flavor is a specific metric, a combination of what is perceived by the tongue and smell. And fat, until recently, was thought to contain neither taste nor smell. But thanks to some new research, it looks like the cooks might have been right all along.

If we can taste it and smell it, then it has flavor.

Our attraction to fats has been widely assumed to stem from the fact that fat is the most calorie-dense type of food we eat. Our hunter-gatherer ancestors were programmed to eat as much fat as they could find, goes the logic, and this genetic disposition remains to this day.

But in a surprising twist, the fats to which these receptors are tuned taste bad, not good. They detect free fatty acids, which are found in large quantities in rancid fats. Rancid fats, which can be poisonous, are worth avoiding, which is why they taste bad.

By contrast, the form of fat that is so pleasing in our mouths is a type in which the fatty acids are bound into molecules called triglycerides. 

Thus, it appears we're programmed to be attracted to the triglyceride form of fat, while being repulsed by free fatty acids. But there's yet another rub: When we chew those yummy, nontoxic triglycerides, enzymes in our saliva break them down and release the dreaded free fatty acids.

Richard Mattes, a professor of nutrition science at Purdue University, has researched and published extensively on fat perception. He told me he believes there is a delicate balance at work here. A small quantity of free fatty acids coupled with the glorious mouthfeel (and subtle smell) of triglycerides tells the body that this is good stuff to eat. But too many free fatty acids triggers a rejection of the food in question.

These fatty acid taste receptors aren't just present in the mouth, but in other parts of the body as well, including muscle, skin, blood, spleen, intestine and brain cells. Free fatty acids are the breakdown products of triglycerides, and it is thought that these receptors are widely dispersed in the body so the various tissues can detect and appropriately deal with the free fatty acids that result from fat consumption.

So one doesn't just “taste” fat in one's mouth, but in one's whole body. This revelation suggests a broader level of meaning to the idea of taste perception. One thing that all of these new developments haven't changed is that eating fat makes us happy. On that note, could you please pass the mayo?