Sensing Fat

[salvorhardin]

This is a really good article that gives an overview of current research into the ways our bodies sense fat, including the possibility that we might taste fat (like we taste sweet, bitter, sour, salty, and umami).

-20 points though for the cliched use of Headless Torso Fat Guy with a box of fried chicken. We don't use pictures of developmentally delayed children failing to stuff square pegs into round holes, so why do we do the equivalent when we illustrate articles about obesity? The use of such pictures only serves to dehumanize overweight and obese people, and lead readers to make moral judgments about them.

Can we taste fat?

Until recently, it was assumed that the perception of fat was based on textural cues and its role as a carrier for flavor in foods such as bacon or strawberry ice cream, rather than any explicit lingually perceived “taste.” (The five basic tastes only include sweetness, bitterness, sourness, saltiness, and umami or savory taste.) This was based on the common observation that the presence of fat in the mouth did not evoke a recognizable taste sensation. Another problem was the absence of any known receptor mechanism for “fatty” taste. However, accumulating evidence now challenges this view. Studies in rats have shown that fatty acids placed on the tongue cause taste cells to depolarize, initiating a signal that is transmitted to the brain.10 Human studies have also shown that individuals can detect free fatty acids in the mouth when all other cues—visual, textural, olfactory—are controlled with red light, homogenization of the food texture, and nose clips.11 In addition, subjects are able to perceive different concentrations of fatty acids; in fact, according to one 2010 study, subjects most sensitive to differences in fatty acid levels also had a lower body mass index (BMI) than others.12

Despite these provocative findings, the concept of an oral fat sensor in humans is not widely accepted. One argument is that dietary fats are composed almost exclusively of triglycerides, not free fatty acids. What is the significance of an oral mechanism for fatty acid perception when these molecules are not normally present in a free form in the foods we eat? We know that in rats the tongue releases copious amounts of lipase, an enzyme that rapidly hydrolyzes triglycerides to free fatty acids in the mouth. And although humans aren’t known to produce lingual lipase in high quantities, historical studies have reported that they can produce this enzyme.

Indeed, the presence of fat in the mouth spurs the release of some lingual lipase, converting triglycerides into micromolar concentrations of free fatty acids—concentrations theoretically sufficient to depolarize taste neurons.12 Furthermore, research now shows that small amounts of free fatty acids are normally present in most dietary fats.11 These findings support the idea that fat could elicit an oral response in humans, as it does in animals, and a human fatty acid taste mechanism is plausible.

...

The picture that is emerging from this research is that fats may be perceived in the mouth by a combination of taste and texture cues. The ability to detect the bitterness of PROP may serve as a marker for the ability to perceive the texture of fats through the density of taste buds and surrounding somatosensory nerve endings influenced by gustin and TAS2R38. Variation in this trait alters the preference for fat, which may predict the amount of fat consumed in the diet, and potentially, the risk for obesity. In contrast, CD36 may be a marker for long-chain fatty acid perception that might inform the body of the nutritional composition of fats. Imbalances in fatty acid composition of the diet may also have implications for the development of nutritional diseases. Based on the animal literature and on our studies, it seems likely that there are multiple, overlapping mechanisms for oral fat detection that provide an array of information about the quantity and composition of fats in the foods we eat. Future studies will reveal the roles of these receptors and their underlying genes in humans.
Full article: http://the-scientist.com/2011/12/01/sensing-fat

[xchrom]

1. now i want bacon. nt

[Duer 157099]

2. Rancid fat certainly has a distinct taste

So why wouldn't non-oxidized fat also? Makes sense to me.

[salvorhardin]

3. I agree

And as the article notes, the idea certainly isn't a new one. It's just that until recently we haven't found a likely mechanism for how fat could be tasted. I wonder, if this proves out, will we adopt another Japanese word ("futoi" maybe) like we did for umami?

[BadgerKid]

4. A little surprised/skeptical about linking taste to BMI.

I'd contend it's a matter of what you get used to tasting.

I remember switching from whole to skim and 2% milk at college. After that, the whole milk back home felt as if it was coating my tongue and had no taste.

[salvorhardin]

5. Frankly I am too

On the other hand, wouldn't it be cool if we could actually taste fat?

[CTyankee]

6. well, I don't know. I do know that I had a taste of straight olive oil in a restaurant

in Florence, Italy that made me madly desire to pour it into a glass and drink it. Ihave never before or since had an olive oil that tasted like that.

[salvorhardin]

7. Oh, I had an experience with olive oil like that too.

Never really cared for the stuff before, until one of my friend's Italian grandmother served us some homemade bread with an olive oil she imported from Italy for dipping. I'd never tasted anything like it before. Slightly fruity, thick, almost creamy, and with a slight peppery burn to it. Awesome! I've tried buying expensive olive oils in the grocery stores but nothing comes close.

[CTyankee]

8. I figured you have to live in Tuscany and have an olive grove and

pick the stuff and have it processed locally for it to taste like that...nothing commercial in this country tastes like this did...