Jan. 22, 2014 — New research from the Monell Center
reveals humans can use the sense of smell to detect dietary fat in food. As
food smell almost always is detected before taste, the findings identify one of
the first sensory qualities that signals whether a food contains fat.
Innovative methods using odor to make low-fat foods more palatable could
someday aid public health efforts to reduce dietary fat intake.
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"The human sense of smell is far better at
guiding us through our everyday lives than we give it credit for," said
senior author Johan Lundström, PhD, a cognitive neuroscientist at Monell.
"That we have the ability to detect and discriminate minute differences in
the fat content of our food suggests that this ability must have had
considerable evolutionary importance."
As the most calorically dense nutrient, fat has been
a desired energy source across much of human evolution. As such, it would have
been advantageous to be able to detect sources of fat in food, just as sweet
taste is thought to signal a source of carbohydrate energy.
Although scientists know that humans use sensory
cues to detect fat, it still remains unclear which sensory systems contribute to
this ability. The Monell researchers reasoned that fat detection via smell
would have the advantage of identifying food sources from a distance.
While previous research had determined that humans
could use the sense of smell to detect high levels of pure fat in the form of
fatty acids, it was not known whether it was possible to detect fat in a more
realistic setting, such as food.
In the current study, reported in the open access
journal PLOS ONE, the researchers asked whether people could detect and differentiate
the amount of fat in a commonly consumed food product, milk.
To do this, they asked healthy subjects to smell
milk containing an amount of fat that might be encountered in a typical milk
product: either 0.125 percent, 1.4 percent or 2.7 percent fat.
The milk samples were presented to blindfolded
subjects in three vials. Two of the vials contained milk with the same percent
of fat, while the third contained milk with a different fat concentration. The
subjects' task was to smell the three vials and identify which of the samples
was different.
The same experiment was conducted three times using
different sets of subjects. The first used healthy normal-weight people from
the Philadelphia area. The second experiment repeated the first study in a different
cultural setting, the Wageningen area of the Netherlands. The third study, also
conducted in Philadelphia, examined olfactory fat detection both in
normal-weight and overweight subjects.
In all three experiments, participants could use the
sense of smell to discriminate different levels of fat in the milk. This
ability did not differ in the two cultures tested, even though people in the
Netherlands on average consume more milk on a daily basis than do Americans.
There also was no relation between weight status and the ability to
discriminate fat.
"We now need to identify the odor molecules
that allow people to detect and differentiate differentiate levels of fat. Fat
molecules typically are not airborne, meaning that they are unlikely to be
sensed by sniffing food samples," said lead author Sanne Boesveldt, PhD, a
sensory neuroscientist. "We will need sophisticated chemical analyses to
sniff out the signal."
