People can use the sense of smell to detect dietary fat in food, according to new findings from research centre on human senses the Monell Centre (Monell).

Researchers said innovative methods using odour to make low-fat foods more palatable could someday aid public health efforts to reduce dietary fat intake.

“The human sense of smell is far better at guiding us through our everyday lives than we give it credit for,” said Johan Lundstrom, PhD, Cognitive Neuroscientist and Monell and senior author of the study. “That we have the ability to detect and discriminate minute differences in the fat content of our food suggest that this ability must have had considerable evolutionary importance,” he said.

Researchers said that, 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 for humans 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 contributed 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.

Study method

The Monell study, which was published in open access journal PLOS ONE, aimed to determine whether people could detect and differentiate the amount of fat in a commonly consumed food product: milk.

Researchers asked healthy subjects to smell milk containing an amount of fat that might be encountered in a typical milk product: either 0.125 per cent, 1.4 per cent or 2.7 per cent fat.

The milk samples were presented to blindfolded subjects in three vials. Two of the vials contained milk with the same per cent of fat, while the third contained a milk with a different fat concentration. The participants’ 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 in both normal-weight and overweight subjects.

In all three experiments, participants could use the sense of smell to discriminate between 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 US consumers do. The study also found no relation between weight status and the ability to discriminate fat in this way.

“We now need to identify the odour molecules that allow people to detect and differentiate levels of fat,” said Sanne Boesveldt, PhD, Sensory Neuroscientist from Wageningen University and lead author on the study. “We will need sophisticated chemical analyses to sniff out the signal,” she said.

Support for the study was provided in part by the Knut and Alice Wallenberg Foundation and a grant from the Netherlands Organisation for Scientific Research.

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