Odor of Fatty Acids: Differences in Threshold and Perception Intensity Between Sexes

In humans, food choice, nutrient intake, and meal size are strongly influenced by sense of smell. It is known that individuals differ in their olfactory abilities and may show a normal, reduced, or absent sense of smell. Previous findings have also suggested that males are more deficient than females in their olfactory performance. Recent studies have shown that humans could perceive the odor of free fatty acids, providing information about the nutritional content of foods. The aim of this research was to study the orthonasal perception of palmitic, oleic, and linoleic fatty acids in 70 healthy subjects (38 females and 32 males). First, participants were classified as normosmic or hyposmic by means of the Sniffin' Sticks test. Second, the ability to detect the odor of fatty acids was assessed using the gas chromatography-olfactometry technique, a combination of sensory and instrumental analysis that allows for simultaneous chromatographic separation and odor evaluation by a human subject. Finally, the olfactory threshold to fatty acids was also evaluated by means of a three-way forced-choice test, using a presentation procedure of ascending concentration with seven dilution steps. The results highlighted differences in perception ability, perception intensity, and olfactory threshold in relation to the lipophilicity of the molecule, olfactory function, and sex. Our findings confirm the human ability to perceive the odor of fatty acids, with females and normosmic individuals performing better than males and hyposmic ones, respectively. They also show that the intensity of perception increases with the decreasing lipophilicity of fatty acids; consequently, the olfactory perception threshold also decreases.