Previous research has suggested that we may be able to "taste" fat. And now, researchers at the Monell Chemical Senses Center have found evidence that we might be able to smell it, too.
"The human sense of smell is far better at guiding us through our everyday lives than we give it credit for," study researcher Johan Lundström, PhD, a cognitive neuroscientist at Monell, said in a statement. "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."
Lundström and colleagues conducted a fat sniff test with milk with three groups of participants: the first group included 30 people of normal weight from the Philadelphia area; the second group included 18 people of normal weight from the Wageningen area in the Netherlands (people in the Netherlands drink more milk than Americans); and the third group included 60 people from the Philadelphia area, half of whom were of normal weight and half of whom were overweight.
All of the participants were given three samples of milk made from milk powder instead of fresh milk (to account for potential variations in farm practices). One sample had a different fat concentration than the other two samples. While blindfolded, participants were asked to identify the one sample with the different fat concentration, using only their sense of smell. The milk fat concentrations used in the study were 0.125 percent fat, 1.4 percent fat and 2.7 percent fat.
Researchers found that all three groups of people were able to tell the differences in fat levels.
"Participants were able to discriminate between skim, medium, and fat milk samples, with an overall accuracy of 40–55% correct trials in three consecutive experiments, a value that is significantly above the expected chance level (33.3%)," the researchers wrote in the PLOS ONE study. "The consistency between studies clearly suggests that humans have a functional olfactory detection system that allows us to detect fat content within natural food sources."
Plus, researchers found that the ability to identify the differences in fat levels did not differ based on body mass index or dairy fat consumption. This suggests "that olfactory-based fat discrimination is a stable trait that does not directly depend on previous exposure or learned associations," they wrote.