Fatty food triggers taste buds.

It wasn't your imagination that the fat-free chocolate chip ice cream didn't taste as good as the creme de la creme version, despite what the label said. Contrary to current scientific dogma, fat does have taste, according to Purdue University researchers (Department of Foods and Nutrition, Stone Hall, West Lafayette, IN 47907). But product developers probably already knew that.

Yet nutritionists and other researchers said for years that fat only provides texture to foods, and that pure fat itself doesn't have any taste. Fat has been thought to be a flavor carrier that could deliver taste and odor compounds derived from different parts of food, and a component that provided texture and mouth feel in foods.

But new research indicates that humans can indeed taste fat. The finding is more than a physiological curiosity. It also could explain why fat-free foods aren't as popular as full-fat versions. Investigators wonder if the less-than-perfect performance of some fat replacers may be due to a lack of understanding of all mechanisms for fat perception.

Recent studies with rats have shown that fats were capable of causing electrical changes in taste cells of rats, indicating there was a chemical detection system there. Studies in mice and rats also have shown that in carefully controlled taste tests--ones so brief that there's no metabolic feedback, and, using taste solutions, one so dilute that there's a minimal textural component--rats easily detect and prefer the foods with fat, we're told. Some hypothesized that animals and perhaps people detect fat by smelling it.

Purdue researchers decided to determine if humans were tasting fat or merely smelling it. Their initial hypothesis was that odor was responsible. Previous studies had shown that blood fat levels changed in humans just by putting fat in their mouths. That suggested that there was some sort of chemical detection, but scientists didn't know if it was a taste or an odor. In general, with humans, if you pinch the nose, a person's ability to detect fats declines. In rats, if you damage the nerves that respond to odors, their ability to detect fats declines.

In a study, subjects had their blood fat levels checked before and after the test. The test used cream cheese on crackers to determine if people could taste fat. Some people were allowed to taste and smell fat; some, wearing nose plugs, were only allowed to taste or smell fat, but not both. A control group received no sensory stimulation at all.

The study found that blood fat levels in the group that had been allowed to taste and smell the fat rose three times more than the control group. However, the study also found that blood levels rose as much in people who were wearing nose plugs as in people who could both taste and smell the cream cheese. Blood fat levels didn't rise in people who could only smell the cream cheese but not taste it.

This tells researchers that taste is the stimulus that causes the rise in blood fat levels. The taste, and not the smell, is what the body is responding to. If further studies confirm the findings, textbooks have to add fat to the list of taste sensations. The ability to taste fat could hold evolutionary advantages in the ability to absorb essential fatty acids from food, according to researchers.

Further information. Richard Mattes; phone: [phone]; fax: [phone]; email: [e-mail]; URL: www.cfs.purdue.edu/fdsnutr/people/mattes.html.