April 27, 2010 -- Red cayenne pepper may help burn calories and curb appetite, especially in people who aren’t used to eating it, says a new study that was partly supported by the National Institutes of Health and the McCormick Spice Company.
The study found that about half a teaspoon of cayenne pepper either mixed in food or swallowed in a capsule helped normal-weight young adults burn about 10 more calories over a four-hour period, compared to eating the same meal but without the red pepper.
Pepper also decreased appetite, especially in people who said they didn’t already eat spicy foods.
Study researcher Richard Mattes, PhD, RD, distinguished professor of foods and nutrition at Purdue University in West Lafayette, Ind., thinks that the pepper is stimulating the trigeminal nerve, one of the main nerves in the head and neck.
“Chemesthesis is the term for chemical irritation, and that’s the sense that this work focused on,” Mattes says. “What we were interested in is, does activation of that system lead to increases in energy expenditure, alterations in appetite and food intake, and so on.”
"The appetite responses were different between those who liked red pepper and those who did not, suggesting that when the stimulus is unfamiliar it has a greater effect,” Mattes says in a news release.
Based on his study, Mattes says it appears that once a person gets used to the spicy foods, their effects start to wear off.
“So the question is, how long does the phenomenon last once you start using red pepper. And if it starts to diminish, how long do you have to wait to obtain the same benefits?” Mattes says. “Those are future studies. This was just our observation that the effect was bigger in people who were not regular users.”
The study is published in Physiology & Behavior.
Previous studies had tested the thermogenic, or calorie-burning, effects of red pepper but had used quantities that were too large to be practical for most people.
Testing the Effect of Pepper
For the study, researchers recruited 25 men and women from a college campus. The average age of study participants was 23. The average BMI (body mass index) was 22.
Thirteen of the study participants reported regularly eating spicy food before the study, while 12 didn’t eat hot spice.
Participants were asked to complete a total of six study visits, each separated by a week.
Participants fasted for 12 hours before coming for a lab visit in which their resting energy expenditure, core body and skin temperatures, and appetites were measured.
They were then randomly assigned to eat meals with or without red pepper added. There were three visits with red pepper and three without.
Sometimes the study participants got the pepper in gelatin capsules, so they couldn’t taste it. In other cases, it was mixed with food.
Using a ventilated hood, researchers measured energy expenditure before and after meals, which allowed them to track the calories burned with or without pepper.
Appetite was measured by a questionnaire before the test meal and every 30 minutes after they ate.
At the end of each visit, about four hours after eating the pepper, study participants were given access to as much macaroni and cheese as they wanted.
On average, those who were new to eating spicy foods ate about 66 fewer calories of the macaroni-and-cheese meal on the days they ate red pepper compared to the days they didn’t.
People who were already spicy-food eaters before the study ate the same amount of macaroni and cheese after each visit.
Red Pepper and Weight Loss
“The bottom line is if you like spicy food, enjoy it, but don’t torture yourself because it’s not going to turn you into a size 2,” says Andrea Giancoli, MPH, RD, a spokeswoman for the American Dietetic Association.
And the study’s researchers agree.
“We’re not proposing a diet, we’re just saying that incorporating red pepper in your diet works more toward moderation of energy intake and energy balance than working against you,” Mattes says.
“This is a subtle effect, but if it is an easily incorporated change in the diet, even a palatable change in the diet, and it’s combined with other small, easily accommodated adjustments, collectively they add up to caloric savings and energy savings,” he says.