Dear Doctors: In my personal experience, fermented foods such as sauerkraut have the ability to decrease hunger. I have read they do this by shutting down the hormones that create hunger. They have the benefits of few calories, leaving you feeling full and causing fewer cravings. Is this true, and how does it work?
Dear Reader: Fermented foods have been on the menu for 10,000 years. Quite likely discovered by accident, fermentation occurs when microorganisms such as bacteria and yeast break down the natural sugars that are present in food. This results in changes to flavor that, along with fermentation's ability to act as a preservative, have made these foods a worldwide staple of the human diet.
An impressive array of the foods we eat are fermented. These include dairy products such as yogurt, kefir and skyr; aged cheeses; soy products such as tempeh, tamari and miso; sourdough breads; numerous types of sausage; alcoholic and nonalcoholic beverages; and a wide array of preserved vegetables. It is this last category that your question about fermented foods and hunger addresses. And thanks to recent research, we are beginning to get some answers.
Studies have found that certain fermented foods may affect appetite. It appears they do this by interacting with, and in some cases decreasing, hormones that tell our bodies it's time to fuel up. That feeling of fullness and satisfaction you get when you appease your hunger is known as satiety. Among the metabolic compounds involved in this cycle is a hormone called ghrelin, which is produced by cells in the stomach lining. Often called "the hunger hormone," it lets your brain know it's time to eat by stimulating your appetite. Some studies have found that eating certain fermented foods results in decreased levels of ghrelin. Other research has associated fermented foods with similar metabolic changes that can diminish hunger.
In one study, people who regularly ate fermented vegetables had higher levels of certain types of short-chain fatty acids. These are compounds that are produced in the gut. Short-chain fatty acids are known to be associated with metabolic signals that decrease appetite and promote satiety. In another study, researchers were interested in whether eating whole-meal sourdough could affect hunger. They found that the group of study participants who ate the fermented bread had a small but consistent increase in levels of satiety when compared with the control group, which ate conventional yeast bread. The researchers also found that the sourdough bread slowed the rate at which food left the stomach. Slower emptying of the stomach is another factor in feelings of satiety.
The idea that fermented foods "shut down" hunger may be a bit of an overstatement. That's not surprising, considering the complexity of the many mechanisms involved. However, emerging research backs up your own experience. What we do know for sure is that a diet rich in fermented foods that contain live cultures can contribute to the diversity of the gut microbiome. And that has been linked to beneficial effects on immune function and overall health and well-being.
(Send your questions to [email protected], or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)
