The short answer

Natural flavors are flavor and aroma-enhancing ingredients that are derived from a natural food source. However, they are typically not 100% natural as they often contain additives, preservatives, and other artificial substances.

The long answer

Natural flavors – the fourth most common ingredient on food labels today – are defined as those that are derived from plant or animal sources, which are then distilled, fermented, or otherwise tinkered with in a laboratory setting. This differs from artificial flavors which use man-made chemicals to achieve the same result.

Take for instance the flavor of butter. The classic taste and smell of hot buttered popcorn arises from the chemicals diacetyl and acetoin, both of which are byproducts of working with cultured dairy products. However food companies want to enhance the taste and smell of their products, so they take it up a notch and add natural or artificial flavors.

To create a concentrated butter flavor that can be defined as natural, professional flavorists will perform industrial fermentation that is purely optimized for strong flavor and aroma production. Since the process begins with actual dairy, it is deemed a natural flavor. Artificial flavors will instead be produced through chemical synthesis, but it results in exactly the same chemical composition that natural flavors do.

Interestingly, while natural flavors must derive from natural ingredients, there are plenty of artificial additives that flavorists use to enhance the flavor and aroma. The raw material of fruits, meat, fish, spices, herbs, roots, leaves, buds or bark generally don't have a high concentration of the chemicals that give the food the taste or smell that flavorists are going after. So ironically, the production of natural flavors can include more than 100 processing aids, preservatives, and other artificial substances, which are similarly included in the production of artificial flavors.

Food companies are not required to disclose whether these "incidental additives" come from artificial or natural sources. As long as the key flavoring source comes from plant or animal material, it’s classified as a natural flavor.

Sources

Kennedy, C. R. (2015, September 21). The Flavor Rundown: Natural vs. Artificial Flavors. Science in the News. https://sitn.hms.harvard.edu/flash/2015/the-flavor-rundown-natural-vs-artificial-flavors/

Rabin, R. C. (2019, February 1). Are ‘Natural Flavors’ Really Natural? The New York Times. https://www.nytimes.com/2019/02/01/well/eat/are-natural-flavors-really-natural.html

Raeder Schumacher, J. (2021, May 6). Ask a Redbird Scholar: What does ‘naturally flavored with natural flavors’ mean? Illinois State University. https://news.illinoisstate.edu/2017/08/ask-redbird-scholar-naturally-flavored-natural-flavors-mean/

Spritzler, F. (2023, April 24). Natural Flavors: Should You Eat Them?. Healthline. https://www.healthline.com/nutrition/natural-flavors