You see them on many ingredients lists:
This is a catch-all term for many ingredients that are added for flavoring purposes. Some of those flavors come from vegan sources, and some do not.
So this puts us in a bind.
It’s not safe in most cases to assume that natural flavors are vegan-friendly.
In the United States (and similar in most other places), the FDA says this about natural flavors in their guidelines:
The term natural flavor or natural flavoring means…which contains the flavoring constituents derived from a spice, fruit or fruit juice…or similar plant material, meat, seafood, poultry, eggs, dairy products…
I cut out some to save some time, but the important takeaway is that flavors derived from animal products can be included in foods and not specifically labelled.
The term “natural flavors” covers for both plant and animal derived ingredients.
What should you do if you see natural flavors in the ingredients list? If you want to be safe, don’t buy it.
If you want to buy, contact the company and ask for clarification. It’s a pain, but it’s the only way to be sure (or at least quite confident) about whether or not the food is vegan friendly.
Finally, if you’re in a bind, you can take an educated guess. For example, a granola bar with “natural flavors” likely won’t have meat-derived flavors. However, there is a chance it could have egg-derived flavor, although probably not too high.
It’s up to you how strict you’d like to be.
In summary, natural flavors can be vegan, but also might not be vegan, because it covers a wide range of ingredients, some of which come from animal sources.