Diacetyl vs Natural Flavors: which is worse?

What is Diacetyl?

Diacetyl (2,3-butanedione) is a naturally occurring compound produced during fermentation — it is found in beer, wine, and fermented dairy. Synthetically produced diacetyl is used as an artificial butter flavoring in microwave popcorn, snack foods, and margarines. It provides the characteristic buttery aroma and taste.

What is Natural Flavors?

Under FDA regulation (21 CFR 101.22), 'natural flavors' are flavoring substances derived from plant or animal sources including spices, fruits, vegetables, herbs, meats, seafood, dairy products, fermentation products, or edible yeast. The term is intentionally broad and does not require disclosure of the specific chemicals involved — a single 'natural flavor' entry on a label can represent a complex mixture of hundreds of compounds.

Documented risks

Diacetyl: Diacetyl is most infamously linked to 'popcorn lung' (bronchiolitis obliterans) — a severe, irreversible obstructive lung disease first identified in workers at a microwave popcorn factory in Missouri in 2000. Multiple epidemiological studies, including NIOSH investigations, have confirmed the link between occupational diacetyl inhalation and bronchiolitis obliterans. At least 30 workers developed the condition. OSHA issued a Permissible Exposure Limit (PEL) recommendation in 2016. Consumer risk from eating foods containing diacetyl is considered far lower than occupational inhalation exposure, but consumer lung injury cases from eating large amounts of microwave popcorn have been reported, including a widely cited 2012 case report in Flavor and Fragrance Journal. California enacted stricter workplace exposure limits.

Natural Flavors: The term itself presents no specific health risk, but the lack of transparency is a significant concern for consumers with allergies, dietary restrictions, or sensitivities. 'Natural flavors' may contain allergens (such as shellfish, wheat, or soy derivatives), animal-derived ingredients (problematic for vegans), or added glutamates that some people wish to avoid. The Environmental Working Group (EWG) has noted that 'natural flavors' is the fourth most common ingredient on food labels, yet consumers have no right to know what specific compounds are included.