Azodicarbonamide vs Olestra: which is worse?

What is Azodicarbonamide?

Azodicarbonamide (ADA) is a synthetic chemical used in the food industry as a flour bleaching agent and dough conditioner, and industrially as a blowing agent in foam rubber and plastic production. Its chemical formula is C2H4N4O2. When it reacts with water or heat, it breaks down into biurea (primary product) and semicarbazide (SEM).

What is Olestra?

Olestra (brand name Olean) is a synthetic fat substitute made from sucrose and fatty acids. Unlike regular fats, olestra is not absorbed by the digestive system — it passes through the body unchanged, providing zero calories while mimicking fat's texture and taste in food. It was developed by Procter & Gamble and FDA-approved in 1996.

Documented risks

Azodicarbonamide: ADA's primary food safety concern is its breakdown to semicarbazide (SEM) during baking. In a 2002 study, SEM was found to increase the incidence of vascular tumors in female mice at high doses. This single animal finding was sufficient under the EU's precautionary principle to ban ADA in food use in 2005. The FDA conducted a comprehensive SEM exposure assessment in 2016, concluding that US population exposure to SEM from ADA-treated bread is many orders of magnitude below doses showing tumor effects in rodents and does not warrant regulatory change. This reflects the FDA's risk-based approach. Urethane (ethyl carbamate) is another potentially harmful breakdown product of ADA. Urethane is classified as an IARC Group 2A probable human carcinogen. Small amounts of urethane can form from SEM in fermented or alcohol-containing environments. The 2014 'yoga mat chemical' controversy highlighted ADA's dual use: it is the same chemical used as a blowing agent in foam rubber and plastic manufacturing — including yoga mats. Consumer advocacy blogger Vani Hari's 'Food Babe' campaign led over 50,000 people to petition Subway, which voluntarily removed ADA from its bread in 2014. The dual industrial-food use raised public concern even though ADA's behavior in each context is chemically different. From occupational health: workers exposed to ADA powder in bakery or plastic manufacturing settings can develop occupational asthma. WHO recognizes ADA as a respiratory sensitizer in occupational settings, though dietary exposure through bread is fundamentally different from inhalation exposure.

Olestra: Olestra caused significant gastrointestinal side effects that were prominently noted on mandatory warning labels: 'This Product Contains Olestra. Olestra may cause abdominal cramping and loose stools. Olestra inhibits the absorption of some vitamins and other nutrients. Vitamins A, D, E, and K have been added.' Reported gastrointestinal effects included diarrhea, abdominal cramping, oily anal leakage ('anal leakage' or 'rectal leakage'), and fatty stools. These effects were often embarrassing and uncomfortable. Multiple consumer complaints documented GI distress from Olean chips. Beyond GI effects, olestra significantly inhibits the absorption of fat-soluble vitamins (A, D, E, K) and fat-soluble carotenoids (lycopene, lutein, beta-carotene). Since fat-soluble vitamins require fat for absorption, and olestra passes through without being absorbed, it 'captures' these vitamins and carries them out of the body. Studies found olestra consumption reduced serum carotenoid levels, prompting Frito-Lay to fortify olestra products with fat-soluble vitamins to compensate. The FDA removed the mandatory GI warning requirement in 2003 after Frito-Lay argued the warning was overstated, though olestra's use had already declined dramatically due to consumer avoidance.