Social Media Claim

Onions don't become ‘highly poisonous’ if cut the day before cooking

A Facebook post from November 1, 2015 features a picture of a sliced red onion and claims it is dangerous to cook them the next day.

The Statement

AAP FactCheck examined a Facebook post from November 1, 2015 by Health Is Everything which features a picture of a sliced red onion and claims it is dangerous to cook them the next day.

The text of the post reads: “Please remember it is dangerous to cut an onion and try to use it to cook the next day, it becomes highly poisonous for even a single night and creates toxic bacteria which may cause adverse stomach infections because of excess bile secretions and even food poisoning".

The post also features red text that says Dangerous, Share With Everyone and features an image of a red onion that has been sliced.

The post, which has been shared by Australian users, has attracted more than 4700 shares and has more than 250 reactions and 40 comments.

A dietitian from the Dietitians Association of Australia told AAP FactCheck she had never come across any evidence to substantiate the claim about onions.

The Analysis

The NSW Food Authority states on its website that most foodborne illness is caused by pathogenic bacteria or viruses in food. Other less common foodborne illness occurs from accidental chemical poisoning and natural contaminants.

Accredited practising dietitian Simone Austin of the Dietitians Association of Australia told AAP FactCheck she had never come across any evidence to substantiate the claim about onions.

“I haven’t seen any research to see why that would be true,” Ms Austin told AAP FactCheck. “Particularly because of the fact that onions have very little protein, and most often foods that are going to develop bacteria are often due to protein in the food.”

She said dirt should be removed to prevent any contamination or listeriosis and to chop onions on a clean board.

“Make sure you are not cutting an onion on the same board as your raw poultry or raw meat, there is possible cross-contamination there,” Ms Austin said.

Once chopped, Ms Austin advised onions should be stored correctly in a container so no moisture can cause mould issues.

US fact checking unit Snopes traced the initial onions claim back to March 2008. Snopes looked into the claim and found it was false as did another US-based site PolitiFact in 2019 and Queensland-based fact check site Hoax-Slayer in 2017.

In 2018, the National Onion Association’s Rene Hardwick sent a letter to concerned customers addressing both chain email messages and social media marketing claiming “cut onions can cure the flu, are magnets for bacteria, and are responsible for food poisoning". The letter stated that all claims were unsubstantiated, and that “when handled properly, cut onions can be stored in the refrigerator in a sealed container for up to seven days".

The Verdict

Based on the evidence, AAP FactCheck has found the Facebook post to be false. The post incorrectly states that it is dangerous to cut an onion and try to use it to cook the next day.” DietSimone Austin of the Dietitians Association of Australia said she had never come across any evidence to substantiate any truth in this claim.

  • False - The primary claims of the content are factually inaccurate.

First published November 8, 2019, 16:47 AEDT