Day 102. Onions

In November 2012 on November 22, 2012 at 1:54 pm

Have you read information suggesting that onions are the harbingers of death and destruction due to their propensity to absorb bacteria and viruses?

This morning I read a shared Facebook update regarding this popular vegetable which apparently was aimed at saving my life.

Here’s how it started:

In 1919 when the flu killed 40 million people there was this Doctor that visited the many farmers to see if he could help them combat the flu…

Many of the farmers and their families had contracted it and many died.

The doctor came upon this one farmer and to his surprise, everyone was very healthy. When the doctor asked what the farmer was doing that was different the wife replied that she had placed an unpeeled onion in a dish in the rooms of the home, (probably only two rooms back then). The doctor couldn’t believe it and asked if he could have one of the onions and place it under the microscope. She gave him one and when he did this, he did find the flu virus in the onion. It obviously absorbed the bacteria, therefore, keeping the family healthy.

Firstly, it’s was a pretty futuristic microscope that could see a virus in an onion back in 1919 (the Electron Microscope was invented in the early 1930s). Secondly, the writer is improperly interchanging the terms ‘virus’ and ‘bacteria’. Yes, both can make you sick but they are very different in size, structure and how they live and infect humans.

Next was this:

Now, I heard this story from my hairdresser. She said that several years ago, many of her employees were coming down with the flu, and so were many of her customers. The next year she placed several bowls with onions around in her shop. To her surprise, none of her staff got sick. It must work. Try it and see what happens. We did it last year and we never got the flu.

Having two cases studies which report an association (not the same as a mechanism or a causal relationship) between placing an onion in a room and low incidence of flu infection is not enough to make it science. See this great Critical Thinking animation (only 2.20 minutes) on the tricks our brains play to deal with information.

There are many, many reasons which might explain why the groups of people had low incidence of flu. For example, in the hairdressing salon, perhaps because the staff experience flu the first year, in the second year they all had immunity? In the farmer example, perhaps all members of that family had a particular arrangement of genes which made them better able to fight flu infection? Perhaps they never showered, and hence were so smelly nobody came near them to share common viruses? We just don’t know.

It may be hard for us to accept, but unless there is a specific study involving unbiased researchers and large groups of subjects all exposed to the same dose of a virus under similar conditions while sitting near to or far from an onion or a proxy of an onion (a control vegetable) which then shows high levels of the pathogen in question we cannot say that onions prevent infection.

The information then continues, including the following snippets:

Onions and garlic placed around the room saved many from the black plague years ago. They have powerful antibacterial, antiseptic properties.

–> Anecdotal and no evidence is provided.

Lots of times when we have stomach problems we don’t know what to blame. Maybe it’s the onions that are to blame.

–> Guesswork at best.

Dogs should never eat onions. Their stomachs cannot metabolize onions.

–> Tell that to my labrador. Jokes aside, searching the database at the US National Library of Medicine, I did find one paper suggesting problems for dogs after eating onions.

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.

–> No evidence provided. I searched, and couldn’t find a single supporting publication. I did find some papers which report bacteria and viruses in association with many vegetables, including onions, but  not from absorption sitting in kitchens or fridges. It would be reasonable to assume that most bacteria and viruses found in association with vegetables are derived from unclean water and organic matter applied to gardens.

A few others have written more comprehensive debunks of the onion story than I: see HoaxSlayer and Waffles at Noon.

[image thanks to SoraZG on flickr]

  1. The one I’ve heard about onions is that if you feed it to seagulls, they can’t fart and so they explode from the build-up of gases in their stomach as they break it down! Also probably not true, but as a child it was an awesome thing to imagine….

  2. Exploding seagulls, I wanna see that! Let’s do an experiment…..

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