FDA Avocado Warning: Unwashed Skins Could Lead to Listeria Poisoning

Avocados are one of the nation's favorite foods. But did you know you should wash the skin before eating them? That's the advice of a Food and Drug Administration report which found that pathogens can be transferred from the peel to the edible flesh inside when you cut them open.

As part of an initiative to keep contaminated food from reaching consumers, the FDA collected more than 1,500 avocado samples over a period of 18 months between 2014 and 2016 to determine the prevalence two types of bacteria which can cause potentially serious infections; salmonella and listeria monocytogenes.

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Around 70 percent of the avocado samples the agency collected had been imported into the country, while the rest were grown domestically. These proportions are roughly equivalent to the actual share of imported and home-grown avocados in the U.S. market.

The FDA tested the prevalence of salmonella on the skin of avocados, as well as listeria on the skin and in its pulp—the edible portion of the fruit. The results showed that 12 out of 1,615 sampled products, or 0.74 percent, contained salmonella on the skin (11 green-skinned avocados and one of the dark-green, rough-skinned, Hass variety—all of which were domestically grown.)

The FDA also tested 361 of the avocado samples for listeria on the skin, finding the pathogen on 64, or 17.73 percent, of them (33 domestic and 31 imported.) They then tested 1,254 of the avocados for listeria in the pulp, finding three of the samples—all of which were imported—contained the bacteria.

It is important to note that the latest report did not look into the concentrations of pathogens in these samples. In most healthy adults, low levels of exposure to listeria bacteria does not tend to cause severe illness. However, high-risk individuals—including pregnant women, the elderly, and people with weakened immune systems—could be vulnerable to small amounts of the pathogen.

Being infected with listeria can lead to listeriosis, which affects about 1,600 people every year in the United States, leading to 260 deaths, according to the Centers for Disease Control and Prevention (CDC.)

Symptoms vary but can include headache, confusion, stiff neck, loss of balance, convulsions, fever and muscle aches. The infection is particularly dangerous for pregnant women because it can lead to miscarriage, stillbirth, premature delivery or life-threatening illness in the baby.

While there have been no listeria outbreaks linked to eating avocados reported in the U.S., the FDA say that the strains they detected in their research are "highly related" to those found in contaminated people. However, avocados are thought to have been responsible for a handful outbreaks involving salmonella and the bacteria e. coli, according to the CDC.

Salmonella causes about 1.2 million illnesses every year in the U.S., CDC data suggests, leading to about 450 deaths—although most people recover without treatment. Common symptoms include diarrhea, fever and abdominal cramps.

In order to reduce the risk of infections from eating avocados, the FDA recommend that you should wash the fruit thoroughly with water beforehand, even if you plan to cut off the skin first. This will ensure that dirt and bacteria are not transferred from the knife to the fruit.

Furthermore, foodsafety.gov recommends that consumers should scrub firm produce, such as avocados, with a clean produce brush, before drying it with a clean paper towel.

The FDA says it is currently working with the food industry to try and reduce contamination of avocado skins. Furthermore, the agency has also begun a large-scale study looking into the prevalence of listeria and salmonella in processed avocado products, such as guacamole.

This photograph taken on July 25, 2018 shows 73 year-old Kenyan avocado farmer Simon Kimani posing with some of his crop in Kandara, central Kenya. KEVIN MIDIGO/AFP/Getty Images