A couple of weeks ago, I dropped a sprig of fresh, aromatic organic rosemary in a pretty bottle and filled it with olive oil. What I didn’t know then is that I might have killed us with that oil.
It turns out, herb-infused oil is one of the twelve foods, or more precisely, food groups, that can cause botulism, a rare, but life-threatening food-borne illness that causes paralysis and may take weeks, even months to recover.
If you read me regularly, you’ll know I included an herbed oil in a post, 5 Ways to use fresh rosemary. A few hours after I published that post, an alert blogger friend notified me of the danger. I retracted the tip immediately.
To reach as many people as possible, I also published–and publicized as best I know how–a new article, clearly warning of the risk, along with a link to the University of Maine Cooperative Extension office article, Safe Homemade Flavored and Infused Oils.
How did this happen?
How could I, a grandmother who has known about botulism since my teens, not know that fresh herbs carry the bacteria, Clostridium botulinum, which causes botulism, or that putting them in oil would provide exactly the environment the bacteria needs to grow?
It never occurred to me such a thing could be harmful. In how many gourmet gift shops have I seen such bottles filled with oil and herbs? Turns out, commercial purveyors add a special acid-rich ingredient to their herbed oils, in a process not easily duplicated at home.
But also, the Center for Disease Control and Prevention (CDC), in “Botulism prevention: Many cases of botulism are preventable“, tells us that new sources of botulism poisoning are found nearly every decade. Given I’m more than five decades away from my last Home Ec class, where we learned about what causes botulism, I may have some catching up to do.
What else might I have missed in the last 50-some years?
My experience set me to wondering. What other foods carrying the bacteria escaped my ken? How we can protect ourselves when cleaning, preparing, eating and storing those foods? I did some digging.
In my research, I found twelve foods and/or food groups that can put us and our families at risk for botulism. Most I already knew about. But baked potatoes wrapped in foil? That one’s new too. Thankfully, we’ve never baked our potatoes in foil.
Is this a comprehensive list? Don’t count on it. I’ve done my best to ferret out the foods that may put us at risk. The twelve foods in the joint lists you’ll find on this page come from no less authoritative sites than the websites of the CDC and the United States Food and Drug Administration (FDA).
Before I share the lists, you may be wondering what botulism is and what causes it. Here are the facts as I understand them.
What is botulism?
Botulism is a deadly food-borne disease caused by the bacterium C. botulinum. This rod-like bacteria lives in the soil and can be found in many plants and animals.
When active, it produces a neurotoxin that attacks the nerves in our muscles, including the ones that help us breathe.
Only a small amount–we’re talking nano grams–can immobilize and kill a person. Because the symptoms are similar to other diseases, such as Guillain-Barré Syndrome, doctors find it difficult to detect. Diagnosis takes a week or more.
Thankfully, an anti-toxin is available to help treat the illness, and in most cases, prevent death. Recovery, however, may take weeks or months.
Other ways we can get botulism
While this article concerns itself with food-borne botulism, you should know that it can invade our bodies through other means, such as wounds and, possibly, according to the FDA, through invasive digestive-track surgeries.
In addition to these, MedScape, which lists six forms of botulism, includes inhalational botulism and adult intestinal colonization botulism.
Infants can get it from eating dirt, as well as from certain foods that are not dangers to children over one year old or to adults. Those foods are on the list, in their own section.
Fortunately for humans, C. botulinum needs oxygen to grow, and doesn’t like acid. Air and acids such as vinegar, lemon and lime juice help to keep us safe from food-borne botulism.
That’s one reason people preserve foods by pickling them in vinegar.
Three botulism facts to keep in mind
While it is deadly, C. botulinum needs a specific environment to grow. We can lessen our chances of getting this disease if we remember these three facts.
- C. botulinum may be carried on almost any food that has little or no acid. Green beans, Brussels sprouts, carrots and cabbage, like most vegetables and many fruits, contain very little acid. Other low-acid foods include mushrooms, meats, fish and eggs. C. botulinum spores may piggy-back on any such foods.
- C. botulinum needs a low-oxygen, low-acid environment.
When we place non-acidic foods in a low-oxygen environment, such as a home-canning jar, we give them the perfect environment to go forth and multiply. Similarly, covering low-acid foods in oil reduces or eliminates oxygen availability and provides a botulinum-loving environment. That’s why my herbed oil could have become a deadly, if tasty, food.
- C. botulinum is heat tolerant but can be killed by boiling at-risk foods for ten minutes, rendering them safe to eat. Add one minute for every thousand feet above sea level.
Now, on to that food list. There are two, actually–one for infants, and another for everyone else.
Which foods most likely carry botulism?
Reports from the FDA, as well as the CDC, name twelve foods, or food groups that may carry C. Botulinum to humans. They break it up into three foods for infants under one year, and nine that may pose a risk to all the rest of us.
Keep in mind that the FDA, in its Bad Bug Book, says
Most of the 10 to 30 [botulism] outbreaks that are reported annually in the United States are associated with inadequately processed, home-canned foods, but occasionally commercially produced foods have been involved in outbreaks. [Emphasis mine.] Sausages, meat products, canned vegetables and seafood products have been the most frequent vehicles for human botulism.
On its FoodSafety.gov website, the United States Department of Health and Human Services (DHHS), under which both the CDC and FDA run, breaks these twelve at-risk foods down this way.
Infants one year of age and under must never eat the following foods.
- Home-canned vegetables and fruits
- Corn syrup
Note that infant botulism is classified separately, not as a food-borne illness. The Minnesota Department of Health explains it this way: An infant can get botulism
When a baby eats or drinks something that contains spores of the bacteria – the hard-shelled form that the bacteria take on when they aren’t able to grow and reproduce.
Because honey, home-canned vegetables and fruits, and corn syrup may contain the spores, even if they’re not actively reproducing, these foods, as well as soil and even dirt in the carpet, may cause infant botulism.
Sometimes you have to wonder how we ever managed to over-populate Mother Earth, don’t you? Not that we should look at these dangers flippantly. Not at all! But to remind ourselves, lest we think we have to put our babies in bubble suits, that this disease is relatively rare.
Children and adults
For children one year and older, and for adults, the DHHS identifies the following high-risk foods.
- Home-canned foods with a low acid content
- Improperly canned commercial foods
- Home-canned or fermented fish
- Herb-infused oils
- Baked potatoes in aluminum foil
- Cheese sauce
- Bottled garlic
- Foods held warm for extended periods of time
- Frozen, fully cooked products (Not on the DHHS list, but found in a separate article published by the FDA).*
*The FDA , in its article titled Frozen, Fully-Cooked Products & Botulism – Food Safety Advisory, explains why they’ve issued this caution and what we need to do to protect ourselves.
How do we protect ourselves?
The DHHS offers this somewhat cryptic prevention advice.
- Be very careful when canning foods at home
- Do not let babies eat honey
- Get prompt medical care for infected wounds
The CDC gives a longer version, which I’ll break down into bullet points. I’ve gone over and over this list, but just in case I’ve misinterpreted or misunderstood something, please do read the entire CDC paragraph. We don’t want to take any more risks than we have to!
Many cases of botulism are preventable
Foodborne botulism has often been from home-canned foods with low acid content, such as asparagus, green beans, beets and corn and is caused by failure to follow proper canning methods. However, seemingly unlikely or unusual sources are found every decade, with the common problem of improper handling during manufacture, at retail, or by consumers; some examples are chopped garlic in oil, canned cheese sauce, chile peppers, tomatoes, carrot …
[More–Follow this link to read the entire paragraph on the CDC web site]
Breaking it down
If you followed the link, you know that’s a long, messy paragraph. Let’s break the prevention steps down a bit. I’ll include the prevention steps for wound botulism they’ve provided as well, even though it’s outside the scope of this article.
- Avoid home-canned foods with low acid content such as asparagus, green beans, beets and corn (not a complete list).
- Follow safe, hygienic canning methods, using appropriate equipment for the specific food, as outlined by your local extension service or the FDA. You can find your county extension office through this interactive map on the Gardening KnowHow site. Sure, it’s a gardening site. The extension offices help gardeners as well as home food preservationists.
- Watch out for commercially prepared or home canned foods that are likely to have a low-oxygen and/or low-acid environment. Examples not included elsewhere on this page include the following.
- Chili peppers
- Carrot juice
- Refrigerate oils infused with garlic or herbs.
- Keep baked potatoes wrapped in foil hot until ready to eat or refrigerate them.
- Boil home-canned foods for 10 minutes before eating them.
- Get prompt medical care for wounds
- Don’t use injectable street drugs. (Apparently most wound botulism is found in people who use street drugs.)
- Don’t let infants under one year eat dirt or honey.
What to do if you think you may have botulism-infected food
The first rule of thumb in food safety is always, When in doubt, throw it out.
With this bug, it’s more complicated than that. We can’t just chuck it down the drain or into the dumpster.
C. Botulinum is a bio toxin. Handle suspect foods with, if not kid, then plastic gloves, and a lot of care.
How to tell when to doubt? Check out the CDC guide for that. Please read the complete guide, especially this section: Safely dispose of food and cans that may be contaminated.
Stay safe–Do a little research
That’s what I’ve learned about botulism so far. I’ll return and post updates as I learn more.
I hope the links on this page help you to make healthy decisions about preserving the foods you love and help to keep you and your loved ones safe
Thankfully, botulism is rare. Please don’t assume I’ve covered every food and every possibility. Follow the links. Do the research. Ask questions of the folks at your local county extension office.
Do what you can to keep yourself and your loved ones safe from this deadly disease.
Last updated: July 17 2016, to repair broken links