From the mouths of babes — Clostridium botulinum and why you shouldn’t feed honey to babies

Our food is under attack from all sorts of enemies. At every step of the chain, something wants to eat your lunch. Some have even evolved nefarious tactics — they’ve learned to colonize quickly or poison environments to keep others from enjoying their spoils. Of all of food’s foul scourges, none is more deadly than Clostridium botulinum (or C. bot among those in the know). C. bot is dangerous because of a toxin it produces, which causes a condition called ‘botulism’ who’s symptoms include: paralysis and death.

C. botulinum is a bacterium that’s found in soil and ends up in all parts of our food. It’s usually not a big deal, we eat the cells whole and they pass right through us, nothing really happens. C. bot is special for a few reasons. For one, it’s a spore former. Unlike your run-of-the-mill bacteria, C. bot can form a hard coating to protect it from unfavorable conditions like the heat and chemicals that normally kill microbes in food. In spore mode, C. bot is mostly harmless; it can’t reproduce and it can’t produce dangerous toxins. C. bot is also really fussy about leaving its spore mode.

“You haven’t even seen my final form!” — SEM image of C. botulinum exiting a spore coat and sporulated [what a word!] bacteriums. (Image:

To begin with, the spores can’t grow under a number of conditions: they need an environment that isn’t too acidic (anything with a pH below 4.6, about the acidity of fresh tomatoes or cottage cheese), they need an oxygen free environment, and they don’t like other microbes present to compete with for food. These conditions aren’t met in most foods but as we’ll see in later discussions, extra care needs to be taken to prevent its growth in many packaged foods — especially acidified and low-acid canned foods.

Before I say more, let me also make a few notes. While exceedingly dangerous, botulism is also exceedingly rare. There was 1 case of botulism in 2017 and most cases come from improperly home-canned food. From 1990 to 2000 there were 160 botulism related events and most of them came from homemade food that was not properly processed or stored. Botulinum toxin is also readily destroyed by heat. ~10 minutes at 85 C can render it harmless if present in food.

For the chemistry fans out there. Botulism toxin is a really interesting protein. It doesn’t contains an intramolecular disulfide bond which gets cleaved to make the toxin active. Before this bond is broken, the toxin is innocuous. (Image:

If caught early, botulism is also treatable. However, treatment can include being paralyzed and hooked up to a breathing machine for months with full cognition. (this could be a disaster, as one woman who was affect by botulism once had to listen to Celine Dion for weeks, unable to tell the doctors she wasn’t a fan. Apparantly her first words were: “I hate Celine Dion”.)

You can also inject botulism into your face! Botulinum toxin (in very, very dilute quantities) is the active ingredient in Botox. The temporary paralysis caused by the toxin is perfect for smoothing out wrinkles, just don’t overdo it. (Image:

As far as the spores, consumed spores can’t really grow in our bodies and cause problems. Our stomachs are very acidic and our guts contain an enormous host of competitive bacteria that prevent the spores from growing. We’re pretty safe to eat C. bot spores, we just can’t consume the toxin. Infants are a different story though. Newborn babies may still have a high stomach pH, as high as 5 which could support C. bot growth. (Interestingly, this high stomach pH is very important for milk digestion, more on that to come). Moreover, newborns don’t yet have a robust and competitive microflora which could prevent C. bot growth. For newborns, C. bot spores can colonize and grow, producing the toxin that can lead to botulism and death.

Honey is a water activity controlled food and can contain high loads of dormant botulinum spores. Harmless to adults and toddlers, these spores can be a serious risk for infants.

Again, the actual incidence of infant botulism is very, very low. There are fewer than 100 cases a year in the USA. Still, honey presents unique risks for infants. Honey often contains high loads of botulism spores (which can’t outgrow and produce toxins because of honey’s very low moisture content). These spores can be dangerous for infants until they can grow their own gut bacteria and reduce their stomach pH’s to fight it off. Botulinum in other raw foods could be a risk too (albeit generally lower than the risks from honey) but most infants below 1 year of age don’t consume much besides milk or formula — both of which have controls in place to prevent the entrance of botulism spores.

Here’s the TL;DR and basic botulism safety:

  • Don’t feed infants honey.
  • Learn what you’re doing before you try canning food at home.
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