Honey and infant botulism
Last week, in the space of a couple of days, the subject of honey came up both during the play-date we hosted with some of the kids from our NCT group and at drop-in nursery. Pretty much all the parents were aware of the advice to avoid giving their kids honey at least until they were a year old (although figures like 3 years and 6 years old also came up in the conversation), but the precise reasons were a little unclear.
I knew that the main reason was the risk of infant botulism, but beyond that, I didn’t really have much of a clue about how botulism works or what the actual risks are, so, naturally, I thought it would make for an interesting thing to look into and blog about.
Infant botulism is caused by the toxin released by the bacteria Clostridium botulinum. C. botulinum and the spores they germinate from are found in pretty much universally in soil, and the plants that bees feed on in order to make honey grow in that soil.
It isn’t just raw honey that’s the problem. Botulism spores can only really be destroyed by boiling, so pasteurized honey can still be contaminated, and it’s also best to avoid using honey in cooking (especially if the food is meant for the baby, obviously; always remember to wash your hands carefully afterwards), as the temperatures (even in an oven baking bread) don’t get anywhere near high enough to negate the risk.
Infant botulism is special because it’s caused by the growth and toxin production by C. botulinum within the intestine, rather than by eating food contaminated with botulinum toxin. Babies under the age of one are especially vulnerable as their guts haven’t yet matured enough to cope with the spores and stop them germinating and multiplying.
Once the C. botulinum bacteria have colonized a little pouch at the beginning of the large intestine, they start releasing botulinum toxin, which, once it has been absorbed through the intestine, irreversibly binds to specific nerve cell receptors and basically blocks the release of an important neurotransmitter, acetylcholine. Acetylecholine is needed to excite muscle, so if there isn’t enough of it to do its job, muscles can’t be activated and contracted properly and you get symptoms like weakness or floppiness, lethargy or decreased activity, breathing difficulties and seizures (other symptoms include constipation, irritability and weak crying). Fun fact: this is exactly how cosmetic botox injections work – tiny amounts of botulinum toxin is injected into the muscle, blocking acetylchoeline, causing the muscle to relax and the temporary disappearance of wrinkles.
Approximately 90% of reported cases of infant botulism seem to occur in the US (I've seen figures ranging from 150 to 450 cases a year), but this is probably due to increased awareness rather than perhaps increased risk (although unusually high rates are reported in California, which may actually be because the soil there is especially chock full of C. botulinum). It’s hard to get a handle on the exact numbers as, despite C. botulinum being found universally in soil across the world, there are surprisingly few recorded cases of infant botulism, suggesting that the condition is under-recognised and/or underreported.
In Norway, there have been 78 cases of any type of botulism between 1977 and 2015, the overwhelming majority of them in adults (split between food poisoning and infection through injected drugs). There have been just three reported cases of infant botulism (1 in 2013 and 2 in 2014) between 2008 and 2015.
The American FDA refers to a study from a while back (1992) that reported that 13% of the samples of honey tested contained low numbers of C. botulinum spores. I couldn’t find any newer figures (and I didn’t want to fall too far down in the rabbit hole), but it looks like the reason for the strong recommendation to avoid honey is not because there is necessarily a high chance of the honey being contaminated with spores and botulism occurring (especially with good hygiene practice), but because the consequences are pretty serious. Even with timely and proper treatment, recovery from infant botulism can take months as the nerve endings regenerate, but the good news is that there’s only a 2% fatality rate, and in most cases kids make a full recovery with no lasting damage.
Interestingly, it has been suggested that breast-fed infants are at increased risk of infant botulism, but also that breastfeeding might also delay the severity of symptoms. Unfortunately, I don’t have access to either of these papers so can’t I dig any further into it, but I’m absolutely intrigued as I find the immune properties of breast milk endlessly fascinating. Incidentally, breastfeeding mothers don’t need to worry about passing on c. botulinum to their babies as the (comparatively) large spore cells are filtered out way before they the chance to get anywhere near the breast milk, and the toxin doesn’t get into the breast milk either.
After the age of around 12 months, the risk of infant botulism is much lower as by then the gut has matured enough and is host to a whole load of other bacteria that are able to ‘outcompete’ any C. botulinum spores for resources.
It's a bit of an arbitrary time to do it, but I can’t wait to give the Troll his first little taste of honey on his first birthday!
- Cox, N. and Hinkle, R. (2002). Infant botulism. American Family Physician. 65, 7, 1388-1393.
- Golding, J., Emmett, P.M., Rogers, I.S. (1997). Does breast feeding protect against non-gastric infections? Early Human Development. 49(suppl) S10520.
- Grant, K.A.; McLauchlin, J., Amar, C. (2013). Infant botulism: advice on avoiding feeding honey to babies and other possible risk factors. Community Practitioner. 86, 7, 44-6.
- Koepke, R., Sobel, J., Arnon, S.S. (2008). Global occurrence of infant botulism. Pediatrics. 122, 1, e73-82.
- World Health Organisation: http://www.who.int/mediacentre/factsheets/fs270/en/