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Ask the Armadillo - making up infant feeds, what's the deal?

Q.  Dear Armadillo
Would you consider an article about making up infant formula please?  I've read you have to use water hotter than 70 degrees and make the feeds up as required, but a lot of mums I speak to don't do this as it's quite new information and babies have been fine for years without it and over cleaning is just as bad.  Who is right?

A.  Hi Sarah
You are correct that Department of Health guidelines are to use water of at least 70 degrees and discard a bottle after two hours (some sources suggest one if baby has been drinking from it)  but there does generally seem to be quite a lot of confusion over the guidelines and whether they are applicable to countries such as the UK & US where water contamination is not an issue.  I wanted to answer this question as for mums not breastfeeding, it's important to make the alternatives as safe as possible.  I should add at this point that I generally had quite a laissez-faire attitude to sterilisation of things when mine were little - I mean once they were crawling on the floor and chewing things that had been on it, I didn't really see much point ensuring toys were sterilised.  I do also think generally that over use in the home of things like antibacterial sprays on every surface, bleaching floors constantly etc carries more risk than the germs they protect from.  Breastmilk substitutes however are a little bit different.

Unlike ready to feed liquid milk, a tin of powder is not sterile and there are risks of contamination all the way through the process - starting with the raw ingredients, during production after pasteurisation and thirdly in the reformulation or in the can at home.  Because of this there are different problems associated with reconstituting incorrectly.

Let's start with the most serious risks.

Without a doubt these are are Enterobacter sakazakii and Salmonella.  The first is a bit of an interesting one as it is found in the gut of healthy humans (probably as an intermittent guest) as well as in the gut of animals and in the environment.  A 2005 study found the prevalence in infant formula varied from 0 to 12% in samples from five different companies.  To give more of an idea of frequency, a 2010 study found 9 out of 149 samples were contaminated with E Sakazakii.

When it strikes it can be extremely nasty, and there are strong links with meningitis, septicemia, and necrotizing enterocolitis.   In the outbreaks reported 50-70% of the infants who contracted the disease died; for those who survive, severe lasting complications can result in various problems including neurological disorders

The trouble with breastmilk substitutes is that they provide the perfect environment for bacteria to grow and thrive, and in 50-80 % of cases powdered infant formula is both the vehicle and the source (direct or indirect) of E. sakazaki induced illness, whilst no exclusively breastfed infants have to date been reported to have Enterobacter sakazakii infections (WHO).
Because of the high mortality rate, when links with disease were made investigations immediately began as to how to best minimise risks; scientists discovered boiling water at 70 degrees resulted in a more than 4-log reduction in E. sakazakii levels.  Furthermore, not leaving the made product to sit around prevented any remaining pathogens from increasing  to dangerous levels, a risk that increases further once the enzymes from baby's saliva have entered the mix.  This is really important as in the above mentioned study, 8 of the 9 cases of contamination were low and therefore mixing with water of an adequate temperature and using immediately is likely to reduce this risk to a nominal level.  However using water that is too cool, then leaving the milk to sit around can very quickly lead to high levels of harmful bacteria.
Although found less frequently in breastmilk substitutes, more people have heard of Salmonella; it can cause anything from mild diarrhoea, vomiting and cramps to the rarer Salmonella bacteremia which can result in septicemia and meningitis.  Again using water at 70 degrees minimises risks.
Because formula contamination rarely hits the news unless it's a large "official outbreak" which is less common, many people are under the impression that the risk of formula contamination is negligible; but WHO feel differently:
Is the risk similar in all regions and countries?

There have been reported cases of Enterobacter sakazakii infections due to contaminated infant formula in only a few developed countries. It is likely that there is a significant under reporting of  infections in all countries. The absence of reports is probably due to a lack of awareness of the  problem rather than an absence of illness. In general, the limitations of current surveillance systems in most countries would add to the explanation for the lack of reported cases. Since infant formula is widely used, the presence of Enterobacter sakazakii in infant formula and its potential effects in infants could well be a significant public health problem in most countries.
Another condition heavily linked with incorrect preparation of infant formula is gastroenteritis, often called stomach flu.  Symptoms include diarrhoea, sickness and stomach cramps - in people able to consume enough fluids it is generally not serious; however infants and young children are at risk from loss of fluids and may need to be hospitalised for treatment to correct or prevent dehydration.
Sue Battersby, a midwife stated in a 2009 report:
Formula is not sterilised and bacteria can be present. When it is made up or stored incorrectly there is a big risk that it could cause gastroenteritis. "Formula fed babies are five times more likely to be admitted to hospital with gastroenteritis, which in the majority of cases is preventable."
It's as usual all about risks rather than certainties - not every baby who drinks milk prepared incorrectly will become ill and nor is meticulously following the guidelines a guarantee baby will remain well; but for the sake of the extra few minutes is it really worth the risk?  Of course good hygiene such as sterilisation of bottles and other equipment (domestic dishwashers usually are not hot enough), effective hand washing and careful storage all contribute too .  My personal experience is that gastroenteritis is still common at 9-24 months, when many parents relax a little - whilst this may be ok for other items such as toys, things that come in contact with breastmilk substitutes are still prime breeding ground.

For people who say they didn't do it with other children and theirs have always been fine, I always think that given the advancements in what we know about bacteria and how to reduce the risks of it - why ignore this?

Is it hard to do in practice?

Guidelines suggest using water that has been boiled and left for no more than around 30 minutes.  For a couple of pounds it's worth buying a thermometer and checking the temperature of your water a couple of times to get a feel for how fast it cools.  It is just as important not to add boiling water to the powder as manufacturers suggest this may damage vitamins/nutrients.

If baby has a rough feeding routine, you can then build in cooling time when at home.  If going out and about, carrying the powder in a sterilised container, water in a flask and then combining the two when required works - again worth checking the temperature a few times if there's risk it could have cooled.  I've heard a lot of mums do this at night too!   Another option is to keep cooled boiled water in the fridge, and work out how much needs to be added to the boiling water to get an appropriate temperature.  If you decide to use thermal bags for carrying ready made bottles, it's even more important to check temperatures after storage as many mums report large differences in how long milk remains at temperature.

Hope that answers your question - it also neatly dispels the myth infant formula is a handy, convenient alternative!


  1. Yes, you have dispelled the myth that formula is handy and convenient! I can not be faffed with all that messing around and tryong my best to limit the risks, which to be fair aren't worth it at all. I would rather abolish the risks all together and that is why I breastfeed! I'm glad you wrote this :)

  2. There have always been issues with the idea of rehydrating at 70 C, such as the risk of scalding, the risk of destroying nutrients/vitamins in the formula and it is inappropriate for formula that contains probiotics. If formula is prepared with cooled boiled water, fed immediately to the child and then disgarded there is very little risk of illness from Cronobacter (E. sakazakii). The major outbreaks of illness have usually been linked with endemic failures in proper hygiene (cleaning) and/or keeping the formula at room temperature or 37 C for several hours allowing growth. The main risk is for babies less than 1 month old so breastfeeding for at least the first month, ideally longer, is the best approach.

  3. I know this may not be the case in developing countries, but from what I understand most hospitals in the US no longer use any powder formula for newborns as Enterobacter sakazakii can be caused from improper storage of powdered infant formula. It is also recommended that you should not use powdered infant formula in the first month for babies. Most hospitals use ready-to-feed formula with disposable bottles and you can find this at most grocery stores.
    I used glass baby bottles in the beginning and sterilized by boiling them or in the dishwasher. The same with the nipples and rings. The formula was always given freshly made and to this date she has never had any gastrointestinal illness so safe handling is very important. My DD is well past the formula stage now, but I thought I would share since I agree there needs to be more education on safe formula handling when a mom cannot breastfeed.

  4. Hi Civersen - thanks for your comments.
    I have heard the same points raised before, interestingly by the "Infant Nutrition Council" (INC) which might sound impressive but to those not "in the know" it is an amalgamation of the Infant Formula Manufacturers’ Association of Australia and the New Zealand Infant Formula Marketers’ Association - so basically those with an interest in not making formula complicated (doesn't help sales)

    So the points - scalding. We can't suggest mothers use the right temperature water because they might scald themselves or baby, and according to their comments a thermometer is not a standard household item. Well nor are bottles or sterilisers or anything else baby related, so it's another thing to add to the shopping list if using substitutes. Perhaps though we should ban steam sterilisers, in case mother burns herself on that? or suggest they drink luke warm cups of tea just in case?

    They then present sterilising the thermometer as a problem because boiling isn't good for glass and nor are chlorine sterilising solutions - but am pretty sure there must be a way around this. My jam thermometer has no issue with boiling water! don't hospitals have to sterilise thermometers between patients? does it have to be stuck IN the bottle or could a few drops be tipped into the lid and tested before discarding so no need for sterilisation.

    If parents had a thermometer, surely it would be pretty easy to work out what ratio of boiling to cooled boiled water made 70 degrees? As totally random figures if it's a 6oz bottle, say 4oz boiling, 2oz cooled might create an ok temperature - you wouldn't need to check it every time unless volume changed?

    Vitamin destruction is another interesting theory - in particular the INC highlight vitamin C and thiamin.

    There is apparent misconception about the extent to which boiling temperatures destroy vitamin C -probably as a result of flawed research. Contrary to what was previously and is still commonly assumed, it can take much longer than two or three minutes to destroy vitamin C at boiling point. Vit C enriched teas and infusions are sold, surely such products would be nonsense if boiling temperatures did indeed destroy vitamin C at the rate it had previously been suggested?

    BUT - let's not forget, the guidelines are NOT to use boiling water, but water at 70°C.

    The Infant Nutrition council state: thiamin is destroyed at 100°C. But again nobody is suggesting mums use 100° - the guidelines are 70°.

  5. The INC then state:

    "If parents fail to allow the boiled water to cool then the hot water can destroy some of the nutrients"

    ah so the problem isn't with the ACTUAL guideline then, it's with a perceived problem of people not following instructions. Maybe the tin could clearly state do not use boiling water? There are a lot of ways people can potentially make infant formula wrong, with various risks associated.

    WHO's opinion on this is if it's that much of a concern, add extra vitamins during manufacturing to allow for loss. The INC claim this isn't possible due to difficulty establishing dosing given different temperatures of reconstitution. But er, isn't this the case now then? with parents reconstituting at allsorts of temperatures? surely a set temperature would actually be beneficial in establishing dosing by their logic?

    The topic of probiotics is probably one for another blog post entirely. But parents can also choose a non PB milk and add a decent quality supplement if they prefer.

    QUOTE If formula is prepared with cooled boiled water, fed immediately to the child and then disgarded there is very little risk of illness from Cronobacter (E. sakazakii).

    This is an interesting comment, again one the INC made - but is there evidence to support this claim? In the study I quoted, 1 out of 149 samples had a HIGH level of contamination - if not destroyed, what is the impact of this? As I also stated in the posting, WHO feel there are actually a lot more cases than are recorded. Yes only the major outbreaks get press, as I stated - but that doesn't really mean much though does it?

  6. Quote Civersen "There have always been issues with the idea of rehydrating at 70 C, such as the risk of scalding, the risk of destroying nutrients/vitamins in the formula and it is inappropriate for formula that contains probiotics."

    Kind of proves the point that Armadillo is making, BF easier and safer all round ;-)

  7. HI!

    It is very interesting what you´re talking about. Especially when you mention gastroenteritis. People don´t feel it´s all that important unless your child ends up hospitalised due to dehydration (another problem with formula milk as a breastfed child tolerates breastmilk better than water when vomitting). I was one of those babies. My mum once pointed out how these days people were obsessed about sterilising and how she didn´t think it was that important. Well, like you, AA, I didn´t bother to sterilise much as I din´t have anything to sterilise when they were little because they were breastfed. By the time they were on solids they were also on the floor picking things up and putting them in their mouths. But, mine were breastfed. I was, however, bottlefed after 2 months of failed breastfeeding and, at the age of around 7 months (which coincidentally was summer-time) I ended up in hospital dehydrated due to gastroenteritis.

    So, if you are going to bottlefeed, for whatever reason, please do it properly. Don´t be casual because bacteria do grow very easily and if none of your children ever had any problems, well, you either did things properly or you were lucky.

  8. So basically, breastfeed. If you don't you must go to science lab lengths to avoid contamination or you *might* kill your baby? Why not build a clean room in your house and buy a couple of Nuclear / Biological / Chemical suits to prepare a feed, even at 3am? It's not one big conspiracy you know- the formula manufacturers' sales would suffer far more if they had dozens of dead babies poisoned by their supposedly shoddy guidelines. There really are minimal risks to using a sterile bottle, boiling or close to boiling water on a couple of oz of formula, cooled, boiled water to top up, fed to baby immediately providing temp is OK. You can never ensure 100% safety whatever feeding method you use. Yet again using a one-sided campaign-led analysis to prove your breadfeeding dogma, intended to make mums feel bad about their 'failure' to breastfeed is plain wrong. Don't insult readers by dressing this blog as impartial analysis of fact.

  9. When I was a nanny in Dublin 11 years ago I made up all formula feeds by boiling the kettle, then leaving it to cool for 20 minutes (oven timer great for this) then making up the bottle.

    Its absolutely doable, altho far more faff than breastfeeding as I've done with my own children.

  10. To previous anonymous poster, you're arguing (pretty much) in favour of following the guidelines which is exactly what this blog post was about. I'm not sure what you're disagreeing with?

  11. Nestle have finally accepted that their claims that probiotics in their infant milks protect babies from gastroenteritis are not actually true - although they still refuse to remove them from their tins.

    A post on probiotics and other additives would be interesting!

  12. " Yet again using a one-sided campaign-led analysis to prove your breadfeeding dogma, intended to make mums feel bad about their 'failure' to breastfeed is plain wrong. Don't insult readers by dressing this blog as impartial analysis of fact."

    Given that the AA devotes most of her life to voluntarily (ie not paid) supporting women who want to breastfeed TO breastfeed, it's utterly wrong of you to say that she's trying to make mums feel bad. The AA feels so frustrated about women not getting the support to BF, thus leading to many women feeling guilty about it, that she works with women every day who need the help - and get it from her. Clearly, stating that she intends to make women feel "guilty" is ignorant and offensive.

    Many breastfeeding women who are struggling for one reason or another need incentives to keep going. The articles that the AA writes are brilliant for reminding mums why they are doing this and also that the grass is not actually greener.

    Yay for the AA, that's what I say.

  13. I wonder if people use anon - could they use a made up signoff? just so we can reply to more than "anon" pls - otherwise gets a bit confusing when there's a few.

    Anon 1 QUOTE It's not one big conspiracy you know- the formula manufacturers' sales would suffer far more if they had dozens of dead babies poisoned by their supposedly shoddy guidelines

    Have you seen the gastro rates for the UK and the cost to the NHS?

    QUOTE There really are minimal risks to using a sterile bottle, boiling or close to boiling water on a couple of oz of formula, cooled, boiled water to top up, fed to baby immediately providing temp is OK.

    Boiling water or water close to boiling destroys vits in the powder as I believe someone else said. However if you make a set feed - i's pretty easy to work out what ratio of boiling to boiled and cooled water you need for 70 degrees - as I believe I state somewhere else.

    QUOTE Yet again using a one-sided campaign-led analysis to prove your breadfeeding dogma, intended to make mums feel bad about their 'failure' to breastfeed is plain wrong. Don't insult readers by dressing this blog as impartial analysis of fact.

    Well I've heard it all now!! LOL sorry but that's actually quite chuckle worthy. Giving mums who do formula feed, details to ensure they do so as safely as possible is proving a breastfeeding "dogma" and making mums feel bad?! Blinking heck I obviously don't know the depth of my own writing skills!

    Thanks to everyone else, much appreciated :D and yes will add probiotics to my list!

  14. QUOTE: If formula is prepared with cooled boiled water, fed immediately to the child and then disgarded there is very little risk of illness from Cronobacter (E. sakazakii).

    This sounds like the '5-second rule' being applied to baby feeding. I don't believe there's any evidence to support that theory though ;)

  15. I formula fed my son. I expressed for 10 weeks but due to a number of factors my breast milk supply or let down or something stopped and I couldn't re establish feeding He was born at 27 weeks gestation and was severely IUGR.

    There is a really obvious way of testing the temp of the water without sterilising the themometer. Pour the water into the bottle and into another plastic container, take the temp of the water in the other container.

    I felt it was vital in our case to use freshly boiled water within 30 minutes as my son had had NEC (necrolitising enterocolitis) and remained susceptible to infection. I didn't take the decision to formula feed lightly and unfortunately wasn't given the time and resources to source a donor or I would have used another mother's breast milk.

    I never found using freshly boiled water an issue, and used ready made cartons when out and about to avoid the whole issue, fortunately our specialist preemie formula came in both types.

  16. Hi AA, I was keen to look up the study you give the link for, but it just goes to a 1 page blank pdf, could you double check the link please?

    You say "resulted in a more than 4-log reduction in E. sakazakii levels." its been a while since I did maths at university, but I think you mean log 4 at base 10 which would be = 10,000???

  17. Here's the WHO leaflet on preparing formula feeds if anyone wants to read it.

    Any unused, refrigerated feeds should be used withing 24 hours.

  18. reads: Edelson-Mammel and Buchanan (2004) showed that a greater than 4-log reduction can be obtained by rehydrating dried infant formula with water pre-equilibrated to ≥70˚C. is the link that isn't showing.


  19. When I wrote my article on how to safely prepare formula I also recieved comments from someone working for the Infant Nutrition Council.
    The whole thing about scalding is pretty ridiculous as I'm sure most mothers use boiling water when making a cup of tea or coffee without scalding themselves. You'd have to be pretty dim to feed your baby boiling formula.

    Safely preparing formula adds an extra 26 minutes to a feed time. Obviously this is not something the formula manufacturers want people knowing, they need formula to be seen as the 'easy' option.

    As for the bacteria issue, in New Zealand in 2004 five babies were infected with Enterobacter sakazakii from improperly prepared formula, one of them died. You can't say it is a third world issue, NZ is far from third world.
    Obviously breastfeeding is the easiest (well, with a bit of help and support), safest way to feed your baby, but if you have to, or make the choice to formula feed, you really NEED to do it properly, your baby's life and health are at stake. Why would you put your baby's health at risk for convenience when there is a way to minimise the risks?
    Unfortunatley Plunket here in NZ (our well child providers) tell parents they don't need to use boiled water (fresh from the tap is fine) for preparing formula after six months as "by this stage they put everything in their mouths anyway" - blimmin crazy! Enterobacter sakazakii is totally different to normal household germs.

    :( It makes me sad when parents aren't told ways to keep their children safer. It is the same with rear facing. If you don't go looking for the information yourself, you basically never know that you could be taking these steps to protect your kiddies :(

  20. Totally agree Kirsty re. Plunket comments, I've never looked into their recommendations regarding formula, being a bf mum myself. Given some of the bf "advice" they give out and about starting solids (watties sponsorship a conflict of interest anyone??) and the carseat issue, it sadly doesn't surprise me.

  21. AA so you don't know what log-4 means either! ;-) I'm pretty sure it means the risk was reduced by 10,000 times - which is a lot!

  22. Excellent article. Makes you wonder why so many people claim that formula feeding is more convenient.

  23. Have you seen the recent press that a high percentage of powdered formula is contaminated with botulism spores? My understanding is that only actively boiling water will kill botulism. Is this incorrect?

    Also, back when I was using formula, I would mix up 24hours worth of bottles using freshly sterilized equipment, bottles, rings and nipples, boiled and still hot (though not actively bubbling- I didn't have a thermometer) water and place them all directly into the fridge. You mention the 1 or 2 hour guideline for bottles that have been sitting out at room temperature (untouched, not after baby has already fed from the bottle), but not any guideline for refrigerated formula. Is the current recommendation to make up bottles one at a time? (My most recent documentation says 24 hours in the fridge is fine, but it also says to use cooled boiled water...)