There's a common belief that it's "dangerous" to give cow's milk to a baby before he or she is 12 months old.

Numerous sites say to avoid giving cow's milk to babies under 12 months, however, they vary greatly in their reasoning. Some sites cite the immediate safety concerns (such as overtaxing the baby's kidneys) while others discuss the indirect effect of cow's milk causing the baby to receive insufficient nutrients.

His body won’t be able to digest the proteins in cow’s milk and he may develop an allergy to it

It could overtax his kidneys: Cow’s milk has more sodium, potassium and chloride than a baby can process.

Cow's milk doesn't contain the necessary nutrients such as iron, vitamin c that are present in formula and breast milk. At least not in high enough quantities for your baby to thrive.. However, by the time your baby is 1-year-old, they’re able to compensate for many of those lost nutrients with a well-rounded diet comprising fruits, vegetables, lean protein, dairy, and whole grains..

What scientific evidence exists to support any, or all, of the above reasons given to avoid cow's milk? For example, what evidence exists that cow's milk would "overtax" a baby's kidneys if given before 12 months?

Also, both of the articles above suggest waiting until the infant is 12 months before adding milk to his diet. However, an article published by TodaysParent.com states that:

"Official guidelines recommend parents hold off until babies are between nine and 12 months old before introducing cow’s milk".

I think that for many parents, the "extra" three month span from 9 and 12 months is a big deal because many moms lose their ability to produce breast milk right around 9 months and would love to immediately transition to bovine milk if it is safe to do so.

Is it really necessary to wait 12 months before adding milk to a baby's diet or is 9 months sufficient?

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    Note that "can cow milk be safely added to a baby’s diet?” and “can cow milk replace breast milk/ formula?” are two entirely different questions.
    – TimRias
    Commented Jan 6, 2021 at 9:16
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    Brucellosis is a risk in raw milk. The risk is low in US because of tests done on cows but I don't know about the rest of the world. Commented Jan 6, 2021 at 16:43
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    @mmeent And the answer to replacing breast milk, in case it isn't obvious, is a very solid NO. Only baby formula can replace breast milk.
    – Nelson
    Commented Jan 7, 2021 at 0:43
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    @blacksmith37 a LOT of the guidance you find repeated has it's origins in WHO advice against cows milk and formula because they have to consider the global position, with many billions of mothers being in countries where cows milk and water are less safe than breast milk; in most western countries those concerns are unfounded.
    – JeffUK
    Commented Jan 7, 2021 at 8:03
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    Note that there is a massive difference between the cow milk fresh from the cow in the backyard versus cow milk from a carton box from the super market both in terms of nutrition and food safety. I assume you mean the latter?
    – quarague
    Commented Jan 7, 2021 at 10:37

1 Answer 1


Cow's milk contains both casein and whey protein. Both contain the same amino acids, but casein is "slow release" and whey is digested more readily. Like most animals, 80% of cow's milk protein is casein and 20% is whey.

UK figures suggest that 7% of babies under 1 year old are allergic to casein protein, and therefore this is removed when making formula from cow's milk. Note that Mum's milk still contains casein, but at a much lower level: 30% to 70% whey.

Allergies manifest as skin swelling or rashes, upset stomach / vomiting / diarrhoea, or a blocked / runny nose.

When possible, Mum should breastfeed as her milk not only has the right proteins but also antibodies to help baby fight infection.

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