Is cow's milk safe for my baby?

The verdict

Two different questions get asked as one, and they have different answers.

Cow's milk in food is fine from around six months. The NHS says cows' milk can be used in cooking or mixed with food from around 6 months. That covers milk in porridge, in a white sauce, in scrambled egg and in mashed potato, and it covers full-fat yoghurt and pasteurised full-fat cheese too.

Cow's milk as a main drink is a different matter. In the UK and the United States the answer is not before 12 months. In Canada the answer is not before nine to 12 months. Nobody permits it as the main milk in the first six months.

Under 12 months, the only suitable alternative to breast milk is first infant formula. The NHS is specific that follow-on formula, growing-up milks and toddler milks are not needed at all, and that formula milks are not needed once your baby is 12 months old.

Why the delay, mechanically

There are three separate reasons, and they are not the same reason stated three ways.

Blood loss from the gut. This is the one that surprises people. The AAP states that cow's milk protein can irritate the lining of the stomach and intestine, and that this can lead to loss of blood, from small amounts you can't see all the way to bloody stools. The CDC puts it as: giving cow's milk to your baby before 12 months may put them at risk for intestinal bleeding. Health Canada cites the underlying studies directly, noting that use of cow milk as a main milk source for infants younger than six months of age can cause gastrointestinal bleeding and increased occult blood loss in stool. The losses are usually microscopic. They still come out of an iron budget that is already tight.

Iron. Cow's milk is low in iron, and the iron it does contain is poorly absorbed. Worse, it interferes with absorption of iron from other foods. Health Canada's summary is that cow milk is low in iron, can displace iron-rich foods, and can inhibit iron absorption. A baby filling up on milk is a baby not eating meat, lentils or iron-fortified cereal. Iron deficiency in the first two years is not a trivial finding.

Kidney load. The CDC states that cow's milk has too many proteins and minerals for your baby's kidneys to handle easily. The AAP describes the same thing: cow's milk contains high concentrations of protein and minerals, which can stress a newborn's immature kidneys. Infant formula is reworked cow's milk with the protein and mineral load brought down and the missing nutrients added back.

Why cooking is different

The dose differs by an order of magnitude. A splash of milk in porridge is a few tablespoons spread across a meal that also contains iron. A bottle of cow's milk instead of formula is several hundred millilitres displacing the baby's actual nutrition. None of the three mechanisms above are triggered by milk used as an ingredient.

What changes at one year

The NHS position from the first birthday is that pasteurised whole milk and semi-skimmed milk can be introduced as a main drink once your child is 1 year old. Skimmed and 1% milk should not be given as a main drink to children under 5 years old because they do not contain enough calories, though lower-fat milks can be used in cooking from 1 year old.

Volume matters more than most people expect, and this is where iron deficiency actually shows up in toddlers. The AAP's advice for 12 to 24 months is to limit intake of milk to 2 cups, about 16 fluid ounces or roughly 480 ml, per day or less. Health Canada sets its ceiling higher at 750 ml, about 26 UK fluid ounces or one and a third pints, and adds that at volumes in excess of 750 ml, cow milk can displace other foods that are sources of nutrients not found in milk, with fibre intake and constipation as further consequences. Health Canada's positive recommendation for young children is 500 ml a day, about 17 fluid ounces, of homogenised 3.25% milk fat cow milk.

Health Canada also notes that goat milk poses the same risks for the development of iron deficiency as cow milk when consumed in excessive amounts.

Other milks

The NHS treats goats' and sheep's milk exactly like cow's milk: not suitable as a main drink for babies under 1 year old, but fine from 1 year. Goats' milk formula is produced to the same nutritional standards as cows' milk formula, but the NHS warns it is not suitable for babies with cows' milk protein allergy, because the proteins are very similar.

Unsweetened calcium-fortified plant milks can be given from the age of 1 as part of a healthy balanced diet. Rice drinks are the exception and are excluded until age five because of arsenic. Unpasteurised milk should not be given to young children at all, because of the higher risk of food poisoning.

Where guidance genuinely differs

Canada starts three months earlier than everyone else. Health Canada's recommendation is that if parents and caregivers are introducing cow milk, advise them to delay until nine to 12 months of age, with intake limited to no more than 750 ml per day. Its reasoning is conditional rather than calendar-based: once an older infant is regularly eating a wide variety of iron-rich foods such as meat, meat alternatives and iron-fortified cereals, the introduction of cow milk is not associated with iron deficiency.

The UK and the US hold the line at 12 months. The NHS states plainly that cows' milk should not be given as a main drink to babies until they're 12 months old. The CDC lists cow's milk before 12 months among foods to avoid. Neither offers a nine-month route, even for a baby eating well.

The daily ceiling afterwards differs by about 250 ml. The AAP says 2 cups, roughly 480 ml, a day or less for one to two year olds. Health Canada permits up to 750 ml and recommends around 500 ml. The NHS publishes no millilitre figure for toddler milk at all, which is a gap rather than a disagreement.

The reading that satisfies every authority: nothing but breast milk or first infant formula as the main drink until the first birthday, cow's milk freely in cooking from around six months, and once the milk cup starts, keep it under about 500 ml a day so it does not crowd out iron-rich food.