Do not confuse lactose intolerance with cow’s milk allergy

I have written about this topic before, but constantly get reminded through social media posts, how much misconception about still exists and how people who are not specialist in this field allow themselves an opinion that can be so dangerous. I saw a Instagram post by a vegan advocate, talking about lactose intolerance being a primary motivation to why breastfeeding should be motivated and cow’s milk formula not be used but rather a plant-based alternative. In addition, this post makes the statement that many babies are born with a lactose intolerance. Whilst we should motivate ongoing breastfeeding for many many reasons, this is not one of them and again highlights the confusion of distinguishing between lactose intolerance and cow’s milk allergy.

Congenital lactase deficiency (i.e. being born with a lactose intolerance) is an extremely rare genetic condition and in my career as paediatric dietitian working in allergy/intolerances for 23 years, I have only ever seen 1 baby with this. The primary source of energy in breastmilk is lactose (also in standard formula), so if a baby has a congenital lactase deficiency they can not tolerate breastmilk or standard formula due to the lactose content. Conversely primary lactose intolerance is common, but only develops in children from around 3 years of age and affects certain populations more (i.e. Africans, Asians). So the latter develops usually when a baby is off breastmilk or formula. Typically children with primary lactose intolerance can tolerate cheese and some may also tolerate yoghurt, but can not tolerate milk as a drink. Secondary lactose intolerance is more common in babies as a result of chronic diarrhoea (this can occur as a result of a bug or a chronic disease affecting the gastrointestinal tract) where the mucosa is damaged, which leads to an intolerance to lactose that is totally reversible on treatment.

A lactose intolerance is non-immune mediated, whereas a cow’s milk allergy is an immune mediated disorder and is related to an allergic reaction to the protein (not lactose, which is a carbohydrate) in cow’s milk. Cow’s milk protein consumed by the mother can transfer through breastmilk and can ins some cases lead to a reaction through breast milk. This has nothing to do with the lactose content of breastmilk (which can not be changed in mothers milk, even with a vegan diet). For these babies, under the supervision of a dietitian and an allergist/gastroenterologist a maternal elimination diet should be considered and if breastmilk is not available a hypoallergenic formula should be provided. There was a suggestion that there are plenty of suitable plant alternatives available for babies, but that is not necessarily the case and proper advice should be sought as this may differ between countries. For example, no over the counter plant milk (note not formula) is currently suitable (in any country) as a primary drink for any baby < 1 year of age and care should be taken if used > 1 year of age as they are low in protein and lacking many of the essential micronutrients. Soya formula is available, but in the UK about 50% of babies with a delayed cow’s milk allergy will also be allergic to soya. Rice formulas are available in some European countries (but not in the UK), so this is not always an alternative.

Whilst it is really important to think about sustainable choices when feeding the future generation and moving towards an increase in plant-based sources, it is so important that parents get the right advice around infant formulas (allergic or non-allergic) if breast milk is not available. Not all advice provided is correct and can have a negative nutritional impact.