Sir, in response to Dr Yeung and his commentary on BSPD's Infant Feeding position statement, it's true that our advice differs from recommendations issued by WHO and Unicef. However, context is everything.

Our position statement examines the evidence for all aspects of infant feeding to give a child the best start to their oral health. It was produced for those in the UK who advise families on diet, well-being and health, directed principally at health visitors, district nurses, dental teams and doctors.

It's not unusual for guidance to vary according to the audience and this is the case with infant feeding. WHO advice, as it stands, takes into consideration the needs of populations in the Third World, where it's especially important for long-term breastfeeding to be promoted. Clean water is not always readily accessible and it's preferable for babies to have breast milk rather than infant formula which could potentially be mixed with contaminated water.

In the UK, we have a crisis in children's oral health and we need to reduce the number of hospital admissions for multiple extractions. While the majority of children are suffering from early childhood caries (ECC) due to over-exposure to sugar and under-exposure to fluoride toothpaste, a number of these children are undergoing extractions due to a diet which combines long-term on-demand breastfeeding and food and drink containing free sugars.

As paediatric dentists, we have known anecdotally for some time that long-term, on-demand breast-feeding can be a risk factor for early childhood caries. In the last few years, the evidence base has been building. First Tham and colleagues1 identified in 2015 that breastfeeding a baby after their first birthday presents a greater risk of dental caries, especially if the feeds are frequent or nocturnal.

Their paper called for further research because their findings could be associated with unmeasured co-founders including dietary sugars and oral hygiene practices. Two more recent articles, one by Peres et al.2 and the other by Cui et al.,3 delivered further evidence.

They concluded that breastfeeding beyond 12 or 24 months is associated with increased risk of caries. Both control for potential confounders (although they did not assess 'nocturnal' or 'on-demand' breastfeeding).

The latest guidance on the subject comes from the Scientific Advisory Committee on Nutrition (SACN) which states in its report4 Feeding in the first year of life that breastfeeding during the first year of life has oral health benefits and is associated with a decreased risk of dental caries.

However, the report also states that there is limited observational evidence which suggests that once the primary teeth erupt, factors such as breastfeeding ad libitum, nocturnal feeding and sleeping with the breast in the mouth may be associated with increased risk of dental caries.

Whilst we echo calls for more research, we believe enough is now known to highlight to parents the potential risks of nocturnal and on-demand breastfeeding past the age of 12 months and the steps they can take to mitigate those risks. We have communicated this advice to professional groups who work with parents.

Our message to healthcare practitioners is NOT that breastfeeding should stop at the age of one, the message is that parents who wish to continue to breastfeed should do so but be aware of the emerging evidence base so that they are in a position to make an informed decision and ensure that diet and oral hygiene practices are optimised.

Prior to issuing our position statement, we liaised with many representative bodies in healthcare and with the National Childbirth Trust and we ensured that Public Health England was happy with the wording before it went public. To misquote Donald Rumsfeld, the knowns that we now have at our disposal outweigh the known unknowns. We have a duty to our very young patients to advise their parents accordingly.