Issue 134 infant weaning

PAEDIATRIC

INFANT WEANING AND DEVELOPMENT OF TASTE PREFERENCES Jacqui Lowdon Paediatric Dietitian, Leeds Children’s Hospital Jacqui is a Clinical Specialist in Paediatric Cystic Fibrosis at Leeds Children's Hospital. She previously specialised in gastroenterology and cystic fibrosis.

Although her career to date has focused on the acute sector, Jacqui has a great interest in paediatric public health.

REFERENCES For full article references please CLICK HERE . . .

Taste is one of our fundamental senses, essential for us to be able to ingest nutritious food and to be able to detect and avoid potentially poisonous ones.

During the early years, the foundations for healthy growth and development are laid down. Complementary feeding, that is when foods other than milk are first introduced (commonly referred to as weaning), is a critical feature of this time, both in terms of nutrition and eating behaviours.1 As we tend to eat food that we like, the most important aspect to acquire during these early years should be to develop a preference for certain foods that may contribute towards good health. Strong correlations have been found between food preferences during early childhood and preferences in later childhood,2 adolescence3 and young adulthood.4 This implicates early experience as a foundation for food preference development across the course of our life.

THE BASIC TASTES

During the first year of life, we are receptive to all five basic tastes, with varying extents, but willing to try most new foods.5 However, it is well documented that from birth, humans prefer sweet, salty and umami tastes over bitter or sour.6,7 Umami is a strong taste, often referred to as ‘the fifth taste’, that is not sweet, sour, salty, or bitter. It is the intensely savoury taste imparted by glutamates that occur naturally in many foods such as meat, fish and vegetables. More recently, fatty acids and calcium have emerged as potential tastants that can be sensed by taste bud cells.8-12 Humans can also quickly learn to like foods that are energy dense.13 For example, children may be more sensitive to certain tastes (for example, sweet) during periods of maximal growth,14,15 which has been hypothesised to help choose foods that will support rapid development.14

Exposure to a variety of foods during the complementary feeding period helps with the acceptance of new foods in the first year, whereas in the second year, exposure may have a more limited impact.16 VARIETY PROMOTES ACCEPTANCE

Reactions towards new foods can differ according to food groups.17 In one study, mothers were asked to report their infant’s reactions to new foods at the beginning of complementary feeding.

They found that fruits and vegetables, which are often the first foods offered to infants, are less accepted than other food groups.18 However, a more recent investigation demonstrated that early exposure to a rotation of vegetable flavours first added to milk and then to cereals increased the intake and liking of these vegetables. Infants assigned to the intervention ate more of the target vegetables in the laboratory and at home than those assigned to the control group.19 This reinforces the findings that variety can also promote infants’ acceptance of new foods.20 COMMENCEMENT OF COMPLEMENTARY FEEDING AND ITS ROLE IN THE DEVELOPMENT OF TASTE PREFERENCES

Timing of exposure to new foods has also been demonstrated to influence infants’ food acceptance.

Complementary feeding is recommended to start at around six months of age,21 although some suggest that it is www.NHDmag.com May 2018 - Issue 134

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PAEDIATRIC

Food neophobia is defined as ‘an unwillingness to eat novel foods’.

It is thought to be an adaptive behaviour, to ensure that children eat foods that are familiar and safe during a period when they are being exposed to a large number of new foods. appropriate to start between four and six months of age, when the infant can demonstrate signs that they are ready for solid food, e.g. sitting up unaided, co-ordinating hand and mouth movements.22-24 For more on complementary feeding, please turn to Maeve Hanan’s article on pages 29-31.

Potential issues with introducing solid foods after six months, including evidence suggesting that it might increase the risk of developing certain allergies25 and the development of low iron levels,26 is that part of the ‘window of opportunity’ for obtaining a broad range of food preferences may be missed.27 Using a parent-rated scale of four attributes of the infant’s reaction to the food , it has been shown that the earlier the introduction to vegetables during complementary feeding, the greater the acceptance of novel vegetables.28 It is more difficult to increase children’s acceptance of fruits and vegetables after toddlerhood.29,30 It may be acceptable then, in terms of food acceptance, that the four- to sixmonth period can be an appropriate time to introduce ‘tastes’ of solid food. However, it does have to come with strict criteria: a focus on ‘food familiarisation’ rather than nutrition per se, ‘tiny 34

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tastes’ of foods that are appropriate in type and texture suitable for the developmental age of the infant and in amounts that do not compromise breastfeeding.

EARLY YEARS’ FOOD PREFERENCES AFFECTING ACROSS-THE-LIFE-COURSE

It has been well documented, albeit mostly observational, that food preferences developed during the early years can ‘track’ into later childhood. Most of the evidence is derived from prospective cohort studies, including data from large cohorts such as the Avon Longitudinal Study of Parents and Children (ALSPAC)31,32 and the Infant Feeding Practices Study II,33 as well as smaller cohorts.34-36 There is also evidence indicating that early familiarisation can be associated with later acceptance. For example, protein hydrolysate formulas, which have a particularly bitter taste, are associated with later acceptance for bitter foods, including vegetables and fruit.37 Experimental data has also demonstrated a link between introducing a variety of vegetables at the onset of complementary feeding38 with acceptance of these foods in early life and over the longer term, up to six years of age.39

Salt taste is unique, in that a preference for salt taste develops after four months of age and continues into childhood.40 The two strongest predictors of young children’s food preferences are familiarity and sweetness.41 FOOD NEOPHOBIA

Food neophobia is defined as ‘an unwillingness to eat novel foods’. It is thought to be an adaptive behaviour, to ensure that children eat foods that are familiar and safe during a period when they are being exposed to a large number of new foods.42,45

Young children, especially aged two to five years old, exhibit heightened levels of food neophobia during this time of rapid dietary change. Rozin et al43,44 have demonstrated that distaste, defined as the ‘dislike of the sensory characteristics of a food’, appears to be the strongest driver of neophobia in young children, followed by potential harm or sickness. As mentioned above, the two strongest predictors of young children’s food preferences are familiarity and sweetness. These innate tendencies, along with a predisposition to learn from early experiences through associative learning46,47 and repeated exposure,48-50 allow the child to learn to accept and prefer foods that are available within their environment.

Experimental studies have demonstrated that neophobic tendencies can be reduced and preferences increased on exposing infants and young children to novel foods repeatedly,48,49,51,52 suggesting that young children need to be exposed to a novel food six to 15 times before an increase in intake and preferences can be seen.48,49,51,52 Furthermore, exposure needs to

include tasting the food, as merely seeing49 or learning52 about a novel food on repeated occasions does not promote their preferences for that food. A recent intervention study found that repeatedly exposing children to a novel food with positive social environment factors was especially effective in increasing their willingness to try and have preference for the novel food, as well as other novel foods not targeted by the intervention.53 These findings suggest the importance of the act of repeatedly exposing children to new foods and the context within which this occurs.

EUROPEAN APPROACHES TO COMPLEMENTARY FEEDING

This idea of early ‘food familiarisation’ aligns with French, Swedish and Dutch approaches to early complementary feeding, providing the infants with plenty of opportunity to experience different foods, with an emphasis on ‘tiny tastes’ and ‘educating the palate’.54-56 CONCLUSION

It is of paramount importance that, during the early years, we can acquire the preference for foods that promote a varied and healthy diet. The complementary feeding period is a ‘window of opportunity’, familiarising infants with a wide variety of foods. At this stage, their openness to try new foods is at its peak, making early intervention the most promising way of improving children’s diets. Familiar foods are likely to become preferred foods and it has been demonstrated that these acquired preferences can track into later childhood and into adulthood, thus affecting food choices in later life.

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