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There are a number of reviews that aim to assess evidence in relation to the determinants associated with fruit and vegetable consumption in children (Blanchette and Brug, 2005, Cook et al., 2014, Di Noia and Byrd-Bredbenner, 2014, Ong et al., 2016, Rasmussen et al., 2006). However much of this evidence relates to children of school age or higher, with reviews and studies, particularly those of a longitudinal design, in pre-school children being sparse (Hodder et al., 2018). The majority of evidence reported for younger children is cross-sectional and there have been associations reported for various determinants which include; age, gender, food preference, neophobia and parental factors such as maternal age, SES, ethnicity, feeding practices, provision and modelling of fruit

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and vegetable behaviours (Mittmann, 2014, Blissett, 2011, Pearson et al., 2009, Rasmussen et al., 2006, Campbell and Crawford, 2001). Determinants are discussed in greater detail below.

1.8.1 Age

Data relating to fruit and vegetable consumption and age is relatively inconclusive. However there is evidence to suggest that intake generally decreases with age and a number of studies conclude that the decline in consumption occurs before the age of 7 years (Albani et al., 2018, Kim et al., 2014). A review which included 98 studies, of which 22 reported associations with age, found that ten of these studies found an inverse association, whilst nine papers showed that there was no association evident (Rasmussen et al., 2006). Similar results have been shown in a cohort study carried out in 2009 which concluded that more then half the children aged 2-5 years (from a cohort of over 6,000) were meeting recommended daily guidelines for fruit in

comparison to only 26% of 6-11 year olds (Lorson et al., 2009). A similar pattern was seen for vegetable consumption with 22% of 2-5 year olds meeting

guidelines, yet for 6-11 year olds it was approximately 16% (Lorson et al., 2009).

In contrast, another review found that age was not associated with fruit and vegetable consumption in 11 of the 15 included studies (Di Noia and Byrd-Bredbenner, 2014). However, these results must be interpreted with caution as much of this evidence pertains to studies that were carried out in the USA where free fruit and vegetable schemes exist for young children. These schemes generally stop when the child reaches school age (approximately 6 years) and this could potentially be considered a potential confounding factor associated with a decline in consumption (Kim et al., 2014). In the review which found no association with age (Di Noia and Byrd-Bredbenner, 2014), it was also stated that results were aggregated for those studies examining one or more determinant, for example fruit, fruit juice and vegetables. Combining results in this way may lead to inaccurate reporting of results and aggregation error is believed to occur frequently in health related research (Kaplan et al., 2014).

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There were a range of methodological flaws within studies which were often noted as limitations and could also potentially effect results, leading to multiple incidences of study bias including the use of; small sample sizes,

non-representative samples, cross sectional designs, lack of theoretical

underpinning, reliance on self-report measures and unreliable measurement tools (Di Noia and Byrd-Bredbenner, 2014, Kim et al., 2014, Rasmussen et al., 2006).

1.8.2 Gender

Similar to age, evidence in relation to gender is questionable. The review by Rasmussen et al. (2006) reviewed 49 studies asessing gender differences in fruit and vegetable consumption (Rasmussen et al., 2006). Twenty-seven of these studies concluded that girls were more likely to consume a higher or more frequent intake of fruit and/or vegetables than boys. Only four studies observed a higher intake in boys and 18 did not see any gender difference. However, differences apperared to differ depending upon region. Only one third of included studies carried out in the USA found a difference in intake among boys and girls, whereas 14 of the 17 (over 80%) European studies identified a gender difference (Rasmussen et al., 2006). Therefore country of origin may be responsible or attributed to any associated changes rather than gender. Conversely, in another review, no association between gender and consumption was found in 11 out of 13 studies which were all carried out in the USA (Di Noia and Byrd-Bredbenner, 2014). However, there have been a number of European studies that have reported a higher consumption in girls than boys, yet this has only been observed in children of school age and higher (Bere et al., 2008, Currie et al., 2008).

1.8.3 Food preference and neophobia

There is evidence that food preference is initiated before a child is born. In utero transmission of flavours from mother to child are thought to play a role in food preference as does the introduction of milk and eventually, solid food (Mennella and Bobowski, 2016). It has been established that humans have an innate predisposition for sweet and salty tastes and an aversion to bitter or sour tastes (Davison and Birch, 2001, Wardle and Cooke, 2008); however, the extent to which individuals accept these tastes is thought to differ depending upon genetic variability (Drewnowski, 2001). Food preference develops from a combination of

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both genetic and learned behaviour and has been shown to track through into adolescence and adulthood (Finnane et al., 2017). The review by Rasmussen et al. (2006), included 11 papers which assessed the influence of food preference on fruit and vegetable consumption and a positive association was found in all of these studies (Rasmussen et al., 2006). Given that likes and dislikes are somewhat modifiable, repeated exposure has the potential to reinforce acceptance and subsequently preference for specific foods (Appleton et al., 2018, Mela, 2006, Mennella and Bobowski, 2016, Cooke et al., 2006). A recent review supports the idea of repeated exposure in increasing child fruit and vegetable consumption and advocates that both caregivers and practitioners should expose young children to a variety of healthy foods from a very early age, including the prenatal period, early milk-feeding and the introduction to complementary foods, which have all been shown to have the potential to assist with acceptance (Anzman-Frasca et al., 2018).

The development of neophobic tendencies have been well documented as having an influence on fruit and vegetable consumption and are decsribed as an avoidance or reluctance to taste unfamiliar foods (Birch and Fisher, 1998, Cooke et al., 2006, Kral, 2018). Neophobia is believed to develop around the ages of 20-24 months which coincides with cognitive growth when children attempt to categorise foods and make decisions on whether theyA are safe to consume (Harris, 2008). This developmental stage leads children to choose foods with which they are familiar (Wardle et al., 2003). This initial rejection of an unfamiliar food causes parents distress and can result in them limiting, or even omitting, the rejected food from the diet altogether. However, studies have shown that a child needs to be exposed to a food around 10 – 15 times before it is accepted (Birch et al., 1987, Birch et al., 1990). Neophobia is usually associated with a lower consumption of fruit and vegetables (Cooke et al., 2006) and an increase in exposure to high fat, high sugar foods (Liem and Mennella, 2002). An increase in sugary foods then leads to an increase in preference for them (Liem and de Graaf, 2004). Studies have also shown that if a child is able to choose freely from a large variety of food, they will choose those that are of little nutritional value (energy dense foods), if they have previously been exposed to these as opposed to healthier alternatives (Birch, 1992, Klesges et al., 1991, Marty et al., 2018).

Encouraging parents and caregivers to increase exposure to fruit and vegetables

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has been shown to improve consumption and reduce neophobia (Howard et al., 2012, Wardle et al., 2003).

1.8.4 Parental fruit and vegetable consumption

Positive associations between parental and child consumption are apparent in the literature (Pearson et al., 2009, Wyse et al., 2011). A review found that eight out of nine studies observed a positive association and that this association increased further in those homes where fruit and vegetables were freely available (Rasmussen et al., 2006). However, in another review, only maternal, and not paternal, consumption was consistently associated with child consumption (Di Noia and Byrd-Bredbenner, 2014). The majority of evidence is stated as being drawn is from studies in older children and adolescents and it’s transferibility to younger populations is therefore questionable (Blanchette and Brug, 2005, Wyse et al., 2011). Moreover, it becomes difficult to make true assumptions in relation to these findings as the variation in data collection tools used and self-report methods may have introduced bias. Parental food preference has also been shown to impact upon decisions made on whether or not to provide fruit and vegetables to their children (Cooke et al., 2003a, Mittmann, 2014). The Framingham study which was carried out in 1992 revealed that parental eating habits and preferences had a direct influence on their pre-school child’s diet (Oliveria et al., 1992).

1.8.5 Provision (availability and accessibility) 1.8.5.1 Parental provision

Having fruit and vegetables on offer and freely available in the home has been shown to be associated with an increase in child consumption in a number of reviews (Di Noia and Byrd-Bredbenner, 2014, Krølner et al., 2011, Rasmussen et al., 2006). In a large cross sectional survey including over 1,300 children results showed that children whose parents offered them fruit and vegetables daily and who took fruit and vegetables to school ate significantly more than those children who did not (Mittmann, 2014). This was mirrored in another survey of 396 children aged 3-5 years. Multiple regression analysis found positive associations between child fruit and vegetable consumption, availability (p=0.006) and accessibility (p<0.012) and also the number of occasions per day that parents provided their child with fruits and vegetables (p=0.006) (Wyse et al.,

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2011). Rasmussen et al (2006) identified three studies that found positive associations between availability and consumption; however, one of these papers identified an association for girls only (Rasmussen et al., 2006). An earlier review in children over 6 years of age observed similar positive correlations after assessing evidence in four studies (Blanchette and Brug, 2005). There is also evidence to show that availability and accessibility interact with a number of other determinants of consumption such as exposure. For example, when fruits and vegetables are not on offer or accessible then exposure is compromised, which in turn can lead to a low preference for those fruits and vegetables that are offered less frequently (Fisher and Birch, 1999, van der Horst et al., 2007). In addition to this, setting has been shown to have an impact on consumption. For example the review by Rasmussen et al (2006) did not find any association with consumption and fruits and vegetables offered within the school setting, only within the home environment (Rasmussen et al., 2006).

1.8.5.2 Provision from others

Young children are cared for by a number of people who are not their parents including grandparents, friends and other family members. These carers can all potentially have impact upon the amount of fruits and vegetables that children consume yet there is very little evidence in this area. However, recent qualitative evidence has explored parental views on the impact which others have on their child’s consumption, with results indicating that grandparents have a tendency to provide unhealthy foods as opposed to fruits and vegetables (Nepper and Chai, 2017).

1.8.6 Modelling

1.8.6.1 Parental Modelling

There is a large body of evidence which suggests that there is a strong association between parental role modelling and child fruit and vegetable consumption (Anzman-Frasca et al., 2018, Di Noia and Byrd-Bredbenner, 2014, Hodder et al., 2018, Mittmann, 2014). Young children who observe their parents consuming healthy foods such as fruits and vegetables are more likely to mimic and adopt such behaviours themselves (De Bourdeaudhuij et al., 2008, Reinaerts et al., 2007). However, in some studies evidence is stronger for mothers and more significant for girls rather than boys (Kristjansdottir et al., 2006). Reasoning

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for this may be that there is limited research available to assess modelling impact in fathers at this early age. It is somewhat likely that mothers spend more time with their children in infancy than fathers as it is predominantly the mother who takes leave from work to raise children. Hence mother/child populations and their behaviours have been easier to study because they are more accessible than fathers. In addition to this it is suggested that the impact reported in girls is higher than boys as mothers potentially spend more time with daughters than they do with sons (Baker, 2016). Yet, there are some studies which failed to find any association between parental role modelling and child fruit and vegetable consumption (Matheson et al., 2006) and others which suggest that various measurement methods amongst studies such as parental and child reporting could be responsible for outcomes rather than direct effect (Bauer et al., 2011, Palfreyman et al., 2014). Despite this, parental modelling remains an important determinant which has proven to be targetted with success in intervention delivery to increase fruit and vegetable consumption in this age group (Holley et al., 2017).

1.8.6.2 Peer Modelling

There is limited evidence in this age group to support peer modelling of fruit and vegetable behaviour. However, experimental studies show that children are much more likely to eat fruits and/or vegetables if they observe their peers doing the same (Birch et al., 1990, Cooke et al., 2006). Although peers can be used as positive role models, there are also reports of strong associations for negative behaviour. If a child observes another rejecting fruits and vegetables then this has been shown to overide any positive modelling that may have previously taken place (Greenhalgh et al., 2009).

1.8.7 Feeding practices and styles

Parental feeding practices are behaviours which parents adopt that may be used to control how much, what, when and where a child eats (Ventura and Birch, 2008). A recent Cochrane systematic review found evidence that interventions that focus on improving feeding practices are successful in increasing fruit and vegetable consumption in children under the age of 5 years (Hodder et al., 2018).

However, this evidence was deemed to be of low quality and that effect size was small with long term follow-up needed. Parents are often under the assumption

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that if they restrict certain foods (for example, those high in sugar and fat) and do not allow their child access to them then this will prevent consumption and increase their preference for more healthy alternatives. However, evidence suggests that children are much more likely to desire a particular food if they are forbidden to eat it and they will be less likely to regulate intake of unhealthy alternatives in later life (Benton, 2004). Feeding styles which appear to have a positive response on encouraging consumption of fruits and vegetables are those which are described as authoritative. An authoritative feeding style is characterised by one which exhibits clear rules, yet provides explanation and warmth to the child and has shown to provide significant results in terms of increasing fruit and vegetable consumption in comparison to a more forceful/authoritarian style (Hughes et al., 2016, Rodgers et al., 2013). Cross-sectional evidence supports these findings and also advocates the use of structured mealtime practices such as eating as a family, allowing a child to serve themselves fruits and vegetables at mealtimes and eating at consistent times (Finnane et al., 2017, Wyse et al., 2011).

Encouraging children to eat fruits and vegetables can prove difficult and often parents report using food as a reward to persuade their child to eat. However, at times the foods that they reward the child with are high in sugar and fat. This includes foods which are deemed to be a ‘treat’ such as ice cream and sweets which are sometimes held back by parents as a means of punishment if children do not eat the fruit and vegetables they are provided with. There is evidence that this type of parental behaviour is confusing to a young child and more often than not, undermines the establishment of healthy eating behaviours (Hendrie et al., 2017, Lively et al., 2017, O'Connell et al., 2012).

1.9 Tackling low fruit and vegetable consumption through behaviour