N° 17 | January 2017

Acceptance of fruit and vegetables during childhood: the impact of genetics, early experiences and the environment

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Research is in progress regarding low consumption of fruits and vegetables (FVs) by very young children. Two studies in the United States show that 1/3 of children aged 6-9 months and 1/5 of children aged 9-12 months never eat FVs. According to American recommendations, FVs should account for an increasing share of children’s diet from the age of 2 years. For children aged under 2 years, this is more problematic, as babies eat only the foods they like.

Genetically, so-called fussy children consume low levels of FVs

FVs are among the foods most commonly rejected by so-called fussy children. Fussy behaviour reaches its peak at around 20 months of age, and disappears between 5 and 8 years of age. Food neophobia, which is characterised by the refusal of unknown foods, is also linked to low acceptance of FVs. It has a strong genetic base (72-78%) in early childhood. The hypothesis that neophobia and fussy behaviour have the same genetic origin, and that this interacts with children’s taste for FVs, has been made1. This hypothesis was tested using data from the British twin cohort Gemini (2660 children under 3 years old). There was a significant negative correlation between ‘being a fussy eater’ and taste for FVs, particularly for monozygotic twins. Shared genes contributed to the observed phenotypic correlations; thus, if one twin had a high rating for ‘fussy eating’, the other twin tended to have a low rating for FVs. These results show that being fussy and taste for FVs are common hereditary traits among young children.

Infants do not naturally accept fruit and vegetables

The B-24 project (US Department of Health and Human Services) evaluates the scientific evidence regarding children aged under 2 years2. One finding is that babies are naturally able to detect foods that are energy- and nutrient-dense, and they avoid potentially toxic items that have a bitter taste, such as some FVs. A preference for sweet and salty flavours and an aversion towards bitter tastes dominates during childhood and adolescence. The perception of bitterness is extremely variable from one individual to another, and is linked to genetic differences in infants.

How can acceptance be improved? Children may not accept a food item due to an innate dislike, or because they were not introduced to that food during a ‘sensitive’ period for becoming familiar with it. What role might breastfeeding and weaning foods play, given that they are infants’ early experiences of taste and textures3,4.

  • Give pregnant and breastfeeding women FVs. The senses underlying the perception of flavour are malleable and can be modified by the initial experience. It is now known that volatile food substances are transferred to amniotic fluid and to breast milk. A wide range of the flavours ingested by the mother (e.g. fruits, vegetables, alcohol, spices) are transferred to her amniotic fluid and/or milk. In a randomised clinical trial, pregnant women who intended to breastfeed were given carrot juice to drink. Once their breastfed infants had moved on to solid foods, the acceptance of plain cereals compared to carrotflavoured cereals was tested. Infants who had experienced the flavour of carrots in their mother’s amniotic fluid or breast milk responded more favourably. Not only breastfeeding provide an initial advantage to babies in their acceptance of FVs when these foods are part of their mother’s diet, but the continuity in flavour helps with the transition to solid food. Breastfeeding thus has a certain advantage over infant formula.
  • Expose children to FVs. As with children, infants eat more FVs to which they have been exposed on several occasions. Infants who were repeatedly exposed to different vegetables not only ate more of the vegetables to which they had been exposed, but they also ate more new vegetables than infants exposed to a single vegetable.
  • Mask the taste. The two preferred tastes (sweet and salty) can mask bitter tastes from children. A clinical study on schoolage children demonstrated that adding diluted solutions of sweetener to vegetables reduced the children’s perception of bitterness and increased their taste for vegetables. For very young children, during repeated exposure to green beans or to peaches, only those who consumed peaches after the green beans seemed to like the taste of green beans after an 8-day exposure period: the sweet taste of the peaches masked the bitterness of the green beans, improving their palatability and taste.
  • Diversify early. Some data appears to support the idea of sensitive periods for the introduction of complementary foods.

At all stages, the more varied tastes and textures an infant experiences, the more likely he or she is to be willing to try new foods. This means that complementary foods should be given, altering the tastes frequently, and that the early introduction of complementary textured food (other than smooth purées) confers an advantage in terms of the acceptance of other more complex textures, such as those found in the majority of FVs3.

Conclusion
Beginning very early on in life, sensory experiences can shape and alter food preferences. Children’s rejection of some FVs, particularly bitter vegetables, can have a genetic origin, but can also be caused by environmental factors such as the mother’s dietary habits. Breastfeeding and the early introduction of complementary foods are predictors of later acceptance of FVs.

1. Fildes A., Van Jaarsveld C., Cooke L., Wardle J., and Llewellyn C.H. (2016):
Common genetic architecture underlying young children’s food fussiness and
liking for vegetables and fruit. Am J Clin Nutr 2016; 103: 1099–104.
2. Mennella J.A., Reiter A.R. and Daniels L.M. (2016): Vegetable and Fruit
Acceptance during Infancy: Impact of Ontogeny, Genetics, and Early
Experiences. American Society for Nutrition. Adv Nutr 2016; 7 (Suppl):
211S–9S; doi:10.3945/an.115.008649.
3. Harris G. & Coulthard H. (2016): Early Eating Behaviours and Food
Acceptance Revisited: Breastfeeding and Introduction of Complementary Foods
as Predictive of Food Acceptance. Curr Obes Rep (2016) 5:113–120 DOI
10.1007/s13679-016-0202-2.
4. Rigal N. et Nicklaus S. (2015): L’alimentation à découvert, Partie I – Le
mangeur au centre de l’alimentation, chapitre 6 : L’alimentation de l’enfant et
de l’adolescent, CNRS Editions, 328 p., A découvert, 978-2-271-08300-5

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