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RESEARCH PRODUCT

Evolution of olfactory responses in the first two years of life : effect of early exposures and link with food behaviour

subject

description

The role of taste on food preferences has already been investigated, however, little is known about the role of olfaction. The main objectives of this work were to assess infants’ olfactory responses, their dynamic during the first two years of life, and also their links with early food exposures, food liking and infants’ food neophobia. This work was conducted within a longitudinal study named OPALINE (Observatory of food preferences in infants and children). Olfactory responses were assessed, in 8-, 12- and 22-month-old infants, towards pleasant odours, such as vanilla, and unpleasant odours, such as fish. The results reveal that, from 8 months, infants can discriminate pleasant and unpleasant odours. However, only avoidance responses are observed towards some unpleasant odours; no attraction responses are highlighted during the first two years of life. Our results also suggest a plasticity of olfactory responses. Only responses towards some unpleasant odours are stable between two consecutive ages, suggesting that negative hedonic responses towards food odours would appear earlier than positive ones. Concerning the effects of early food exposure, it appears that the more an infant has been exposed, in utero or during breastfeeding, to some unpleasant food odours, the least s/he exhibits avoidance responses towards these food odours at 8 months, but not beyond. When complementary feeding has begun (8 months), olfaction does not seem to impact new food liking. However, at 12 months, olfaction can play a role of modulator in liking of the foods with strong flavour. This role is not observed anymore at 22 months. Our results also highlight that differential olfactory responses, and not gustatory ones, are linked to infants’ food neophobia suggesting that only odours contribute to the suspicion towards unfamiliar foods during the second year of life. This work stresses that early sensory exposures influence responses towards unpleasant odours at the onset of complementary feeding, which is a favourable period to food acceptance. Then, olfaction can play a role in food liking by acting as an alarm system protecting the infants against potentially harmful food