Flavour–nutrient learning in humans: An elusive phenomenon?

Abstract

One widely cited model of how humans acquire liking for different foods is flavour-nutrient learning, where associations between the orosensory properties of the ingested food or drink (the flavour CS) and positive consequences of nutrient ingestion (the UCS) leads to acquired liking for the flavour (flavour-nutrient hedonic learning: FNL-H). Likewise, an association between the CS and the post-ingestive effects of ingested nutrients has been suggested to lead to learning about how satiating a particular food is (flavour-nutrient satiety learning: FNSH).However, whereas there is evidence for both FNL-H and FNL-S in experimental studies with non-human animals, evidence in humans is less convincing, with many failures to find the predicted changes in liking, preference or intake following repeated flavour-nutrient pairings.The present short review considers how subtle differences in experimental design might underlie this inconsistency, and identifies key design features which appear to increase the likelihood of success in human flavour-nutrient learning studies. Key factors include CS novelty, the level of nutrients ingested during training, the appetitive state of the consumer and individual consumer characteristics. A further complication is competition between FNL-H and FNL-S, and with other associations such as flavour-flavour learning. From this it is possible to make important inferences about the nature of human flavour-nutrient learning which firstly suggest that it has important similarities to that seen in other species, but secondly that the laboratory investigations of both FNL-H and FNL-S in humans can be compromised by subtle but important variations in experimental design. Running Head:Human flavour nutrient learning Key terms:Flavour, conditioning, learning, nutrients 3 4 Humans and other animals, in particular omnivores, have a remarkable ability to identify which of the almost endless supply of potential foods in are environment are nutritious and worth consuming and which are poisonous and so should be avoided. However, as described in the Omnivore's Paradox [1], humans are not born with a pre-set menu of preferred foods, but instead have to learn what is safe and nutritious by balancing neophobia and inquisitivity.Arguably the only component of our food preferences that appears to reflect an innate like is the case of a general preference for sweet tastes in humans and other species [2]. But evidence that not all humans do like sweet tastes [3] implies that even our initial liking for sweet tastes can be modified by experience, in line with reversal of an aversion to bitter tastes when the bitterness predicts a benefit, as is the case with caffeinated products [4].So how then do humans acquire liking for nutrient-rich foods? Historically, many different models for how humans acquire liking for novel flavours have been proposed [5,6] but in this brief review only one model, flavour-nutrient hedonic learning (FNL-H), will be considered as many have implied that this is likely to be the ...

The role of dopamine in the pursuit of nutritional value

“…Changes in appetite, satiety, and learning evoked by post-ingestive influences can be observed in humans, although these effects are often complex [95]. How might the postingestive effects of our diet contribute to the onset of obesity and is dopamine involved in this interaction?…”

In search of flavour-nutrient learning. A study of Samburu pastoralists in North-Central Kenya

“…Nevertheless, none of our outcomes provided evidence for F-NL, suggesting that 569 learning is not suppressed by exposure to a Western diet. Instead, our findings add to a 570 broader and emerging consensus that this form of associative conditioning is difficult to 571 demonstrate in humans (Yeomans, 2012). This leads to one of two possibilities.…”

Food Marketing and its Impact on Adolescents' Food Choices

“…Additionally, the ingestion of a food may also improve the acceptance of its sensory properties; this is described as flavor-nutrient learning (Yeomans, 2012). In infants and young children, repeated exposures are as effective as associating a new vegetable with a liked flavor (e.g., sweetness) to increase its intake, whereas associating it with a higher energy content (e.g., addition of oil) did not increase its intake (Caton et Another factor that contributes highly to the acceptance of a new food and expands a child's consideration and choice sets at early stages of life is the extent to which the child has been exposed to a variety of foods.…”