Food behavior: when choosing what to eat, taste, smell and … maybe something more count
Nutrition is an essential requirement for the survival of every living being; yet, in the course of our evolution, the act of eating has taken on multiple meanings, overcoming the simple function of nourishment for the machine-body.
Advertising message We can cite, for example, the social dimension, which comes into play in the convivial moment of sharing meals in the family newspaper or as a community ritual during the holidays, the symbolic meaning of care according to which cooking for someone is a gesture that expresses affection, closeness, intimacy, or even it can be seen as an “emotional drug”; think, for example, of comfort food, or those foods to which each of us turns to pamper ourselves in moments of despair. Yet food can also be an element of social inequality: according to the FAO (Food and Agricolture Organization of United Nations) annual report 2019, there are in fact about 800 million undernourished people (1 out of 9), including 513, 9 million in Asia and 256.1 million in Africa, with more than 49 million children under five years of age in decay; at the same time, 672 million individuals live an obesity condition (1 out of 8) and there are 338 million overweight children and adolescents in the world.
To date, obesity represents the main cause of preventable death and is considered one of the main critical issues in public health of the 21st century (Barness et al., 2007), “weighing” on national health expenditure in a percentage between 4 and 10 % of the annual total (Allender & Rayner, 2007; Tsai et al., 2010) and fueling a trade in products aimed at weight loss that only in the United States exceeded 72 billion dollars in 2018: keeping the weight in the so-called “Welfare society” seems to be more difficult than ever.
The appetitive behavior towards food is therefore a complex multifactorial process, which involves emotions, psychological, physiological, environmental, but above all sensorial aspects; in particular, taste and smell, or chemical senses, are the means by which we appreciate the organoleptic properties of different foods, contributing to the development of preferences and food idiosyncrasies. However, the studies that have proposed to investigate the relationship between these senses and the development of an overweight condition have proved inconclusive, both as regards adults and children. Some research seems to trace a lower sensitivity to tastes (sweet, salty, sour, bitter, umami) in overweight or obese individuals compared to normal weight individuals (Proserpio et al., 2016; Sartor et al., 2011; for children Feeney et al, 2017; Overberg et al., 2012), others found the reverse (Hardikar et al., 2017; Pasquet et al., 2007), still others found no effect (Thompson et al., 1976; Grinker et al., 1972). Equally controversial are the results of studies that investigated the role of smell. Also in this case some results support the thesis of a lower olfactory acuity in overweight or obese individuals compared to the normal weight counterpart (Fernandez-Aranda et al., 2016; Fernandez-Garcia et al., 2017; Skrandies & Zschieschang, 2015; for children Obrebowski et al, 2000), others who find a greater olfactory sensitivity (Patel et al., 2015; Stafford & Welbeck, 2011), in particular towards the smell of chocolate (Stafford & Whittle, 2015),
However, some researchers have suggested how important it is to distinguish childhood and adolescence in research aimed at the chemical senses, as the profound hormonal changes that occur in this stage of development can significantly influence the perception of taste and odors (Martin et al., 2009; Loper et al., 2015).
Advertising message Herz and colleagues (2020) recently conducted a research involving only teenagers between 12 and 16 years of age and subjecting them to olfactory and gustatory sensitivity tests through the use of special strips created in the laboratory and called “sniffin ‘sticks” and “tasting sticks” (Burghart GmbH, Wedel, Germany), containing chemical agents in different concentrations which are interpreted as the main tastes (sweet, salty, bitter, sour) or flavors of common use (eg cinnamon, lemon, mint ) if placed on the tongue and as hints of more or less pronounced odors, if smelled. The goal was to test not only the ability to discriminate between different flavors, but also the sensitivity threshold, which is why PROP (6-n-propylthiouracil) was used,
Adolescents with a higher BMI, and therefore more overweight, reported on average a lower olfactory threshold, therefore being more sensitive; this was especially true of teenagers at an earlier age than those who wanted to develop. The authors underline at this point how in previous research that had obtained contrary results, an earlier version of the sniffin ‘sticks had been used: this information becomes particularly relevant since the agent used saw the involvement of the trigeminal system, which collects the nociceptive components, of heat and tactiles linked to odors, thus potentially reflecting a lower trigeminal susceptibility and not a lower olfactory sensitivity. Supporting this hypothesis is the study by Stafford and Whittle (2015) on the greater sensitivity to the smell of chocolate, an aroma that in fact does not activate the trigeminal system. Assuming a greater sensitivity towards odors that lack this component, typically the aromas of sweet foods, this would motivate an appetitive behavior towards highly caloric foods; conversely, a lower trigeminal sensitivity, activated by salty or tasty foods, would make them less intense in taste, potentially promoting greater consumption to reach satiety. this would motivate an appetitive behavior towards highly caloric foods; conversely, a lower trigeminal sensitivity, activated by salty or tasty foods, would make them less intense in taste, potentially promoting greater consumption to reach satiety. this would motivate an appetitive behavior towards highly caloric foods; conversely, a lower trigeminal sensitivity, activated by salty or tasty foods, would make them less intense in taste, potentially promoting greater consumption to reach satiety.
Regarding the taste, the authors found no significant effects. However, the suggestion of a trigeminal component that may also involve this type of exploration is supported by the fact that the tasting sticks used do not allow to evaluate this effect. For example, the use of capsaicin, the spicy element in food, could provide a means of testing this hypothesis in future studies.