Author: Azita Vatandost
Artist: Jordan Mooney
Editor: Atufa Shabnum
As a self-proclaimed picky eater, I have gone through many culinary experiences that have left me hungry for an answer to how my so-called ‘fussiness’ in food came to be. Family members have scolded me at the dinner table for cringing at the sight of vegetables whilst I’ve alternated between only a handful of preferred meals. This frustrating selectiveness towards food presents a puzzling occurrence in human behaviour–but how exactly do picky eating habits emerge?
Taste buds are a cluster of 50-100 taste bud receptor cells located on the tongue surface. Microvilli, also known as taste hairs, extend from these cell clusters and protrude through an opening called the taste pore. The taste hairs then interact with the chemical properties of food/tastants. This interaction causes taste receptor cells to undergo depolarization, resulting in a change in the electrical charge across a cell membrane. The depolarization sets off an action potential that proceeds to transmit sensory information to the gustatory (taste-sensing) cortex of our brain.
Classification of taste is moulded into five taste qualities: sweet, sour, salty, umami, and savoury. Taste bud cells are further classified into types I, II, III, and IV based on their structural and functional properties. Type I cells are dedicated to distinguishing salty tastes. Type II cells transduce a combination of sweet, umami and bitter tastes. Type III cells detect sour taste whilst type IV taste cells are currently not known to possess taste functions.
The genetic basis of taste: how can genes lead to picky eaters?
Attitudes towards certain foods are far more extensive than just being ‘fussy’; there’s a reason picky eaters love the kids’ section on a restaurant menu.
From a biological perspective, the foundation of picky eating essentially lies within genes.
Genes establish predetermined inclinations and aversions towards certain foods. On that account, it’s common to see children have an evident dislike towards vegetables and a preference for sweets. TAS2R38 is a bitter taste receptor that modulates bitter perception. A study published by Frontiers in Genetics, aiming to explore genetic hallmarks in taste variation across databases, reported that TAS2R38 variants can determine taste sensitivity towards bitter foods.
TAS2R38 variation is induced by three single nucleotide polymorphisms (SNPs), a genetic variant at a single building block of DNA, that can lead to amino-acid alterations. These alterations can cause TAS2R38 variants to perceive taste differently upon consuming substances containing the chemical compound phenylthiocarbamide (PTC). Inheritance of a PTC taster gene is autosomal dominant. Hence, individuals with genotypes Tt and TT are often termed ‘tasters,’ exhibiting either high or intermediate sensitivity to bitter foods. Contrarily, the tt genotype is a recessive trait and is regarded as a “non-taster” ‒ likely to not taste bitterness. Hence, broccoli, cabbage, Brussels sprouts and even alcohol might be the worst nightmare for some but decent for others.
On the opposite end, there’s sweetness. Much like bitter perception, sweet perception also varies. TAS1R2 and TAS1R3 are the sweet taste receptors in humans. A study conducted by the QIMR Berghofer Medical Research Institute reported that certain SNPs can induce different perceptions of sweet intensity. This gives rise to the hypothesis that an inclination towards sugary foods could be correlated with having a weaker recognition of the sweet taste.
Can our taste buds change?
Similar to our other senses, our sense of taste diminishes with age. Our taste buds begin to shrink and are unable to regenerate as quickly, causing us to lose sensitivity to the five taste qualities. However, the natural decline does not occur until after our mid-50s and 60s. Thus, the shift from a bland palette typical of picky eaters to a slightly more diverse one can be better understood through a psychological lens. A systematic review conducted by the USDA has shown that repeated exposure to a certain vegetable/fruit for 8-10 days shows an increase in the acceptability of certain foods in children. Although we cannot alter our genes, disliked foods may become appetising.
Ultimately, taste receptors’ interaction with tastants and the food exposure we’ve had as children can be determinants of picky eating. Particular bitter and sweet receptors can classify us into genotypic categories whilst food exposure can develop potential tolerance to foods. Further studies have begun to highlight connections between the impact of social factors such as parenting habits and food presentation on picky eating. Therefore, could upbringing outweigh the influence of our genes on our taste selectivity? Which side of the nature versus nurture debate will take root in our eating habits?
kinesismagazine.com 