Biology 103
2002 Second Paper
On Serendip

Throughout most of life, humans are taught to disobey their taste buds by eating foods such as brussel sprouts, celery, and liver. How is it that our sense of taste works? Why is it that those things that are so unhealthy for our bodies taste so good? Shouldn't we expect that those foods that are most useful to our bodies are those foods that taste the best? And why is it that those unhealthy foods are enjoyed by practically everyone? Is this sense a biological trait of mammals and if so, is it hereditary?

First, in order to understand the scientific reasons for tasty foods it is necessary to understand the workings of our taste buds. The sense of taste is mediated by both gustatory receptors and olfactory receptors (1); when food or beverages enter our mouth they contact the tongue and palate and volatiles rise into our nasal cavities so that our sense of taste is made up of both smell and taste. Taste, is based upon groups of cells (taste buds) which take oral concentrations of many small molecules, through receptors within the cells, and inform taste characteristics to centers in the brainstem (See Image 1). (2)Taste buds are microscopic onion-shaped bunches of cells buried in the epidermal cell layer of the papillae. Little pores in the cells called, gustatory pores allow the receptors to contact the taste in our mouths. The average adult has about 10, 000 taste buds. These taste buds are most predominant on little knobs of epithelium on the tongue called papillae. Papillae are little bumps on the top of the tongue that increase the surface area for the tastes buds. The papillae also aid in the mechanical handling of food in the mouth. (3)There are four types of papillae (See image 2). The most abundant of the papillae are the filiform, but these contain no taste buds. Fungiform papillae are those that are located on the front of the tongue and appear most noticeably to the human eye. Foliate papillae are the series of folds on the rear edges of the tongue. Lastly, circumvallate papillae are the large bumps on the back of the tongue. (4)

Humans discern four types of taste: saltiness, sourness, sweetness and bitterness. (5) Notably though, scientists have suggested that there is another category, umami, the sensation induced by glutamate, an amino acid that composes proteins in meat, fish and legumes and is also included in MSG. Before this, it was thought that fat did not have a specific taste, but rather provided texture in food. (6) Richard Mattes, professor of foods and nutrition at Purdue proved differently. He proved that humans can taste fat therefore explaining why fatty foods taste so much better than fat-free foods. So, when someone says "this fat-free cookie tastes like cardboard," it is due to the lack of tasty fat in it. Here, though is where the slogan, "Eat everything in moderation," comes to mind. The reason for unhealthiness is not so much because we eat fatty foods, but because we do not eat them in moderation for they are certainly somewhat healthy.

Furthermore, it is true that those foods that are most tasteful are useful in our bodies systems. Glutamate is the major fast excitatory neurotransmitter in the brain. In fact, it is believed that 70% of the fast excitatory CNS synapses employ glutamate as a transmitter. Therefore, glutamate is an essential nutrient to our bodies, particularly our brains. (7)
Also, humans and most mammals share the composite structure of taste buds; practically all mammals have a sense of taste. However, there have been categorized three different types of tasters: super-tasters, medium tasters and non-tasters. Scientists have found that the distinction lies within the amount of taste buds on the tongue; the less the taste buds the less the sensitivity to taste. (4) The difference is due to age, whether or not someone smokes and hereditary. Children born of non-taster parents will most likely also be non-tasters.

So, indeed there are biological reasons for the tastiness of pizza and also reasons for difference in particular tastes. I love spicy food so, I am most likely a non-taster because the spiciness does not affect me the way it would affect a super-taster. And lastly, it is important to listen to your bodies cravings, because there is a high chance that your body lacks a particular nutrient that you are craving. Eat what tastes good. Eat pizza.

References

1) Campbell, Neil and Jane Reece. Biology. 6th edition. Pearson Education Inc; San Francisco, 2002. p.1074.
2)Physiology of Taste, abundant resource on taste buds
3)Mythos Anatomy homepage, on Mythos Anatomy website
4)"A Taste Illusion: Taste Sensation Localized by Touch", article written by Lina M. Bartoshuk
5)Scientific American homepage, on the Scientific American website
6)Cosmiverse homepage, Purdue University's journal
7)Glutamate as a Neurotransmitter, Glutamate information


| Forums | Serendip Home |