November 24, 2020

The tendency to eat more food when a larger variety is available is termed the variety effect.  The variety effect is relevant to flavor perception, and flavor is a salient, important feature of food.

Taste & Flavor

Taste is determined by the gustatory system (sensory system of taste) located in the mouth.  Flavor is determined by taste, smell and somatosensation.  Flavor includes taste; when referring to whether or not we like the taste, we are more precisely concerned with whether on not we like the flavor.  Flavor is a broader term that is a better determinant of the food experience, than taste alone.

Taste preference is strongly influenced by innate factors (Barotshuk & Beauchamp, 1994).  Flavor preference is also influenced by innate factors, but more dependent on learning (Beuachamp & Menella, 2009).  Humans display a strong innate preference for sweet and salty foods and beverages.  Presumably, liking for sweet tastes is an evolutionary development in plant eating animals.  It is proposed that sweet tastes reflect caloric sugars, and distinguishes poisonous from non-poisonous plants (bitter taste in poisonous plants) (Beauchamp & Mennella, 2009).  Getting caloric sugars and avoiding poisonous substances were both important aspects involved with survival in our ancestors.    Preference for salty tastes may have evolved due to salts importance to neuronal health and hydration status.  Sodium must be present in relatively large quantities to maintain nerve and muscle function (Wolfe, Kluender, Levi, Barotshuk, Herz, Klatzky & Lederman,  2006).  Human infants as young as 4 months of age prefer salt water to plain water, and by the age of 2 their preference for salty foods is even greater (Cowart & Beauchamp, 1986).  Bitter tastes are innately disliked, presumably because many bitter compounds in the wild are poisonous.  From an evolutionary perspective we have evolved sensory systems that protect us from being poisoned, presumably leading to a natural dislike for bitter compounds (Beauchamp & Menella, 2009; Drewnowski, Henderson, & Fornell, 2001).  Sour tastes are also innately disliked  (Wolfe, Kluender, Levi, Barotshuk, Herz, Klatzky & Lederman, 2006).  Sour tastes are the tastes of acids which at high levels may lead to tissue damage.

Smell (olfaction) occurs when chemicals stimulate olfactory receptors on a relatively small area of tissue found high in the nasal cavity.  Olfaction is important for flavor perception. Olfactory receptors are thought to bind with odorants (smell / chemical molecules) that have been dissolved in mucus in the olfactory region of the nose.  Each receptor is able to recognize only a small number of odorants.  In contrast to the small number of tastes we detect, we can detect thousands of odors. Thus, contributing to the wide range of flavors we experience. When we chew and swallow, food molecules are released into the air inside of our mouths and forced up behind the palate into the nasal cavity where they stimulate olfactory receptors.

Evidence indicates that most odor preferences are learned.  As an example, infants find the smells of sweat and feces pleasant and toddlers do not differentiate between odorants that adults find pleasant or unpleasant.

Somatosensation is detected by receptors in the skin throughout the head; and in particularly in regards to food- receptors in the mouth and nose- an example is the burn of hot peppers and the cooling effect of menthol (Mennella, Jagnow, & Beauchamp, 2001).  Somatosensation results from chemicals stimulating receptors and free nerve endings of the trigeminal (pair of cranial nerves which transmits somatosensation information from the face) and vagus nerves (pair of cranial nerves which transmits information about the heart, lungs, gastrointestinal tract, bronchi, trachea and larynx) leading to oral perceptions such as heat, coolness, tickle, itch and tingling. Studies indicate that irritating sensations are important for flavor evaluation (Beauchamp & Mennella, 2009).

The most prominent feature of the food and drinks we consume is flavor.  Flavor is defined as the perceptual combination of taste, smell, and somatosensation.  Flavor preferences are highly influenced by early life experiences, even in utero experiences.  Prenatal exposure to food flavors, which are transmitted from mother’s diet to amniotic fluid, lead to increased acceptance and pleasure from these foods during weaning.  In an experimental study, it was found that infants whose mother’s drank carrot juice during the last trimester of pregnancy liked carrot-flavored cereals more than infants whose mothers did not drink carrot juice or eat carrots (Mennella, Jagnow & Beauchamp, 2001).  Flavor learning also occurs as a consequence of exposure to nutrients in human milk.  Human milk is composed of the flavors that represent the food, and drinks ingested by the mother.  Exposure to specific flavors in the mother’s milk affects infants’ liking of that flavor (Mennella, Jagnow & Beauchamp, 2001).

Variety Effect

People tend to eat more food when a larger variety of food is available (McCroy, et al., 1999; Rolls, Rolls, Rowe, & Sweeney 1981; Smiciklas-Wright, Kreb-Smith, & Krebs-Smith, 1986). This variety effect of food has been found to increase consumption in an array of different areas, in both genders and across a wide range of ages ( Raynor & Epstein, 2001). The variety effect is particularly interesting, as its influence might be partly due to variety, just for the sake of variety.

After a thorough review of the scientific literature on the variety effect I decided to investigate further. The study investigated whether or not participants would eat more M&M’s from a bowl containing a single color versus a bowl containing a variety of colors (Hale & Varakin, 2016). We were also interested in whether or not people who eat more M&M’s from the multicolor bowl would indicate they ate more due to variety. The results showed participants ate more M&M’s from the multi-color bowl than the single-color bowl. Participants who ate more from the multicolor bowl were more likely to mention variety as a reason for the increased consumption than those who did not eat more from the multicolor bowl. The results suggest there is a relationship between actual consumption and people’s reports of consumption.  One of the important limitations of the study was it couldn’t specify whether awareness of variety’s influence was a cause or a consequence of eating. It is possible that participants only realized they had eaten more M&Ms from the multi-color bowl after they had started to do so. Even if this is the case, it is important to realize that the questions participants answered were carefully worded to avoid prompting participants to think about color variety – the bowls were no longer in sight, and the questions didn’t mention anything about color. Thus, when variety was mentioned it was under conditions of minimal prompting, suggesting that it was highly accessible to conscious awareness.

A comprehensive approach to eating- Cognitive Behavioral Nutrition- requires further investigations on variety and a plethora of factors involved with flavor perception, and the dynamic qualities the food environment.

References are available upon request