Human sense of sight, smell, heat and taste are enabled by biological sensors in various organs. As an example, sense of sight requires vision sensors in our eyes, which enable us to see. Majority of the people are able to see colors in objects, however, some people are not able to see colors due to the absence or deficiency in color sensors in their eyes, due to genetic abnormalities. Similarly, some people are more or less sensitive to heat depending upon the number and type of heat sensors they have on their skin. So goes with taste as well. Just as there are differences among humans in various physical traits due to genetics, there are myriad differences among humans, sometimes major and often minor when it comes to our senses. These differences are genetically encoded.
Taste preference is a complex interplay of physiological, psychological, genetic factors and social behavior of an individual. Among these factors, Genes play a significant role in influencing an individual’s taste and food preferences. Being less sensitive to a certain taste means it takes a larger quantity of the molecule to “experience” the taste, whereas sensitive individuals require less to achieve the same “experience”.
These variations might lead to an increased preference for certain foods, which could lead to increased consumption and hence increased risk of obesity and related conditions. An understanding of why people prefer certain foods will help design personalized health interventions that could fight obesity and depression.
Taste preferences are known to influence energy intake and there are many genes that are important in determining taste preferences, with the gene TAS2R38 being a significant one. The search for taste receptor genes began with TAS2R38, when Fox et al showed that some people found Phenylthiocarbamide (PTC) bitter while certain others couldn’t taste it at all. This taste receptor gene was found to follow a Mendelian recessive form of inheritance but was initially believed to be a form of natural selection. This was because the ability to recognize bitter taste would aid in identifying toxic substances in the food, especially in the Neanderthal age, however, there are large numbers of non-taster variants of the gene that are present in the general population. Recent studies have shown that this gene is largely influenced and selected based on demographic pressures.
Recent studies have substituted the use of 6-n-propylthiouracil (PROP) for PTC to understand the phenotypic variance among people with the taste for bitter foods. TAS2R38 is found to influence 70% of the preference for bitter foods.
There are certain variants of TAS2R38 gene associated with greater BMI. The three variants of the gene can result into classification of non-tasters, tasters and super -tasters. The non- tasters have high threshold and low sensitivity while tasters have low threshold and high sensitivity. The third category is the super tasters who have an increased sensitivity. The taste perception of these three variants differs considerably, for example non-tasters perceive scotch as less bitter and more sweet than super tasters.
People with the non-taster version of the gene should modulate their energy intake to prevent excess intake of alcohol, or other high calorie bitter foods which can potentially increase their risk of obesity and other associated conditions.
Among the tastes that guide food preferences, sweet taste is a powerful factor that determines preference for sweet foods. Sweet taste preference can influence sweetened food consumption behavior, insulin response and are found to produce an analgesic response in humans. The ingestion of sweet tasting food is found to give a positive feedback and could encourage further consumption. Important genes that influence sweet taste preference are TAS1R3, TAS1R2 and TAS1R1. The protein produced by TAS1R3 binds to the protein TAS1R1 to form a pleasant savoury taste, umami response or it could bind with TAS1R2 to form a sweet taste response.
The variants of TAS1R1 play an important role in food preferences. Apart from food preference, TAS1R2 is present in various parts of the body and could play a role in sugar metabolism, contributing to inter-individual difference in energy intake.
Individuals with the ‘high risk’ genotype can modulate the effect of the risk variant by controlling the amount of carbohydrate consumed.
An important food preference that can directly affect the risk for obesity is fat taste preference. Fat from dietary sources is not only required for energy storage but is also needed for temperature regulation. Though there is a need to consume fat for physiological needs, extremely high consumption of high fat food could lead to associated disease conditions. The fat taste preference gene provided a potential physiological advantage under conditions when food was scarce by creating a preference for foods that were rich in fat, and were dense sources of energy. For long it was believed that fat was detected based on texture preference but recent studies have shown that gustation, or fat tasting, could play an important role in dietary fat preference.
Detecting fatty foods during consumption would aid in getting metabolic processes ready for breaking fats down. It is important to consume the right amount of fat from the diet, while high fat intake can result in obesity and associated disorders, low fat intake can result in growth retardation, impairment in vision, learning disability and skin lesions. A good candidate gene for fat perception is CD36 that is found to play a major role in fat taste perception.
The gene CD36 induces the production of CD36 protein which influences the amount of fat consumed. Individuals with a low amount of CD36 are less sensitive to fat with higher threshold for oral fat while individuals with high amounts of CD36 are more sensitive to fat in their diet, and hence consume less fat.
Individuals with a high preference for food rich in fat should modulate their risk for obesity by controlling fat content in their diet. Studies have also shown that such individuals could lower risk for cardiovascular disease and obesity by following a mediterranean diet.
Taste is an individual preference, influenced by the genes that we carry, and dictating energy intake. Understanding the genes we carry will aid in making intelligent food choices for better health. The first step would be to identify the variations in our genes.
Find out which variations of genes you carry and more at www.xcode.in.