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Name______________Chocolate Lover or Broccoli Hater? Answer's on the Tip of Your TongueBy SANDRA BLAKESLEEPublished: February 18, 1997Babies are born with a number of obvious genetic traits, like brown or blue eyes, black or red hair, dark or light skin. But parents take note: infants also enter this world equipped with a genetically determined number of taste buds in the tips of their tiny tongues. Some have a few hundred or so buds while others have tens of thousands of receptors for sweet, sour, salty or bitter foods. From birth to old age, this inborn characteristic helps determine what foods people crave or leave on their plates, scientists say. It explains why some people hate double chocolate fudge frosting on cake while others take an end piece with twice as much goop. It sheds light on why some individuals hate broccoli, raw cabbage or grapefruit juice, while others look forward to eating those foods every day.It is the reason some people like food close to room temperature and others like it hot, or cold, why certain people can gobble down spicy foods laced with red chili pepper, why some children are notoriously picky eaters and why many older people lose their appetites.It may also lead pregnant women to avoid bitter foods that might be toxic to the fetus and prompt men to eat everything in sight, on the assumption that they require more calories.Research has shown that people live in vastly different taste worlds. Genetic differences in taste lead people to eat or refuse certain foods and play a role in how fat or thin they are.Such differences may even influence who gets cancer. Those who avoid the sharp or bitter tastes of many fruits and vegetables might be at a higher risk for some diseases.Food preferences and eating habits are profoundly influenced by a person's family and life experiences. It’s amazing that a biological variable like taste genetics shows up at all. But the tongue is hardwired for behavior in ways scientists are only beginning to understand.''The study of human taste genetics got under way when a chemist created a chemical called PTC. After some of the PTC exploded into the air, a colleague commented on how bitter it was, yet the chemist tasted nothing. Intrigued, he handed out crystals of PTC at the meeting, asking how many passers-by could taste it. About a quarter of the people were nontasters, while everyone else said PTC was bitter.That fascinated the geneticists of the day. They determined that nontasters carried two recessive genes that played a role, still unknown, in taste and that tasters carried at least one dominant gene for the trait. People all over the world can be grouped as tasters or nontasters of PTC.PTC testing remained a curiosity until the early 1970's a scientist decided to expand the question to ask: What difference does it make in everyday life if someone is a taster or a nontaster of PTC?Instead of PTC, researchers now test with a similar chemical called PROP. Again, some people cannot taste it, while others retch because it is so bitter.''We now divide the world into three groups,'' the scientist said. A quarter of all people tested are nontasters, half are medium tasters and one quarter are supertasters -- people who react violently to PROP. Medium tasters say it is bitter, but they are less sensitive than supertasters to small amounts. Genetically speaking, two medium taster parents can produce a supertaster or a nontaster child, or a medium taster like themselves.In looking at people's tongues with a special blue dye, researchers have found that supertasters have as many as 1,100 taste buds per square centimeter of tongue, while nontasters have as few as 11 buds per square centimeter.''I am a nontaster,'' the scientist said. ''The dye on my tongue produces a pink and blue polka-dot pattern, with blue dots indicating a taste bud. A supertaster's tongue has dense blue patches.''Each taste bud feeds information into two types of nerves. One sends taste signals to the brain for processing. A second senses pain, temperature and touch.This is really important. It tells us that supertasters are superfeelers and superpain-perceivers, at least with their tongues.''These findings led scientists to begin studying food preferences with regard to taste genetics. While all humans are born with a liking for sweets, she said, supertasters find many sugary foods to be sickeningly sweet. Frosting is yucky. Coffee is too bitter. Hot peppers and ginger produce an unpleasant burn. Food should be tepid.Supertasters are sensitive to fats. Taste buds do not react to any flavor of fat, but they react to its touch. Fat molecules press against the taste buds, producing a tactile sensation that is interpreted by the brain as slippery or greasy, she said.In an experiment, people were asked to taste different milk samples -- skimmed, 1 percent fat, 2 percent fat, 4 percent fat, half and half, heavy cream and cream with oil added. Nontasters could not tell the difference between skim milk and the heavy creams, she said. Supertasters were extremely sensitive to gradations in fat. As fat content increased, they perceived more creaminess.If you go through life as a nontaster it takes more to get the flavor out of food than it does for a supertaster.The world is built for regular tasters. For them, most foods are not too sweet, bitter, salty or sour. And their diets may be healthier because of it.Scientists have found that supertasters tend not to like the strong tastes of many fruits and vegetables, which are the main sources of cancer-preventing nutrients. PROP tasters do not like grapefruit juice, and many even find orange juice unpleasant, he said.One's PROP status may also play a role in weight control. A small study of older women found that supertasters tend to be thinner than nontasters. That makes sense. Supertasters tend to avoid sugary, fatty foods throughout their lives. Preliminary data suggests that the same holds true for younger women.At the same time, sensitivity to PROP tends to decline with age, suggesting that hormones play a role in taste. After menopause, women who are supertasters tend to be less sensitive to bitter foods.Studies now under way suggest that monthly changes in estrogen alter PROP sensations in younger women so that the sense of bitterness in foods varies throughout each month. And during the first trimester of pregnancy, even nontaster and medium-taster women find many previously acceptable foods, like coffee, to be suddenly unpalatable.That makes sense. Bitterness often predicts toxicity. Pregnant women are good poison detectors because their tastes are designed to protect the developing fetus.Morning sickness would therefore not be an accidental misery that just has to be put up with, but a way of avoiding harmful foods -- a useful, if troublesome, gift.Glossary:Notoriously- being very well known, famouslyPrompt- cause the start of somethingChemist- someone who studies chemistryColleague- a person you work withIntrigued- making someone curiousRetch- gag or even vomitUnpalatable- distastefulTepid- blandTactile- of touchPreliminary- early, or beginning version of somethingHoromones- chemicals that send messages in the bodyMenopause- when women become too old to ovulate/have periodsToxicity- “poisonousness” ................
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