If your parents find you eating a gooey candy bar, one of them might say, "You have an awful sweet tooth!"
But it's not your teeth that notice the sweet taste -- in fact, your teeth would be better off without the sugar in the candy bar. You taste the sweetness through taste buds on your tongue.
Under a microscope, taste buds look a little bit like flower buds. If you look at your tongue in a mirror, you'll notice that it isn't smooth. The tiny bumps that cover it contain your taste buds. They pick up chemical signals from the foods you eat. These signals say "sweet," "sour," "salty" and "bitter." Those are the four taste groups that your tongue can experience. Many foods combine these different tastes -- and add a pleasant smell to make an even more appealing flavor.
The way a food smells is an important part of the experience you have when you eat it. You can find this out by doing a simple experiment with a partner. Cut and peel small pieces of several fruits and vegetables. You could try apple, potato, pear, peach, cucumber, carrot, turnip or celery. Ask your parents which fruits and vegetables in the refrigerator you can use for your experiment.
Now, close your eyes and hold your nose tightly. Have your partner place each piece of food on your tongue in turn. Without opening your eyes or letting go of your nose, say what the food is. Have your partner write your answers down.
Next, repeat the experiment with your eyes still closed, but without holding your nose. Don't bite down on the food -- just see if you can tell what it is with your taste buds. Again, name the food and have your partner write down your answer.
When you compare the two lists, you'll probably see that you got more right answers when you used taste and smell to guess the food. Your taste buds are pretty sensitive -- but your nose has an important role to play in the pleasure of eating, too.
If you have ever had a bad cold, you probably already figured out the results of that experiment. When your nose is stuffed up from a cold virus, your food often seems tasteless. Now you know why.
You taste different flavors with different parts of your tongue. With the tip, you taste sweet and salty things. You taste sour things most strongly with the outer edges of the tongue. You taste bitter things on the back of the tongue.
Scientists have wondered why people enjoy sweet-tasting things so much. Experiments have shown that babies suck longest and hardest on bottles of sweet liquid. This may be nature's way of getting babies to like the sweet milk they drink from their mothers' body to grow.
Another possible explanation for a "sweet tooth" has to do with the days long ago when people lived on food they gathered. Healthful fruits, nuts and berries usually have a sweet taste. But berries and plants that contain poison often taste bitter. So the taste buds' ability to detect bitterness may have served as a warning system for our earliest ancestors. If something tasted good, it was probably safe to eat. If it tasted bitter, it was a good idea to spit it out.
Dr. Diana Spillman, a scientist who studies taste at Florida State University, has found that young children have many more taste buds than adults do. Before you were 5, you even had taste buds on your lips and the inside of your mouth. As you get older, the number of taste buds on your tongue slowly decreases. As an adult, you'll have between 9,000 and 10,000 taste buds left -- which is still plenty. But Dr. Spillman thinks the extra taste buds may help explain why kids like sweets so much.
Even so, it's a good idea to develop a taste for other foods, too. Our bodies need some sugar. But too much of it can cause tooth decay and other health problems later on in life. So the next time you reach for a candy bar, remember that your taste buds might like to experience a carrot or a peanut butter sandwich just as much. Tips for Parents
Here are two experiments children can try:
* The chemical signals for sweet, sour, salt or bitter must be dissolved before taste buds can recognize them. If the tongue is dry, even the difference between sugar and salt can be unclear.
Have your child pat the surface of his or her tongue until it is dry. Then sprinkle a few grains of sugar or salt and let the child guess which.
* Prepare four half-cups of water, one with a teaspoon of sugar, one with salt, one with lemon juice or vinegar and one with a half a crushed aspirin (or Tylenol if the child is allergic). Stir well.
Using a toothpick, dip into the mixtures and touch various parts of the tongue. Rinse with clean water between tastes. This will locate the taste buds for sweet, salty, sour and bitter.