FATS AND OILS

Most of the compounds found in living organisms are made up of only a few of the ninety-eight naturally occurring elements. Carbon, hydrogen, and oxygen are found in a countless number of compounds. The differences in these compounds are due to the amounts of each element that are present and the way the atoms are arranged in the molecules.

Fats and oils, like carbohydrates, are a group of compounds made of only carbon, hydrogen, and oxygen. Fats and oils are produced by animals and plants as a method of storing food. Molecules of sugars and starches become fat or oil molecules as the atoms are rearranged. Stored fats and oils protect an organism against a time when food is scarce. Fats, starches, and sugars are needed for energy.

You can find out if a food contains fat or oil by rubbing it on a piece of brown paper bag. If the food contains a greasy substance, a translucent spot (an area that lets light through) will appear where you rubbed. Water in food will also produce a translucent spot, but a water spot disappears when the water dries. A fat or oil spot will not disappear.

Animal fats, such as butter or lard, are usually solids at room temperature, while vegetable fats are liquids. Vegetable oils can be made into solid fats in a laboratory by adding hydrogen gas under pressure. The terms saturated and unsaturated fats refer to the amount of hydrogen in a fat. Saturated fats contain more hydrogen than unsaturated or polyunsaturated. Saturated fats are usually solid, while unsaturated fats are oils. Margarine, which is advertised as being made from oil, contains some saturated fat. Hydrogen was added to make the fat solid.

Is there a difference between the ways these two kinds of fats act in the body? This is a question that has occupied scientists for years. When some people age, yellowish, fatty deposits of a substance called cholesterol form inside the arteries, leaving a narrower passage for blood to get through. This condition, called arteriosclerosis, can cause blood clots, which may block an artery and cause it to burst. It may also completely close an artery, cutting off the blood supply to a part of the body. If this happens in one of the arteries that nourishes the heart or brain, death can result. It appears that saturated fats in the diet may increase the amount of cholesterol in the body, and unsaturated fats may lower blood-cholesterol levels. For this reason, doctors suggest that older people cut down on the amounts of butter, cheese, and fatty meats in their diets. It is also behind the recent rulings to ban “trans” fats (which are saturated) from processed foods.

By Vicki Cobb in "Science Experiments You Can Eat",(revised edition) Harper-Collins Publishers, New York, 2016,excerpts chapter 4. Adapted and illustrated to be posted by Leopoldo Costa.