The life cycle of plants helps to explain the chemistry of carbohydrates. All forms of life on this planet get their energy, directly or indirectly, from the sun. Through photosynthesis, plants are able to use the energy of sunlight to combine water and carbon dioxide from the air into a molecule that stores energy – a carbohydrate. When plants are eaten and digested, this molecule is broken down and its energy is released.
All living matter contains carbon and other elements attached to the carbon. The shape of the carbon-containing molecule and the other elements joined with the carbon determine the nature of this living matter. Carbohydrates link carbon with oxygen and hydrogen in single molecules, or in groups ranging up to hundreds of molecules.
The three types of carbohydrates are monosaccharides, disaccharides, and polysaccharides. The simplest group are monosaccharides – single molecules of sugar. These are glucose (sometimes known as dextrose, corn sugar, or grape sugar); fructose, found in fruits, vegetables, and honey; and galactose, usually combined with glucose to form the lactose found in milk.
Disaccharides are the double sugar molecules: sucrose, from sugarcane or sugar beets; maltose, from grain; and lactose. Although most people can safely eat all carbohydrate foods, some individuals have a problem with lactose because they have low amounts of the enzyme lactase. Because their digestive systems cannot break down lactose, drinking too much milk can cause these people to experience cramps, diarrhea, and other symptoms. Lactase deficiency symptoms are most common in children from 11 months to 11 years old; the condition appears to be inherited, and it is found to a large degree among certain ethnic groups such as blacks, Arabs, and Orientals.
Complex carbohydrates, or polysaccharides, are made up of molecules that break down into two or more sugars during digestion or other chemical processes. (Complex carbohydrates are discussed further on page 15). These polysaccharides include starch, dextrin, glycogen, and glucose. Starch is the most important polysaccharide for human nutrition and is found in staple foods such as cereals, grains, potatoes, carrots, turnips, beets, and squash. Fresh starch granules are insoluble and practically indigestible, but cooking causes them to swell and break down, thus forming a digestible solution. Cooked carrots, therefore, are a better source of carbohydrate balanced diet, alcoholic beverages, in moderation, pose no health problems as long as their caloric content is kept in mind. Several studies have shown that small amounts of alcohol can aid circulation in healthy people. However, overconsumption can damage the heart muscle and liver and may be associated with vitamin and mineral deficiencies. What do the experts recommend? Most agree that a small amount of alcohol can be good for the healthy person, especially before or with a meal, to improve the appetite and enhance enjoyment of the meal. Pregnancy is a special condition during which extreme moderation in alcohol consumption is probably a good idea.