disorders of nutrition
Carbohydrates, Proteins, and Fats
Carbohydrates
Depending on the size of the molecule, carbohydrates may be simple or complex. Simple carbohydrates:Various forms of sugar, such as fructose (fruit sugar) and sucrose (table sugar), are simple carbohydrates. They are small molecules, so they can be broken down and absorbed by the body quickly and are the quickest source of energy. They quickly increase the level of blood glucose (blood sugar), which is also a simple carbohydrate. Fruits, dairy products, honey, and maple syrup contain large amounts of simple carbohydrates, which provide the sweet taste in most candies and cakes. Complex carbohydrates:These carbohydrates are composed of long strings of simple carbohydrates. Because complex carbohydrates are larger molecules than simple carbohydrates, they must be broken down into simple carbohydrates before they can be absorbed. Thus, they tend to provide energy to the body more slowly than simple carbohydrates but still more quickly than protein or fat. Because they are digested more slowly than simple carbohydrates, they are less likely to be converted to fat. They also increase blood sugar levels more slowly and to lower levels than simple carbohydrates but for a longer time. Complex carbohydrates include starches and fibers (which occur in wheat products such as breads and pastas), other grains (such as rye and corn), beans, and root vegetables (such as potatoes and sweet potatoes). Carbohydrates may be Refined Unrefined means that the food is highly processed. The fiber and bran, as well as many of the vitamins and minerals they contain, have been stripped away. Thus, the body processes these carbohydrates quickly, and they provide little nutrition although they contain about the same number of calories. Refined products are often enriched, meaning vitamins and minerals have been added back to increase their nutritional value. A diet high in simple or refined carbohydrates tends to increase the risk of Obesity and If people consume more carbohydrates than they need at the time, the body stores some of these carbohydrates within cells (as glycogen) and converts the rest to fat. Glycogen is a complex carbohydrate that the body can easily and rapidly convert to energy. Glycogen is stored in the liver and the muscles. Muscles use glycogen for energy during periods of intense exercise. The amount of carbohydrates stored as glycogen can provide almost a day’s worth of calories. A few other body tissues store carbohydrates as complex carbohydrates that cannot be used to provide energy. Most authorities recommend that about 50 to 55% of total daily calories should consist of carbohydrates, most coming from fruits, vegetables. beans and legumes, and unrefined grains. Fewer than 10% of total daily calories should come from added sugars. Added sugars are syrups and other caloric sweeteners used in other food products. Added sugars are listed as an ingredient in food labels. They include brown sugar, corn sweetener, corn syrup,dextrose, fructose, glucose, high-fructose corn syrup, honey, invert sugar, lactose, malt syrup, maltose, molasses, raw sugar, sucrose, trehalose, and turbinado sugar. Naturally occurring sugars, such as those in fruit or milk, are not added sugars. The glycemic index is a way of classifying food based on how quickly consumption of its carbohydrates increases blood sugar levels. Values range from 1 (the slowest) to 100 (the fastest, the index of pure glucose). However, how quickly the level actually increases also depends on what other foods are ingested at the same time and other factors. The glycemic index tends to be lower for complex carbohydrates than for simple carbohydrates, but there are exceptions. For example, fructose (the simple carbohydrate sugar in fruits) has a low glycemic index. The following also influence a food’s glycemic index: Processing:Processed, refined, or finely ground foods tend to have a higher glycemic index. Type of starch:Different types of starch are absorbed differently. For example, potato starch is digested and absorbed into the bloodstream relatively quickly. Starch in barley is digested and absorbed much more slowly. Fiber content:The more fiber a food has, the harder it is to digest. As a result, sugar is absorbed more slowly into the bloodstream. Ripeness of fruit:The riper the fruit, the more sugar it contains, and the higher its glycemic index. Fat or acid content:The more fat or acid a food contains, the more slowly it is digested and the more slowly its sugars are absorbed into the bloodstream. Preparation:How a food is prepared can influence how quickly it is absorbed into the bloodstream. Generally, cooking or grinding a food increases its glycemic index because these processes make food easier to digest and absorb. Other factors:The way the body processes food varies from person to person, affecting how quickly carbohydrates are converted to sugar and absorbed. How well a food is chewed and how quickly it is swallowed also have an effect. may result in low blood sugar levels ( Hypoglycemia ) and hunger, which tends to lead to consuming excess calories and gaining weight. However, diet experts no longer think that eating foods with a low glycemic index helps people lose weight. levels so much. As a result, people feel satiated longer after eating. Consuming carbohydrates with a low glycemic index also tends to result in more healthful cholesterol levels and reduces the risk of Obesity and In spite of the association between foods with a low glycemic index and improved health, using the index to choose foods does not automatically lead to a healthy diet. For example, the glycemic index of potato chips and some candy bars—not healthful choices—is lower than that of some healthful foods, such as brown rice. Some foods with a high glycemic index contain valuable vitamins and minerals. Thus, this index should be used only as a general guide to food choices. The glycemic index indicates only how quickly carbohydrates in a food are absorbed into the bloodstream. It does not take into account how much carbohydrate a food contains, which is also important. Glycemic load includes the glycemic index and the amount of carbohydrate in a food. A food, such as carrots, bananas, watermelon, or whole-wheat bread, may have a high glycemic index but contain relatively little carbohydrate and thus have a low glycemic load. Such foods have little effect on the blood sugar level. Glycemic load also includes how changes in blood sugar are affected by the combination of foods eaten together. The glycemic index does not. 