Carbohydrates In a Healthy Diet
Bread has often been called the “staff of life.” This term is a good description of the role carbohydrates have played in the human diet since the dawn of history. Almost every culture has relied on a particular native starch or grain as a major source of calories. For example:
- Rice in Asia
- Wheat in the Mediterranean, Middle East and North Africa
- Oats and Barely in the British Isles
- Corn and Potatoes in the Americas
- Cassava in mid and southern Africa
- Taro root (used to make poi) in the Pacific Islands
As exploration and transportation connected cultures, carbohydrates native to one region were introduced to other parts of the world. For example, corn from the new world became popular in southern Italy, where it is used to make a commonly eaten mush known as polenta. Similarly, potatoes, which are native to the Andes Mountains, became the dominant form of carbohydrate in Ireland after their introduction there in the mid-1600s. When a plant fungus destroyed the Irish potato crop in the mid-1800s, millions starved to death because there was no other affordable source of carbohydrate being cultivated.
The Role of Carbohydrates in the Diet
In addition to being the primary source of calories in most people’s diets, carbohydrates add natural sweetness (sugar), satisfying texture (fiber), and thickening powder (starches) to our diets. Fiber also slow digestion, making a meal seem more satisfying.
Food Sources of Carbohydrates
Grains (including wheat, corn, and rice), legumes (peas, beans, lentils), root crops (potato, cassava, taro), fruits, and to a lesser extent, vegetables and dairy products all provide carbohydrates.
Milk and yogurt are the only animal-derived foods that provide carbohydrate to the diet. Each 8-ounce cup of milk supplies 14 grams of carbohydrate in the form of the milk sugar lactose.
Climate, native species, local customs, and commercial value influence which carbohydrate crops are grown in each region of the world as well as which crops people want to consume.
The Chemistry of Carbohydrates
The word carbohydrate is Latin for water-containing carbon. It is a good description of the chemical makeup of this class of nutrients. Carbohydrates are made up of simple sugar molecules, the most common of which contain 6 carbon atoms bonded to 6 water molecules. A carbohydrate may contain as few as one or as many as several hundred sugar molecules. If the bonds between chains of sugar molecules are digestible, the carbohydrate is a sugar or starch. If the bonds can’t be digested, the carbohydrate is a fiber. Only plant cells can make fiber molecules. Fiber gives plants structural support the way skeletons support animal bodies.
Refining Reduces Nutrition and Increases Obesity
The industrial revolution produced machinery able to refine carbohydrates. This led to significant changes in carbohydrate consumption patterns. Machines that could quickly remove the nutrient-rich fiber and bran from whole grains made white flour and rice affordable for the masses. Other mechanized devices efficiently extracted sugar from sugar cane and sugar beets. Increased use of refined carbohydrates has produced a cultural diet high in sugar and simple starches and low in healthful bran and fiber. Many experts believe this trend has contributed to the growing incidence of obesity in the US and other industrialized nations.
How Many Carbohydrates Does a Person Need?
For many years, there was no precise recommendation regarding the minimum amount of carbohydrates a person should consume each day to promote health because there were no widely recognized deficiency symptom(s) associated with a lack of carbohydrate intake. The general feeling was that since carbohydrates provide energy, any energy-providing nutrient will do.
Noting the health risks associated with popular very low-carbohydrate diets and the health risks associated with eating too little fiber, the expert committee reviewing the carbohydrate data used to establish the 2005 US Dietary Guidelines sought to change this perception. This panel recommended that people eat:
- at least 100 grams (400 calories) of carbohydrates each day to prevent the body from breaking down vital proteins to produce the glucose (blood sugar) required by nerve, brain, eye, and blood cells
- 20-35 grams of fiber each day to improve digestive health and weight control, while reducing the risk of certain cancers
- no more than 10% of their total calories in the form of sugar
A diet that meets these guidelines would contain 2 or more cups each of fruits and vegetables, 6 servings of grains-3 of them whole grains, and a small serving of dessert once each day.