Let your food be your medicine, and your medicine be your food. ...Hippocrates

Carbohydrates: requirements, function and food sources

Carbohydrates and Sugars
Reprinted from ific.org

Carbohydrates are one of three basic macronutrients needed to sustain life (the other two are proteins and fats). They are found in a wide range of foods that bring a variety of other important nutrients to the diet, such as vitamins and minerals, phytochemicals, antioxidants , and dietary fiber . Fruits, vegetables, grain foods, and many dairy products naturally contain carbohydrates in varying amounts, including sugars, which are a type of carbohydrate that can add taste appeal to a nutritious diet.

Carbohydrate Classification

Carbohydrates encompass a broad range of sugars, starches, and fiber. The basic building block of a carbohydrate is a simple union of carbon, hydrogen, and oxygen. The chemical definition of a carbohydrate is any compound containing these three elements and having twice as many hydrogen atoms as oxygen and carbon.

Carbohydrate and Sugars Consumption Recommendations

The Institute of Medicine’s Dietary Reference Intakes (DRI) Report recommends that Americans get the majority of their daily calories from carbohydrates—about 45 to 65 percent of daily calorie intake. Children and adults need a minimum of 130 grams of carbohydrates per day for proper brain function. The DRI for carbohydrates and sugars recommends a maximum intake level of 25 percent or less from added sugars.

The 2005 Dietary Guidelines for Americans outlines how important it is to eat nutrient-dense foods that are within one’s caloric needs. After basic nutrition requirements are met, any remaining calories in a person’s caloric needs are considered “discretionary” and allow for individual food choices and preferences. How many discretionary calories a person has in his or her diet will vary depending on an individual’s activity level and basic metabolic needs. The Dietary Guidelines suggest that consumers choose and prepare foods and beverages with only those added sugars or caloric sweeteners that fit into their discretionary calorie allowance.

Carbohydrates and Sugars in the Diet

  • Safety: The Food and Drug Administration (FDA) has examined numerous sugars, including glucose, dextrose, fructose, sucrose, high fructose corn syrup, lactose, and maltose, and determined that they are “generally recognized as safe” (GRAS). According to the FDA, sugars for use in foods have a proven track record of safety based either on a history of use or on published scientific evidence, and can be used in food products without further FDA approval.
  • Metabolism: Once ingested, most carbohydrates and complex sugars are broken down into the simple sugar glucose. However, in the digestion of sucrose, both glucose and fructose are released into the bloodstream. Glucose is the primary fuel utilized by the brain and working muscles. To protect the brain from a potential fuel shortage, the body maintains a fairly constant glucose level in the blood. Dietary glucose can be stored in the liver and muscle cells in units called glycogen. When the level of glucose in the blood starts to drop, glycogen can be converted to glucose to maintain blood glucose levels. Several hormones, including insulin, work rapidly to regulate the flow of glucose to and from the blood to keep it at a steady level. Insulin also allows the muscles to get the glucose they need from the blood supply. In the process of breaking down carbohydrates into glucose, the body is unable to distinguish between sugars that are added to foods and sugars that occur naturally in foods, since they are chemically the same.
  • Carbohydrates, Sugars, and Weight Control: Calories are needed for normal body processes. However, people will gain weight when they eat more calories than they use up in daily activities and exercise. These excess calories can come from all macronutrients—fats , proteins , carbohydrates, and even alcohol. Carbohydrates or sugars eaten within daily calorie needs, by definition, do not cause weight gain. The Dietary Guidelines recommend choosing carbohydrates wisely while not exceeding calorie needs by selecting foods like fruits, vegetables, grains, and dairy products that are all nutrient dense.
  • Diabetes: Diabetes is a metabolic disorder that occurs when the body cannot regulate blood glucose levels properly. In diabetes, either the pancreas does not make enough insulin (type 1 diabetes) or the body can not respond normally to the insulin that is made (type 2 diabetes). The causes of diabetes continue to be a mystery, although both genetics and environmental factors seem to play a role. Obesity and lack of exercise are important in susceptibility to type 2 diabetes. Interestingly, sugars are not “off limits” for people with diabetes. Current American Diabetes Association (ADA) nutritional recommendations do not provide specific guidelines for intake of sugars, except to note that sugars and other carbohydrates can be substituted for one another on a calorie-for calorie basis. The ADA also recommends limits on dietary fat and dietary saturated fat for diabetics.
  • Glycemic Index: Glycemic index (GI) is a research tool that measures how carbohydrate-containing foods affect blood glucose levels. It is calculated by having one or more people eat a specific amount of a single food [usually the amount of food containing 50 grams of digestible carbohydrates (total carbohydrate minus fiber)] and then measuring the change in blood sugar levels compared with the levels achieved after they have eaten a control food containing the same amount of digestible carbohydrates, such as white bread or glucose. The average change in blood sugar levels over a set period of time relative to the levels after consumption of the control food, usually white bread or glucose, is the food’s glycemic index. According to the GI theory, the lower the GI number, the slower food is digested, allowing for glucose to be delivered more slowly to the bloodstream than with foods having a higher GI number. It can be very difficult to apply the glycemic index to foods consumed in the real world environment as GI can vary widely depending on the mixture of foods eaten, the ripeness of foods, the degree to which the foods are cooked, and other factors. Most scientists agree that more research is needed prior to recommending GI as a measure on which to base dietary recommendations for the general population.
  • Dental Health: Sugars and cooked starches (e.g.: bread, pasta, crackers, and chips) are fermentable carbohydrates that contribute to the risk for dental caries. The degree of risk from a carbohydrate-rich food is related to several factors such as exposure time and frequency of consumption. However, risk can be decreased through several practices, the most important being proper oral hygiene and the use of topical fluorides, fluoridated toothpaste, and fluoridated water. Also important in reducing the risk of caries is eating a balanced diet in line with current dietary guidelines.
  • Sugars, Mental Performance, and Behavior: Numerous studies with different populations show that sugar consumption does not affect hyperactivity, attention span, or cognitive performance in children.

The Bottom Line

As the main energy source for the body, carbohydrates are an important part of a healthful diet. Currently, experts agree that carbohydrates and sugars in foods and beverages can be enjoyed in moderation as part of a balanced diet and active lifestyle.

Source: International Food Information Council (IFIC). Retrieved April 19 2008.

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