Carbohydrates: structure, function, and biochemical roles

Carbohydrates, The Macronutrient

Carbohydrates are the major sources of energy for the body (Raspberry 2004). They are composed of carbon, hydrogen and oxygen and occur in both simple and complex forms. Food sources of carbohydrates must be digested, absorbed and undergo glycolisis before the body can process them for energy. Experts say that 55-60% of caloric intake should be carbohydrates sources. Plants take in and transform energy from the sun into oxygen and convert it into chemical energy human beings can use. Through the process of photosynthesis, plants absorb carbon dioxide and release oxygen, thus producing carbohydrates (Raspberry).

Simple carbohydrates or simple sugars consist of monosaccharide or disaccharide units (Raspberry 2004). Glucose is the most common type, which is also stored in the body for energy use. It is also called blood sugar or dextrose. The other types include fructose and galactose. Fructose is found in fruits, honey and high-fructose corn syrup. Galactose often combines with glucose to form lactose or milk sugar. Complex carbohydrates or polysaccharides consist of simple sugar units in long chains, which are called polymers. They provide start, glycogen and dietary fiber. Starch and glycogen are digestible forms of complex carbohydrates. Dietary fiber consists of polysaccharides, which are not yet digested when entering the large intestines. Nutrition experts recommend that 55-60% of calorie intake should be complex carbohydrates. Pasta and whole-grain breads contain complex carbohydrates (Raspberry).

Unless digested and absorbed by the body, carbohydrates cannot be used for energy (Raspberry 2004). Adequate food preparation helps in the digestion. Heating makes starches swell and easier to break down. The enzyme amylase in the mouth mixes with the food and breaks some of the starches eaten into smaller units. But the enzyme is inactivated when the food reaches the stomach, which is acidic. In the small intestines, important digestive enzymes are secreted by the pancreas. This is where digestion and absorption take place. Dietary fiber does not get processed in the small intestines. Instead, it proceeds to the colon without change. Simple carbohydrates are absorbed by the cells of the intestines and then move to the liver. In the liver, galactose and fructose are converted into glucose until they are released into the bloodstream. Glucose is sent directly to organs, which need energy. Otherwise, it is stored in the liver or muscles or stored as fat (Raspberry).

Keep Fit with Complex Carbohydrates

Carbohydrates are a vital part of good nutrition and energy. Most of a daily diet should come from complex carbohydrates to stay healthy and fit (Swanson 2007). Bread, rice, pasta and potatoes are common examples. They provide minerals, vitamins and fiber, which should be present in the daily diet. A same rule is to avoid "white" color foods, because they are likely to have been machine-refined and dyed to look attractive. Dieters should avoid fat, not carbohydrates. Avoiding carbohydrates will eventually make the diet boring and develop craving for the sweets being avoided. Reducing carbohydrates intake also leads to a loss of fluid and electrolytes. Dizziness or fainting can also result. Eating too much of other nutrients at the sacrifice of carbohydrates will produce health problems. These include the formation of kidney stones, higher blood pressure and osteoporosis. Following this advice by experts will not only control or lose weight but keep it off long-term (Swanson).

Carbohydrates vs. Protein Supplements for Energy

Some believe that high-protein nutritional bars and drinks but with little carbohydrates would boost or support exercise or high-level performance (Parcell et al. 2005). But the combination will not provide the fuel needed by strenuous activity. It may even impair the performance. This was the finding of a research recently conducted on the glucose and insulin response to certain foods ingested by 12 non-diabetic students at a university. They were given a 50-g glucose feeding; white bagels, a high glycemic-index food; peanuts, a low glycemic food; a protein bar and a protein drink supplement. The study showed that an intake of commercial protein supplement produced a marked insulin response with no glycemic response. This was because of the lack of carbohydrates in the supplement. The study suggested that consumers take more caution in purchasing such supplements, which are often misleading and disadvantageous to them (Parcell et al.).

Carbohydrate Counting for Type 1 Diabetes

Advancements in insulin therapy are a boon to Type 1 diabetics. They may now successfully match their carbohydrate intake with insulin doses in imitating insulin production (Jenkins 2006). In the 80s, they were restricted to rigid meal plans with restricted carbohydrate apportionments. In the 90s, the emphasis was an increase in their awareness of how the diet could pose risks of heart disease and hypertension. But in the 2000s, new insulin therapies were introduced. These therapies offered patients a "more normalized" and flexible diet they can enjoy. Carbohydrate counting is, however, not a new concept. Shortly after the discovery of insulin, it was found that the total glucose value of a diet could determine insulin doses (Jenkins).

In the 80s, many healthcare professionals enforced the 10g "exchange" system (Jenkins 2006). It matched an inflexible twice-a-day insulin regimen with the apportionment of carbohydrates. Patients and professionals who wanted to live a varied and "normal lifestyle" frowned at the regimen. Accurate insulin dose changes were difficult to effect because of the inaccurate blood glucose testing systems in use at the time and the unpredictability of insulin then. Blood glucose testing systems of that decade also took a lot of time to operate. Interests in the 90s were on the glycemic index

Interest in the 90s turned to the glycemic index, which established the variability of blood glucose response to different carbohydrates. The assumption was that low glycemic index diets would improve the diet of Type 1 diabetics who were receiving soluble insulin treatment. Reduced heart disease risk and metabolic symptoms were linked with low glycemic diets. Unfortunately, healthy eating alone failed to improve their glycemic control (Jenkins).

But it was a different turn in the 2000s. New therapies of fast-acting insulin offer shorter duration of action (Jenkins 2006). These more closely mimic the body's natural glycemic response to different carbohydrate loads than did older insulins. Basal insulin regimens also allow patients to reach stable blood glucose levels regardless of meals and meal insulin. These recent developments not only allow patients to enjoy a more "normalized" and flexible diet. They also help them monitor their blood glucose levels more accurately. They are, thus, better able to make better self-management decisions. These elements comprise intensive insulin therapy (Jenkins).

The basic principle is that carbohydrates influence blood glucose levels (Jenkins 2006). But carbohydrate counting is part of the entire procedure of insulin dose adjustment and management of the blood glucose levels of Type 1 diabetics. The overall benefits from training and learning about diabetes are an increase in self-management skills and the confidence in choosing one's food and exercise (Jenkins).