Carbohydrates are organic compounds composed of carbon, hydrogen and oxygen. There are two types of carbohydrate: simple and complex.

Simple (sugar)

Monosaccharides - one sugar molecule (glucose, fructose, galactose)

Disaccharides - 2 sugar molecules linked
> Sucrose = glucose + fructose (table sugar)
> Maltose = glucose + glucose
> Lactose = glucose + galactose

Complex (starch, fiber, glycogen)

Polysaccharides - chains of single sugar molecules

The Process

All digestible carbohydrate are broken down to single sugar molecules by digestive enzymes. Salivary amylase is secreted in the mouth to begin digestion. Then in the intestine, digestion is completed by pancreatic amylase and intestinal dissacharidases. After the single sugar molecules pass through the intestinal wall to the blood stream, they travel to the liver where most fructose and galactose are transformed into glucose. When glucose leaves the liver and returns to the blood stream, the hormone insulin helps glucose enter the cells to be used for energy. Glucose that is not used immediately for energy is stored temporarily as glycogen in the liver and muscles, then released later between meals.

Carbohydrates in Our Bodies

Per current recommendations, carbohydrate should make up 45 to 65 percent of our daily intake. Sources are grains, starchy vegetables, fruits, dairy foods, dried beans, desserts and most snack foods. Carbohydrate is the most readily available source of energy, and glucose is the exclusive source of energy for red blood cells and the brain and central nervous system.

Eating adequate carbohydrate spares protein from being used for energy so it can be used to build and repair body tissue. Hypoglycemia, or low blood glucose, may result from inadequate intake of carbohydrate. Symptoms include extreme fatigue, weakness, irritability and mental confusion. In this situation, to maintain normal blood sugar levels, glycogen stores will first be used up. Then, body protein from muscles is broken down and converted to glucose causing muscle wasting.

In addition, when carbohydrates are severely restricted and since fat cannot be used for energy by some parts of the body, normal fat metabolism is altered and ketone bodies are produced to be used for energy. An excess of ketone bodies lowers blood pH, a condition called ketoacidosis which can be fatal. Low carbohydrate diets can also lead to an increased risk of heart disease, cancer, high blood pressure, kidney stones and osteoporosis.

Carbohydrates and Weight

Carbohydrates do not lead to weight gain, and low carbohydrate diets are not effective for weight management. In fact, glucose helps us know when to stop eating by stimulating insulin production. However, fructose does not have the same effect on insulin which is why some people question use the of high fructose corn syrup. All told, the verdict is just not in yet.

Another controversy concerns artificial sweeteners. Although they can be beneficial for people with diabetes, there is some evidence that for non-diabetics they can interfere with the ability to regulate food intake and increase setpoint weight.

Speaking of diabetes, people sometimes have heard that eating sugar causes diabetes. This is not true. Diabetes is a genetic disorder. However, it is important to balance carbohydrate with protein and fat at meals if you are diabetic (but that’s true for us all, actually). A higher weight also does not cause diabetes although the same genetic factors that lead to diabetes may predispose someone to being a higher weight.

Regarding glycemic index (a measure of the effects of carbohydrates on blood sugar levels), it is probably more important to just make sure you have adequate fiber in your diet. Fiber is an indigestible form of carbohydrate that is found in two forms, soluble and insoluble. In some studies that suggested high glycemic index carbohydrates increased diabetes risk; the risk disappeared with adequate fiber. Whole grains, dried beans, fruits and vegetables are all good sources of fiber.

Hope this has helped you understand carbohydrate a little better. Feel free to share your questions and comments in the section below!

Since 1990 registered dietitian Deborah Kauffmann, RD, LDN has been providing nutrition counseling for disordered eating utilizing an intuitive, Health At Every Size® approach. Deborah works with adults, teens and children/parents. She is one of the pioneers of the HAES (SM) approach in the Baltimore area. Deborah also offers Largely Positive, a free support group for adults of size promoting size acceptance and self care. Her private practice is Nutrition Counseling for Intuitive Eating.