The facts about good and bad carbs, and the glycemic index

Q. What exactly is the difference between good carbs and bad carbs?

In short, good carbs – or carbohydrates – are good for you. Bad carbs aren't.

Carbohydrates from white bread, white rice, pastries, sugared sodas, and other highly processed foods can make you fat. If you eat a lot of bad carbs, they increase the risk for disease.

Whole grains, beans, fruits, vegetables, and other similar sources of carbohydrates make you healthy by delivering vitamins, minerals, fiber, and many nutrients.

Carbohydrates are the most important source of energy for your body. Your digestive system changes carbohydrates into blood sugar (glucose). Your body uses up the glucose and stores any extra sugar for when you need it. A healthy diet should include good carbs.

Carbohydrates were once grouped into two main categories – simple and complex. Simple carbohydrates included sugars such as fruit sugar (fructose), corn or grape sugar (dextrose or glucose), and table sugar (sucrose). Complex carbohydrates included everything made of three or more linked sugars. Complex carbohydrates were thought to be the healthiest to eat. Now there are questions about that assumption.

A new system, called the glycemic index, classifies carbohydrates by how quickly and how high they boost blood sugar. Foods with a high glycemic index, like white bread, cause rapid spikes in blood sugar. Foods with a low glycemic index, like whole oats, are digested more slowly, causing a lower and gentler change in blood sugar.

Diets rich in foods with a high glycemic index have been linked to an increased risk for diabetes, heart disease, obesity, age-related macular degeneration, ovulatory infertility and colorectal cancer. Foods with a low glycemic index have been shown to help control diabetes and improve weight loss.

However, there have been other studies that have found the glycemic index has little effect on weight or health. More research into the glycemic index is needed.

You can't establish a diet by the glycemic index alone. Instead, use it as a general guide. In the meantime, eat foods with a low glycemic index: whole grains, beans, fruits, and vegetables.

The University of Sydney in Australia maintains an updated searchable database at www.glycemicindex.com.

Here are five quick tips about carb consumption from the Harvard School of Public Health:

• Start the day with whole grains. Try a hot cereal, like old-fashioned oats, or a cold cereal that lists a whole grain first on the ingredient list.

• Use whole-grain breads for lunch or snacks.

• Bag the potatoes. Instead, try brown rice, bulgur, wheat berries, whole-wheat pasta, or another whole grain with your dinner.

• Choose whole fruit instead of juice. An orange has two times as much fiber and half as much sugar as a 12-ounce glass of orange juice.

• Bring on the beans. Beans are an excellent source of slowly digested carbohydrates as well as a great source of protein.