What About Carbohydrates?

The Glycemic Load

The glycemic load is based on the glycemic index, a ranking of the effect on blood sugar of a fixed amount of a food compared with that of white bread or pure sugar. Either white bread or sugar is used for comparison because they both cause blood sugar to spike high very quickly. For menu-planning purposes, the glycemic load is more meaningful than the glycemic index because it is based on real-life portions of particular foods eaten throughout a day.

Foods with a high glycemic load are digested more quickly than foods with a low glycemic load (see Foods With Low Glycemic Load). Rapidly digested foods can be dangerous because they flood your bloodstream with sugar all at once. Sudden, high spikes of blood sugar trigger a gush of insulin to clear the sugar from your blood. The problem is that this quick surge of insulin can leave your blood sugar too low after just a few hours. When your blood sugar is too low, you feel hungry; if it's low soon after a meal, you're apt to overeat and possibly gain weight.

Another problem with a steady diet of meals high in glycemic load is that over many years, your body's system of responding to insulin could be impaired. This is called insulin resistance. When your cells are less responsive to insulin, the resulting overload of sugar in your bloodstream forces the pancreas to step up its production of insulin in an effort to move the sugar from the blood into the cells. If the pancreas is forced into overdrive for a sustained period, it may wear down and eventually stop producing insulin altogether, leading to insulin deficiency and type 2 diabetes — the more common type of diabetes, which typically develops in late adulthood. Insulin resistance can also cause other problems, including heart disease and perhaps some cancers.

Foods With Low Glycemic Load

Good Carbs, Bad Carbs

The high-carbohydrate foods that are good for you can help protect against these health problems in part because they have a relatively low glycemic load. They are digested slowly, which means they cause a gradual rise in blood sugar. You can estimate whether a carbohydrate is good or bad based on these characteristics:

Does the starch absorb liquid easily? The more a starchy food absorbs water and expands when cooked, the faster it is digested and the higher its glycemic load. White rice expands more than brown rice does. Potatoes (meaning white potatoes, russets, red potatoes, and others in this family) expand more than do sweet potatoes (which are not related to white-fleshed potatoes, despite their name). Pasta has a somewhat lower glycemic load because it is digested more slowly, especially if it is cooked al dente rather than overcooked until it is swollen and soft.

How heavily processed is the food? One factor in a grain product's glycemic load is its degree of refinement. In general, the smaller the pieces, the faster they are digested. This is one reason finely ground wheat flour is digested faster than coarsely ground (sometimes called "stone-ground") wheat flour. It's the same with steel-cut oats compared with instant oatmeal. Some scientists think that the glycemic load of the average American diet has increased because we're eating greater amounts of heavily processed carbohydrates. Processing removes the fibrous casing from grains. This casing is good for you because it slows digestion and contains a host of nutrients that may lower the risk of some diseases. Studies show that whole-grain foods such as brown rice and barley, which have their fibrous casing intact, are healthier than the more heavily processed refined grains. In results from two large ongoing studies, the Nurses' Health Study and the Health Professionals Follow-Up Study, people who ate the most whole grains (four slices of whole-wheat bread daily) were less likely than other people to develop type 2 diabetes, heart disease, and several types of cancer, including cancer of the mouth, stomach, colon, gallbladder, and ovary.

Is it really whole grain? Not all foods in the grocery store that claim to be "whole-grain" really are. "Whole-wheat" bread may include refined white flour. Look for labels that say "100 percent whole wheat" (or oats or rye). Read the ingredients list to make sure that the first ingredient is a whole grain. Some whole-grain foods can be easily spotted by their colour. Brown rice is a whole grain (it's brown because its casing is intact), but white rice isn't. Oats and oatmeal are whole grains with fibre, but oatmeal is usually processed for quick cooking, and that gives it a high glycemic load. The best choice is steel-cut oats or some less processed oatmeal.

How much fibre is in the food? Fibre is the indigestible part of grains, vegetables, and fruits. Its effect is to delay the time it takes for the food to be digested. Whole-grain foods have more fibre than refined foods.

How much fat is in a meal or snack? Because fats take longer to digest than carbohydrates, the more fat a meal or snack has, the more slowly it will be digested and, possibly, the less detrimental effect it will have on your blood sugar. Just make sure that the fat is one of the good fats. A handful of cashews or other nuts are a better snack than a cookie made with butter or trans fats.

Fibre: The Diet Workhorse

Fibre is a form of indigestible carbohydrate found mainly in plant foods. Over the years, fibre has been hailed as a potential weapon against colon cancer, high cholesterol, and heart disease. Fibre’s sterling reputation was tarnished by findings that it doesn't prevent colon polyps (precursors of colon cancer). But fibre slightly reduces LDL cholesterol, improves insulin resistance, and seems to be linked with a lower rate of heart disease. It is considered one of the most important health attributes of foods.

Fibre slows the digestion of foods and therefore lowers their glycemic load, possibly helping to prevent diabetes. By increasing the bulk of foods and creating a feeling of fullness, fibre may also help you avoid overeating and becoming overweight. There is also some evidence that fibre might reduce the risk for duodenal ulcers, breast cancer, and ovarian cancer. Studies such as the Nurses' Health Study and the Health Professionals Follow-Up Study have found that people with the lowest rates of heart disease and heart attack have the highest intakes of fibre. These studies formed the basis for the DRIs for fibre.

The DRI for fibre is 38 grams for men up to age 50 and 25 grams for women in this age group. For pregnant women, the DRI is 28 grams, and for lactating women, 29 grams. DRIs are lower for people over age 50: 30 grams for men, 21 grams for women. That's because older people tend to eat less food. On average, Americans eat only about 15 grams of fibre a day.

One of the main sources of fibre is cellulose, which comes from plants' tough cell walls. Cellulose can occur naturally in the foods you eat, or manufacturers can add it to foods in a powdered form during manufacturing. Pectin, another common fibre source, is a common ingredient in fruits. It is the substance that causes fruits to jell. Manufacturers often add pectins to foods to make them jell. Fibre can also take the form of supplements that you can buy over the counter. These fibre sources come in pills and powder forms and provide the same benefits as fibre in foods. Take them with plenty of water to get the full benefit.

You can probably identify some high-fibre foods, such as bran cereals and whole-grain bread. But not all foods billed as "high-fibre" really have much fibre; read the labels on packaged foods to see the number of grams of fibre they contain. You can be sure of getting fibre if you eat fruits, vegetables, and whole-grain foods such as whole-wheat bread, brown rice, and oats each day. Bran cereals are also a good choice. Here are some ways to make sure that your diet meets the DRI for fibre.

Eat whole-grain cereal for breakfast. Oatmeal is an excellent choice; steel-cut oats have the most fibre and the lowest glycemic index. If you prefer cold cereal, choose products that contain bran or list whole wheat, oats, barley, or another whole grain first on the list of ingredients.

Choose whole-grain breads. As with cereals, true whole-grain breads list a whole grain first in the ingredients. Whole-grain sliced bread, pita bread, and rolls are equally good.

Skip the french fries and baked potatoes. Instead of white potatoes, eat sweet potatoes or yams. Instead of white rice, eat brown rice or another intact grain as a side dish. Good choices are kasha, bulgur, millet, quinoa, and barley.

Try whole-wheat pizza and pasta. Prepared pizzas made with whole-wheat crust are joining whole-wheat pastas on supermarket shelves. Whole-wheat pasta is a great choice, but if it doesn't appeal to you, try mixing whole-wheat pasta with white pasta.

Cook with whole-wheat flour. You can make breads, muffins, and other home-baked goods healthier if you mix whole-wheat flour with white flour. Because whole-wheat flour is heavier than white flour, a straight substitution won't work for every recipe. Try starting with a ratio of one part whole wheat to three parts white to see if you like the results. If you think the dish could stand a heavier, grainier texture, try increasing the share of whole-wheat flour. You may need to increase the amount of liquid at the same time. Many stores sell a multigrain pancake mix you can use for pancakes or waffles.