Some nutrition experts consider carbohydrates beneficial and advise high levels of whole grain carbohydrate consumption. Others warn that carbohydrates are the very worst of foods and suggest we eat as few as possible. Whom do we believe—Pritikin or Atkins? Both diets rely on whole foods and keep the insulin level low. The modern Western diet is loaded with refined carbohydrates and processed grains that give us weight problems, cardiovascular disease, and diabetes, but the right carbohydrates can play an important role in supporting health. Most of us thrive on moderate consumption of unrefined healthy carbohydrates. But what are healthy carbohydrates?
When I first studied nutrition, more than twenty-five years ago, I was taught that simple carbohydrates (sugars) are unhealthy, and complex or long-chain carbohydrates (starches) are healthy. This view was simplistic and misleading. Instead of thinking in terms of simple or complex, we should consider a food’s effect on the blood sugar. What is the food’s glycemic index (GI) and glycemic load (GL)?
Glycemic index (GI) = speed at which a pure carbohydrate raises blood sugar
Glycemic load (GL) = glycemic index multiplied by the total carbohydrate in the food
Refined Grains and Blood Sugar
Until the last hundred years, humans ate complex carbohydrate from unrefined, coarsely ground or whole kernel grains and other whole plant sources. Unrefined bran from grain delays the absorption of glucose, improves elimination, and lowers cholesterol. Unrefined germ contains nutrients like essential fatty acids, protein, and vitamins E and B. Since most modern refining removes the bran and germ, we are left with low nutrient, high calorie grain products that make our blood sugar soar and crash. If we’re interested in good health and vitality, we can’t afford to eat these foods on a regular basis.
Let me sketch what happens when we eat a large helping of refined carbohydrates such as white bread or white rice:
1. The carbohydrate is quickly broken down and absorbed causing a fast rise in blood sugar
2. Insulin levels rise quickly and lower blood sugar by shunting the sugar out of the blood stream into fat cells, promoting fat storage (just what we always wanted!) and lowering circulating blood sugar
3. Low blood sugar is a threat to the body and results in a natural craving for more refined carbohydrates in order to raise the blood sugar as quickly as possible
4. In response to the raised blood sugar, the body produces high insulin levels again and the cycle repeats endlessly
5. The initial high blood sugar level caused by eating poor quality refined carbohydrates increases circulating fats in the blood stream and lowers beneficial high-density lipoproteins, increasing our risk for heart disease, as well as diabetes
When we eat unrefined whole plant food carbohydrates, like dried legumes, whole grains (except finely ground flours), most vegetables, and many fruits, the blood sugar rises only to healthy levels and holds steady, avoiding high and low blood sugar swings. These carbohydrates also replenish the muscle and liver carbohydrate (glycogen) we use when we exercise. A meal that includes quality carbohydrates after intense exercise quickly restores carbohydrate stores and spares the body from using protein (muscle) as fuel.
Glycemic Index and Glycemic Load
Glycemic index (GI) measures the speed at which a specific type of carbohydrate raises blood sugar. The glycemic index of a food is measured by testing how blood sugar reacts to the pure carbohydrate of that food when it is eaten alone. Of course we don’t eat pure carbohydrate, but eat it mixed with the protein, fat, and indigestible fiber in the food and the entire meal. If the pure carbohydrate portion of a food has a high GI, we consider the total amount of carbohydrate in that food to measure its glycemic load (GL). Then we can decide if its high GI is a problem. For example, the pure carbohydrate in carrots has a high GI, but carrots are fairly low in total digestible carbohydrate, so carrots have a low glycemic load (GL) and won’t disturb our blood sugar.
Eat, Drink, and Be Healthy by Walter Willett (Simon & Schuster Source, 2001, p. 90-91) has a chart showing GI and GL values for major carbohydrate sources. If you haven’t looked at a chart of glycemic index or glycemic load, you’ll find some surprises. Here’s the best GI and GL list I’ve found on the web. In any case, there’s no need to become obsessed about GI and GL levels in every bite we eat, but it helps to understand that a breakfast of bread or cold cereal will raise our blood sugar quickly and then give us an energy crash, while a bowl of cooked whole grain cereal with protein will sustain an even blood sugar level for hours.
Here is a list of factors that affect the glycemic index (GI) and glycemic load (GL) of foods:
- Type of carbohydrate: Our bodies digest different carbohydrates at different rates. For example, we break down the carbohydrate glucose very quickly, but fructose digests slowly and poorly. Since table sugar is half glucose and half fructose, its GI is about half way between the two. Some starches (as in white potatoes and instant rice) are broken down into glucose almost immediately in our bodies and raise our blood sugar levels quickly. Other starches (such as those found in lentils) are broken down slowly. We have to rely on charts to give us this information, because our taste buds aren’t reliable. Surprisingly, sucrose (table sugar) has a lower GI than potatoes. Both raisins and dates are sweet, but dates have a much higher GI.
- Fiber: More fiber in the food usually means a lower GI. Again, an unrefined grain has its fiber intact and digests more slowly, so it will tend to have a lower GI. Legumes like kidney beans, lentils, and soybeans have a low GI partly because of their fiber content (and they are good sources of protein).
- Size of the particles: Digestive enzymes quickly break down the carbohydrate in ground grains, so finely ground flour has a higher GI than the whole or coarsely ground grain. Coarsely ground whole corn meal has a moderate GI, but corn flakes made of finely ground whole corn flour are much higher. Whole grain brown rice has a moderate GI, but whole grain rice cakes, that favorite of the weight-conscious, are made of finely ground rice flour and have a high GI. White and whole wheat bread has a high GI (because the particular carbohydrate in wheat converts to glucose quickly) and GL (because bread is made almost entirely of finely ground easily digested particles). The finer the grind, the more easily digested the carbohydrate and the higher the blood sugar spike. For most grains, quicker cooking time means a higher GI.
- Fat and protein content: Fat mixed with the carbohydrate in the individual food or in the whole meal means a slower digestion time and lowers the GL. We naturally eat carbohydrates mixed with fats or proteins, thus reducing the total GL in a balanced meal. Ice cream has a lower GL than bread or potatoes, because the fat in ice cream slows digestion time. Candy bars high in fat often have a lower GL than 100% whole wheat bread, but of course this doesn’t make ice cream and candy healthy food choices.
- Water saturation: The more swollen the food particle is with water, the more digestible it is and the higher the GI. Grains of starch swell in cooking, so al dente (firmly cooked) pasta has a slightly lower GI than overcooked pasta. Orange juice carbohydrate, saturated in water, has a high GI while a whole fresh orange has a lower GI. Potatoes have highly swollen starch grains, and this adds to their high GI.
Of course it’s good to avoid meals dominated by white potatoes and white bread, but the GI effect of any food is moderated by the company it keeps. A few chunks of potato in a soup made primarily with barley, legumes, and vegetables won’t have a high glycemic effect. Chewy whole grain bread eaten with protein and fat (as in a sandwich or in a balanced meal) is unlikely to give you a blood sugar problem. As with all food, you have to find the balance of carbohydrates that makes you feel best, but my advice is to eat moderate levels of unrefined carbohydrates in mixed meals of whole foods.
- Eat steel-cut, cracked, or whole kernel grain cereals for breakfast. I cook coarsely cut grains (my favorite is Champlain Valley 7 Grain and Seed) in large batches, since they take longer to cook than oatmeal or other finely ground grains. It’s simple to re-heat a single serving in the morning for breakfast. Use whole grains such as brown rice and barley whenever you can. Look under recipes for whole grain cooking ideas, including breakfast cereals, breads, legumes (beans), and soups.
- If you’re interested in weight control, keep portion size small for all carbohydrates.
- Use dense, stone-ground, chewy 100% whole grain breads. It’s not easy to buy bread made with 100% whole grain stone ground flour and healthful oils. Most manufacturers use finely ground flour, plus hydrogenated oils to prolong shelf life. I make my own bread in a Zojirushi bread machine. The machine paid for itself in inexpensive loaves of delicious bread in 6 months, and it takes less than 5 minutes to put together the ingredients for a loaf. The machine does the rest.
- Even though whole wheat flour has a similar GI to white flour, it contains the nutrients and fiber that are refined out of white flour, so it’s a better choice. Experiment with whole wheat pasta. Also, experiment with using coarser stone-ground flours in recipes that don’t call for a light texture.
- Balance the high GL of whole grain breads with protein, legumes (like garbanzo or kidney beans), and good quality oils that delay digestion time.
- Eat winter squash and yams or whole grains instead of white potatoes.
- Avoid high levels of refined, processed carbohydrates, such as white bread products, corn syrup and sugar made from grapes or other fruits. These foods offer you little except calories and blood sugar fluctuations.
In general, you won’t go far wrong if you choose whole unrefined foods. It’s a pleasurable way to protect your good health.