Diabetes Diet

Why Do People with Diabetes Require Special Diets?

The two major forms of diabetes, type 1 and type 2, share a central feature: elevated blood sugar levels due to absolute or relative insufficiencies of insulin, a hormone produced by the pancreas. Insulin is a key regulator of the body's metabolism. After meals, food is digested in the stomach and intestines; carbohydrates are broken down into sugar molecules, of which glucose is one, and proteins are digested into their constituents, amino acids. Glucose and amino acids are absorbed directly into the bloodstream, and blood sugar levels rise. Normally, this signals the beta cells of the pancreas to secrete insulin, which pours into the bloodstream. Insulin, in turn, enables glucose and amino acids to enter cells -- importantly, muscle cells -- where, along with other hormones, it directs whether these nutrients will be burned for energy or stored for future use. As blood sugar falls to pre-meal levels, the pancreas reduces the production of insulin, and the body uses its stored energy until the next meal provides additional nutrients.

In type 1 diabetes, also known as insulin-dependent or juvenile-onset diabetes, the cells in the pancreas that produce insulin, known as beta cells, are gradually destroyed; eventually insulin deficiency is absolute. Without insulin to move glucose into cells, blood sugar levels become excessively high, a condition known as hyperglycemia. The sugar, which the body cannot use without insulin, spills over into the urine and is lost. Weakness, weight loss, and excessive hunger and thirst are among the consequences of this "starvation in the midst of plenty". Patients become dependent on administered insulin for survival. Dietary control is very important and must focus on balancing food intake with insulin intake and energy expenditure from physical exertion.

Type 2 diabetes, also known as noninsulin-dependent or maturity-onset diabetes, is by far the more common type of diabetes. Most type 2 diabetics produce variableeven normalamounts of insulin, but are insulin resistant; that is, they have abnormalities in liver and muscle cells that block its action. Many type 2 diabetics, however, seem to be incapable of secreting enough insulin to overcome this resistance; it is likely in such cases that there is an additional defect in insulin secretion by the beta cells. Obesity is common in type 2 diabetics and this condition appears to be related to insulin resistance. The primary goal for overweight type 2 patients is weight loss and maintenance.

People with both types of diabetes are at risk for a number of medical complications, including heart and kidney disease. Dietary requirements for diabetes must take these disorders into consideration.

What Are the General Guidelines for a Diabetes Diet?

General Goals

For most people with diabetes, diet control is the key to managing this complicated disease. It is also extremely difficult. The current state of the diabetic diet is in flux, and at this time, there is no single diet that meets all the needs of everyone with diabetes. There are some constants, however. All people with diabetes should aim for healthy lipid (cholesterol and triglyceride) levels and control of blood pressure. People with type 1 diabetes and type 2 diabetics on insulin or oral medication must focus on controlling blood glucose levels by coordinating calorie intake with medication or insulin administration, exercise, and other variables. Adequate calories must be maintained for normal growth in children, for increased needs during pregnancy, and after illness. For overweight type 2 diabetics who are not taking medication, both weight loss and blood sugar control are important. A reasonable weight is usually defined as what is achievable and sustainable, rather than one that is culturally defined as desirable or ideal. And the general rules for healthy eating apply to everyone: limit fats (particularly saturated fats and transfatty acids), protein, and cholesterol, and consume plenty of fiber and fresh vegetables. Patients should meet with a professional dietitian to plan an individualized diet that takes into consideration all health needs.

Monitoring

In patients being treated with insulin or insulin-producing or sensitizing drugs, it is important to monitor blood glucose levels carefully to avoid hypoglycemia. Patients should aim for premeal glucose levels of between 80 and 120 and bedtime levels of between 100 and 140. Current intensive treatment for type 1 diabetes to tightly control blood sugar levels usually requires four or more daily blood sugar tests. Blood glucose levels are generally more stable in type 2 diabetes than in type 1, so experts usually recommend measuring blood levels only once or twice a day. Other tests are needed periodically to determine potential complications of diabetes, such as high blood pressure and kidney problems. Such tests may also indicate whether current diet plans are helping the patient and whether changes should be made. Glycolated hemoglobin (hemoglobin A₁) is measured periodically. Levels of 11% to 12% glycolated hemoglobin, for instance, indicate poor control of carbohydrates. High levels also indicate future kidney problems and the need to lower protein intake. Annual urine tests showing even microscopic traces of a protein known as albumin can also indicate a future risk for serious kidney disease. Blood pressure and lipid levels should also be regularly monitored.

Preventing Hypoglycemia (Insulin Shock)

For prevention of long-term complications of diabetes, experts are now recommending that both type 1 and type 2 patients should aim at keeping blood levels as close to normal as possible. Such intensive insulin treatment increases the risk of hypoglycemia, which occurs when blood sugar is extremely low (below 60 mg/dl). Diabetic patients should always carry hard candy, juice, or sugar packets. Family and friends should be aware of the symptoms. If the patient is helpless, they should administer three to five pieces of hard candy, two to three packets of sugar, or half a cup (four ounces) of fruit juice. If there is inadequate response within 15 minutes, additional oral sugar should be provided or the patient should receive emergency medical treatment including the intravenous administration of glucose. Family members and friends can learn to inject glucagon, a hormone, which, unlike insulin, raises blood glucose.

Other Factors Influencing Diet Maintenance

Food Labels. Every year thousands of new foods are introduced, many of them advertised as nutritionally beneficial. It is important for everyone, most especially people with diabetes, to be able to differentiate advertised claims from truth. The current food labels show the number of calories from fat, the amount of nutrients that are potentially dangerous (fat, cholesterol, sodium, sugars) as well as useful nutrients (fiber, carbohydrates, protein, vitamins). They are not required to show trans-fatty oils. If a label lists partially hydrogenated oil as an ingredient, then the produce contains trans-fatty oils. Unfortunately, these oils are categorized as unsaturated fats and not broken out separately. Labels also show "daily values" -- the percentage of a daily diet that each of the important nutrients offers in a single serving. Unfortunately, the daily value is based on 2,000 calories, generally much higher than most diabetics should have, and the serving sizes may not be equivalent to those on the Exchange Lists. Most people will need to recalculate the grams and calories listed on food labels to fit their own servings sizes and calorie needs.

Weighing and Measuring. Weighing and measuring food is extremely important in order to get the correct number of daily calories. Most foods and nutrients are measured in grams. A gram is very small, about 1/28th of an ounce. Food is weighed and measured after cooking it. It is important to have a food scale along with measuring cups and spoons. Scales to measure grams can be found in gourmet stores and medical supply stores. After measuring all foods for a week or so, most people can make fairly accurate estimates without having to measure everything every time they eat.

Timing. The timing of meals is particularly important for people taking insulin; the types and amounts of food as well as meal and snack times must be carefully determined so that blood glucose levels are properly regulated. In general, people with type 1 diabetes should eat about 30 minutes after taking an insulin injection. Three meals should be eaten each day at regular intervalsabout four to five hours apart. Snacks are often needed, but they should be included as part of the total daily calorie requirements. One study of type 2 patients reported that large dinners raise fasting blood glucose levels the next morning, which may affect some patients.

What Are the Guidelines for Major Food Components in a Diabetes Diet?

Carbohydrates

Compared to fats and protein, carbohydrates have the greatest impact on blood sugar, but different carbohydrates have different effects. Carbohydrates are either complex (as in starches) or simple (as in fruits and sugars). One gram of carbohydrates equals four calories. Although the current recommendation is that carbohydrates should provide between 50% and 60% of the daily caloric intake, the high-carbohydrate low-fat diet has recently come under scrutiny. Type 2 diabetics who tend to be overweight and insulin-resistant overproduce glucose after carbohydrate intake, which in turn requires more insulin to process it. This leads to appetite stimulation and production of fat. Some diabetics may have problems with cholesterol and triglyceride levels when carbohydrates constitute over 50% of the diet. If triglycerides are high, carbohydrates should be reduced to 45%.

In all cases, complex carbohydrates found in whole grains and vegetables are preferred over those found starches -- such as pastas, white-flour products, and potatoes. In one study, substituting special starch-free bread for normal bread resulted in a significant decline in blood glucose and hemoglobin A1 in type 2 diabetes.

No difference appears to exist between complex carbohydrates and simple sugars in their ability to raise blood glucose levels and in diets. This does not mean that diabetics should increase their sugar intake, but it indicates that people with diabetes can add fresh fruit to their diets, which have significant health benefits, in higher amounts than previously thought. Sugar from fruit (fructose) produces a slower increase in glucose than sucrose (table sugar). Sugar itself adds calories and increases blood glucose levels quickly. It provides no nutrients. One study also found that sugar was risk factor for heart disease, possibly because sugar produces very low density lipoproteins and triglycerides, which are dangerous for the heart. People with diabetes should avoid products listing more than 5 grams of sugar per serving. If specific amounts are not listed, patients should avoid products with sugar listed as one of the first four ingredients on the label.

Artificial sweeteners include saccharin, aspartame (Nutra-Sweet), and acesulfame K (Sweet One). Sucralose (Splenda), a new sweetener, may also prove to be a good alternative to sugar. It usually leaves no bitter aftertaste and, unlike most other artifical sweeteners, it works well in baking. Dozens of animal studies and some human trials conducted over 15 years have found no health hazards. Early studies found that large amounts of saccharin cause cancer in rats, but these findings do not apply to humans. Aspartame has come under scrutiny because of rare reports of neurologic disorders, including headaches or dizziness, associated with its use. Concern about an association between an increased rate of brain cancer and widespread use of aspartame is unfounded. Brain cancer rates were on the rise before the introduction of aspartame and are now leveling off, although aspartame use is rising dramatically.

Protein

Proteins should provide 12% to 20% of calories. One gram of protein contains four calories. Studies are showing that reducing proteins in the diet helps slow the progression of kidney disease in both diabetics and nondiabetics. Some experts recommend that anyone with diabetes other than pregnant women should restrict protein to about 0.4 grams for every pound of their ideal body weightabout 10% of daily calories. It should be noted that, although it is a very rare occurrence, a severely low-protein low-salt diet coupled with high fluid intake increases the risk for hyponatremia, a condition that can cause fatigue, confusion, and, in extreme cases, can be life-threatening.

Fats and Oils. It is generally advised that total fats should provide no more than 30% of the diet, with saturated fats at a 10% maximum. People with heart disease, with high levels of low-density lipoprotein (LDL) cholesterol, or those trying to lose weight should reduce total fat to 20% to 25% of their caloric intake with no more than 7% from saturated fats. They should also keep their daily cholesterol intake below 200 milligrams. African American women appear to be specifically vulnerable to harm from saturated fats, including being more at risk for insulin resistance than non-African American women.

Saturated fat should be avoided whenever possible. Although mostly derived from animal products, saturated fat is also found in a number of tropical oils -- palm, coconut, and cocoa butter. People with diabetes should avoid fried foods. Fish and poultry with the skin removed are preferable to red meat. Cutting out cold cuts, gravy, and eating low-fat or skim milk cheeses help to reduce saturated fat intake.

Other culprits for heart disease risk are trans-fatty acids -- vegetable oils that have been hardened through a process of hydrogenation. Some reports indicate they may even have a worse effect on cholesterol than saturated fats, because they not only increase harmful LDL cholesterol levels but they also reduce the beneficial HDL levels. Hydrogenated fats are contained in stick margarine, shortening, and many fast foods and baked goods, including most white breads. When buying margarine, look for the liquid tub form made from poly- or monounsaturated fats.

The press has produced conflicting reports on the benefits of monounsaturated fats (found in olive oil, canola oil, some nuts, and avocados) versus polyunsaturated fats (present in sunflower oil, safflower oil, soybean oil, and corn oil). At this time, they appear to have similar beneficial effects on lipid levels. Some studies have found improved triglyceride levels and no difference in glucose control with diets high in monounsaturated oils compared with those high in carbohydrates. Calorie intake was the same for both diets. Nut oils, such as peanut oils, may be particularly beneficial. More studies are needed on the benefits of diets high in monounsaturated fats versus the risk for weight gain in type 2 diabetics. Fish oil, which contains an important compound called omega-3 fatty acid, may improve triglyceride levels. Studies have indicated, however, that fish oil is associated with an increase in blood sugar, and a number of studies have found no overall benefit to the heart from fish oil supplements. (Eating fish itself at least twice a week, however, appears to offer many health benefits.)

One teaspoon of any kind of fat, whether it's olive oil or butter or lard, equals about five grams, or 45 calories. (One gram of all types of fat is equal to 9 calories.) Fat substitutes are also available or in development. One of these, olestra, is made from sugar and vegetable oil and is passed from the body without leaving any calories from fat behind. (It should be noted that foods containing this substance -- usually snacks -- still have calories from carbohydrates and proteins.) Some people have experienced cramps and mild to severe diarrhea after eating olestra. The fat substitute also depletes the body of vitamins A, K, D, and E and also possibly cancer-fighting nutrients. Manufacturers must now add back vitamins but not important nutrients, such as carotenoids.

Fiber

Fiber is an important dietary component in the fight for a healthy cholesterol balance and is found in vegetables, fruits, and whole grains. Fiber cannot be digested but passes through the intestines, drawing water with it, and is eliminated as part of feces content. Recent studies on both men and women reported that diets rich in fiber from whole grains reduce the risk for type 2 diabetes. Fiber is also good for the heart. High-fiber diets (up to 55 grams a day) help improve cholesterol levels, control weight, and improve blood glucose and insulin levels. Fiber also helps prevent certain cancers and many intestinal problems. For weight loss, insoluble fiber (found in wheat bran, whole grains, seeds, and fruit and vegetable peels) is most effective. Soluble fiber (found in dried beans, oat bran, barley, apples, citrus fruits, and potatoes), however, has important benefits for the heart, particularly for lowering blood cholesterol level. People who increase their levels of soluble fiber should also increase water and fluid intake. Psyllium, a grain naturally found in India, is an excellent soluble fiber supplement (Metamucil, Fiberall, Perdiem).

Specifically Healthful Whole Grains, Fruits, and Vegetables

The best sources of dietary fiber, soluble or insoluble, are obtained from whole grains (particularly oats), nuts, legumes, fruits, and vegetables. Such foods also provide many other health benefits. One study, for example, reported that oat-rich diets reduced blood pressure and cholesterol levels significantly better than wheat-rich diets. In one study of 22,000 male physicians, those who ate nuts had the lowest rate of heart disease. Other studies indicate that nuts improve cholesterol levels and may even inhibit tumor growth. Its benefits may derive from a fatty compound called alpha-linolenic acid and from other plant chemicals. (Nuts, unfortunately, are also high in calories.). Pectin, a type of fiber found in apples, grapefruits, and oranges, may also protect against heart disease. Deeply colored green, red, and yellow fruits and vegetables are rich in important antioxidant vitamins and plant chemicals (phytochemicals). Soy, found in soybeans, tofu, and soy milk, deserves special mention. Soy products seem to have major benefits for older people and those with type 2 diabetes. Some studies have found that eating 20 to 25 grams a day (about 5 to 6 ounces of firm tofu) helps maintain healthy cholesterol levels and may also lower the risk for kidney disease and certain cancers. To reduce the gas and bloating accompanying high fiber intake, drink at least 8 glasses of water a day and use enzymes (Beano, Say Yes to Beans) that help digest fiber. (Such products have no effect on gas produced from allergies to milk products.) When preparing dried peas or beans, soak them overnight, then rinse them and discard this water before cooking.

Vitamins and Other Nutrients

Antioxidant Properties. Currently, many researchers are studying vitamins and other nutrients for their role as antioxidants, which are scavengers of particles known as oxygen-free radicals. These unstable particles are by-products of many of the body's normal chemical processes and are increased by smoking, environmental toxins, and stress. They can damage cell membranes and interact with genetic material, possibly contributing to the development of a number of disorders including cancer, heart disease, and complications of diabetes -- including blindness, kidney failure, and amputation. Antioxidants act as scavengers to help mop up these free radicals. Vitamins C, E, and A are powerful antioxidant vitamins currently under investigation. They may also have specific effects on diabetes.

Vitamin E. Vitamin E is one of the important antioxidants. It may help prevent blood clots and coronary artery disease -- two major factors in heart attacks. Vitamin E may also offer some protection against beta-cell deterioration in diabetes type 1 and help counteract the nerve damage that occurs in diabetes. Actual evidence of its beneficial effects on the heart are uncertain, however. In some cases, positive results in patients who consumed high amounts of vitamin E may have been due to a generally healthy diet that contained a team of healthy nutrients, including vitamin E. At this time, some experts are recommending 65 to 260 mg (100 to 400 IU) a day. High doses of vitamin E may increase the risk for hemorrhagic stroke, although the risk is very small.

Vitamin C. Evidence for the heart-protective value of vitamin C, another major antioxidant vitamin, has been even more inconclusive. Some studies have found some benefits against stroke but not heart disease. Others have linked vitamin-C deficiencies with a higher incidence of angina, heart attack, and death from heart-related disorders. One study reported that patients with diabetic nephropathy (kidney damage) had vitamin C deficiencies. Such findings, however, do not prove that taking extra vitamin C protects patients against these conditions. In fact, some studies indicate the vitamin C acts as pro-oxidant in high doses, and everyone is cautioned against taking excessive doses.

B Vitamins. B vitamins are important for a healthy heart and one may have specific benefits for diabetes. Deficiences in the B vitamins folic acid, B6, and B12 result in elevated blood levels of an amino acid homocysteine, which is now considered a risk factor for coronary artery disease. Studies further indicate that taking these vitamins can decrease homocysteine levels. It is not yet clear, however, that reducing homocysteine levels will actually protect against heart disease. Another important B vitamin for people with diabetes is niacin (Vitamin B3), which has special benefits for patients with unhealthy cholesterol levels. Nicotinamide, a derivative of vitamin B3, also may protect beta-cells from the damaging inflammatory processes triggered by the immune system.

Minerals. Magnesium deficiency may have some role in insulin resistance and high blood pressure, but no supplements are recommended unless a patients is found to have low levels of this mineral. For people taking diuretics for high blood pressure, extra potassium may be needed, but in other cases, including certain kidney problems, an overload of potassium may occur, so no regular supplements are recommended without consulting a physician. Chinese studies have indicated that the mineral chromium may help control diabetes, but experts say the study population may not apply to Western groups and it is not clear whether the subjects were deficient in chromium to begin with. Many type 2 diabetics are also deficient in zinc; more studies are needed to establish the benefits or risks of taking supplements. Zinc has some toxic side effects, and some studies have associated high zinc intake with prostate cancer.

Sodium. Salt can raise blood pressure, and people with diabetes should limit salt intake, particularly if they have hypertension. A major on-going study of salt intake has found evidence that diets high in salt accelerate hypertension as people age. People who are most likely to be very salt-sensitive are generally overweight, older, African American, and those who have low levels of renina hormone that prevents reduction of blood pressure. In addition to helping to reduce blood pressure, salt restriction enhances the benefits of certain antihypertensive drugs by reducing potassium loss. One study showed that diets with very low salt intake helped protect against kidney disease in patients who were also taking calcium-blocker drugs for high blood pressure. Possibly even more important, one study found that salt restriction reduced levels of protein in the urine (albuminuria) of diabetic rats. Albuminuria is an indicator of kidney damage. About 75% of consumption of sodium and salt in Europe and the U.S. comes from commercially processed foods. New labels on foods now indicate amounts of sodium, and less salty commercially prepared foods are becoming increasingly available. Salt substitutes containing mixtures of potassium, sodium, and magnesium are now available. Of note is a study that found an increased rate of heart attacks in people with very restrictive low-salt diets; some sodium may be needed to protect the heart. Even simply eliminating table salt can be beneficial.

Caffeine and Alcohol

Alcohol. Wine appears to have some health benefits if used in moderation (one or two glasses a day). In those taking insulin or sulfonylureas, however, alcohol may cause a hypoglycemic reaction, of which the drinker may not be aware. Pregnant women or those at risk for alcohol abuse should not drink alcohol.

Caffeine. A review of life-time records of male medical students found that by age 60, 19% of noncoffee drinkers had high blood pressure and 25% of coffee drinkers were hypertensive. Caffeine may have greater effect in people who already have elevated blood pressure. Drinking coffee increases excretion of calcium, which in turn may increase the risk for high blood pressure, so anyone who drinks coffee should maintain an adequate calcium intake. Studies have indicated that unfiltered coffee may increase levels of LDL (the so-called bad cholesterol) and alanine-aminotransferase (an indicator of liver damage). (Filtered coffee poses no such risk.)

What Are the Specific Diabetic Diet Methods?

Anyone who has diabetes needs some diet plan. One 18-month study of people with type 2 diabetes found no difference between a high-carbohydrate/high-fiber diet, a low-fat diet, and a weight management diet; all groups, however, experienced lower glycolated hemoglobin levels and lower LDL cholesterol levels. There were no changes in HDL cholesterol or triglycerides. The researchers concluded that the positive benefits of the diets derived not from the specific regimens, but because the people in the study were attentive and focused. In other words, any diet works if patients work at it. Choosing a healthy diet and then making the effort are the primary requirements for successful control of blood glucose levels.

Several dietary methods are available for controlling blood sugar levels. The simplest method is to follow the Food Guide Pyramid, recommended by the government for everyone. Some experts believe this may be sufficient for many people with diabetes. More intricate dietary methods are available for control of blood sugar. They can be effective, but they are also complex and many patients become discouraged using them. The most common method for controlling blood sugar is the use of The Diabetic Exchange Lists, designed by the American Diabetic and American Dietetic Associations. More sophisticated methods include counting carbohydrate grams and adjusting them according to blood glucose levels and tabulating the total available glucose (TAG) derived from foods that are eaten. Counting calories is usually the basis for weight loss. If one of these methods works in controlling glucose levels, there is no reason to choose another. Each of them can be effective, but because regulating diabetes is an individual situation, everyone with this condition should get help from a dietary professional in selecting the best method. For instance, a type 2 diabetic who is overweight and insulin-resistant may need to have a different carbohydrate-protein balance than a thin type 1 diabetic in danger of kidney disease.

Weight Control

Weight control is an especially important part of the management of type 2 diabetes. Health benefits are highest with the first pounds lost, and losing only 10% of body weight can control progression of diabetes type 2. Weight loss can be gradual -- about one pound per week. The first step is to calculate the daily caloric need for maintaining a healthy weight. This is typically 12 to 15 calories for each pound of ideal body weight, but it varies depending on gender, age, and whether a person is active or sedentary. As a rough rule of thumb, one pound of fat equals about 3,500 calories, so one could lose a pound a week by reducing daily caloric intake by about 500 calories. Naturally, the more severe the daily calorie restriction, the faster the weight loss. Many dietitians recommend avoiding the scale during dieting; weighing oneself daily is self-defeating and even looking at the scale once a week may be discouraging.

Some studies suggest that replacing foods high in fats and sugars with low-fat complex carbohydrates (fruits, vegetables, and whole grains) may be more effective for weight control than calorie counting. In a one-year study, those on low-fat diets lost three times as much weight as those on a standard low-calorie diets. Very low-fat diets however (15% or less of daily calories) may increase triglycerides and reduce HDL cholesterol levels -- risk factors for heart disease. Many people who reduce their fat intake may also not consume enough of the basic nutrients, including vitamins A and E, folic acid, calcium, iron and zinc, and they often increase their intake of carbohydrates. People on low fat diets should consume a high variety of foods and take a multivitamin if appropriate. Simply switching to low-fat or skimmed milk may help people achieve the recommended dietary goal of 30% or fewer calories from fat and also help provide calcium. Some dietary fat is essential; such fats should be derived from non-tropical plant oils and fish. All healthy diets should also be high in fiber, which studies are reporting to be an important weight loss-factor.

Meals should not be skipped, particularly for those who are on insulin. Skipping meals can upset the balance between food intake and insulin and also can lead to weight gain if extra food is needed too often to offset low blood sugar levels.

Up to one third of young women with type 1 diabetes have eating disorders that prompt them to underdose insulin to lose weighta very hazardous practice. Healthy eating habits along with good insulin control are essential in managing this complex disease.

Food Guide Pyramid and Mediterranean Diet

The food guide pyramid contains the U.S. Department of Agriculture's general nutritional guidelines, but it has some problems. Some nutritional experts have recommended modifying it to adapt to the so-called Mediterranean diet. A recent study of heart attack patients found that those on the Mediterranean diet had a 76% lower risk of for major adverse cardiovascular events, including subsequent heart attacks, unstable angina, and stroke compared to those on a normal diet. Although the study does not constitute proof for the superiority of the Mediterranean diet, it does lend additional support to that possibility. Research indicates that it is not a single food but the spectrum of foods in this diet that has the benefits. The table below indicates the differences. Of some concern with the Mediterranean diet are added calories from the high intake of olive oil, reduced iron levels, and possible lack of calcium from fewer dairy products. Experts recommend that those who choose the Mediterranean diet should use only olive oil (no margarine or butter even on bread) to avoid excess fat. They should cook in iron pans and eat foods that contain iron and those rich in vitamin C, which boosts iron intake. They might need a calcium supplement. The recommendation of wine may be problematic for some people with diabetes and for anyone who is pregnant or abuses alcohol. In addition, all people with diabetes who have indications of kidney damage should restrict protein below the intake of the general population.

Diabetic Exchange Lists

The diabetic exchanges are six different lists of foods grouped according to similar calorie, carbohydrate, protein, and fat content; these are starch/bread, meat, vegetables, fruit, milk, and fat. The objective of the exchange lists is to maintain the proper balance of carbohydrates, proteins, and fats throughout the day. The Exchange Lists can be obtained by calling or writing the American Diabetes Association.

In developing a menu, patients must first establish with a doctor or dietitian their individual dietary requirements, particularly the optimal number of daily calories and the proportion of carbohydrates, fats, and protein. A person is allowed a certain number of exchange choices from each food list per day. The amount and type of these exchanges are based on a number of factors, including the daily exercise program, timing of insulin injections, and whether or not an individual needs to lose weight or reduce cholesterol or blood pressure levels. The exchange lists should then be used to set up menus for each day that fulfill these requirements. Foods can be substituted for each other within an exchange list but not between lists even if they have the same calorie count. In all lists, except in the fruit list, choices can be doubled or tripled to supply a serving of certain foods (e.g., 3 starch choices equal 1 1/2 cups of hot cereal or 3 meat choices equal a 3-ounce hamburger). On the exchange lists, some foods are "free". These contain less than 20 calories per serving and can be eaten in any amount spread throughout the day unless a serving size is specified. The following are the categories given on the exchange lists:

Starches and Bread. Each exchange under starches and bread contains about 15 grams of carbohydrates, 3 grams of protein, and a trace of fat for a total of 80 calories. A general rule is that 1/2 cup of cooked cereal, grain, or pasta equals one exchange and one ounce of a bread product is one serving.

Meat and Cheese. The exchange groups for meat and cheese are categorized by lean meat and low fat substitutes, medium-fat meat and substitutes, and high-fat. High fat exchanges should be used at a maximum of 3 times a week. Fat should be removed before cooking. Exchange sizes on the meat list are generally one ounce and based on cooked meats (3 oz of cooked meat equals 4 oz of raw meat).

Vegetables. Exchanges for vegetables are 1/2 cup cooked, 1 cup raw, and 1/2 cup juice. Each group contains 5 grams of carbohydrates, 2 grams of protein, and between 2 to 3 grams of fiber. Vegetables can be fresh or frozen; canned vegetables are less desirable because they are often high in sodium. They should be steamed or microwaved without added fat.

Fruits and Sugar. Sugars are now included within the total carbohydrate count in the exchange lists. Sugars still should not be more than 10% of daily carbohydrates. Each exchange contains about 15 grams of carbohydrates for a total of 60 calories.

Milk and Substitutes. The milk and substitutes list is categorized by fat content similar to the meat list. A milk exchange is usually one cup or 8 oz. For those who are on weight-loss or low-cholesterol diets, the skim and very low-fat milk lists should be followed, and the whole milk group avoided. Others should use the whole milk list very sparingly. All people with diabetes should avoid artificially sweetened milks.

Fats. A fat exchange is usually 1 teaspoon but it may vary. People, of course, should avoid saturated and trans-fatty acids and choose polyunsaturated or monounsaturated fats instead.

Carbohydrate Counting and Blood Glucose Control

Of the nutrients, carbohydrates have the greatest impact on blood sugar; fats and protein play only minor roles. If all other dietary methods fail, carbohydrate counting may be beneficial, but it is very complex and requires the collaboration of the physician. This technique relies on knowing the number of carbohydrate grams needed during the day, how to calculate them from food, and how rapidly different foods increase blood sugar levels. Multiple blood sugar readings are taken over a few days to determine the daily insulin requirements that will keep blood sugar balanced. A special calculation is then made for the number of carbohydrate grams that are covered by that daily insulin dose. The next step is to find the number of carbohydrates in foods, so that the right amount can be eaten to balance insulin. Commercial foods are labeled with carbohydrate amounts and for other foods, a number of books are available that provide the percentage of carbohydrates to the total nutrients.

In general, one gram of carbohydrate raises blood sugar by 3 points in people who weigh 200 pounds, 4 points for weights of 150 pounds, and 5 points for 100 pounds. Patients must choose not only the appropriate amount of carbohydrates needed to raise glucose levels, however, but they must also know which carbohydrate-containing foods will raise blood sugar within a desired time frame. For instance, foods with fast carbohydrates may be needed for sudden blood sugar drops shortly before a meal. Foods with slow carbohydrates may be useful for long periods of exercise

To determine fast and slow carbohydrates, a glycemic index of foods has been developed. The glycemic index is an indicator of how quickly specific foods affect blood sugar (see Table below). The index is based on a scale of 1 to 100. (For example, a glucose tablet equals 100 and has the most rapid effect; when taken for hypoglycemia can bring relief in 10 to 15 minutes.) Some studies have shown that diets high in foods that have a low glycemic index improve blood sugar, cholesterol, and triglyceride levels and may even reduce the risk for kidney disease. It should be noted that numbers attributed to each food are not additive. In other words, adding All Bran cereal with a glycemic index number of 49 to a banana with an index of 61 does not equal 110. Combinations with fats or protein, however, do change the impact on blood sugar. For instance, a baked potato has a very high index of 87, but when a fat such as butter is added to, the impact slows down and the glycemic index of the combined foods is considerably less than the potato alone.

No one should use the glycemic index as a complete dietary guide, since it does not provide nutritional guidelines for all foods. The Food Pyramid, Mediterranean Diet, or Exchange Lists should still serve as the basis for planning meals; the index is simply an indication of how the metabolism will respond to carbohydrates eaten. Low glycemic index numbers, however, are often associated with whole grains and other beneficial complex carbohydrates. One study tracked the glycemic indices for the traditional foods (corn, lima beans, white and yellow teparies, mesquite, and acorns) of the Pima Native American. The foods had a very low index and experts believe they had protected this genetically susceptible population from the high incidence of type 2 diabetes the Pimas are experiencing now, most likely from the Western diet.

What Other Behaviors Help Control Diabetes?

Professional Help

It is very important to work with a physician and dietitian to establish the best meal plan for individual needs, particularly for those needing to maintain tight insulin control. Patients can find a dietitian in their area by contacting the American Dietetic Association. Unfortunately, although a trained dietitian is as critical a medical partner as a physician for people with diabetes, as yet few insurance policies reimburse nutritional education.

Exercise

Regular exercise is important for the management of both types of diabetes. Aerobic exercise is best; walking, jogging, biking, swimming, and aerobic dances are examples. Even moderate regular exercise helps lower blood sugar by increasing tissue sensitivity to insulin. It also helps lower blood pressure, improve cholesterol levels, decrease body fat, and reduce the risk of cardiovascular disease. In fact, studies of older people who engage in regular moderate aerobic exercise (e.g., brisk walking, biking) lower their risk for diabetes even if they don't lose weight. Patients who are taking medications that lower blood sugar, particularly insulin, should take special precautions before embarking on a workout program. Because glucose levels can swing dramatically during workouts in uncontrolled diabetes, diabetics should monitor their levels carefully before, during, and after workouts. Delay exercise if blood glucose is over 250 mg/dl or under 100 mg/dl. To avoid hypoglycemia, diabetics should inject insulin in sites away from the muscles they use the most during exercise. They should also avoid alcohol. Finally, insulin-dependent athletes may need to decrease insulin doses or take in more carbohydrates, especially in the form of pre-exercise snacks (skim milk is particularly helpful). Because diabetics may have silent heart disease, they should always check with their physicians before undertaking vigorous exercise.

Recent Literature

B vitamins and the heart : What men can learn from women. Harvard Men's Health Watch, June 1998

Chromium and exercise training: effect on obese women. Am J Clin Nutr 1997;66:639-642.

Eating disorders and diabetic complications. The New England Journal of Medicine, 6/26/97

The facts about fats. Consumer Reports on Health. March 1997

Fighting diabetes with fiber. Harvard Health Letter. April 1997

Lowering blood homocysteine with folic acid based supplements: Meta-analysis of randomised trials. British Medical Journal, 3/21/98

No apparent benefit of liquid formula diet in NIDDM. Exp Clin Endocrinol Diabetes 1997;105(3):134-9

Reduction of plasma homocysteine levels by breakfast cereal fortified with folic acid in patients with coronary heart disease. The New England Journal of Medicine, 4/9/98

Splenda, another sugar substitute. Consumer Reports on Health, September 1998

Very low fat diets questioned. Harvard Health Letter, December 1998

Yet another French Connection. Consumer Reports on Health, February 1997

Well-Connected Board of Editors

Harvey Simon, M.D., Editor-in-Chief
Massachusetts Institute of Technology; Physician, Massachusetts General Hospital

Masha J. Etkin, M.D., Gynecology
Harvard Medical School; Physician, Massachusetts General Hospital

John E. Godine, M.D., Ph.D., Metabolism
Harvard Medical School; Associate Physician, Massachusetts General Hospital

Daniel Heller, M.D., Pediatrics
Harvard Medical School; Associate Pediatrician, Massachusetts General Hospital; Active Staff, Children's Hospital

Irene Kuter, M.D., D. Phil., Oncology
Harvard Medical School; Assistant Physician, Massachusetts General Hospital

Paul C. Shellito, M.D., Surgery
Harvard Medical School; Associate Visiting Surgeon, Massachusetts General Hospital

Theodore A. Stern, M.D., Psychiatry
Harvard Medical School; Psychiatrist and Chief, Psychiatric Consultation Service, Massachusetts General Hospital

Carol Peckham, Editorial Director

Cynthia Chevins, Publisher

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