Compared to fats and protein, carbohydrates have the greatest impact on blood sugar (glucose). Except for dietary fiber, which is not digestible, carbohydrates are eventually broken down by the body into glucose. Carbohydrate types are either complex (as in starches) or simple (as in fruits and sugars).
One gram of carbohydrates provides 4 calories. The current general recommendation is that carbohydrates should provide between 45 - 65% of the daily caloric intake. Carbohydrate intake should not fall below 130 grams/day.
Complex carbohydrates are broken down more slowly by the body than simple carbohydrates. They are more likely to provide other nutritional components and fiber.
- Vegetables, fruits, whole grains, and beans are good sources of carbohydrates. Whole grain foods provide more nutritional value than pasta, white bread, and white potatoes. Brown rice is a better choice than white rice.
- Patients should try to consume a minimum of 20 - 38 grams of fiber daily (or even up to 50 grams/day), from vegetables, fruits, whole grain products such as cereals and breads, and nuts and seeds.
- Whole grains specifically are extremely important for people with diabetes or those who are at risk for it. [For specific benefits, see: "Whole Grains, Nuts, and Fiber-Rich Foods," below.]
Simple carbohydrates, or sugars (either as sucrose or fructose), adds calories, increases blood glucose levels quickly, and provides little or no other nutrients.
- Sucrose (table sugar) is the source of most dietary sugar, found in sugar cane, honey, and corn syrup.
- Fructose the sugar found in fruits, may produce a slower increase in blood sugar than sucrose. Dark-colored fruits are rich in important vitamins and other nutrients. Other fruits, such as apples and grapes also have important beneficial food chemicals.
- People with diabetes should avoid products listing more than 5 grams of sugar per serving, and some doctors recommend limiting fruit intake. If specific amounts are not listed, patients should avoid products with either sucrose or fructose listed as one of the first four ingredients on the label. [See: "Fat Substitutes and Artificial Sweeteners," below.]
The Carbohydrate Counting System. Some people plan their carbohydrate intake using a system called carbohydrate counting. It is based on two premises:
- All carbohydrates (either from sugars or starches) will raise blood sugar to a similar degree, although the rate at which blood sugar rises depends on the type of carbohydrate. In general, 1 gram of carbohydrates raises blood sugar by 3 points in people who weigh 200 pounds, 4 points for people who weigh 150 pounds, and 5 points for 100 pounds.
- Carbohydrates have the greatest impact on blood sugar. Fats and protein play only minor roles.
In other words, the amount of carbohydrates eaten (rather than fats or proteins) will determine how high blood sugar levels will rise. There are two options for counting carbohydrates: advanced and simple. Both rely on collaboration with a doctor, dietitian, or both. Once the patient learns how to count carbohydrates and adjust insulin doses to their meals, many find it more flexible, more accurate in predicting blood sugar increases, and easier to plan meals than other systems.
The basic goal is to balance insulin with the amount of carbohydrates eaten in order to control blood glucose levels after a meal. The steps to the plan are as follows:
The patient must first carefully record a number of factors that are used to determine the specific requirements for a meal plan based on carbohydrate grams:
- Multiple blood glucose readings (taken several times a day)
- The time of meals
- Amount in grams of all the carbohydrates eaten
- Time, type, and duration of exercise
- The time, type, and dose of insulin or oral medications
- Other relevant factors, such as menstruation, illness, and stress
The patient works with the dietitian for two or three 45 - 90 minute sessions to plan how many grams of carbohydrates are needed. There are three carbohydrate groups:
One serving from each group should contain 12 - 15 carbohydrate grams. (Patients can find the amount of carbohydrates in foods from labels on commercial foods and from a number of books and web sites.)
The dietitian creates a meal plan that accommodates the patient's weight and needs, as determined by the patient's record, and makes a special calculation called the carbohydrate to insulin ratio. This ratio determines the number of carbohydrate grams that a patient needs to cover the daily pre-meal insulin needs. Eventually, patients can learn to adjust their insulin doses to their meals.
Patients who choose this approach must still be aware of protein and fat content in foods. These food groups may add excessive calories and saturated fats. Patients must still follow basic healthy dietary principles.
The Glycemic Index. The glycemic index helps determine which carbohydrate-containing foods raise blood glucose levels more or less quickly after a meal. The index uses a set of numbers for specific foods that reflect greatest to least delay in producing an increase in blood sugar after a meal. The lower the index number, the better the impact on glucose levels.
There are two indices in use. One uses a scale of 1 - 100 with 100 representing a glucose tablet, which has the most rapid effect on blood sugar. [See Table: "The Glycemic Index of Some Foods," below.] The other common index uses a scale with 100 representing white bread (so some foods will be above 100).
Choosing foods with low glycemic index scores often has a significant effect on controlling the surge in blood sugar after meals. Many of these foods are also high in fiber and so have heart benefits as well. Substituting low- for high-glycemic index foods may also help with weight control.
One easy way to improve glycemic index is to simply replace starches and sugars with whole grains and legumes (dried peas, beans, and lentils). However, there are many factors that affect the glycemic index of foods, and maintaining a diet with low glycemic load is not straightforward.
No one should use the glycemic index as a complete dietary guide, since it does not provide nutritional guidelines for all foods. It is simply an indication of how the metabolism will respond to certain carbohydrates.
Low-Carbohydrate Diets. Low carb diets generally restrict the amount of carbohydrates but do not restrict protein sources. Popular low-carb diet plans include Atkins, South Beach, The Zone, and Sugar Busters.
- The Atkins diet restricts complex carbohydrates in vegetables and fruits that are known to protect against heart disease. The Atkins diet also can cause excessive calcium excretion in urine, which increases the risk for kidney stones and osteoporosis.
- Low-carb diets such as South Beach, The Zone, and Sugar Busters rely on the glycemic index. Foods on the lowest end of the index take longer to digest. Slow digestion wards off hunger pains. It also helps stabilize insulin levels. Foods high on the glycemic index include bread, white potatoes, and pasta while low-glycemic foods include whole grains, fruit, lentils, and soybeans.
- The Mediterranean Diet is a heart-healthy diet that is rich in vegetables, fruits, and whole grains as well as healthy monounsaturated fats such as olive oil. It restricts saturated fat proteins like red meat. In studies of patients with type 2 diabetes, a low-carb version of the diet (restricting carbohydrates to less than 50% of total calories) worked better than a low-fat diet in promoting weight loss, reducing A1C levels, and improving insulin sensitivity and glycemic control.
According to the American Diabetes Association (ADA), low-carb diets may help reduce weight in the short term (up to 1 year). However, because these diets tend to include more fat and protein, the ADA recommends that people on these diet plans have their blood lipids, including cholesterol and triglycerides, regularly monitored. Patients who have kidney problems need to be careful about protein consumption, as high-protein diets can worsen this condition.
Whole Grains, Nuts, and Fiber-Rich Foods
Fiber is an important component of many complex carbohydrates. It is found only in plant foods such as vegetables, fruits, whole grains, nuts, and legumes (dried beans, peanuts, and peas). Fiber cannot be digested. Instead, it passes through the intestines, drawing water with it, and is eliminated as part of feces content. The following are specific advantages from high-fiber diets (up to 50 grams a day):
- Insoluble fiber (found in wheat bran, whole grains, seeds, nuts, legumes, and fruit and vegetable peels) may help achieve weight loss. Consuming whole grains on a regular basis appears to provide many important benefits, especially for people with type 2 diabetes. Whole grains may even lower the risk for type 2 diabetes in the first place. Of special note, nuts (such as almonds, macadamia, and walnuts) may be highly heart protective, independent of their fiber content. However, nuts are high in calories.
- Soluble fiber (found in dried beans, oat bran, barley, apples, and citrus fruits) has important benefits for the heart, particularly for achieving healthy cholesterol levels and possibly reducing blood pressure as well.
- Soluble fiber supplements, such as those that contain psyllium or glucomannan, may be beneficial. Psyllium is taken from the husk of a seed. It is found in laxatives (Metamucil), breakfast cereals (Bran Buds), and other products. Soluble fiber requires water to help dissolve, so people who increase their levels of soluble fiber should drink more water.
The Glycemic Index of Some Foods
Based on 100 = a Glucose Tablet
Kidney (dried and boiled, not canned)
Spaghetti (boiled 5 minutes)
Spaghetti (boiled 15 minutes)
Note. These numbers are general values, but they may vary widely depending on other factors, including if and how they are cooked and foods they are combined with.
Fat Substitutes and Artificial Sweeteners
Replacing fats and sugars with substitutes may help some people who have trouble maintaining weight.
Fat Substitutes. Fat substitutes added to commercial foods or used in baking, deliver some of the desirable qualities of fat but do not add as many calories. They cannot be eaten in unlimited amounts. Fat substitutes include:
- Plant substances known as sterols, and their derivatives called stanols, reduce cholesterol by blocking its absorption in the intestinal tract. Margarines containing sterols are available.
- Olestra (Olean) passes through the body without leaving behind any calories from fat. However, it can cause cramps and diarrhea, and even small amounts of olestra may deplete the body of certain vitamins and nutrients.
Artificial Sweeteners. Artificial sweeteners use chemicals to mimic the sweetness of sugar. These products do not contain calories and do not affect blood sugar. Artificial sweeteners approved by the FDA include:
- Aspartame (Nutra-Sweet, Equal). Aspartame is generally considered safe, but people with phenylketonuria (PKU), a rare genetic condition, should not use it.
- Saccharin (Sweet'N Low). Saccharin is the oldest artificial sweeteners. Although early studies in rats indicated a potential risk for cancer, subsequent research has shown that saccharin does not cause cancer.
- Sucralose (Splenda). Sucralose has no bitter aftertaste and works well in baking, unlike other artificial sweeteners. It is made from real sugar by replacing hydroxyl atoms with chlorine atoms.
- Rebiana (Truvia, PureVia) is an extract derived from stevia, a South American plant. (Stevia is also sold in health food stores as a dietary supplement.)
- Acesulfame Potassium, also known as Acesulfame-K (Sweet One, Sunette).
- Neotame (Neotame). Neotame is structurally similar to aspartame. Unlike other artificial sweeteners, neotame is not available as a table sweetener. It is only used as a general-purpose sweetener in commercial food products such as baked goods and soft drinks.
Sugar alcohols (which include xylitol, mannitol, and sorbitol) are often used in “sugar-free” products, such as cookies, hard candies, and chewing gum. Sugar alcohols can slightly increase blood sugar levels. The American Diabetes Association recommends against consuming large amounts of sugar alcohol as it can cause gas and diarrhea, especially in children.
Protein intake in diabetes is complicated and depends on various factors. These factors include whether a patient has type 1, type 2, or pre-diabetes. There are additional guidelines for patients who show signs of kidney damage (diabetic nephropathy).
In general, diabetes dietary guidelines recommend that proteins should provide 12 - 20% of total daily calories. This daily amount poses no risk to the kidney in people who do not have kidney disease. Protein is important for strong muscles and bones. Some doctors recommend a higher proportion of protein (20 - 30%) for patients with pre- or type 2 diabetes. They think that eating more protein helps people feel more full and thus reduces overall calories. In addition, protein consumption helps the body maintain lean body mass during weight loss.
Patients with diabetic kidney problems need to limit their intake of protein. A typical protein-restricted diet limits protein intake to no more than 10% of total daily calories. Patients with kidney damage also need to limit their intake of phosphorus, a mineral found in dairy products, beans, and nuts. (However, patients on dialysis need to have more protein in their diets.) Potassium and phosphorus restriction is often necessary as well.
One gram of protein provides 4 calories. Protein is commonly recommended as part of a bedtime snack to maintain normal blood sugar levels during the night, although studies are mixed over whether it adds any protective benefits against nighttime hypoglycemia. If it does, only small amounts (14 grams) may be needed to stabilize blood glucose levels.
Good sources of protein include fish, skinless chicken or turkey, nonfat or low-fat dairy products, soy (tofu), and legumes (such as kidney beans, black beans, chick peas, and lentils).
Fish. Fish is probably the best source of protein. Evidence suggests that eating moderate amounts of fish (twice a week) may improve triglycerides and help lower the risks for death from heart disease, dangerous heart rhythms, blood pressure, a tendency for blood clots, and the risk for stroke.
The most healthy fish are oily fish such as salmon, mackerel, or sardines, which are high in omega-3 fatty acids. Three capsules of fish oil (preferably as supplements of DHA-EPA) are about equivalent to one serving of fish.
Women who are pregnant (or planning on becoming pregnant) or nursing should avoid fish that contains high amount of mercury. These high-mercury fish include swordfish, tuna, bass, and mackerel.
Soy. Soy is an excellent food. It is rich in both soluble and insoluble fiber, omega-3 fatty acids, and provides all essential proteins. Soy proteins have more vitamins and minerals than meat or dairy proteins. They also contain polyunsaturated fats, which are better than the saturated fat found in meat. The best sources of soy protein are soy products (such as tofu, soy milk, and soybeans). Soy sauce is not a good source. It contains only a trace amount of soy and is very high in sodium.
For many years, soy was promoted as a food that could help lower cholesterol and improve heart disease risk factors. Recent studies have found that soy protein and isoflavone supplement pills do not have major effects on cholesterol or heart disease prevention. The American Heart Association still encourages patients to include soy foods as part of an overall heart healthy diet but does not recommend using isoflavone supplements.
Meat and Poultry. Lean cuts of meat are the best choice for heart health and diabetes control. Saturated fat in meat is the primary danger to the heart. The fat content of meat varies depending on the type and cut. For patients with diabetes, skinless chicken or turkey is a better choice than red meat. (Fish is an even better choice.)
Dairy Products. A high intake of dairy products may lower risk factors related to type 2 diabetes and heart disease (insulin resistance, high blood pressure, obesity, and unhealthy cholesterol). Some researchers suggest the calcium in dairy products may be partially responsible for these benefits. Vitamin D contained in dairy may also play a role in improving insulin sensitivity, particularly for children and adolescents. However, because many dairy products are high in saturated fats and calories, it’s best to choose low-fat and nonfat dairy items.
Fats and Oils
Some fat is essential for normal body function. Fats can have good or bad effects on health, depending on their chemistry. The type of fat is more important than the total amount of fat when it comes to reducing heart disease. Monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) are “good” fats that help promote heart health, and should be the main type of fats consumed. Saturated fats and trans fats (trans fatty acids) are “bad” fats that can contribute to heart disease, and should be avoided or limited.
Current dietary guidelines for diabetes and heart health recommend that:
- Total fat from all fat sources should be 25 - 35% of total daily calories.
- Monounsaturated fatty acids (found in olive oil, canola oil, peanut oil, nuts, and avocados) and omega-3 polyunsaturated fatty acids (found in fish, shellfish, flaxseed, and walnuts) should be the first choice for fats.
- Omega-6 polyunsaturated fatty acids (corn, safflower, sunflower, and soybean oils and nuts and seeds) are the second choice and should account for 5 - 10% of total calories as part of total fat intake. Linoleic acid, the main omega-6 fatty acid found in food, has anti-inflammatory properties. Higher intakes of omega-6 fatty acids may help improve insulin resistance, reduce diabetes risk, and lower blood pressure.
- Limit saturated fat (found predominantly in animal products, including meat and full fat dairy products, as well as coconut and palm oils) to less than 7% of total daily calories.
- Limit trans fats (found in margarine, commercial baked goods, snack and fried foods) to less than 1% of total calories.
All fats, good or bad, are high in calories compared to proteins and carbohydrates. In order to calculate daily fat intake, multiply the number of fat grams eaten by nine (1 fat gram provides 9 calories, whether it's oil or fat) and divide by the number of total daily calories desired. One teaspoon of oil, butter, or other fats contains about 5 grams of fat. All fats, no matter what the source, add the same calories. The American Heart Association recommends that fats and oils have fewer than 2 grams of saturated fat per tablespoon.
Try to replace saturated fats and trans fatty acids with unsaturated fats from plant and fish oils. Omega-3 fatty acids, which are found in fish and a few plant sources, are a good source of unsaturated fats. Generally, two servings of fish per week provide a healthful amount of omega-3 fatty acids. Fish oil dietary supplements are another option. Fish and fish oil supplements contain docosahexaenoic (DHA) and eicosapentaenoic (EPA) acids, which have significant benefits for the heart. Discuss with your doctor whether you should consider taking fish oil supplements.
Low-Fat Diets. The American Diabetes Association states that low-fat diets can help reduce weight in the short term (up to 1 year). Low-fat diets that are high in fiber, whole grains, legumes, and fresh produce can offer health advantages for blood sugar and cholesterol control.
Animal-based food products contain cholesterol. High amounts occur in meat, dairy products, egg yolks, and shellfish. (Plant foods, such as fruits, vegetables, nuts, and grains, do not contain cholesterol.) The American Heart Association recommends no more than 300 mg of dietary cholesterol per day for the general population and no more than 200 mg daily for those with high cholesterol or heart disease.
Vitamins and Supplements
Research has shown that vitamin supplements have no benefit for heart disease and diabetes. Because of the lack of scientific evidence for benefit, the American Diabetes Association does not recommend regular use of vitamin supplements, except for people who have vitamin deficiencies.
Patients with type 2 diabetes who take metformin (Glucophage) should be aware that this drug can interfere with vitamin B12 absorption. Calcium supplements may help counteract metformin-associated vitamin B12 deficiency.
It is important for everyone to restrict their sodium (salt) intake. People with diabetes should reduce sodium intake to less than 1,500 mg daily. Limiting or avoiding consumption of processed foods can go a long way to reducing salt intake. Simply eliminating table and cooking salt is also beneficial.
Salt substitutes, such as Nusalt and Mrs. Dash (which contain mixtures of potassium, sodium, and magnesium) are available, but they can be risky for people with kidney disease or those who take blood pressure medication that causes potassium retention. Similarly, while eating more potassium-rich foods is helpful for achieving healthy blood pressure, patients with diabetes should check with their doctors before increasing the amount of potassium in their diets. [For more information on potassium, see “Other Minerals,” below.]
Calcium. Calcium supplements may be important in older patients with diabetes to help reduce the risk for osteoporosis, particularly if their diets are low in dairy products.
Potassium and Phosphorus. Potassium-rich foods, and potassium supplements, can help lower systolic and diastolic blood pressure. Current guidelines support the use of potassium supplements or enough dietary potassium to achieve 3,500 mg per day for people with normal or high blood pressure (who have no risk factors for excess potassium levels). This goal is particularly important in people who have high sodium intake.
The best source of potassium is from the fruits and vegetables that contain them. Potassium-rich foods include bananas, oranges, pears, prunes, cantaloupes, tomatoes, dried peas and beans, nuts, potatoes, and avocados. No one should take potassium supplements without consulting a doctor. Kidney problems can cause potassium overload, and medications commonly used in diabetes (such as ACE inhibitors or potassium-sparing diuretics) also limit the kidney's ability to excrete potassium. Patients with diabetic nephropathy (kidney disease) and kidney failure need to restrict dietary potassium, as well as phosphorus. Phosphorus-rich foods that should be avoided include meats, dairy products, beans, whole foods, and nuts. In addition, many processed and fast foods contain high amounts of phosphorus additives.
Magnesium. Magnesium deficiency may have some role in insulin resistance and high blood pressure. Research indicates that magnesium-rich diets may help lower type 2 diabetes risk. Whole grain breads and cereals, nuts (such as almonds, cashews, and soybeans), and certain fruits and vegetables (such as spinach, avocados, and beans) are excellent dietary sources of magnesium. Dietary supplements do not provide any benefit. Persons who live in soft water areas, who use diuretics, or who have other risk factors for magnesium deficiency may require more dietary magnesium than others.
Chromium. Most studies have indicated that chromium supplements have little or no effect on glucose metabolism and may cause adverse side effects.
Selenium. Selenium, a trace mineral, may increase diabetes risk. An average healthy diet supplies adequate amounts of selenium. There is no need to take dietary supplements.
Zinc. More studies are needed to establish the benefits or risks of taking zinc supplements. Large doses of zinc can have toxic side effects.
Alcohol and Coffee
Alcohol. The American Diabetes Association recommends limiting alcoholic beverages to 1 drink per day for non-pregnant adult women and 2 drinks per day for adult men.
Coffee. Many studies have noted an association between coffee consumption (both caffeinated and decaffeinated) and reduced risk for developing type 2 diabetes. Researchers are still not certain if coffee protects against diabetes.
Generally, manufacturers of herbal remedies and dietary supplements do not need FDA approval to sell their products. Just like a drug, herbs and supplements can affect the body's chemistry, and therefore have the potential to produce side effects that may be harmful. There have been a number of reported cases of serious and even lethal side effects from herbal products. Patients should always check with their doctors before using any herbal remedies or dietary supplements.
Traditional herbal remedies for diabetes include bitter melon, cinnamon, fenugreek, and Gymnema sylvestre. Few well-designed studies have examined these herbs’ effects on blood sugar, and there is not enough evidence to recommend them for prevention or treatment of diabetes.
Various fraudulent products are often sold on the Internet as “cures” or treatments for diabetes. These dietary supplements have not been studied or approved. The FDA warns patients with diabetes not to be duped by bogus and unproven remedies.