General Dietary Guidelines
Lifestyle changes of diet and exercise are extremely important for people who have pre-diabetes, or who are at high risk of developing type 2 diabetes. Several studies have shown that lifestyle interventions are very effective in preventing or postponing the progression to diabetes. These interventions are especially important for overweight people. Even moderate weight loss can help reduce diabetes risk.
The American Diabetes Association recommends that people at high risk for type 2 diabetes eat high-fiber (14g fiber for every 1,000 calories) and whole-grain foods. A 2007 study in the Archives of Internal Medicine also suggested that high intake of fiber and magnesium, especially from whole grain cereals and breads, can help reduce type 2 diabetes risk.
For people who have diabetes, the treatment goals for a diabetes diet are:
- Achieve near normal blood glucose levels. People with type 1 diabetes and people with type 2 diabetes who are taking insulin or oral medication must coordinate calorie intake with medication or insulin administration, exercise, and other variables to control blood glucose levels. New forms of insulin are now allowing more flexibility in timing meals.
- Protect the heart and aim for healthy lipid (cholesterol and triglyceride) levels and control of blood pressure.
- Achieve reasonable weight. Overweight patients with type 2 diabetes who are not taking medication should aim for a diet that controls both weight and glucose. A reasonable weight is usually defined as what is achievable and sustainable, rather than one that is culturally defined as desirable or ideal. Children, pregnant women, and people recovering from illness should be sure to maintain adequate calories for health.
- Manage or prevent complications of diabetes. People with diabetes, whether type 1 or 2, are at risk for a number of medical complications, including heart and kidney disease. Dietary requirements for diabetes must take these disorders into consideration.
- Promote overall health.
Overall Guidelines. There is no such thing as a single diabetes diet. Patients should meet with a professional dietitian to plan an individualized diet within the general guidelines that takes into consideration their own health needs.
For example, a patient with type 2 diabetes who is overweight and insulin-resistant may need to have a different carbohydrate-protein balance than a thin patient with type 1 diabetes in danger of kidney disease. Because regulating diabetes is an individual situation, everyone with this condition should get help from a dietary professional in selecting the diet best for them.
Healthy eating habits along with good control of blood glucose are the basic goals in managing this complex disease, and several good dietary methods are available to meet them. General dietary guidelines for diabetes recommend:
- Carbohydrates should provide 45 - 65% of total daily calories. The type and amount of carbohydrate are both important. Best choices are vegetables, fruits, beans, and whole grains. These foods are also high in fiber. Patients with diabetes should monitor their carbohydrate intake either through carbohydrate counting or meal planning exchange lists.
- Fats should provide 25 - 35% of daily calories. Monounsaturated (olive, peanut, canola oils; avocados; nuts) and omega-3 polyunsaturated (fish, flaxseed oil, walnuts) fats are the best types. Limit saturated fat (red meat, butter) to less than 7% of daily calories. Choose nonfat or low-fat dairy instead of whole milk products. Limit trans-fats (hydrogenated fat found in snack foods, fried foods, commercially baked goods) to less than 1% of total calories.
- Protein should provide 12 - 20% of daily calories, although this may vary depending on a patient’s individual health requirements. Patients with kidney disease should limit protein intake to less than 10% of calories. Fish, soy, and poultry are better protein choices than red meat.
- Lose weight if body mass index (BMI) is 25 - 29 (overweight) or higher (obese).
Several different dietary methods are available for controlling blood sugar in type 1 and insulin-dependent type 2 diabetes:
- Diabetic exchange lists (for maintaining a proper balance of carbohydrates, fats, and proteins throughout the day)
- Carbohydrate counting (for tracking the number of grams of carbohydrates consumed each day)
- Glycemic index (for tracking which carbohydrate foods increase blood sugar)
Monitoring
Tests for Glucose Levels. Both low blood sugar (hypoglycemia) and high blood sugar (hyperglycemia) are of concern for patients who take insulin. It is important, therefore, to monitor blood glucose levels carefully. Patients should aim for the following measurements:
- Pre-meal glucose levels of 90 - 130 mg/dL
- Bedtime levels of 110 - 150 mg/dL
In general, patients who are tightly controlling glucose levels need to take readings four or more times a day. Blood glucose levels are generally more stable in type 2 diabetes than in type 1, so experts usually recommend that these patients measure blood levels only once or twice a day. Different goals may be required for specific individuals, including pregnant women, very old and very young people, and those with accompanying serious medical conditions.
Tests for Glycosylated Hemoglobin. Another test examines blood levels glycosylated hemoglobin, also known as hemoglobin A1c (HbA1c). Measuring glycosylated hemoglobin is useful for determining the severity of diabetes. The test is not affected by food intake so it can be taken at any time. A home test has been developed that may make it easier to measure HbA1c. In general, measurements suggest the following:
- Normal HbA1c levels should be below 7%
- Levels of 11 - 12% glycosylated hemoglobin indicate poor control of carbohydrates. High levels are also markers for kidney trouble.
Other Tests. Other tests are needed periodically to determine potential complications of diabetes, such as high blood pressure, unhealthy cholesterol levels, and kidney problems. Such tests may also indicate whether current diet plans are helping the patient and whether changes should be made. Annual urine tests showing even microscopic traces of a protein known as albumin can indicate a future risk for serious kidney disease.
Preventing Hypoglycemia (Insulin Shock)
For prevention of long-term complications of diabetes, experts now recommend that all patients with diabetes try to keep blood levels as close to normal as possible. Such intensive insulin treatment can increase the risk of hypoglycemia, which occurs when blood sugar is extremely low (below 60 mg/dL). The following tips may help patients avoid hypoglycemia or prepare for attacks.
- Patients are at highest risk for hypoglycemia at night. Bedtime snacks may be helpful.
- Patients who intensively control their blood sugar should monitor blood levels as often as possible, four times or more per day. This is particularly important for patients with hypoglycemia unawareness.
- In adults, it is also particularly critical to monitor blood glucose levels before driving, when hypoglycemia can be very hazardous.
- Patients on therapies that put them at risk for hypoglycemia should always carry hard candy, juice, sugar packets, or commercially available glucose substitutes designed for individuals with diabetes.
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).
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 what most patients with diabetes should have, and the serving sizes may not be equivalent to those on diabetic exchange lists. Most people will need to recalculate the grams and calories listed on food labels to fit their own serving sizes and calorie needs.
Weighing and Measuring. Weighing and measuring food is extremely important to get the correct number of daily calories.
- Along with measuring cups and spoons, choose a food scale that measures grams. (A gram is very small, about 1/28th of an ounce.)
- Food should be weighed and measured after cooking.
- After measuring all foods for a week or so, most people can make fairly accurate estimates by eye or by holding food without having to measure everything every time they eat.
Timing. 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 the patient eats extra food too often to offset low blood sugar levels.
The timing of meals is particularly important for people taking insulin:
- Patients should coordinate insulin administration with calorie intake. In general, they should eat three meals each day at regular intervals. Snacks are often necessary.
- They should try to take an insulin injection 30 minutes before they eat, although this timing could vary, depending on the form. Some experts recommend a fast acting insulin (insulin lispro) at each meal and a longer (basal) insulin at night.
Special Considerations for People with Kidney Failure
Diabetes can lead to kidney disease and failure. People with early-stage kidney failure need to follow a special diet that slows the build-up of wastes in the bloodstream. The diet restricts protein, potassium, phosphorus, and salt intake. Fat and carbohydrate intake may need to be increased to help maintain weight and muscle tissue.
People who have late-stage kidney disease usually need dialysis. Once patients are on dialysis, they need more protein in their diet. Patients must still be very careful about restricting salt, potassium, phosphorus, and fluids. Patients on peritoneal dialysis may have fewer restrictions on salt, potassium, and phosphorus than those on hemodialysis.
Major Food Components
Carbohydrates
Compared to fats and protein, carbohydrates have the greatest impact on blood sugar. Both the amount and type of carbohydrate affect blood glucose. Carbohydrate types are either complex (as in starches) or simple (as in fruits and sugars). One gram of carbohydrates equals 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.
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 - 35 grams of fiber daily (ideally 50 grams/day), from vegetables, fruits, whole grain cereals, breads, nuts, and seeds.
Complex Carbohydrates. Complex carbohydrates found in whole grains and vegetables are preferred over carbohydrates found in starch-heavy foods, such as pastas, white-flour products, and potatoes. Most of these are high in fiber, which is important for health. Whole-grains specifically are extremely important for people with diabetes or at risk for it. [For specific benefits, see: "Whole Grains, Nuts, and Fiber-Rich Foods."]
Simple Carbohydrates (Sugar). Sugars are generally one of two types:
- Sucrose (table sugar). Sucrose has been associated with higher triglycerides and harmful cholesterol levels.
- Fructose (sugar found in fruits). Fructose may produce a slower increase in blood sugar than sucrose, which may have some advantages for people with diabetes. However, fructose may adversely affect lipid levels. Dark-colored fruits are rich in important vitamins and other nutrients, and studies continue to report their benefits for the heart and health in general. Other fruits, such as apples and grapes also have important beneficial food chemicals.
Sugar itself, either as sucrose or fructose, adds calories, increases blood glucose levels quickly, and provides no other nutrients.
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."]
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 sugar or starch) will raise blood sugar to a similar degree. 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 scale 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. Some evidence suggests that the benefit of foods with a low glycemic index is due to their ability to increase insulin levels quickly (thus removing blood sugar) rather than their ability to slow the release of blood sugar itself.
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"]. The other common index uses a scale with 100 representing white bread (so some foods will be above 100).
A major analysis suggested that choosing foods with low glycemic index scores may have a small but 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 prevent weight gain.
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. The following are some considerations:
- The numbers attributed to each carbohydrate-rich food cannot be added to equal a certain number. In other words, adding All Bran cereal (index of 49) to a banana (index of 61) does not equal 110.
- Adding certain fats to a food (for example butter to potato) can slow down the food's impact on blood sugar. One study reported that when patients ate fatty foods first, their blood glucose levels were significantly lower an hour after the meal than when carbohydrates were eaten first.
- Adding foods with organic acids (pickles, yogurt) to meals may reduce the impact of foods with high glycemic scores on blood sugar. (It should be noted that yogurt alone, however, has the same high glycemic index as regular milk.)
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. Some experts believe it is too complicated to be practical and that simply tracking carbohydrates, eating healthily, and maintaining a healthy weight is sufficient. Nevertheless, a study on children with type 1 diabetes suggested that the glycemic index offered as many choices as the exchange diet, and they did not report feeling any greater limitations.
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.
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 almost always found only in plants (particularly vegetables), fruits, whole grains, nuts, and legumes (dried beans, peanuts, and peas). (One exception is chitosan, a dietary fiber made from shellfish skeletons.) 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 55 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, citrus fruits, and potatoes) has important benefits for the heart, particularly for achieving healthy cholesterol levels and possibly reducing blood pressure as well. Evidence on the heart benefits of beans continues to grow. For example, a 2001 study indicated that eating beans four or more times a week reduced the risk for heart disease by 22%.
- Soluble fiber supplements, such as those that contain psyllium or glucomannan, may be beneficial. Psyllium is taken from the husk of a seed grown in India. It is found in laxatives (Metamucil), breakfast cereals (Bran Buds), and other products. In a 2002 study, patients with type 2 diabetes who consumed psyllium (Plantaben) for breakfast for 11 weeks had lower total and LDL cholesterol levels. There was no difference in glucose or HbA1c levels. Psyllium can increase sodium so people who increase their levels of soluble fiber should also drink more fluids (espcially water).
The Glycemic Index of Some Foods |
Based on 100 = a Glucose Tablet | |
BREADS | |
Pumpernickel | 49 |
Sour dough | 54 |
Rye | 64 |
White | 69 |
Whole wheat | 72 |
GRAINS | |
Barley | 22 |
Sweet corn | 58 |
Brown rice | 66 |
White rice | 72 |
BEANS | |
Soy | 14 |
Red lentils | 27 |
Kidney (dried and boiled, not canned) | 29 |
Chickpeas | 36 |
Baked | 43 |
DAIRY PRODUCTS | |
Milk | 30 |
Ice cream | 60 |
CEREALS | |
Oatmeal | 53 |
All Bran | 54 |
Swiss Muesli | 60 |
Shredded Wheat | 70 |
Corn Flakes | 83 |
Puffed Rice | 90 |
PASTA | |
Spaghetti-protein enriched | 28 |
Spaghetti (boiled 5 minutes) | 33 |
Spaghetti (boiled 15 minutes) | 44 |
FRUIT | |
Strawberries | 32 |
Apple | 38 |
Orange | 43 |
Orange juice | 49 |
Banana | 61 |
POTATOES | |
Sweet | 50 |
Yams | 54 |
New | 58 |
Mashed | 72 |
Instant mashed | 86 |
White | 87 |
SNACKS | |
Potato chips | 56 |
Oatmeal cookies | 57 |
Corn chips | 72 |
SUGARS | |
Fructose | 22 |
Refined sugar | 64 |
Honey | 91 |
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. They are considered most useful for helping keep down total calorie count.
Plants substances known as sterols, and their derivatives called stanols, reduce cholesterol by blocking its absorption in the intestinal tract. Margarines containing sterols (such as Benecol and Take Control) are available. Benecol is derived from pine bark, and Take Control from soybeans. These products do not appear to block absorption of fat-soluble nutrients or vitamins, as olestra does. They may be hydrogenated and include some trans fatty acids, however.
Olestra (Olean) passes through the body without leaving behind any calories from fat. Studies suggest that it helps improve cholesterol levels and may help overweight people lose weight. Early reports of cramps and diarrhea after eating food containing olestra have not proven to be significant. Of greater concern is the fact that even small amounts of olestra deplete the body of certain vitamins and nutrients that may help protect against serious diseases, including cancer. The Food and Drug Administration (FDA) requires that the missing vitamins be added back to olestra products, but not other nutrients.
Beta-glucan is a soluble fiber found in oats and barley. Products using this substance (Nu-Trim) may reduce cholesterol and have additional health benefits.
A number of other fat-replacers are also available. Although studies to date have not shown any significant adverse health effects, their effect on weight control is uncertain, since many of the products containing them may be high in sugar. People who learn to cook using foods naturally lacking or low in fat eventually lose their taste for high-fat diets, something that may not be true for those using fat substitutes.
Artificial Sweeteners. Artificial sweeteners use chemicals to mimic the sweetness of sugar. These products do not contain calories and do not affect blood sugar. Five artificial sweeteners are approved by the FDA:
- 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.
- Acesulfame Potassium, also known as Acesulfame-K (Sweet One, Sunette).
- Neotame (Neotame). Neotame is structurally similar to aspartame. Unlike the other four 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.
Another sweetener, stevia, is derived from a South American plant. Although stevia is widely used in many parts of the world, the FDA has not approved it as an artificial sweetener due to safety concerns. (However, stevia is sold in health food stores as a dietary supplement.) It has not been rigorously tested and it is not clear if it is safe for people with diabetes. Because stevia has not been approved by the FDA, the American Diabetes Association does not endorse it as a sweetener.
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
Protein intake in diabetes is complicated. Protein recommendations vary among experts and depend 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 (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 bone. Some experts 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 nephropathy 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 contains 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 (kidney beans, black beans, chick peas, 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.
Some studies have reported a higher incidence of heart attack in men who ate fish daily. Such findings may be due to mercury toxicity, which has harmful effects on the heart. High mercury content has been observed in swordfish and shark and, to some extent, in tuna, trout, pike, tilapia, and bass.
Fish oil supplements may also have some adverse effects on LDL levels and glucose control in type 2 diabetes. More research is needed to further define the risk and benefits of fish, but at this time most guidelines recommend eating fish two or three times a week.
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 (tofu, soy milk, 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. But an important 2006 American Heart Association (AHA) review of studies found that soy protein and isoflavone supplement pills do not really have any effects on cholesterol or heart disease prevention. The AHA 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, experts recommend choosing skinless chicken or turkey over red meat. (Fish is an even better choice.) A large, long-term 2006 study found that high heme iron intake from red meat increases the risk of developing type 2 diabetes in women. Another 2006 study suggested that replacing red meat with chicken improves kidney function and lipid levels in patients with diabetic nephropathy.
Dairy Products. A 2002 study reported that a high intake of dairy products can 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. However, because many dairy products are high in saturated fats and calories, doctors recommend that patients choose low-fat and nonfat dairy items. Other studies have indicated that increasing the amount of low-fat diary products in a daily diet may help reduce type 2 diabetes risk, particularly for women.
Fats and Oils
Some fat is essential for normal body function. Fats can have good or bad effects on health, depending on their chemistry. New research suggests that the type of fat is more important than the total amount of fat when it comes to reducing heart disease.
Current dietary guidelines for diabetes and heart health recommend that total fat be 25 - 35% of total daily calories. Monounsaturated fats (olive oil, canola oil, peanut oil, nuts, and avocados) and omega-3 polyunsaturated fats (fish, flaxseed, andwalnuts) should be the first choice for fats. Omega-6 polyunsaturated fats (corn, safflower, sunflower, and soybean oils) are the second choice. Limit saturated fat to less than 7% of total daily calories. Limit trans-fats (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 is equal to 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 equals 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 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.
All fats and oils found in foods are made up of chains of molecules called fatty acids. There are three major chains: saturated fatty acid (found mostly in animal products) and two unsaturated fatty acids -- monounsaturated and polyunsaturated fatty acids (found in plant products). The oils and fats that people and animals eat are nearly always mixtures of these three chains, but one type of fatty acid usually predominates in specific oils or fats.
Harmful Fats. Reducing consumption of saturated fats and trans-fatty acids is the first essential step in managing cholesterol levels through diet.
- Saturated Fats. Saturated fats are found predominantly in animal products, including meat and dairy products. They are strongly associated with higher cholesterol levels, and they may be even more dangerous in women than in men. High-fat meals are associated with sudden surges in triglyceride levels and other lipids, along with impaired blood flow in the arteries to the heart. (Tropical oils, such as palm, coconut, and cocoa butter, are also high in saturated fats.) The American Heart Association recommends limiting saturated fat consumption to less than 7% of total calories per day.
- Trans Fatty Acids. Trans fatty acids are manufactured fats created during a process called hydrogenation, which is aimed at stabilizing polyunsaturated oils to prevent them from becoming rancid and to keep them solid at room temperature. They are particularly dangerous for the heart and may pose a risk for certain cancers. These partially hydrogenated fats are even worse than saturated fats. Studies report that high consumption of these fats reduces HDL ("good cholesterol") levels, has harmful effects on the linings of the arteries, and may increase the risk for type 2 diabetes. Hydrogenated fats are used in stick margarine and in many fast foods and baked goods, including most commercially produced white breads. (Liquid margarine is not hydrogenated and is recommended.) The FDA ordered that food labels list the amount of trans fatty acids in food products beginning in January 2006. The American Heart Association recommends limiting daily consumption of trans fats to less than 1% of total daily calories.
Beneficial Fats and Oils. Some fat is essential for health, and fat is essential for healthy development in children. Public attention has mainly focused on the possible benefits or hazards of monounsaturated (MUFA) and polyunsaturated (PUFA) fats.
- Polyunsaturated fats are found in safflower, sunflower, corn, and cottonseed oils and fish.
- Monounsaturated fats are mostly present in olive, canola, and peanut oils and in most nuts. (Canola is the least saturated of all the fats.) Studies report that replacing carbohydrates with monounsaturated fats improves glucose control after meals and reduces triglycerides in people with type 2 diabetes. Oils are more calorie-dense, however, and people with diabetes should be wary of weight gain.
Researchers are most interested in the smaller fatty-acid building blocks contained in both oils, which may have more specific effects on lipids. Three important fatty acids are the essential fatty acids omega-3, omega-6, and omega-9.
Omega-3 fatty acids are found in fish oil (docosahexaenoic and eicosapentaneoic acids) and plants (alpha-linolenic acid).
- Docosahexaenoic (DHA) and Eicosapentaneoic (EPA) Acids. DHA and EPA are found in fish oils, and evidence suggests that they have significant benefits for the heart, including reducing sudden death from heart disease, inflammation, blood clotting factors, blood pressure, and improving triglyceride and HDL levels. Results from a study presented at the 2005 meeting of the American Heart Association suggested that daily EPA supplements plus statin therapy can protect against heart attack, angina, and coronary artery disease. However, although fish and fish oil are good for the heart, patients who have an implantable defibrillator should not take fish oil supplements.
- Alpha-linolenic Acid. Alpha-linolenic acid is a plant precursor of DHA, which means the body can convert it to DHA. Sources include canola oil, soybeans, flaxseed, and certain nuts and seeds (walnut, flax, chia and sometimes pumpkin seed). Some, but not all, studies suggest that oils or foods containing these oils may also be heart-protective. Supplements or foods containing these oils may also protest the heart. For example studies have reported heart protection from flaxseed supplements and also from nuts, such as almonds, macadamia, and walnuts. Nuts are high in calories, however.
Omega-6 polyunsaturated fatty acids are found in corn, safflower, soybean, and sunflower oil. PUFA oils containing omega-6 fatty acids constitute most of the oils consumed in the US. Some omega-6 fatty acids are important for health. However, high intake of these fats may be associated with weight gain in the abdomen (the so-called apple shape), a risk factor for heart disease. High consumption is also associated with a higher risk for certain cancers and some chronic diseases.
Omega-9 monounsaturated fatty acids are contained in canola and olive oil, which help protect the heart.
Research suggests that a healthy balance of all these fats may be important and that our current Western diet contains an unhealthy ratio of omega-6 to omega-3 fatty acids (10 to 1). Omega-9 fatty acids may also contain chemicals that block harmful factors found in omega-6 fatty acids. Researchers suggest that the most benefits may be found in a mixture of all three fatty acids found in both poly- and monounsaturated oils, but in modest amounts that do not add too many calories.
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 cholesterol control. These foods are also lower on the glycemic index than high-glycemic foods such as white bread, white potatoes, and pasta.
Dietary Cholesterol
The story on cholesterol found in the diet is not entirely straightforward. The body produces cholesterol naturally or obtains it through meals. Animal-based food products contain cholesterol. High amounts occur in meat, dairy products, egg yolks, and shellfish. (Plant foods, such as fruits, 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.
Vitamins and Supplements
Antioxidant Vitamins. Vitamins C and E are most studied for their health effects because they serve as antioxidants. Antioxidants are chemicals that act as scavengers of particles known as oxygen-free radicals (also sometimes called oxidants). High intake of foods rich in these vitamins (as well as other food chemicals) have been associated with many health benefits, including prevention of heart problems.
Research on the effects of vitamin supplements on heart disease and diabetes, however, has been mixed. Although some research initially observed favorable effects from vitamin E in preventing blood clots and build-up of plaque on blood vessel walls, most studies found no heart protection from either vitamin E or C supplements. A 2005 Journal of the American Medical Association study found that vitamin E supplements can actually increase the risk of heart failure, especially for patients with diabetes or vascular diseases. In addition, vitamin E had no effect on preventing cancer or heart disease.
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. Researchers, however, are still studying the treatment possibilities of antioxidants. A 2006 study suggested that alpha-lipoic acid, another type of antioxidant, may have promise as a treatment for diabetic peripheral neuropathy, the nerve damage condition that is a common complication of diabetes.
B Vitamins and Folic Acid. Deficiencies in the B vitamins folate (known also as folic acid), B6, and B12 have been associated with a higher risk for heart disease in some studies. Such deficiencies produce higher blood levels of homocysteine, an amino acid that has been associated with a higher risk for heart disease, stroke, and heart failure.
Researchers have been studying whether vitamin B supplements can reduce homocysteine levels and, consequently, heart disease risks. Several major 2006 studies indicated that while B vitamin supplements help lower homocysteine levels, they have no effect on heart disease. The studies, published in the New England Journal of Medicine, examined patients who had either recently had a heart attack or who suffered from diabetes or heart disease. Results showed a similar number of heart attacks and strokes among patients who took folic acid, B6, and B12 vitamins and those who received placebo. Some experts think that homocysteine may be a marker for heart disease rather than a cause of it.
Niacin (vitamin B3) is used for lowering unhealthy cholesterol levels. Although vitamin B3 is available over the counter, it can have significant side effects. A doctor should prescribe niacin in order to ensure its safety and effectiveness.
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.
Salt (Sodium)
Most experts recommend salt restriction in people who have high blood pressure. Some people, however, are much more sensitive to harmful effects from salt than others:
- People at Risk for Salt-Sensitivity. About half of people with hypertension have blood pressure that reacts significantly to salt. Such people are known as salt-sensitive. Among those at highest risk for salt sensitivity are African-Americans, people with diabetes, and elderly people.
- Overweight People. Overweight individuals may absorb and retain sodium differently from people with normal weights. One study reported that high sodium intake was associated with an increased risk of heart disease and all-cause mortality in overweight, but not in normal weight, people. Reducing sodium can also help reduce the risk of stroke in people who are overweight.
Simply eliminating table and cooking salt can be beneficial. Salt substitutes, such as Cardia, (containing mixtures of potassium, sodium, and magnesium) are available, but they are expensive. About 75% of the salt in the typical American diet comes from processed or commercial foods, not from food cooked at home, so the benefits of table-salt substitutes are likely to be very modest. Some sodium is essential to protect the heart, but most experts agree that the amount is significantly less than that found in the average American diet. If people cannot significantly reduce the amount of salt in their diets, adding potassium-rich foods might help to restore a healthy balance. Patients with diabetes should always check with their doctor before increasing the amount of potassium in the diet, particularly if they have kidney problems.
Other Minerals
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. Evidence strongly indicates that a potassium-rich diet can help achieve healthy blood pressure levels, and that potassium supplements can lower systolic blood pressure by 1.8 m Hg and diastolic blood pressure by 1 mm Hg. In fact, some evidence indicates that a potassium-rich diet can reduce the risk of stroke by 22 - 40%. 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.
However, patients with diabetic nephropathy (kidney disease) and kidney failure need to restrict dietary potassium, as well as phosphorus. 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. No one should take potassium supplements without consulting a doctor. The best source of potassium is the fruits and vegetables that contain it.
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 (almonds, cashews, soybeans), and certain fruits and vegetables (spinach, avocados, 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. Some studies have reported an association between deficiencies in the mineral chromium and a higher risk for type 2 diabetes. Studies on fat rats that were given chromium reported improvement in insulin sensitivity and glucose metabolism. Most studies on type 2 patients, however, reported little or no effect on glucose metabolism and some even reported adverse side effects.
Selenium. Selenium, a trace mineral, does not reduce diabetes risk. In fact, it may increase it. An average healthy diet supplies adequate amounts of selenium. There is no need to take dietary supplements.
Zinc. Many patients with type 2 diabetes 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.
Herbal Remedies
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, fenugreek, and Gymnema sylvestre. These herbs may have properties that help lower blood sugar. However, few well-designed studies have examined these effects, 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. In 2006, the FDA and Federal Trade Commission (FTC) launched a crackdown on these scams. The FDA and FTC warn patients with diabetes not to be duped by bogus and unproven remedies.
Fluids: Water, Caffeine, and Alcohol
Water. Many heart risk factors, especially those associated with blood clotting, are elevated with dehydration. In one study, drinking five or more glasses of water a day was significantly associated with a lower risk for fatal heart events than drinking two or fewer glasses a day.
Alcohol. A number of studies have found that light-to-moderate intake of alcohol may provide protection from heart disease and type 2 diabetes. Some research suggests that alcohol has anti-inflammatory properties that protect arteries from injury. Red wine in particular may have specific benefits for people with type 2 diabetes. It has strong antioxidant effects that benefit the heart. Some evidence also suggests that red wine may improve insulin sensitivity and reduce blood glucose levels and may even protect against type 2 diabetes. 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.
Tea. Although it contains caffeine, tea, both black and green, is often cited for its health benefits. Green tea is especially is rich in chemicals that offer protection against damaging forms of LDL.
Coffee. Many studies have noted an association between coffee consumption and reduced risk for developing type 2 diabetes. A 2006 study of 29,000 postmenopausal women confirmed this reduced risk. Compared to non-coffee drinkers, women who drank at least 6 cups a day of coffee (either regular or decaf) were 22% less likely to develop type 2 diabetes. Decaffeinated coffee was even more beneficial -- women who drank at least 6 cups a day of decaf were 33% less likely to develop diabetes than women who did not drink coffee. Researchers are still not certain how coffee protects against diabetes. Neither the caffeine in coffee nor the mineral magnesium have a preventive effect. It may be that coffee contains antioxidant properties that protect the pancreas’ insulin-producing cells.
References
American Diabetes Association. Standards of medical care in diabetes -- 2008. Diabetes Care. 2008 Jan;31 Suppl 1:S12-54.
American Diabetes Association, Bantle JP, Wylie-Rosett J, Albright AL, Apovian CM, Clark NG, et al. Nutrition recommendations and interventions for diabetes: a position statement of the American Diabetes Association. Diabetes Care. 2008 Jan;31 Suppl 1:S61-78.
American Heart Association Nutrition Committee; Lichtenstein AH, Appel LJ, Brands M, Carnethon M, Daniels S, et al. Diet and lifestyle recommendations revision 2006: a scientific statement from the American Heart Association Nutrition Committee. Circulation. 2006 Jul 4;114(1):82-96. Epub 2006 Jun 19.
Barnard ND, Cohen J, Jenkins DJ, Turner-McGrievy G, Gloede L, Jaster B, et al. A low-fat vegan diet improves glycemic control and cardiovascular risk factors in a randomized clinical trial in individuals with type 2 diabetes. Diabetes Care. 2006 Aug;29(8):1777-83.
Gardner CD, Kiazand A, Alhassan S, Kim S, Stafford RS, Balise RR, et al. Comparison of the Atkins, Zone, Ornish, and LEARN diets for change in weight and related risk factors among overweight premenopausal women: the A TO Z Weight Loss Study: a randomized trial. JAMA. 2007 Mar 7;297(9):969-77.
Gillies CL, Abrams KR, Lambert PC, Cooper NJ, Sutton AJ, Hsu RT, et al. Pharmacological and lifestyle interventions to prevent or delay type 2 diabetes in people with impaired glucose tolerance: systematic review and meta-analysis. BMJ. 2007 Feb 10;334(7588):299. Epub 2007 Jan 19.
Halton TL, Willett WC, Liu S, Manson JE, Albert CM, Rexrode K, et al. Low-carbohydrate-diet score and the risk of coronary heart disease in women. N Engl J Med. 2006 Nov 9;355(19):1991-2002.
Lindstrom J, Ilanne-Parikka P, Peltonen M, Aunola S, Eriksson JG, Hemio K, et al. Sustained reduction in the incidence of type 2 diabetes by lifestyle intervention: follow-up of the Finnish Diabetes Prevention Study. Lancet. 2006 Nov 11;368(9548):1673-9.
Liu S, Choi HK, Ford E, Song Y, Klevak A, Buring JE, et al. A prospective study of dairy intake and the risk of type 2 diabetes in women. Diabetes Care. 2006 Jul;29(7):1579-84.
McMillan-Price J, Petocz P, Atkinson F, O'Neill K, Samman S, Steinbeck K, et al. Comparison of 4 diets of varying glycemic load on weight loss and cardiovascular risk reduction in overweight and obese young adults: a randomized controlled trial. Arch Intern Med. 2006 Jul 24;166(14):1466-75.
Schulze MB, Schulz M, Heidemann C, Schienkiewitz A, Hoffmann K, Boeing H. Fiber and magnesium intake and incidence of type 2 diabetes: a prospective study and meta-analysis. Arch Intern Med. 2007 May 14;167(9):956-65.
Stranges S, Marshall JR, Natarajan R, Donahue RP, Trevisan M, Combs GF, et al. Effects of long-term selenium supplementation on the incidence of type 2 diabetes: a randomized trial. Ann Intern Med. 2007 Jul 9; [Epub ahead of print]
Ting RZ, Szeto CC, Chan MH, Ma KK, Chow KM. Risk factors of vitamin B(12) deficiency in patients receiving metformin. Arch Intern Med. 2006 Oct 9;166(18):1975-9.
Ziegler D, Ametov A, Barinov A, Dyck PJ, Gurieva I, Low PA, et al. Oral treatment with alpha-lipoic acid improves symptomatic diabetic polyneuropathy: the SYDNEY 2 trial. Diabetes Care. 2006 Nov;29(11):2365-70.
