Nutrition

Nutrition Therapy

One of the more fundamental components of the diabetes treatment plan for all patients with type 2 diabetes (T2D) is nutrition therapy. Specific goals of nutrition therapy in T2D are to:

• Achieve and maintain as near-normal blood glucose levels as possible by balancing food intake with physical activity, supplemented by oral hypoglycemic agents, injectable non-insulin agents and/or insulin as needed
• Normalize blood pressure
• Normalize serum lipid levels
• Help patients attain and maintain a reasonable body weight (defined as the weight an individual and health care provider acknowledge as possible to achieve and maintain on a short- and long-term basis)
• Prevent or delay diabetes-related complications
• Provide patients with tools for day-to-day mean planning
• Promote overall health through optimal nutrition and lifestyle behaviors.

Because no single dietary approach is appropriate for all patients, and given the heterogeneous nature of T2D, meal plans and diet modifications should be individualized to meet a patient’s unique needs and lifestyle. Accordingly, any nutrition intervention should be based on a thorough assessment of a patient’s typical food intake and eating habits and should include an evaluation of current nutritional status.

Some patients with mild-to-moderate diabetes can be effectively treated with an appropriate balance of diet modification and exercise as the sole therapeutic intervention, particularly if their fasting blood glucose (FBG) level is <140 mg/dL and their glycosylated hemoglobin (A1C) is near goal. The majority of patients, however, will require pharmacologic intervention in addition to diet and exercise prescriptions. It is important to note that pharmacologic treatment is often less successful when the patient is not on some type of dietary and exercise regimen.

Dietary changes do not have to be dramatic to produce clinically important results in terms of improving blood glucose, blood pressure and lipid levels. Regular monitoring of blood glucose, glycated hemoglobin, lipid levels, blood pressure and body weight serves as an ongoing assessment of the nutrition intervention.

Nutrition Consult

Because nutrition issues and meal planning are complex, a registered dietitian who is familiar with the current principles and recommendations for managing diabetes may be consulted after a patient is diagnosed with diabetes. This health care professional can be an essential member of the diabetes management team and perform a number of valuable functions:

• Conducts initial assessment of nutritional status:
• Diet history
• Lifestyle
• Eating habits
• Provides patient education regarding:
• The basic principles of diet therapy for diabetes
• Meal planning
• Problem-solving techniques for changing eating behaviors
• Develops an individualized meal plan:
• Emphasizing one or two priorities
• Minimizing changes from the patient’s usual diet (to encourage compliance)
• Provides follow-up assessment of the meal plan to:
• Determine effectiveness in terms of glucose and lipid control and weight loss
• Make necessary changes based on weight loss, activity level, or changes in medication
• Provides ongoing patient education and support (particularly for those on weight-loss regimens), helping patients learn to adjust their meal plans for various situations.

Body Weight Considerations

Weight loss frequently is a primary goal of nutrition therapy because 80% to 90% of people with T2D are obese. Caloric restriction and weight loss, even as small as 2 kg to -8 kg in body weight, can provide clinical benefits, including:

• Improved glucose control
• Increased sensitivity to insulin
• Improved lipid levels (an increase in HDL cholesterol and a decrease in triglycerides)
• Decrease in blood pressure
• The need for a corresponding lowering of the dosage of pharmacologic agents (eg, oral antidiabetic medications and insulin).

Weight loss is associated with improved glucose uptake and insulin sensitivity as well as decreased hepatic glucose production. Consequently, the therapeutic regimen most useful for individuals with obesity and glucose intolerance is weight reduction via nutrition therapy and increased physical activity. If moderate weight loss does not improve metabolic parameters, however, pharmacologic therapy (oral antidiabetic agents or insulin) may need to be added to the regimen. Suggested weights for adults, based on guidelines from the National Institutes of Health (NIH), are shown in Table 5-1.

Weight loss and subsequent weight maintenance can be one of the more difficult and challenging aspects of managing diabetes. Therefore, emphasis should be placed on achieving and maintaining normal blood glucose control as the goal of nutrition therapy, using nutritionally balanced meal plans that promote gradual weight loss as a means of achieving this metabolic goal. A reasonable approach that provides a combination of the following strategies increases the chances of a successful outcome:

• Modest caloric restriction
• Restriction of saturated fat intake
• Spreading caloric intake throughout the day
• Increased physical activity
• Behavior modification techniques for changing eating habits and attitudes and promoting healthy, long-term lifestyle behaviors
• Psychosocial support.

Approximately 10% of patients with T2D are of normal weight and do not need to restrict their caloric intake. For these individuals, nutrition therapy focuses on distributing caloric as well as nutrient intake and content throughout the day to achieve optimal glucose, lipid and blood pressure control. The pattern of spreading out calories and carbohydrates between meals and snacks is individualized based on results of self-monitoring of blood glucose.

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Caloric Intake

Adult caloric needs vary according to age, activity level and desired weight change. The following formula can be used to determine adult caloric requirements. First calculate desired body weight:

• Women: 100 lb for the first 5 ft of height plus 5 lb for each additional inch over 5 ft
• Men: 106 lb for the first 5 ft of height plus 6 lb for each additional inch over 5 ft
• Add 10% for larger body builds; subtract 10% for smaller body builds.

Then, multiply the resulting weight by one of the following to compute caloric need based on desired weight:

• Men and physically active women: multiply by 15
• Most women, sedentary men and adults over age 55: multiply by 13
• Sedentary women, adults with obesity, sedentary adults over age 55: multiply by 10.

If weight loss is indicated, daily caloric intake needs to be adjusted to produce the necessary deficit. Given that a 3,500-calorie deficit per week is required to produce a 1-lb loss of fat, a decrease of approximately 500 to 1,000 calories per day is needed to lose 1 to 2 lb of fat per week. Regular exercise is an excellent way to create a caloric deficit and has been associated with successful weight maintenance. Because caloric restriction alone can be difficult to maintain, some people have greater success by eliminating 250 to 500 calories from their daily diet and increasing daily activity by 250 to 500 calories.

Nutrient Composition of the Diet

A nutritionally balanced diet is as important for individuals with diabetes as for nondiabetics. Diet prescriptions for those with T2D need to take into account the higher prevalence of dyslipidemia, atherosclerosis, and hypertension in this population. Practical dietary recommendations are outlined in Table 5-2.

There is no clear evidence that a particular eating pattern or macronutrient distribution is more effective in promoting weight loss. However, several eating patterns have been shown to be more effective at managing diabetes, including plant-based, lower-fat, lower-carbohydrate, Dietary Approaches to Stop Hypertension (DASH)-style, intermittent fasting diet and Mediterranean-style patterns. Since there is no ideal diet for all patients, eating patterns should be individualized to the patient’s goals and preferences. In general, the USDA recommends that 85% of daily calories fall into healthful, nutrient dense food groups (vegetables, fruits, grains, dairy, and protein foods); the remaining 15% is the maximum recommended allowance of less nutritively rich foods, including added sugars and saturated fats. The macronutrient needs of people with T2D do not differ from those of the general population.

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Protein Intake

The evidence for recommending an ideal amount of dietary protein to optimize glycemic control or improve cardiovascular (CV) risk measures is inconclusive. For this reason, the relative contribution of protein to daily energy needs should be individualized. The United States Department of Agriculture (USDA) recommends a dietary allowance for protein foods of between 10% and 35% of total daily calories for all adults, including individuals without diabetes.

In the past, it was believed that excessive protein intake may aggravate renal insufficiency, so limiting protein intake was encouraged. However, the American Diabetes Association (ADA) does not currently recommend that patients with both diabetes and kidney disease (with albuminuria) adjust their protein intake. This is because it has been shown to have no effect on altering glycemic measures, CV risk measures, or glomerular filtration rate decline. The long-term consequences of high-protein (>30% of total daily calories) and low-carbohydrate diets are unknown, but may aggravate renal impairment in diabetic individuals. High-protein diets are often high in saturated fats, which have an adverse effect on LDL cholesterol. In patients with diabetic kidney disease (DKD) and macroalbuminuria, adopting soy-based protein sources may lower CV disease risk.

Fat Intake

The remaining daily calories are distributed between fat and carbohydrate intake. The USDA recommends that between 20% and 35% of daily calories come from fat sources in all adults; however, no tolerable upper intake level is defined. The fat intake should also include 27 grams of oil (including vegetable oils and oils in food) per day on a 2,000-calorie diet. Saturated fats should not exceed 10% of daily calories. These recommendations are not specific to patients with diabetes, since limited data are available in these individuals. In terms of achieving metabolic goals and reducing CV risk, research indicates that the type of fat consumed is more important than the total amount.

The following guidelines are recommended by the ADA regarding dietary fat intake:

• Eating plan emphasizing elements of a Mediterranean-style diet rich in monounsaturated fats
• The consumption of foods rich in long-chain omega-3 fatty acids (such as fatty fish) and nuts and seeds
• The consumption of saturated fat, cholesterol and trans fat in line with recommendations for the general population; in general, trans fats should be avoided

Several clinical trials have demonstrated that a Mediterranean-style eating pattern, which is rich in monounsaturated fatty acid, is effective at improving glycemic control and/or blood lipids. In contrast, there is strong evidence indicating that taking omega-3 fatty acid supplements is ineffective at improving glycemic control in people with T2D.

Carbohydrate Intake

Clinical studies have not identified an ideal daily amount of carbohydrate intake for individuals with diabetes, although the USDA recommends that adults obtain between 45% and 65% of their daily energy from carbohydrate sources. Emphasis is placed on whole grains, legumes, fruits, dairy products and vegetables to provide the necessary vitamins, minerals and fiber in the diet. These sources are advised over other carbohydrate sources, such as those containing added sodium, fats and sugar. The recommended daily consumption of fiber is the same for people with diabetes as for nondiabetics (14 g per 1,000 calories). Although dietary fiber can lower all-cause mortality and improve serum cholesterol levels and other CV risk factors (e.g., blood pressure), the effect on glycemic control is modest at best. The consumption of whole grains is not associated with improvements in glycemic control in patients with T2D, but there is evidence that it may reduce systemic inflammation, mortality and CV disease.

Traditionally, complex carbohydrates were thought to produce lower blood glucose responses than simple sugars because sugars are digested and absorbed more rapidly. This belief, which influenced previous recommendations of replacing simple sugars in the diet with complex carbohydrates, has been largely disproved by clinical research. For example, the glycemic response to fruits and milk has been found to be lower than the response to most starches, and sucrose has been found to produce a glycemic response similar to that with bread, rice and potatoes. The rate of digestion of a given food seems to be more related to the presence of fat, degree of ripeness, cooking method, form and preparation.

Sucrose

A modest amount of sugar is allowed in the daily diet of patients with T2D. Sucrose and sucrose-containing foods may be substituted for other carbohydrates in the meal plan, but not simply added. Patients need to be taught how to make such substitutions using self-monitoring of blood glucose (SMBG) to evaluate the glycemic response. The total nutrient content of the sucrose-containing food should be considered, particularly because sugar and fat are the main ingredients in many sweets.

Fructose

Fruits and vegetables are a natural source of dietary fructose. In addition, some sweeteners are derived from these sources. Moderate consumption is recommended, particularly concerning foods in which fructose is used as a sweetening agent. Although fructose has a lower glycemic effect than sucrose, it contains the same amount of calories and therefore should be limited in hypocaloric diets. People with dyslipidemia also are advised to limit their consumption of fructose because of the potential adverse effects on serum tri­glyceride and LDL cholesterol levels.

Sodium

The ADA recommends that individuals with diabetes follow the same recommendations as the general public, which is to reduce sodium to less than 2,300 mg/day. Further reduction in sodium should be individualized for patients with both diabetes and hypertension.

Other Nutritive/Nonnutritive Sweeteners and Fat Substitutes

Nutritive sweeteners such as corn syrup, fruit juice/concentrate, honey, molasses, dextrose and maltose do not seem to have a greater advantage or disadvantage over sucrose in terms of impact on caloric content or glycemic response, but they need to be accounted for in the meal plan. Certain sugar alcohols (sorbitol, mannitol, xylitol) that are commonly used as sweeteners can produce a lower glycemic response than sucrose but seem to have no real advantage over sucrose or other nutritive sweeteners when consumed as part of mixed meals. Excessive consumption of sugar alcohols may cause laxative effects.

Nonnutritive sweeteners (saccharin, aspartame, acesulfame K, sucralose) have been approved by the Food and Drug Administration (FDA) for consumption by people with diabetes. These sweeteners are useful because they contribute minimal or no calories or carbohydrates to the diet when they are used as tabletop sweeteners or in soft drinks. However, when sweeteners are used in foods that contain other nutrients and calories (ice cream, cookies, puddings), the foods must be worked into the meal plan or consult with a nutritionist.

Because many of the fat substitutes, such as Olestra, currently being used are derived from carbohydrate or protein sources, the content of these compounds is increased above the usual amounts in such products. Patients need to be advised to review the carbohydrate and/or protein content when using products that contain fat substitutes.

Vitamins, Minerals and Herbs

Supplementation generally is not recommended for people with diabetes when dietary intake is adequate and balanced. Patients who become chromium deficient as a result of long-term parenteral nutrition may require chromium supplementation. However, most people with diabetes are not chromium deficient and do not benefit from supplementation. Similarly, magnesium does not need to be added to the diets of most patients with diabetes unless routine evaluation of serum magnesium reveals a deficiency. Patients taking diuretics may need potassium supplementation. However, hyperkalemia may require potassium restriction in patients with renal insufficiency, or hypo­reninemic hypoaldos­teronism, or in those taking ACE inhibitors. Due to concerns over efficacy and long-term safety, the ADA does not recommend routine supplementation with antioxidants, such as vitamin E and C and carotene.

There are many nonprescription herbal remedies being touted in health food stores as being beneficial for people with diabetes. While some of these herbs may have some rational scientific basis, most have not been well studied and the benefits are questionable. Some of these compounds have the potential to produce toxicity. The ADA recommends against the use of vitamins, minerals, herbs, or spices (e.g., cinnamon and aloe vera) for glycemic benefit.

Alcohol Intake

The same recommendations used for the general population are appropriate for people with T2D. Moderate consumption will not adversely affect blood glucose in patients whose diabetes is well controlled. Calories from alcohol should be included as part of the total caloric intake and reflected in the meal plan as a substitute for fat (one alcoholic beverage = two fat exchanges). For patients taking insulin, one (for women) or two (for men) alcoholic beverages per day are acceptable (one alcoholic beverage = 12 oz beer, 5 oz wine, or 1½ oz distilled spirits; sweet drinks should be avoided) taken with or in addition to the meal plan. However, some special considerations exist regarding alcohol intake. Patients taking insulin or insulin secretagogues (eg, sulfonylurea) are susceptible to hypoglycemia if alcohol is consumed on an empty stomach. Therefore, these individuals should be sure to take any desired alcohol with a meal and to perform frequent home glucose monitoring.