© 2002 by the American Diabetes Association, Inc.
Evidence-Based Nutrition Principles and Recommendations for the Treatment and Prevention of Diabetes and Related ComplicationsAmerican Diabetes Association
Medical nutrition therapy is an integral component of diabetes management and of diabetes self-management education. Yet many misconceptions exist concerning nutrition and diabetes. Moreover, in clinical practice, nutrition recommendations that have little or no supporting evidence have been and are still being given to persons with diabetes. Accordingly, this position statement provides evidence-based principles and recommendations for diabetes medical nutrition therapy. The rationale for this position statement is discussed in the American Diabetes Association technical review "Evidence-Based Nutrition Principles and Recommendations for the Treatment and Prevention of Diabetes and Related Complications," which discusses in detail the published research for each principle and recommendation (1). Historically, nutrition recommendations for diabetes and related complications were based on scientific knowledge, clinical experience, and expert consensus; however, it was often difficult to discern the level of evidence used to construct the recommendations. To address this problem, the 2002 technical review (1) and this position statement provide principles and recommendations classified according to the level of evidence available using the American Diabetes Association evidence grading system. However, the best available evidence must still take into account individual circumstances, preferences, and cultural and ethnic preferences, and the person with diabetes should be involved in the decision-making process. The goal of evidence-based recommendations is to improve diabetes care by increasing the awareness of clinicians and persons with diabetes about beneficial nutrition therapies. Because of the complexity of nutrition issues, it is recommended that a registered dietitian, knowledgeable and skilled in implementing nutrition therapy into diabetes management and education, be the team member providing medical nutrition therapy. However, it is essential that all team members be knowledgeable about nutrition therapy and supportive of the person with diabetes who needs to make lifestyle changes.
Goals of medical nutrition therapy that apply to all persons with diabetes are as follows: 1. Attain and maintain optimal metabolic outcomes including
Goals of medical nutrition therapy that apply to specific situations include the following:
Carbohydrate and diabetes When referring to common food carbohydrates, the following terms are preferred: sugars, starch, and fiber. Terms such as simple sugars, complex carbohydrates, and fast-acting carbohydrates are not well defined and should be avoided. Studies in healthy subjects and those at risk for type 2 diabetes support the importance of including foods containing carbohydrate particularly from whole grains, fruits, vegetables, and low-fat milk in the diet of people with diabetes. A number of factors influence glycemic responses to foods, including the amount of carbohydrate, type of sugar (glucose, fructose, sucrose, lactose), nature of the starch (amylose, amylopectin, resistant starch), cooking and food processing (degree of starch gelantinization, particle size, cellular form), and food form, as well as other food components (fat and natural substances that slow digestionlectins, phytates, tannins, and starch-protein and starch-lipid combinations). Fasting and preprandial glucose concentrations, the severity of glucose intolerance, and the second meal or lente effect of carbohydrate are other factors affecting the glycemic response to foods. However, in persons with type 1 or type 2 diabetes, ingestion of a variety of starches or sucrose, both acutely and for up to 6 weeks, produced no significant differences in glycemic response if the amount of carbohydrate was similar. Studies in controlled settings and studies in free-living subjects produced similar results. Therefore, the total amount of carbohydrate in meals and snacks will be more important than the source or the type. Studies in subjects with type 1 diabetes show a strong relationship between the premeal insulin dose and the postprandial response to the total carbohydrate content of the meal. Therefore, the premeal insulin doses should be adjusted for the carbohydrate content of the meal. For individuals receiving fixed doses of insulin, day-to-day consistency in the amount of carbohydrate is important. In persons with type 2 diabetes, on weight maintenance diets, replacing carbohydrate with monounsaturated fat reduces postprandial glycemia and triglyceridemia. However, there is concern that increased fat intake in ad libitum diets may promote weight gain. Therefore, the contributions of carbohydrate and monounsaturated fat to energy intake should be individualized based on nutrition assessment, metabolic profiles, and treatment goals.
Glycemic index. Although it is clear that carbohydrates do have differing glycemic responses, the data reveal no clear trend in outcome benefits. If there are long-term effects on glycemia and lipids, these effects appear to be modest. Moreover, the number of studies is limited, and the design and implementation of several of these studies is subject to criticism.
Fiber.
Sweeteners. In subjects with diabetes, fructose produces a lower postprandial response when it replaces sucrose or starch in the diet; however, this benefit is tempered by concern that fructose may adversely effect plasma lipids. Therefore, the use of added fructose as a sweetening agent is not recommended; however, there is no reason to recommend that people with diabetes avoid naturally occurring fructose in fruits, vegetables, and other foods. Sugar alcohols produce a lower postprandial glucose response than fructose, sucrose, or glucose and have lower available energy values. However, there is no evidence that the amounts likely to be consumed in a meal or day result in a significant reduction in total daily energy intake or improvement in long-term glycemia. The use of sugar alcohols appears to be safe; however, they may cause diarrhea, especially in children. The Food and Drug Administration has approved four non-nutritive sweeteners for use in the U.S.saccharin, aspartame, acesulfame potassium, and sucralose. Before being allowed on the market, all underwent rigorous scrutiny and were shown to be safe when consumed by the public, including people with diabetes and during pregnancy.
It has been proposed that foods containing naturally occurring resistant starch (cornstarch) or foods modified to contain more resistant starch (high amylose cornstarch) may modify postprandial glycemic response, prevent hypoglycemia, reduce hyperglycemia, and explain differences in the glycemic index of some foods. However, there are no published long-term studies in subjects with diabetes to prove benefit from the use of resistant starch.
A-Level evidence
B-Level evidence
C-Level evidence
Expert consensus
In the U.S., protein intake accounts for 1520% of average energy intake, is fairly consistent across all ages from infancy to older age, and appears to be similar in persons with diabetes. It has been assumed that in people with diabetes, abnormalities of protein metabolism were less affected by insulin deficiency and insulin resistance than glucose metabolism. However, in subjects with type 2 diabetes, it has been demonstrated that moderate hyperglycemia can contribute to an increased turnover of protein, which suggests an increased need for protein. In subjects with type 1 diabetes treated with conventional insulin therapy, short-term kinetic studies have demonstrated increased protein catabolism, suggesting that near-normal glycemia and an adequate protein intake are needed. Because most adults eat at least 50% more protein than required, people with diabetes appear to be protected against protein malnutrition when consuming a usual diet. Dietary intake of protein is reported to be similar in patients with or without nephropathy, but in all studies, protein intake was in the range of usual intake and rarely exceeded 20% of the energy intake. Intake of protein in the usual range does not appear to be associated with the development of diabetic nephropathy. However, the long-term effects of consuming >20% of energy as protein on the development of nephropathy has not been determined, and therefore it may be prudent to avoid protein intakes >20% of total daily energy. A number of studies in healthy subjects and in persons with controlled type 2 diabetes have demonstrated that glucose from ingested protein does not appear in the general circulation, and therefore protein does not increase plasma glucose concentrations. Furthermore, the peak glucose response to carbohydrate alone is similar to that of carbohydrate and protein, suggesting that protein does not slow the absorption of carbohydrate. In subjects with type 1 diabetes, the rate of restoration of euglycemia after hypoglycemia, time to peak glucose levels, and subsequent rate of glucose fall were similar after treatment with either carbohydrate alone or carbohydrate and protein. The effects of protein on regulation of energy intake, satiety, and long-term weight loss have not been adequately studied. The long-term efficacy and safety of high-protein low carbohydrate diets remains unknown.
B-Level evidence
Expert consensus
Fatty Acids and Dietary Cholesterol The primary dietary fat goal in persons with diabetes is to limit saturated fat and dietary cholesterol intake. Saturated fat is the principal dietary determinant of plasma LDL cholesterol. Furthermore, persons with diabetes appear to be more sensitive to dietary cholesterol than the general public. In nondiabetic persons, low saturated fat and cholesterol diets decrease plasma total cholesterol, LDL cholesterol, and triglycerides with mixed effects on HDL cholesterol. Positive correlations between dietary total and saturated fat and changes in plasma total cholesterol and LDL and HDL cholesterol are observed. Adding exercise results in greater decreases in plasma total and LDL cholesterol and triglycerides and prevents the decrease in HDL cholesterol associated with low-fat diets. However, studies in persons with diabetes demonstrating effects of specific percentages of dietary saturated fatty acids and specific amounts of dietary cholesterol are not available. Therefore, the goal for persons with diabetes remains the same as for the general population. In metabolic study diets, in which energy intake and weight are held constant, diets low in saturated fat and high in carbohydrate or enriched with cis-monounsaturated fatty acids (monounsaturated fat) lower plasma LDL cholesterol equivalently. Low saturated fat (i.e., 10% of energy) high carbohydrate diets increase postprandial levels of plasma glucose, insulin, triglycerides and, in some studies, decrease plasma HDL cholesterol when compared in metabolic studies to isocaloric high monounsaturated fat diets. However, high monounsaturated fat diets have not been shown to improve fasting plasma glucose or HbA1c values. There is concern that when such high monounsaturated fat diets are eaten ad libitum outside of a controlled setting, it may result in increased energy intake and weight gain. Therefore, both the metabolic profile and the need to lose weight will determine nutrition therapy recommendations. Furthermore, ethnic or cultural preferences may play a role in determining whether saturated fat is to be replaced with carbohydrate or monounsaturated fat. Polyunsaturated fats have not been well studied in persons with diabetes. When compared with saturated fat, polyunsaturated fats appear to lower plasma total and LDL cholesterol, but not as well as monounsaturated fats. N-3 polyunsaturated fatty acid supplements have been shown to lower plasma triglyceride levels in persons with type 2 diabetes. Although the accompanying rise in plasma LDL cholesterol is of concern, glucose metabolism is not likely to be adversely affected with their use. N-3 supplements may be most beneficial in the treatment of severe hypertriglyceridemia. While n-3 fatty acid studies in persons with diabetes have primarily used supplements, there is evidence from the general population that foods containing n-3 fatty acids have cardioprotective effects. Two to three servings of fish per week provide dietary n-3 polyunsaturated fat and can be recommended. The effect of trans-unsaturated fatty acids (formed when vegetable oils are processed and made more solid [hydrogenation]), is similar to saturated fats in raising plasma LDL cholesterol. In addition, trans-fatty acids lower plasma HDL cholesterol. Therefore, intake of trans-fatty acids should be limited.
Plant sterol and stanol esters block the intestinal absorption of dietary and biliary cholesterol. Plant sterols/stanols in amounts of
Low fat diets
Fat replacements
A-Level evidence
B-Level evidence
C-Level evidence
Because of the effects of obesity on insulin resistance, weight loss is an important therapeutic objective for persons with type 2 diabetes. Short-term studies have demonstrated that weight loss in subjects with type 2 diabetes is associated with decreased insulin resistance, improved measures of glycemia and dyslipidemia and reduced blood pressure. However, long-term data assessing the extent to which these improvements can be maintained are not available. The reason long-term weight loss is difficult for most people to accomplish is probably because energy intake, energy expenditure and thereby body weight are regulated by the central nervous system. This regulation appears to be influenced by genetic factors. Furthermore, environmental factors often make losing weight difficult for those genetically predisposed to obesity. Evidence demonstrates that structured, intensive lifestyle programs involving participant education, individualized counseling, reduced dietary fat and energy intake, regular physical activity and frequent participant contact are necessary to produce long-term weight loss of as much as 57% of starting weight. When dieting to lose weight, fat is probably the most important nutrient to restrict. Spontaneous food consumption and total energy intake are increased when the diet is high in fat and decreased when the diet is low in fat. Exercise by itself has only a modest effect on weight loss. However, exercise is to be encouraged because it improves insulin sensitivity, acutely lowers blood glucose, and is important in long-term maintenance of weight loss. Weight loss with behavioral therapy alone also has been modest and behavioral approaches may be most useful as an adjunct to other weight loss strategies. However, optimal strategies for preventing and treating obesity long-term have yet to be defined. Standard weight loss diets provide 5001,000 fewer calories than are estimated to be necessary for weight maintenance. Although many people can lose some weight (as much as 10% of initial weight) with such diets, the medical literature documents that without the other components of an intensive lifestyle program, long-term outcomes are poor. The majority of people regain the weight they have lost. Meal replacements provide a defined amount of energy often as a formula product. Use of meal replacements once or twice daily to replace a usual meal can result in significant weight loss, but meal replacement therapy must be continued if weight loss is to be maintained. Very low calorie diets (VLCDs) provide 800 or fewer calories daily and produce substantial weight loss and rapid improvements in glycemia and lipemia in persons with type 2 diabetes. When VLCDs are stopped and self-selected meals are reintroduced, weight gain is common. Thus, VLCDs appear to have limited utility in the treatment of type 2 diabetes and should only be considered in conjunction with a structured weight maintenance program. The available data suggest that weight loss medications may be useful in the treatment of overweight persons with type 2 diabetes. However, their effect is modest. Moreover, the available data suggest that these medications only work as long as they are taken and should be used in conjunction with lifestyle strategies. These drugs should be used only in people with BMI >27.0 kg/m2.
Although gastric reduction surgery can be an effective weight loss treatment for severe obesity (including severe obesity in persons with type 2 diabetes), this surgery should only be considered for patients with a BMI
A-Level evidence
Persons with diabetes should be educated about the importance of consuming adequate amounts of vitamins and minerals from natural food sources as well as the potential toxicity of megadoses of vitamin and mineral supplements. Although difficult to ascertain, if deficiencies of vitamins and minerals are identified, supplementation can be beneficial. Select populations, such as the elderly, pregnant or lactating women, strict vegetarians, and those on calorie-restricted diets may benefit from supplementation with a multivitamin preparation. Because diabetes may be a state of increased oxidative stress, there has been interest in prescribing antioxidant vitamins to people with diabetes. In general, megadoses of dietary antioxidantsvitamin C, vitamin E, selenium, beta carotene, and other carotenoidshave not demonstrated protection against cardiovascular disease, diabetes, or cancer. Although large observational studies have shown a correlation between dietary or supplemental consumption of antioxidants and cardiovascular benefit, large placebo-controlled trials have failed to show a benefit and, in some instances, have suggested adverse effects of antioxidant vitamins. The role of folate in preventing birth defects is widely accepted, but the role of folate supplementation to lower homocysteine and to reduce cardiovascular events is not clear. The role of vitamins B1, B6, and B12 in the treatment of diabetic neuropathy has not been established and cannot be recommended as a routine therapeutic option. The use of nicotinamide to preserve ß-cell mass in newly diagnosed subjects with type 1 diabetes is under investigation; however, a beneficial effect has not been clearly demonstrated. Deficiencies of certain minerals, such as potassium, magnesium, and possibly zinc and chromium, may aggravate carbohydrate intolerance. Whereas the need for potassium or magnesium replacement is relatively easy to detect based on low serum levels, the need for zinc or chromium supplementation is more difficult to detect. Beneficial effects on glycemia from chromium supplementation have been reported. However, the populations studied may have had marginal baseline chromium status, and in the largest study, chromium status was not evaluated either at baseline or following supplementation. Other well-designed studies have failed to show any significant benefit from chromium supplementation on glycemic control in people with diabetes. At the present, benefit from chromium supplementation in persons with diabetes has not been conclusively demonstrated. A daily intake of 1,0001,500 mg of calcium, especially in older subjects with diabetes, is recommended. This recommendation appears to be safe and likely to reduce osteoporosis in older persons. The value of calcium supplementation in younger persons is uncertain. The role of vanadium salts in diabetes has been explored. There is no clear evidence of efficacy, and there is potential for toxicity. A variety of herbal preparations have been shown to have modest beneficial effects on glycemia. However, commercially available products are not well standardized and vary greatly in the content of active ingredients. In persons with diabetes, there is no evidence to suggest long-term benefit from herbal preparations. They also have the potential to interact with medications. Therefore, it is important that health care providers be aware when patients with diabetes are using these products. There is no clear evidence of benefit from vitamin or mineral supplementation in people with diabetes who do not have underlying deficiencies. Exceptions include folate for prevention of birth defects and calcium for prevention of bone disease.
B-Level evidence
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