Nutrition therapy for new diabetes patients
Fruits and starchy vegetables contain carbohydrates, which affect postprandial blood glucose levels.
The CDC estimates that 23.6 million people — 7.8% of the population — have diabetes, 5.7 million of whom are undiagnosed. It is also estimated that 1.6 million new cases of diabetes are diagnosed each year in people aged 20 years and older.1 A significant number of new diabetes diagnoses occur in the primary-care setting following routine laboratory work. This is also the appropriate time to provide general nutrition guidelines to patients with diabetes.
The American Dietetic Association recommends that patients be provided with individualized medical nutrition therapy (MNT) implemented by a registered dietitian (RD).2 However, an immediate appointment with a dietitian is rarely possible. Therefore, it is important for the primary-care provider (PCP) to be able to educate a newly diagnosed patient on the fundamentals of MNT for use until the patient is able to attend a diabetes-education class or meet with an RD.
Nutrition recommendations that are not supported by evidence have led to a number of misconceptions.2 One such misconception is that there is a single diet that is appropriate for every person with diabetes. The American Diabetes Association (ADA) recommends the use of the term "ADA Diet" be discontinued since a specific meal plan is no longer endorsed.3 The most current evidence-based recommendations for diabetes MNT concern the prevention and treatment of the condition and its complications (Table 1).
In the past, the ADA's nutrition recommendations were based on scientific knowledge, clinical experience, and expert consensus. These recommendations are now categorized using a grading system according to the level of evidence available. The recommendations with the strongest evidence should be utilized while taking into consideration each patient's individual circumstances, culture, ethnicity, and personal preferences.4 Table 2 can be used to provide accurate nutrition information for diabetes care. The highest rank A is assigned when there is supportive evidence from multiple, well-conducted studies; B is an intermediate rating; C is a lower rating; and E represents expert consensus.
Out of the macronutrients, carbohydrates have the greatest impact on postprandial blood glucose levels. According to the ADA, all patients can benefit from basic information about carbohydrates, namely knowing which foods contain carbohydrates (starches, fruit, starchy vegetables, milk, sweets), average portion sizes, and how many servings to select for meals and snacks.5 Evidence shows that it is the total carbohydrate consumed—rather than the source or type of carbohydrate—that matters most for blood-sugar control.2 A six-week trial involving people with either type 1 or type 2 diabetes and both acute and longer-term consumption of an array of starches or sucrose found no significant difference in glycemic response as long as the amount of total carbohydrate was similar. Sucrose has not been shown to worsen blood glucose control provided that it is used in place of other carbohydrate-containing foods. Therefore, simple sugars do not need to be totally eliminated from the diet but instead should be worked into the meal plan.6
Different carbohydrate foods have different glycemic responses, but the evidence is lacking to support the benefit of using low- versus high-glycemic-index diets. Despite the fact that low-glycemic-index diets may decrease postprandial glycemia, it is not feasible for most people to maintain this diet long enough to achieve the glycemic benefit. In individuals with type 1 diabetes who followed low-glycemic-index diets, there was not significant evidence of benefit compared with those on high-glycemic-index diets.4
Saccharin, aspartame, acesulfame potassium, and sucralose have been approved by the Food and Drug Administration (FDA) and are safe for use by people with diabetes and during pregnancy. Before approval, each of these sweeteners was rigorously tested and scrutinized and ultimately shown to be safe for the public when consumed within the acceptable daily intake level established by the FDA.4
Protein's role in diabetes and glycemic control is widely misunderstood. Multiple studies of subjects with controlled type 2 diabetes have shown that ingested protein may result in gluconeogenesis, but the amount of glucose produced is small and does not appear in general blood circulation. For this reason, protein does raise plasma glucose concentrations. Protein also has not been found to slow the absorption of carbohydrate, nor has it been found to assist in the treatment of hypoglycemia.4
Evidence shows there may be increased protein catabolism in subjects with type 1 diabetes treated with conventional insulin. There is also evidence demonstrating that moderate hyperglycemia can contribute to increased protein turnover in subjects with type 2 diabetes. These data indicate that euglycemia and adequate protein intake are important in persons with diabetes. In the United States, 15%-20% of average energy intake is supplied by protein. A majority of adults consume 50% or more protein intake than needed, so a typical diet will be more than adequate to prevent protein malnutrition.4