Chapter 13 Nutritional Aspects of Diabetes

The overall purpose of nutrition therapy that applies to all adults with diabetes is to promote and support healthful eating patterns, emphasizing a variety of nutrient-dense foods in appropriate portion sizes and amounts, in order to improve overall health (9). Nutrition therapy for the older adult with diabetes should include meeting the DRI for age for nutrients, evaluating fluid intake, avoiding significant weight loss, and being sensitive to individual preferences and long-standing food habits (4).

Knowing outcomes from nutrition interventions and when to evaluate intervention outcomes is import- ant. Randomized controlled trials and other outcome studies of MNT delivered by registered dietitian nutri- tionists (RDNs) document mean decreases in HbA1c by approximately 1% to 2% (up to about 3% in newly diagnosed persons), depending on the type and dura- tion of diabetes and level of glycemic control (14). The evidence suggests that MNT is most beneficial at diag- nosis but is effective at any time during the disease process. The outcomes of MNT on glycemia and lipids will be known by 6 weeks to 3 months, and at that time an evaluation of the need to combine (or adjust) medi- cations with MNT should be undertaken.

Carbohydrate

Evidence is inconclusive for an ideal amount of carbo- hydrate intake for persons with diabetes. For good health, carbohydrate intake from vegetables, fruits, whole grains, legumes, and dairy products are preferred over intake from other carbohydrate sources, especially those that contain added fats, sugars, or sodium. With regard to the effects of carbohydrate on glucose concen- trations, the total amount of carbohydrate in meals (and snacks, if desired) is more important than the source (starch or sugar) or the type (high or low glycemic index) (9). Numerous studies have reported that when subjects are allowed to choose from a variety of starches and sugar, the glycemic response is similar, as long as the total amount of carbohydrate is kept con- stant. Therefore, monitoring carbohydrate intake, whether by carbohydrate counting or experience-based estimation, remains a key strategy in achieving glyce- mic control. The first decision for food and meal plan- ning is the total amount of carbohydrate that the person with diabetes chooses to have for meals or snacks.

Fiber

Fiber is an important component of a healthful eating pattern, but there is no reason to recommend that people with diabetes eat a greater amount of fiber than other Americans. Very large amounts of fiber (50 g/d; usual intake is 15 to 20 g/d) may have beneficial effects

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on postprandial glycemia, insulin, and lipid levels; however, it is not known whether most persons will regularly consume enough dietary fiber over the long- term to see this benefit (15). Any increase in dietary fiber should be done cautiously in older adults, espe- cially in those who are not ambulatory or are likely to become dehydrated.

Protein

There is no evidence to suggest that usual intake of protein (15% to 20% of energy intake) be changed in persons with diabetes. For persons with diabetic kidney disease (either micro- or macroalbuminuria), reducing the amount of protein below usual intake is not recom- mended because it does not alter glycemic measures, cardiovascular risk measures, or the course of glomeru- lar filtration rate (9).

Protein is probably the most misunderstood nutri- ent, and inaccurate advice is frequently given to persons with diabetes. Although nonessential amino acids undergo gluconeogenesis, in subjects with con- trolled diabetes, the glucose produced does not enter the general circulation (16). Adding protein to a meal or snack does not slow the absorption of carbohydrate, and adding protein to the treatment of hypoglycemia does not prevent subsequent hypoglycemia (9). Although protein is just as potent a stimulant of insulin secretion as carbohydrate (17), adding protein to meals has not been shown to improve the glucose response. It should be remembered that insulin not only impacts carbohydrate and glucose metabolism but is also neces- sary for protein synthesis, inhibition of protein degra- dation, and metabolism of fats. Therefore, encouraging protein intake above what an individual desires often only adds unnecessary and unwanted calories without any known benefits.

Fat

Evidence is also inconclusive for an ideal amount of total fat intake for people with diabetes. The type of fatty acids eaten is more important than total fat in the eating plan in terms of supporting metabolic goals and influencing the risk of cardiovascular disease (9). Unsaturated fatty acids, both mono- and poly-, are rec- ommended; however, a moderate fat intake is sug- gested based on calorie goals.

Micronutrients There is no evidence of benefit from vitamin or mineral supplementation in persons with diabetes who do not have underlying deficiencies. Routine supplementation of the eating plan with antioxidants is not advised because evidence of efficacy is lacking and there is concern about long-term safety. However, a daily