This study showed that the registered dietitian–led diabetes management program in the primary care clinics significantly improved the glycemic control of type 2 diabetic patients with baseline A1C ≥7%. We found a strong and independent association between a reduction in carbohydrate intake and improvements in A1C (P < 0.001). We observed a much greater reduction in A1C in our poorly controlled intervention group (0.7%) than in the control group (0.2%) (P = 0.034). Our intervention group also had a 13.4 mg/dl reduction in mean fasting glucose plasma, whereas our control group had a 16.9 mg/dl increase in that measure (P = 0.007).
Recently, some large randomized controlled trials have also documented the effectiveness of lifestyle or nutrition interventions on delaying the progression from impaired glucose tolerance to diabetes in high-risk individuals (13
). However, most of those studies were based on patients receiving care in academic or medical centers with more departments and greater capacity to provide individualized nutrition counseling than primary care clinics. Although there have been studies on the management of diabetes in primary care (15
), none have studied the effect of the kind of registered dietitian–led management of diabetes on glycemic and diet controls that was proposed in this study.
The effects of diabetic self-management education focusing on dietary or lifestyle changes have been reported in some trials in primary care settings (16
). The results of those studies showed the intervention groups to have greater reductions in A1C (−0.92 to −1.8%) than the control groups (−0.16 to −0.4%). In one French study using the Staged Diabetes Management Program (18
) in a primary care setting, the intervention group had a 0.31% decrease in A1C, whereas the control group had a 0.56% increase, which made an overall difference of 0.86%. The intervention group in this study had improvements comparable in magnitude to those reported by other trials (16
) as well as to those reported by the UKPDS study, which reported a 1% decrease in A1C for the invention group and a 0.1% increase in the control group (6
). Another study of a French population also demonstrated that by introducing a diabetic management program, glycemic control can be improved without increasing the total health care cost (18
In this study, we tried to identify how on-site nutrition counseling would affect not only glycemic control but also adherence with dietary recommendations and self-management of disease in a primary care setting. Although this study showed no differences in A1C when the two groups were considered as a whole, it should be noted that in our study the patients in the intervention group with fair baseline A1C (<7%) had significantly greater reductions in fasting plasma glucose and intake of energy (kilocalories per day) and fat (grams per day), but not in overall change in A1C, compared with control subjects. This finding provides valuable information for future diabetes care.
Imparting knowledge about nutrition to patients is essential when one is teaching diabetic patients how to self-manage their diseases (11
). Previous studies analyzing data by the India Health Service Diabetes Care and Outcome Audit of 7,490 medical charts showed that patients receiving clinical nutrition education from a registered dietitian or a registered dietitian along with another staff member had greater improvements in A1C levels (−0.26 and −0.32%, respectively) than those receiving nutrition education from either a non–registered dietitian staff member or no nutrition education (−0.19 and −0.10%, respectively) (19
). Furthermore, one study entitled the Improving Control with Activity and Nutrition Study, which randomly assigned obese type 2 diabetic patients to a registered dietitian–led case management group and a usual care group, reported that their registered dietitian–led case management group had greater reductions in weight, waist, A1C, and use of prescription medication than the control subjects (20
). To our knowledge, the current study is the first in Taiwan to demonstrate that effective glycemic control can be achieved by interventions by registered dietitians providing both diabetic self-management education and intensive dietary counseling in a primary care setting. After 1 year, energy intake had decreased by 229 ± 309.16 kcal/day in the intervention group but increased by 56.10 ± 309.41 kcal/day in the control group with A1C ≥7%. We also found concomitant reductions in the intake of absolute amounts of all three macronutrients in our intervention group. However, despite the significant reduction in total energy intake, we did not find significant reductions in body weight in the intervention group. The lack of weight loss in the intervention group might have occurred because most diabetic patients were taking a sulfonylurea drug, which stimulates storage of glycogen and lipogenesis. It has been well documented that the use of these drugs is often associated with weight gain (6
Most randomized controlled trials evaluating the effectiveness of diabetes-self management or lifestyle education have reported improvements in clinical indexes (5
), but few have documented dietary changes (21
). One study (21
) using lifestyle education in diabetic patients reported significant differences in reductions in total fat (percent energy, P
< 0.001) and saturated fat (percent energy, P
= 0.001) and nonsignificant (P
= 0.13) decreases in the total energy intake between their intervention and control groups (−215 vs. −144 kcal/day, respectively). Another randomized controlled trial (22
), evaluating the effect of a weight reduction (including dietary counseling) and exercise program on diabetes management in older overweight patients, reported significant net differences in total energy intakes over 3 months (control 210.9 kcal/day, intervention −200.4 kcal/day, and net difference −411.3 kcal/day). However, these studies did not examine simultaneous association between changes in dietary components and metabolic parameters. Our study showed that energy intake was decreased by 229 ±+ 309.16 kcal/day in the intervention subjects and increased by 56.10 ± 309.41 kcal/day in the control subjects with A1C ≥7% (P
< 0.001) after 1 year. Significant net differences were also observed between the absolute amounts (grams per day) of carbohydrate/fat/protein consumption in the intervention group (−31.24/−7.74/−10.91) and the control group (7.15/3.84/2.94). After adjustment for confounders, independent associations were found between changes in carbohydrate intake and A1C, indicating that carbohydrates may be the most important among macronutrients in influencing changes in A1C. This finding is consistent with the finding that the amount of carbohydrates consumed is a strong predictor of glycemic response (23
). Therefore, portion size control or carbohydrate counting such as those suggested by the ADA may remain a key dietary strategy in achieving desirable glycemic control. Registered dietitians can play an important role in imparting this knowledge to diabetic patients and in helping them implement changes in diet.
There are some limitations in the current study. Twenty-four-hour dietary recall is commonly used in routine clinical nutrition counseling to estimate the food intake of patients in Taiwan. Although 24-h recall has been found to be confounded by recall bias (24
), interviews of patients by trained dietitians who are able to retrieve more accurate dietary information may attenuate such errors. In addition, because both groups were likely to have recall bias, the rates of underreporting are probably comparable. Second, we did not analyze insulin sensitivity at baseline and only began doing it after the 1-year follow-up (unpublished data). Therefore, the present study did not report changes in insulin sensitivity after intervention was started.
In summary, we found that the registered dietitian–led diabetes management program aimed to increase a diabetic patient's knowledge of how to self-manage his or her illness was an effective strategy for controlling glycemic status and improving dietary habits for patients with poorly controlled type 2 diabetes. Changes in carbohydrate intake were independently associated with improvements in glycemic control, emphasizing the need for carbohydrate counting in nutrition education programs for diabetic patients.