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Introduction
The prevalence of type 2 diabetes mellitus (DM) has drastically increased in recent years in Korea. Type 2 diabetes is accompanied by complications such as dyslipidemia, hypertension and obesity (Gray et al., 1998; Hopkins et al., 1996). These complications can be prevented if glycemic control is maintained within a normal range (Genuth et al., 2003; Ko et al., 2007).
Dietary management is considered the cornerstone of glycemic control in DM patients (Lindstorm et al., 2003). Patient education including nutrition education is now accepted as an essential component of diabetic management (Jiang et al., 1999). Numerous studies with DM patients have shown the association of nutrition education with improving dietary behavior (Albarran et al., 2006; Norris et al., 2001), nutritional knowledge (Bruce et al., 2002; Lim et al., 2001) and improving clinical outcomes such as lower blood glucose and HbA1c levels (Christensen et al., 2000; Delahanty & Halford, 1993; Johnson & Valera, 2001; Miller et al., 2002) and lipid concentrations (Lee, 2007; Norris et al., 2001).
Since the diabetes educational program began in Korea in the 1970s, there were over 170 hospitals providing diabetes educational program nationwide in 2005 (Park & Ahn, 2007). Most of these programs consisted of one class session focusing on principles of diet therapy and were delivered in a group setting (Lim et al., 2001). Thus patients have found it difficult to understand and follow dietary advice at home. For most patients, they do not have channels to communicate with dietitians. Nutrition intervention through telephone consultation is a strategy for extending diabetes management into the patient's home (Kim & Oh, 2003). But few studies have identified and documented individualized nutrition education and telephone interviews for DM patients in Korea. Woo et al. (2005) reported that individualized dietary consultation using a diabetic buffet system was effective for helping patient to understand their diet prescriptions and controlling body weight and blood sugar level. Hayes et al. (2001) and Maljanian et al. (2005) have demonstrated the effectiveness of telephone consultations in diabetes management. Therefore, various approaches of nutrition education including telephone consultation are urgently needed to achieve more effective management of diabetes.
In this study, we aimed to examine the effect of individualized nutrition education for type 2 DM patients by evaluating changes in dietary behavior, nutritional knowledge, nutrient intakes and the effect of nutrition education followed by telephone consultation once a month for the following 3 months.
Subjects and Methods
Subjects
To recruit the subjects, an announcement on diabetic nutrition class was made at a DM clinic center in Seoul. The program was open to all type 2 DM patients who had gone through the baseline tests including FFQ at the clinic from September 2007 through April 2008, and 67 DM patients were voluntarily participated in the program. The control group composed of patients who visited the same clinic at the same period but did not join the program and 34 subjects were selected by medical record review. Patients were aged 33-81 years old and had no identifiable language barrier or known mental disability.
After the nutrition education session, 67 subjects in the education group were divided into the telephone follow-up group (34 subjects) and no telephone consultation group (33 subjects). The telephone follow-up group subjects were completed the intensive telephone follow up and no telephone consultation group subjects had any further contact for 3 months. This study was approved by the institutional review board (IRB) of Yonsei University Medical Center and written informed consent was obtained from all subjects.
Measurements
Diet survey and clinical measurements were made before enrolling the nutrition program and all the measurements were repeated at the end of study period for all subjects including control group.
General characteristics and dietary behaviors and nutrient intakes
An interview using a questionnaire was performed to get general characteristics and health behavior data. Dietary behavior and food exchange knowledge were assessed by the questionnaire developed for this study.
The dietary behavior questionnaire was developed based on questionnaire by Dunn et al. (1990), Fitzgerald et al. (1998), Kim and Seung (1985), Lee et al. (1985) and Lim et al. (2001).
The questionnaire was composed of 6 questions of diet adequacy, compliance with diet prescription using food exchange units, meals regularity, and food variety, frequency of salty food, and high fat/high cholesterol food use.
It was preliminarily tested before using and subjects were asked to answer 'often and always' (5 points), 'seldom and sometimes' (3 points), or 'never' (1 point) to get dietary behavior score.
To assess food exchange knowledge, subjects were asked to match 12 food items (① Rice, ② Laver, ③ Oil ④ Soy milk ⑤ Bean ⑥ Orange juice ⑦ Kim-chi ⑧ Acorn starch jelly ⑨ Yogurt ⑩ Apple ⑪ Peanuts ⑫ Beef) to food exchange groups. For a correct answer, 1 point was assigned and the possible total score was 12 points.
Nutrient intakes were measured by trained nutrition graduate students using 114-item FFQ previously validated (Oh et al., 2007). Dietary intakes data were analyzed by using Can-pro 2.0 software (The Korean Nutrition Society, Korea).
Anthropometric and serological variables
The standing height was measured using a stadiometer. Body weight, body fat mass (kg), % body fat and waist hip ratio (WHR) were measured with an In-body 4.0 (Biospace Co., LTD., Seoul, Korea) and BMI (body mass index, kg/m2) was calculated. Blood samples were collected after a 12-h overnight fast. FBS, total cholesterol, triglyceride, and HDL-cholesterol were measured by using an auto analyzer (COBAS MIRA, Roche, Switzerland). LDL-cholesterol was calculated as described by Friedewald et al. (1972)
[LDL-cholesterol = Total cholesterol - HDL cholesterol - (Triglyceride/5)]
Hemoglobin A1c was measured by HLC-723 G7 (Toche, Japan). Systolic and diastolic blood pressures were measured in the sitting position after 10-minute rest by using an automatic pressure calculator (Biospace co, Seoul Korea).
Contents and procedure of nutrition education
Diet planning
Energy requirement was prescribed by physicians for each subject based on the subject's height, weight, and activity level according to the guidelines of Korean diabetes association (KDA).
Energy distribution was set in accordance with Korean Dietetic Association recommendation (protein 15-20%, fat 20-25%, carbohydrate 55-60%).
Individualized diet planning using food exchange system was given considering food preference and dietary behavior shown in the results of FFQ and dietary behavior questionnaire. Also, diabetic complications were taken into account, if any.
Curriculum of nutrition education
The curriculum of nutrition education was structured to provide an understanding of meal planning and dietary recommendation (Fig. 1). The purpose of this program was to encourage and support self-management leading to long-term adherence to diet recommendation. Food model was used to help subjects understand the food exchange system.
Procedures of nutrition education
The nutrition education program consisted of one session for 1 to 2 hours long according to individualized diet prescription and was performed in a small group of 4~5 patients. The control group subjects were given written results of the FFQ after baseline examination and had no further contact for following 3 months.
After the education session, the 34 telephone follow-up group subjects received intensive consultation for 3 months. The telephone consultation focused on checking their adherence to diet recommendation leading to long-term dietary behavior maintenance. No telephone consultation group subjects had any further contact after the nutrition education session.
Statistical analysis
Statistical analyses were conducted using SPSS program (version 12.0). All data were expressed as mean and standard error (continuous variables) or number and percentage (categorical variables). Chi-square test was performed to determine differences in frequencies of categorized variables including use of medication between two groups. Comparison analysis between baseline and after 3 months was done by paired t-test. Data within each group were analyzed by repeated measures analysis of variance to establish significant differences in treatment. In all statistical tests, p values of less than 0.05 were considered significant.
Results
General characteristics and health behavior of the subjects at baseline
As shown in Table 1, mean age and DM duration were 59.0 y and 7.1 y for education group and 58.0 y and 8.6 y for control group, respectively. About two thirds of patients had DM family history and one third had previous education on DM diet. There were no significant differences between education and control group in baseline characteristics such as sex, age, duration of DM, cigarette smoking and alcohol consumption.
Baseline mean BMIs for education and control groups were 24.4 kg/m2 and 24.8 kg/m2, respectively, which were in the overweight range. The mean WHR was 0.90 cm for education and 0.91 cm for control group which were higher than normal range. Baseline FBS levels for both groups were higher than the normal range and the level of lipid profile was in the normal range. There were no significant differences in mean height, weight, BMI, and blood levels of glucose and lipids. Systolic blood pressure for both groups were higher than the normal value, however, diastolic blood pressure was in the normal range.
Also, no significant differences were found in macronutrients and micronutrients intakes between two groups. Dietary behavior score and food exchange knowledge score were 18.2 and 8.68 for education group and 18.8 and 7.93 for control group, respectively, and the differences between two groups were not significant.
Effect of nutrition education program
Dietary behavior and food exchange knowledge score: Table 2 shows the changes of dietary behavior and food exchange knowledge after 3 months of intervention period. In education group, the scores for 3 questions on food adequacy, compliance with prescription, and low fat meal were significantly increased. The scores on food regularity, variety, and salty food intake did not change. The total score of dietary behavior was significantly increased from 18.2 to 20.5 out of possible score of 30. On the other hand, in control group, only the score for meal adequacy was significantly increased and total scores did not change.
The food exchange knowledge score of education group was significantly increased from 8.68 to 9.91, however, no significant change was found in control group.
Repeated tests for treatment showed significant effects of nutrition education on increasing knowledge score (time × education interaction, P < 0.05).
Anthropometric and serological variables: After 3 months of intervention period, subjects in education group showed significant decreases in the body weight, BMI and WHR compared to the baseline values. Significant reductions were also found in FBS, HbA1c, total cholesterol, and triglyceride. No changes in HDL and LDL cholesterol levels were observed during the same period. However, no significant changes of all anthropometric and blood variables were found in control group (Table 3). Repeated tests for treatment showed significant effects of nutrition education on lowering HbA1c and total cholesterol (time × education interaction, P < 0.05).
Both systolic and diastolic blood pressures were significantly decreased in education group and reached the normal range, however, only SBP was significantly decreased in control group.
Nutrient intakes: In education group, the intakes of protein, calcium, vitamin B2, and folate were significantly increased and cholesterol intake was significantly decreased. The intakes of energy, carbohydrate, lipid, and fiber did not change. On the contrary, in control group, the carbohydrate intake was significantly increased and the intakes of lipid, sodium, vitamin A, vitamin B1, vitamin B2, and vitamin B6 were significantly decreased after 3 months.
Effect of telephone follow-up
To evaluate the effect of follow-up telephone consultation, the results of 34 participants were compared with those of 33 subjects in education group who did not join the telephone follow-up. In telephone follow-up group, BMI was significantly decreased from 23.7 kg/m2 to 23.3 kg/m2 and there were no significant changes in weight, body fat (%), and WHR. Also, significant decreases in FBS and triglyceride were found. No changes were observed in total cholesterol, HDL cholesterol, and LDL cholesterol. The subjects who did not receive telephone consultation also showed significant decrease in body weight, BMI, FBS and HbA1c. SBP and DBP were significantly decreased in both groups and reached a normal range after 3 months.
For nutrient intakes, in the subjects who did not receive telephone consultation, only cholesterol intake was significantly decreased and no significant changes were observed in other nutrients. On the other hand, in telephone follow-up group, energy intake was significantly decreased and the intakes of calcium, phosphorus, vitamin B2 and folate were significantly increased and the intakes of carbohydrate, lipid, fiber, and cholesterol did not change after 3 months. Repeated tests for treatment showed no significant effects of telephone follow-up consultation.
Discussion
Many studies have reported that patients who have participated in diabetes education program improved dietary behavior and nutritional knowledge, resulting in the positive changes in nutrients intake such as increase in vitamin intake and decrease in fat and cholesterol intake (Elshaw et al., 1994; Lee, 2007; Woo et al., 2005) as well as improvement in clinical outcomes such as lower blood levels of glucose and HbA1c (Christensen et al., 2000; Delahanty & Halford 1993; Johnson & Valera, 2001), lower cholesterol and lower triglyceride concentrations (Franz et al., 1995; Lee, 2007; Norris et al., 2001; Shabbidar et al., 2006).
In our study, subjects who joined nutrition education program showed an improvement in dietary behavior score and food exchange knowledge score. Also, nutrition intakes of education group were improved. Intakes of calcium, and vitamins were increased and cholesterol intake was decreased. These results were similar to the results from the study by Lee (2007) and Woo et al. (2005) in which intakes of vitamins and minerals in education group subjects were significantly increased to meet the prescription.
The education group subjects in our study also showed improvements of anthropometric variables and clinical outcome. Weight and BMI of education group were significantly decreased and these results were consistent with the study by Lemon et al. (2004). The improvement in glycemic control shown by reduction of FBS and HbA1c in this study was similar to that of the study by Christensen et al. (2000) in which medical nutrition therapy brought about mean reduction of HbA1c levels to < 8% . Franz et al. (1995) and Shabbidar et al. (2006) have reported that the concentrations of serum cholesterol and triglyceride were decreased significantly and reached the normal range after medical nutrition therapy, which is consistent with our results of reduction in serum cholesterol level.
The repeated education session seems to be essential for diabetic diet consultation. However, it is often difficult for patients to attend classes regularly. Kim and Oh (2003) reported that telephone care programs were a viable strategy for bringing diabetes management into the patient's home, improving glycemic control and increasing compliance with diet recommendations. Maljanian et al. (2005) showed that an intensive telephone follow-up for 12 weeks as an additional component of diabetes management was effective in improving glycemic control and adherence to dietary recommendations. In our study, to examine the effect of nutrition education session followed by telephone consultation, telephone interview was given once a month for the following 3 months. There were no significant differences in changes of BMI, glycemic control and lipid profiles whether or not the subjects received telephone consultation after individualized nutrition education. However, nutrient intakes of the subjects who received telephone consultation were improved and these results were similar to the study by Kim and Oh (2003). It seemed that one class session of our individualized nutrition education was effective in adherence to diet recommendation and in improving glycemic control and lipid concentrations while follow-up by telephone helped encourage adherence to diet prescription.
In summary, in our education group, dietary behavior and food exchange knowledge score were significantly increased. Also, intakes of protein, calcium and vitamins were significantly increased, while FBS, HbA1c, total cholesterol, and triglyceride significantly decreased. Even though diet education was performed only one time, it was effective in rectifying dietary behavior problems and, improving food exchange knowledge, and quality of diet, leading to an improvement in the clinical outcomes. This study proves that individualized diabetes education is effective for diabetes management. To assess that the effect of individualized nutrition education is continually maintained, constant monitoring for diabetes patients is necessary.
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