1. Introduction
Diabetes is a public health problem that is increasing worldwide [
1]. According to International Diabetes Federation (IDF), in Europe, in 2017, there were 58 million individuals with diabetes [
2]. This number is expected to increase by 16% until 2045, reaching the value of 67 million people with diabetes [
2]. In Portugal, more than 1 million people between the ages of 20 and 79 have diabetes [
3]. Type 2 diabetes (T2D) is the most common type of diabetes [
3], and its prevalence is likely to increase with age [
4]. The adverse effects of hyperglycemia can be categorized into microvascular (diabetic nephropathy, neuropathy, and retinopathy) and macrovascular complications [
5]. Cardiovascular and cerebrovascular diseases are the most common macrovascular complications and the main causes for morbidity and mortality among T2D patients [
6]. The adoption of a balanced diet is one of the pillars of diabetes control [
7]. For T2D patients, the reduction of energy intake is recommended through the maintenance of a healthy eating pattern based on the intake of unsaturated fats, high fiber foods such as fruits, vegetables, whole grains, and legumes, and limited alcohol intake [
2,
8]. However, the adherence to nutritional recommendations is generally disregarded by these patients [
9]. Nutrition-related knowledge is one of the factors that can influence the adoption of a healthy diet [
10] and T2D patients tend to present deficits in this area [
11,
12,
13,
14,
15]. Therefore it is urgent that this population has access to self-management education focused on nutritional contents. In what concerns diabetes, despite the existence of general nutrition recommendations for self-management education [
16], the best intervention remains to be identified [
17]. In Portugal, as in many other European countries, caring for people with T2D occurs essentially within the primary health care system [
18], which may be a successful place for the implementation of nutritional interventions, due to the fact that there is a closer contact with the patients, and the possibility to provide permanent care [
19]. Despite the importance of primary health care, supportive environments are also required to promote behavior changes [
20]. Thus, community-based interventions are of particular public health interest as they reach T2D patients in their natural living environment and, when replicated, may attain population level impact [
21]. It is the responsibility of nutrition educators to find out innovative solutions so that the community can be aware of the indispensable role of diet in diabetes management [
22]. We only found one study in the community setting that analyzed nutrition-related knowledge after the application of a food education program (developed for Korean American Immigrants) [
23]. Hence, we carried out a pilot study to evaluate the impact of a community-based food education program on nutrition-related knowledge in middle-aged and older patients with T2D.
4. Discussion
Our study revealed that a community-based food education program significantly increased nutrition-related knowledge in middle-aged and older patients with T2D. Participants’ global improvements are mostly derived from the evolution in scores of sources of nutrients. The emphasis of our food education program on contents from this knowledge area is likely to be the reason for this change. On the contrary, differences between groups were not found in dietary recommendations and diet-disease relationship areas. In dietary recommendations, participants from CON and EXP groups started with a high score (5.0 and 4.9 points respectively) in a maximum section scale of 6 points, which makes improvements harder to achieve. Regarding the diet-disease relationship area, the results may have been conditioned by the design of the questions, as half of questions were open-ended [
32]. Furthermore, this was the final section of the instrument and, according to Rolstad et al. [
33], the length of the survey can increase response burden.
The increase of nutrition-related knowledge is associated with healthier food patterns [
10] and may lead to a better glycemic control in T2D patients [
34]. Nutrition-related knowledge is a key component of diabetes knowledge. Most educational interventions analyzed in scientific studies with T2D patients focused on diabetes knowledge without presenting results for patients’ knowledge about nutrition management of diabetes [
35,
36,
37,
38,
39]. Some studies showed the effectiveness of a nutritional intervention in nutrition-related knowledge of T2D patients [
22,
40,
41,
42,
43]. However, as far as we know, there is only one published RCT conducted in a community setting, with Korean American immigrants [
22], that assessed the effectiveness of a nutrition education program on nutrition-related knowledge in patients with T2D (
n = 79; 56.5 ± 7.9 years). After two group face-to-face sessions (two hours each; one week apart) devoted to nutritional contents, there were significant differences in nutrition-related knowledge with the intervention group scoring better, as assessed after 30 weeks.
It is difficult to discuss between our study and that of Song et al. [
22] because of different sample characteristics, assessment instruments, and baseline scores. As explicit memory (recognition) declines with age, the fact that average age of our participants was higher than Song’s study (65.9 ± 6.0 vs. 56.5 ± 7.9 years) makes their learning more difficult [
44]. Song et al. [
22] used the Diabetes Knowledge Test with seven multiple choice questions for nutrition-related knowledge, while in our trial we applied the GNKQ, comprised of three different areas of nutrition-related knowledge (DR, SN, and DDR). According to Worsley [
45], it is of crucial importance to measure different areas of nutrition-related knowledge, as this outcome is not one dimensional. Contrary to Song’s results, participants from our trial started with a baseline score above 50% (29.8 out of 56 points), being more difficult to improve nutrition-related knowledge.
In our study, we used face-to-face group education delivered over 16 weeks, lasting a total of 12 h. The classes were based on IDF nutrition teaching modules [
27] and ADA dietary recommendations for T2D control [
28], given through theoretical classes together with dual-task problem solving strategies during exercise.
Face-to-face education is one of the most common educational methods, as it enables patients to ask and discuss their doubts, allowing the construction of a dynamic relationship between the educator and patients [
46]. Despite this, there are a rising number of studies conducted in T2D patients delivering education through technology-based methods [
35,
47,
48,
49,
50]. Although technology-based programs have the potential to solve the problem of distance to the place of intervention, they can represent a barrier to patients from lower socioeconomic and educational groups, such as the patients from our EXP group, who are more likely to have lower digital literacy and more difficulties in the access and use of technologies [
51].
According to Coppola et al. [
52], there are three different methods to provide patient education: during usual care, structured group, and individual education. Two meta-analyses [
53,
54] showed the benefits of group-based education on diabetes knowledge, when compared with individual education. Group education provides opportunities for patients’ interactions, making possible discussions about several topics. Moreover, it provides support from others facing similar challenges, allowing participants to feel integrated in a group context [
55].
In what concerns the duration of nutritional programs, interventions conducted in T2D patients presented variable results, ranging from 2 h and 40 min [
56] to 25 h [
42] and being delivered between 1 week [
22,
49] to 6 months [
43,
57]. Steinsbeck et al. [
54], in a systematic review of group-based T2D self-management education, concluded that interventions delivered between 6 and 10 months and with 19 to 52 h of duration give the best results in diabetes knowledge.
Regarding the development of food education programs, ADA recommendations for T2D management were also used by Song et al. [
22], with some contents similar to those used in our study, such as carbohydrate counting, food pyramid, healthy eating plate, and meal planning. Other nutritional interventions that improved diabetes knowledge in T2D patients also had similar contents to our study: definition of diabetes [
36,
37,
38], meal planning [
38], meal frequency [
38], cooking methods [
37], importance of fruit, vegetable, and whole grains [
37], and healthy eating [
36,
38].
Our intervention was centered on two teaching methods: structured lecture (15-min group class) and dual-task problem solving (30 min integrated in one exercise session). Lectures are the best teaching method to transmit declarative knowledge [
58]. Problem solving tasks are a great indicator of functional ability in the elderly [
59]. Furthermore, dual-task problem solving—in this study the completion of a secondary task while walking—is a key contributor for the prevention of falls in the elderly [
60]. The use of this technique during exercise was the most innovative aspect of our study. In addition to preparing our patients to the dual-task problem solving of the daily life, it also allows them to target the lifestyle factors of T2D management. Although cognitive impairment may affect learning behaviors [
61], the evolution of nutrition-related knowledge, even in these patients (assessed with Mini Mental State Examination), proves the efficacy of these simple teaching methods.
As expected, attendance to food education program was an independent factor associated with the increase of nutrition-related knowledge in our EXP group. As in our study, Bruce et al. [
62] and Brown et al. [
63] also found that higher attendance to educational sessions was related to greater knowledge levels.
Attendance to our food education program presented lower values compared with other educational interventions in T2D patients (47.5% vs. 72.5% [
64], 74% [
65], and 78% [
66]). Attendance to interventions has a natural influence on its efficacy [
67]. Identification of the motives of low attendance rates is of crucial importance for food education program feedback [
68]. In our study, participants’ attendance was tracked. Whenever an individual missed two sessions in a row, a phone call was made to record the cause. Patients reported health status, weather, work, family activities, and transportation as constraints, meeting the reasons listed by Brzoska and Misra [
69]. Therefore, there is a need for strategies to increase attendance to education sessions in people with T2D. Miller et al. [
41,
42] also tracked participant’s attendance. If T2D patients missed a group session, they were stimulated to attend a backup session. Participation of family members in the education sessions [
22,
70] and the presence of the community health professionals [
22,
71] are two other strategies that were used in interventions with T2D patients to promote class attendance.
The negative association between diabetes duration and the evolution in nutrition-related knowledge is another finding from our study. Hassing et al. [
72] reported an association between diabetes mellitus and mild cognitive impairment, which is higher with longer duration of diabetes [
73]. The accurate pathophysiology of cognitive dysfunction in diabetes is not totally defined, but probably hyperglycemia, vascular disease, hypoglycemia events, and insulin resistance are the main factors [
74]. Diabetes is typically a progressive chronic disease that is often related to emotionally stressful events [
75]. Chronic stress affects the function of the cognitive system, having implications for educational contexts [
76]. According to Eom et al. [
77], individuals with more years of diabetes have more diabetes-related stress.
The present study has some limitations that need to be addressed. Our food education program had an average low attendance level (48%). Another factor that should be highlighted was the existence of 37% of declines to participation from those originally selected by their medical doctors. Besides, we had 16% of dropouts following randomization. This underlines the difficulty in implementing lifestyle interventions for this population, even when culturally adapted and free of charge. Despite randomization, there is a five-year difference in the mean of the age between CON and EXP groups, quite a large difference for such a small trial.
Our study was strengthened by its randomized controlled design, the control of the effects of covariates on the evolution of nutrition-related knowledge in the EXP group, the application of short-duration lectures and the use of an innovative method (dual-task strategy) to give nutritional contents. Moreover, our questionnaire allowed data collection from three different areas of nutrition-related knowledge. In accordance to our search, this was the first study conducted in Portugal that evaluated the effect of a community-based food education program in nutrition-related knowledge, in middle-aged and older patients with T2D, in primary health care. Diabetes is a major public health problem in Portugal and worldwide.